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Volume 11, Number 1, January 2008
Special Feature Issue on
Intelligent Materials, Structures & Systems – 3
Modeling of the Visco-elastic Properties of PVDF through the Fractional Differential Model
S. Satiya Narayan, C. Lakshmana Rao and S.M. Siva Kumar; India
Abstract: Polyvinylidene Flouride (PVDF), a piezoelectric material has many useful applications like sensor transducers and surface acoustic wave devices. Since PVDF is a polymer, it is possible that its mechanical response is likely to be frequency and time dependent. It is important therefore, to characterize the frequency or time dependent behaviour of PVDF using appropriate models that are based on experimental observations. In this paper, a four parameter model with fractional dashpot was used and it is found that it models the loss and storage modulus results better than the model with ordinary dashpot.
Key words: Fractional Differential Modeling, Viscoelastic properties, PVDF; pp 2 – 8; No of References 9.
Structural Health Monitoring of Ribbon Reinforced Composite Laminate using Piezoelectric Sensory Layer
A.K. Jaiswal, A. Kumar and B. Bhattacharya; India
Abstract: The ribbon reinforced composites are widely used in prosthetics. These structures typically work like a bridge between the canines. They are subjected to central loading and also support yielding due to unequal movement of the end supports. However, due to high strains in the laminate, the chances of delamination and laminate failures are quite high in such structures. In this paper, the finite-element model based development of knowledge-base technique has been used in delamination detection in such composites and which may help in timely replacement of the bridge.
Key words: Structural Health Monitoring; smart plate element; ribbon reinforced composite; delamination in composite laminate. Pp 9 – 17; References 10.
Development of Micromachined Silicon Accelerometers with improved Off-axis Sensitivity
A. Ravi Sankar, S. Das and S. Kal; India
Abstract: Development of micromachined silicon piezoresistive accelerometers with improved off-axis sensitivity has been presented in this paper. Two accelerometer structures have been designed for low off-axis sensitivity. Complete comparative analysis based on simulation results has been given in this paper. Both the structures have been fabricated and testing results of structure 1 have been presented.
Key words: Piezoresistive accelerometers, Off-axis sensitivity,TMOH/CMOS compatibility. Pp 18 – 24. References 26.
Remote Structural Health Monitoring of Civil Infrastructures – Recent Trends
S. Sridhar, K.Ravisankar, P. Sreeshylam, S. Parivallal, K. Kesavan and S.G.N. Murthy; India
Abstract: Construction and maintenance of large civil infrastructures are very much essential for development of any country. The modern constructed facilities involve a huge capital cost and complex design procedures to ensure longer service life and better performance in adverse environmental conditions. There is a growing demand to monitor the health of these structures to increase its safety and serviceability. Remote health monitoring (RHM) is a recent methodology, whereby the instrumented structure is continuously monitored from a distant place, using the latest communication and IT tools. This paper discusses the various aspects of RHM techniques, the latest development in software and hardware.
Key words: Remote Health Monitoring, wireless communication, GSM/RF/PSTN.MOTES, Data acquisition, Embedded algorithms, Civil Infrastructures. Pp. 25 – 35. References 26.
Volume 11, Number 2, April 2008
Advanced Vibration Analysis to Support Prognosis Rotating Machinery Components
M.J. Roemer, C.S. Byington and J. Sheldon; USA
Abstract: Advanced vibration analysis technologies that provide incipient fault detection to enable longer time horizons for failure prediction of critical machine components (prognostics) has the potential to significantly reduce maintenance costs and increase availability and safety. This paper summarizes a comprehensive approach to enhancing prognostic accuracy through more intelligent utilization of relevant vibration diagnostic information coupled with advanced physics-of-failure modelling. Failures and associated predictions of critical rotating machinery components are used as a case study to introduce the concept of adapting key failure mode variables at a local damage-site based on fused vibration features. The overall prognostic system architecture is focused on minimizing inherent modelling and measurement uncertainties by updating material/fatigue properties; spall propagation rates etc., via sensed system measurements that evolve as damage progresses. A specific case study related to aircraft engine rolling element bearing is presented.
Keywords: Machinery diagnostics, prognostics, rolling element bearings, vibration analysis;
Pp 2 -11; References 10.
Energy Losses caused by Misalignment in Rotating Machinery: A Theoretical, Experimental and Industrial Approach
E. Estupinan, D. Espinoza and A. Fuentes; Chile
Abstract: This paper deals with one of the most common malfunctions in rotating machinery, namely Misalignment. Several studies have shown that misalignment produces at least 30% of the faults caused by vibration. In this paper, an analysis of energy losses generated by misalignment in rotating machinery has been carried out, with the main objective of finding a correlation between vibration levels and energy consumptions for different degrees of misalignment. A laboratory test rig has been implemented to carry out experimental work for various degrees of misalignment. Two industrial case studies, one from a mining company and the other from a thermoelectric company have been included. A statistical model based on the response surface methodology (RSM) was employed for the data analysis. A simplified economic study illustrates the industrial benefits when a predictive and preventative methodology is implemented.
Key words: Shaft misalignment, Energy loss monitoring, response surface methodology. Pp 12 – 18. References 11.
Dynamics of Large Power Turbo-Set with Cracked Shaft
S. Banaszek; Poland
Abstract: This paper presents the research and the results of crack propagation simulation investigation. The object of this investigation is to take into account of a large turbo-set rotor. A computer code system NLDW is presented. This uses a non-linear model of journal bearings, and a well known crack model. Crack depth is represented by a crack coefficient. It is shown that a crack generates a coupled form of lateral, axial and torsional vibrations in multi-support rotor. Its intensity depends upon the axial and angular crack location on the shaft. An attempt is made at pointing a proper diagnostic indicator for crack detection in large rotating machine.
Key words: crack propagation, large power turbo-set, cracked shaft, crack model. Pp 19 – 28. References 24.
A New Recursive Structure-Adaptive Filter for Impulse Noise Removal
S. Md. Mansoor Roomi, V. Abhaikumar and T. Krishnan; India
Abstract: A new recursive structure-adaptive filter for effective suppression of impulse noise is presented in this paper. In the first stage, at every noise location in a corrupted image the structure activity is identified by quadratic decomposition. Based on the local structure activity and noise statistics, a recursive window adaptive filtering mechanism is proposed to switch between simple mean, median and centre weighted median filters to provide detail preserving filtering of corrupted pixels. Extensive simulation shows that the proposed filter restores fairly well even when the images are highly corrupted.
Key words: Impulse noise, Structure activity index, discrete cosine transform. Pp. 29 – 35. References 23.
Core Concepts and Technologies of Machinery Oil Analysis for Performance Excellence and Failure Prevention
S. Li and V. Palekar; USA
Abstract: Machinery oil analysis (MOA) is a tribology and lubricant based maintenance tool and failure prevention technology for machinery systems. Once as a practice-focused enabling technology for machinery condition monitoring, MOA is currently advancing to shape its characteristic conceptual framework and technological system. The core concept of MOA is expressed by a triangle representing machinery system contamination, component part wear, and oil physical chemistry respectively. This concept, as a whole or in part, has been gaining wider and wider real-world applications. The uniqueness of this concept in the roles it plays in setting up application-oriented MOA facilities, designing case-sensitive MOA profiles, conducting MOA data-based root-cause analysis, and diagnosing machine/oil health status. In this paper, accounts have been made of the historical evolutions of MOA application phases, technology milestones, instrumentation modes, laboratory types , practice features, parameter characteristics, and service forms.
Key words: Machinery Oil Analysis, condition monitoring, Lubrication management, Tribology. Pp 35 – 42. References 18.
Volume 11, Number 3. July 2008
A Reconfigurable Watchdog Agent for Machine Health Prognostics
L. Liao, H. Wang and J. Lee; USA
Abstract: This paper presents a scalable Watchdog Agent-based toolbox approach for machine health prognostics. The toolbox consists of modularized embedded algorithms for signal processing and feature extraction, performance assessment, diagnostics and prognostics, which can be reconfigured for different machinery prognostic applications, and can be extensible and adaptable to most real-world machine situations. A decision making technique, Quality Function Deployment (QFD)- based tool section method, is applied for the automatic selection of algorithms from the Watchdog Agent toolbox using multiple criteria. In addition, the architecture for the Watchdog Agent-based real-time remote machinery prognostics and health management, which incorporates remote and embedded predictive maintenance technologies, is presented. An industrial case study involving the automatic tool changer of a machine tool is presented to illustrate how the Watchdog Agent toolbox can be used in diverse scenarios.
Key Words: Watchdong Agent, Toolbox, Machine health monitoring, diagnostics, prognostics. Pp 2 – 15. References 30.
Effects of Couple Stresses in Rolling and Normal Motion
R. Raghavendra Rao and K. Raja Sekhar; Eritrea and India
Abstract: Generally, a small amount of additives are added to the lubricant to increase its efficiency in the lubrication process. Usually, these additives are in the form of long-chain molecules. These produced couple stresses and also have an affect on the lubrication process. A generalized Reynolds equation is derived for roller bearings lubricated by couple stress fluid as a lubricant under dynamically loaded condition. This equation is applied to study the effect of couple stresses on the combined rolling and normal motion under cavitation boundary conditions. The load capacity, frictional drag are analysed by velocity ratio parameter and also the effects of couple stress of these parameters on cavitation point is discussed.
Key words: Rolling and normal motion, Couple stresses, Frictional drag, cavitation points. Pp 16- 22. References 19.
Computer Interface for Tapered Roller Bearing Diagnostics
A. Andhare and D. Manik; India
Abstract: This paper presents details of a computer interface developed for vibration monitoring and diagnostics of tapered roller bearings, based on experiments conducted for bearing fault diagnosis. An experimental set up was designed and fabricated for testing various tapered roller bearings to obtain their vibration characteristics – three defect-free and nine defective tapered roller bearings were tested. The defective bearings tested were: bearings with outer race defects, roller defects and combination of both. The bearing vibration data were acquired using NI DAQ and LabView Virtual Instrumentation Software, which were further processed using computer interface developed for diagnostics. The computer interface used various time and frequency domain parameters like: peak to valley, RMS value, kurtosis, skewness, envelope analysis, etc. to diagnose faults in bearings. The interface was able to diagnose point defects in the tapered roller bearings. The above computer interface, with some modifications can as well be used for diagnosing defects in plain roller bearings also.
Key words: Tapered roller bearings, Failure diagnosis, Computer interface. Pp 23 – 35, References 32.
Volume 12, Number 3, July 2009
Detection of Crack in Vessels by Monitoring Changes in Natural Frequencies
Choubey, A, N. Tandon and D.K. Sehgal
Abstract: When significant damage occur a change in stiffness occurs which affects natural frequency. In this paper the authors present the reduction of natural frequencies of vessel structures due to the presence of cracks. Finite element analysis has been used to obtain the dynamic characteristics of intact and damaged structures for the first five modes. Two kinds of vessels (boiler and storage tanks) were chosen as test structures. Models of vessels were prepared and boundary conditions (which were closely resembled original strucutes) were applied to the models. Acceleration frequency response functions were monitored at different points on each model by changing crack sizes and locations.
Key Words: Structural monitoring, vessels, crack investigation, FEM.
Number of pages: 5; References; 4.
Health Assessment of Mechanical Systems
Abstract: A procedure based on digraph and matrix method is suggested to assess the health of mechanical systems. Node in the digraph represents the health parameters and their interrelations are represented by the edges. A one to one matrix (also known as Permanent Matrix) is used to define the health function of the system. From this the Health Index of the system is derived. A higher value in the Health Index implies good health of the system.
Key Words: Health assessment, Mechanical systems, Health Index, Digraph, Graph Theory.
Number of pages: 8; References: 11
Increased Safety Protection and Energy Conservation for Motors installed in Zones 1 and 2 Hazardous Areas using Variable Speed Drives
B. Ahirwal, A.K. Singh, R.K. Vishwakarma and A. Sinha
Abstract: Energy efficient motors with variable speed drives (VSDs) differ from other types of motors in a number of ways. Where increased safety, better performance and energy savings are concerned these motors are the most preferred solution. This paper describes the application of these motors in the Indian mining industry.
Key Words: Variable Speed Drive motors; Indian Mining industry
Number of pages: 9; References: 3
Motor Fault Classification using Wavelet Energy and Artificial Neural Network
P. Dubey and C. Sujatha
Abstract: In this paper the authors investigates the vibration and motor current signatures using Wavelet Transform for feature extraction and Artificial Neural Networks (Error Back Propagation type) for classification of electrical and mechanical faults in a three-phase induction motor. Three sets of electrical and mechanical faults (such as bearing faults, rotor unbalance, rotor bar damage, single phasing and stator winding short) have been investigated on a 5 HP induction motor.
Key Words: Induction motor failures, application of Wavelet Transforms and ANNs
Number of pages; 6; References; 11
Quality Improvements at an Automobile Components Manufacturing Plant: A Case Study
D. R. Jana and A.P. Singh
Abstract: In this paper the authors investigates the implementation of Statistical Process Control (SPC) techniques at a washer manufacturing plant.
Key Words: Automated Process Control; Process Capability; Pareto Analysis; Cause and Effect Analysis
Number of pages; 9; References; 11
Volume 12, Number 4, October 2009
Dynamic Modelling and Empirical Mode Decomposition of Spur Gear Vibration for Early Detection of Cracks
Parey, A. And N. Tandon
Abstract: This paper describes a six-degree-of-freedom gear dynamic model including a crack. The model consists of a spur gear pair, two shafts, bearings and inertias representing load and a prime mover. The experimental results support the effectiveness of the gear dynamic model. The authors propose a method for early detection of defects.
Key Words: Gear vibration, dynamic modelling, crack detection. Empirical mode decomposition, Kurtosis
Number of pages: 8; References; 9
Essential Information forms of Condition Monitoring in a Condition Based Maintenance Context
Carina Andersson and M. Bengtsson
Abstract: In this paper the authors discuss an important aspect of information theory to achieve some benefits in the context of condition based maintenance of industrial assets. A case study is presented on four Swedish paper mills and one condition monitoring equipment supplier. The outcome of this study resulted in a framework that visualizes how data and five different forms of information interacts to yield knowledge about the condition of machines.
Key Words: Information theory, Condition based maintenance, Case study on Swedish paper mills
Number of pages: 11; References; 43
A Neuro-Fuzzy System for Thermal Ageing Prediction of Paper/Oil Transformer Insulation Properties
L. Mokhnache, A. Boubakeur, P. Verma and R. Kattan
Abstract: In this paper the authors have applied a neuro-fuzzy system to predict thermal ageing of oil/paper transformer insulation. The fuzzy system is coupled with a Radial Basis Function Neural Network to investigate the physical phenomena leading to a sudden change in the behaviour of the insulation property of paper/oil transformer.
Key Words: Thermal ageing; paper/oil transformer insulation; neuro-fuzzy system
Number of pages; 4; References; 9
Rolling Element Bearing Fault Diagnosis using Adaptive Morlet Wavelet Filter
Verma, A.K. and B. Sreejith
Abstract: The impulses generated by the roller element bearings are relatively of low energy spread over a wide frequency bandwidth. These periodic impulses may be modulated and masked by noise. This paper discusses the application of a method using Morlet Wavelet Filter (MWF) for diagnosing the bearing failures. The parameters of the Morlet wavelet are optimised using Shannon Entropy and Kurtosis. The results obtained are promising.
Key Words: Rolling element bearing, localized defects, diagnosis, Morlet Wavelet Filter
Number of pages 8; References 21
Ontologies for Condition Monitoring and Maintenance
Abstract: Ontology plays a very important role in knowledge sharing, reuse and communication. The paper discusses this subject under three headings; repository ontology, software application ontology and user interface ontology. A short description of the use of software application ontology and the user interface ontology in the field of condition monitoring and maintenance management is presented in this paper.
Key Words: Ontology; Condition monitoring; Maintenance management
Number of pages 7; References 41
Volume 13, Number 1, January 2010
Special Feature Issue on: Structural Health Monitoring
A Review of Impact Damage Detection in Structures using Strain Data
Mujica, L.E., J. Rodellar and J. Vehi
Abstract: This paper aims to provide a state-of-the-art review on impact damage detection techniques in structures using strain data. An overview of impact detection systems is provided. These include sensors, specimens, and impact sources used for developing and testing strategies. This review focuses on approaches that use impact strain data to determine simultaneously the location of an impact at the time it occurs. These approaches are classified into two groups; one based on analytical models and the other based on data-driven models.
Key Words: Impact damage detection; Structural health monitoring, strain models
Number of pages 16; References 92
Leak Detection in Pipes using Induced Water Hammer Pulses and Cepstrum Analysis
Taghvaei, M., S.B.M. Beck and J.B. Boxall
Abstract: Leakage from pipes transporting fluids, such as water distribution networks or oil transport pipelines is a major problem throughout the world. One promising approach to identifying leakage points has been to analyse the reflections from a pressure wave caused by shutting a valve, using a wavelet to filter the data followed by a cepstrum to extract the reflection points. The work reported in this paper takes this technique and applies it to a laboratory based pipe test facility. A novel device is also reported for the creation of the water hammer pulse and the acquisition of the reflected signals from the pipe system. Results reveal that the signal analysis approach combined with the device is able to identify the leaks in the large diameter pipe to accuracy better than one quarter of a metre. When the four thirds power of the amplitude of the processed peak was plotted against leak rate, a straight line was produced, indicating that not only position, but also leak rate can be identified using this technique.
Key Words: Condition monitoring, leaks in pipes, water hammer pulses, Cepstrum analysis
Number of pages 7; References 21
Quantitative Structural Health Monitoring by Ultrasonic Guided Waves
Srivaastava, A. and F. Lanza di Scalea
Abstract: This paper presents a Global-Local (GL) method to simulate the interaction of ultrasonic guided waves with structural defects in plate-like structures. The GL method uses a Full Finite Element discretization of the defected region to properly represent wave diffraction phenomena and a suitable set of wave functions to simulate regions away from the joint. Displacement and stress continuity conditions are imposed at the boundary between the global and the local regions. The radiated wave field can then be calculated by using the least square method. The novelty of the proposed approach over previous GL techniques is the use of Semi Analytical Finite Element (SAFE) modelling for the “global” simulation and the use of this technique to quantify defects by guide waves. The SAFE method only requires the discretization of the waveguide’s cross-section in a computationally efficient manner.
Key Words: Structural health monitoring, plate-like structures, ultrasonic guided waves, Semi Analytical Finite Element (SAFE) modelling
Number of pages 8; References 18
Vibration-based Structural Damage Identification using Active sensing to measure Internal Forces that represent Damage in a Honeycomb Panel
Adams, D.E. and J.R. White
Abstract: This paper uses a vibration based structural damage identification technique which represents damage as a change in the internal mechanical forces within a structural component. To validate the method, an analytical two degree of freedom model is first developed to provide the physical insight into the meaning of the damage indicators, which are extracted from measured data. The results from this model are then compared to the numerical results from a finite element model of a free-free metallic beam and experimental results from a modal vibration test on this beam. After establishing the agreement between theoretical and experimental damage indicators for this simple beam structure, the methodology is applied to a more complicated A1-A1 sandwich structure with a honeycomb core. The experimental results on the sandwich panel demonstrate that impact damage can be detected, located and quantified. A final experiment is then conducted by loosening the piezoelectric actuator attachment causing a change in the resulting damage indicator. This falsie indication of damage is then suppressed by tuning the actuator force signal automatically based on the frequency response measurement between the driving voltage and measured input force to the panel.
Key Words: Structural health monitoring, vibration-based damage identification, honeycomb panels.
Number of pages 13; References 11
Wave Propagation Modelling for Structural Damage Detection
W. Ostachowicz, M. Krawczuk, A. Zak and P. Kudela
Abstract: This paper presents some results of the analysis of elastic wave propagation in one-dimensional and two-dimensional elements of structures with damage. The problem of elastic wave propagation has been solved by the use of the Spectral Element Method. In this approach elements of structures are modelled by a number of spectral finite elements with nodes defined at appropriate Gause-Lobatto-Legendre points. As approximation polynomials high order orthogonal Lagrange polynomials have been used. In order to calculate the elements characteristic stiffness and mass matrices the Gauss-Lobatto quadrature has been applied. In the current analysis damage in the form of crack has been considered. It has also been assumed that the damage can be of an arbitrary length, depth, and location and can be simulated as a line spring of varying stiffness. Numerical calculations illustrating the phenomena of elastic wave propagation in isotropic and orthotropic media have been carried out for the case of a rod and a beam, as well as a flat panel and a plate. Certain results related to a damage detection algorithm developed by the authors have also been shown and discussed.
Key Words: Elastic wave propagation, one-dimensional and two-dimensional structural elements, spectral element method, damage detection
Number of pages 16; References 47
Volume 13, Number 2, April 2010
Special Feature Issue on Knowledge-based Failure Diagnosis and Prognosis of Engineering Systems
Towards a rapid considerable Embedded Development for Manufacturing Prognostics: A Review and Proposed Framework
Kia Mok Goh, Benny Tjahjono and Tim Baines
Abstract: With the fast changing global business landscape, manufacturing companies are facing the increasing challenge to reduce the cost of production, increase equipment utilisation and rapidly provide innovative products in order to compete with low cost economies. One of the methods is zero or near zero downtime. Unfortunately, the current research and industrial solutions do not provide a user friendly and rapidly configurable environment to create ‘adaptive microprocessor size with supercomputer performance’ solution in order to reduce downtime. Most of the current solutions are PC-based with off-the-shelf software tools, which are found to be inadequate for adaptive prognostics near the sensor source using embedded devices. On the other hand, developing a solution for various industrial domains can be too time consuming because the tools and rapid methods for creating adaptive or real time reconfigurable solutions are lacking. A total of 175 papers , rom 38 refereed journals and international conferences are collated and reviewed. Based on the review, some of the potential industrial needs, research trends and gaps in manufacturing prognostics are discussed. Finally, a research agenda towards a rapid configurable embedded development environment for manufacturing environment is identified.
Key words: Manufacturing prognostics, embedded development
Number of pages 15; References 62
A Two-stage Neural Network Classifier for Condition Based Maintenance in Wireless Sensor Networks
Ramani, A. C. McMurrough, M. Middleton, P. Ballal, A. Athamneh, W. Lee, C. Kwan and F. Lewis
Abstract: Motor failures in aerospace applications can lead to serious compromises in safety, overall effectiveness, and maintenance costs. In mission critical applications, it is important that motor fault signatures are identified before a failure occurs. It is known that 40% of mechanical failures occur due to bearing faults. Bearing faults can be identified from the motor vibration signatures. Three key contributions are outlined in this paper. First, we develop a low cost test bed for simulating bearing faults in a motor. Second, the authors develop a wireless sensor module for collection of vibration data from the test bed. Finally, The authors use a novel two stage neural network to classify various bearing faults using the Generalized Hebbian Algorithm (GHA) in the first stage and a supervised learning vector quantization network (SLVQ) with a self organizing map approach for fault classification in the second stage.
Key Words: Condition based maintenance, bearing failures, artificial neural networks
Number of pages 8; References 45
Sensorless Detection of Cavitation in Centrifugal Pumps
P.P. Harihara and A.G. Parlos
Abstract: Electrical signal analysis (ESA) has been in use for quite some time in detecting faults occurring in induction motors. In industrial applications, the induction motors are always coupled to dynamic loads such as pumps, blowers, compressors, etc. Failure to either the motor or the dynamic load is critical to the operation of the plant and results in loss of production and unscheduled downtime leading to increased costs. Hence there is a need for a cost effective early failure detection system not only for induction motors but also for the dynamic loads connected to the motor. In this paper, an experimentally demonstrated model-based sensorless approach to detect varying levels of cavitation in centrifugal pumps is presented.
Key Words: Sensorless detection, cavitation, centrifugal pumps
Number of pages 7; References 6
Identification of precursory Alarm Sequence Patterns for Predicting equipment failures using Ant Colony-based Algorithm
M.Luo, D.H. Zhang, L.L. Aw and F.L. Lewis
Abstract: In industry, enormous files of historical data are collected from equipment monitoring prior to failures. The search for reliable precursory alarm patterns, that is, specific sequences of alarm events, in such data sets is a challenging task. This paper describes an algorithm for identifying precursory alarm patterns from historical measured event data containing numerous fault alarms and equipment states. The algorithm is based on modifications to ant colony optimization (ACO), which is an effective probabilistic learning method for finding shortest paths in large complex graphs. An actual industry application is used to verify the algorithm.
Key Words: Alarm sequence patterns, ant colony based algorithm
Number of pages 12; References 16
Intelligent Diagnostic Health Management of Power Transmission Systems: An Experimental Validation
Onsy, A. R. Bicker and B. Shaw
Abstract: Power transmissions are one of the most important parts of any mechanical system, and in order to achieve reliable operation robust and effective maintenance strategies must be used to trace the condition of the operating transmission, classifying faults, and predicting the onset of failure. This paper presents a novel intelligent diagnostic health management system that is able to monitor different gear faults by combining vibration, acoustic emission, and oil debris analysis with fuzzy logic sensory fusion algorithms. The authors have implemented an intelligent diagnostic health management system (IDHMS) on a back-to-back gear box which can be adapted to monitor the behaviour of transmission systems in automotive, aircraft, wind turbine and industrial machinery.
Key Words: Diagnosis of power transmission systems, intelligent diagnostic health management system
Number of pages 13; References 35
Volume 13, Number 3, July 2010
The effect of Shaft Unbalance on the operation of Worm Gear Rolling Bearings
S. Strzelecki and Z. Towarek
Abstract: This paper presents a case study of worm gears coupled to a Cardan shaft. These gears underwent a failure caused by vibration of the roller bearings which are very sensitive to vibration. The damage of such elements leads to gearbox damage. An analysis was done on the machine drive system, the shaft was examined, the natural frequencies of the shaft were calculated and the life of the roller bearings was estimated.
Key Words: Shaft unbalance, worm gear roller bearings, life-cycle estimation
Number of pages 8; References 10
Comparison of Wavelet Coefficients for Condition Monitoring of Ball Bearings using Kolmogorov-Smirnow (KS) test
M.S. Patil, J. Mathew, P.K. Rajendrakumar and S. Desai
Abstract: This paper presents an application of discrete wavelet analysis of the vibration signals to study the effect of damage in ball bearings. Signal to Noise Ration (SNR) and Retained Signal Energy (RSE) of wavelet coefficients of simulated signal was determined using Daubechies Wavelet for four thresholding rules, namely, Rigrsure (SURE), Sqtwolog (S), Heusure (H) and Minimax (M). SNR and RSE values were obtained using simulated signals to select Rigrsure as the thresholding rule and Db8 wavelet as the mother wavelet. This paper explores the possibility of applying the KS test. The feasibility of using this technique is checked by comparing the outcome of the KS test method with that of other statistical methods such as rms, crest factor and kurtosis.
Key Words: Diagnosis of ball bearings, Kolmogorov-Smirnov (KS) test
Number of pages 8; References 18
eMaintenance readiness of Swedish Process Industry: A Case Study
R. Karim and A. Parida
Abstract: The industries are focusing more on e-business intelligence in managing their assets. This is putting increasing pressure to minimize the downtime and improve the performance of their assets. The purpose of this paper is to undertake a mapping of the present status of the maintenance of Swedish Process Industry in order to identify the feasibilities and challenges for implementing eMaintenance system.
Key Words: e-Maintenance, Swedish Process Industry
Number of pages 7; References 13
Evaluation of Unbalance and Misalignment effect on Forward Curved Centrifugal Blower using Coast-down Time Analysis
G.R. Rameshkumar, K.P. Ramachandran and B.V.A. Rao
Abstract: In this paper unbalance and misalignment effects are investigated experimentally in forward curved centrifugal blower test rig using coast down time analysis as condition monitoring parameter. The results are analysed to assess the potential of using Coast Down Time (CDT) as a diagnostic tool for detecting these conditions.
Key Words: Forward curved centrifugal blower, unbalance, misalignment, coast down time analysis
Number of pages 11; References 18
Condition Monitoring of Railway Switches and Crossing by using Data from Track Recording Cars
Arne Nissen, A. Parida and Uday Kumar
Abstract: Switches and crossings are vital components within the railway system and contribute to many of the maintenance activities to keep the track section available for traffic. Banverket administers about 12000 switches and crossings which contribute to about 13% of the maintenance budget for Banverket. In this paper using Excel and the track recording car data on level, alignment, cant, curvature and guage have been gathered and analysed.
Key Words: Condition monitoring, railway switches and crossings, track recording car, Excel
Number of pages 5; Reference 12
Volume 13, Number 4, October 2010
Special Feature Issue on Energy and Environment
Future Transportation with Smart Grids and Sustainable Energy
Abstract: Transportation is facing fundamental change due to the raped depletion of fossil fuels, environmental and health problems, the growing world population, rising standards of living with more individual mobility and the globalization of trades with its increasing international transport volume. To cope with these problems benign, renewable energy systems and much more efficient drives must be multiplied as rapidly as possible to replace the polluting combustion engines with their much too low efficiency and high fuel logistics cost. Consequently the vehicles of the future must be non-polluting and super efficient. The energy supply must come via smart grids from clean energy sources not affecting the health, climate and bioshphere. It is shown how this transition to the clean, sustainable energy age is possible, feasible and most urgent.
Key Words: Sustainable energy, environmental protection, smart grid
Number of pages 6; References 6
Augmentation of Heat Transfer Coefficient using Chamferred Rib-grove Compound Roughness on Absorber Plate of Solar Air Heater
Abstract: An experimental investigation into the heat and fluid flow characteristics of a fully developed turbulent flow in a rectangular duct having repeated integral transverse chamfered rib-grove roughness on one broad wall has been carried out. The roughened wall was uniformly heated while the remaining three walls were insulated. The flow Reynolds number of the duct varied in the range of approximately 3000 – 21000. Experiments were carried out on 61 roughened surfaces provided with chamfered rib grove roughness having relative roughness pitch of 4.5, 6. 7, 8 and 10 and chamfer angle of 50, 120, 150, 180, 220 and 300, while 600 V groove were placed by varying the relative groove positions 0.3, 0.4, 0.5 and 0.6. The effects of relative roughness height and duct aspect ratio were kept constant at 0.03, 5 and 10 respectively. The effects of relative roughness pitch, chamfer angle and relative groove position on Nusselt number and friction factor have been discussed.
Key Words: Turbulent flow, rectangular duct, heat transfer coeffient, solar air hearter
Number of pages 8; References 13
A different approach to Economic Load Dispatch of Thermal Power Plants using Exponential Cost Function
M. Mohatram, P. Dhyani and P. Tiwari
Abstract: In this paper the problem of Economic Load Dispatch (ELD) in power systems is resolved by considering the operating cost of a thermal power plant as an exponent function. Equality constraints of power balance and inequality plant generation capacity constraints are taken into consideration. The problem is formulated with the transmission losses in the lines and is solved by Lagrangian approach of equal incremental cost. The results of the proposed method are tested for a system consisting of six generating units and the results are compared with a similar problem having quadratic cost functions. Finally the significance of the proposed method is highlighted.
Key Words: Economic Load Dispatch, power systems, exponential cost function
Number of pages 6; References 15
When will Fossil Fuels finally run out and What is the Technical Potential for Renewable Energy Resources?
Abstract: Reserves to Production ratios (R/P) are widely used indicators of the time to depletion of fossil fuel resources. But they are not reliable indicators of the longevity of fossil fuels. This paper examines historical data from 1985, relating to proven resources of fossil fuels and trends in consumption. Based on the increase in consumption as well as reserves, the conclusion is that the current trends suggest that all fossil fuels (oil, gas and coal) could be depleted within decades, possibly as early as 2060. The annual solar energy incident on Earth is some 13500 times more than the annual commercial consumption, and various ideas have been put forward to harness the earth’s renewable flows of energy on a major scale. This paper reviews some of these ideas and examines the technical potential for renewable energy to become a major energy resource in the future.
Key Words: Fossil fuels, renewable energy resources, historical data analysis
Number of pages 6; References 12
Modelling Industrial Energy Flow on a National Scale
Abstract: This paper describes possible means of modelling industrial energy flow on a national base, along with discussions on how useful they would be for better utilization of energy and enhanced policy making. Models for energy inputs and allocation of them among specific end-uses in various US manufacturing industries are given as examples. The energy types included in the given end-use models are: fuel, steam, waste heat and electricity. These models provide a useful tool to characterize industrial energy usage. Similar energy end-use models can serve as key for other studies such as energy process-step models and energy cost analysis for manufacturing industries.
Key Words: Industrial energy flow, modelling
Number of pages 9; References 23
Volume 14, Number 1, January 2011
Special Feature Issue on Failure Diagnosis and Prognosis of Mining Machinery & Systems
Shovel Teeth monitoring and Maintenance in Open-pit Mines
H. Schunnesson, H. Mwagalanyi and Uday Kumar
Abstract: Significant problems exist during the loading of ore in open-pit mines. The problems arise when parts from the bucket follow the ore into the crusher pit causing jamming and damage to the crusher. Repairing this is not only time consuming and very expensive. In this paper a system for detecting the broken teeth and adapters based on infrared images is investigated.
Key Words: Open-pit mining machinery, shovel teeth monitoring
Number of pages 8; References 6
Dragline Maintenance Data Analysis using Logarithmic Scatterplot
S. Elevli, O. Uysal and B. Erdem
Abstract: In this paper maintenance data of two draglines is analysed using Logarithmic Scatterplot method. The data gathered in this investigation reveal how to prioritize maintenance of mechanical and electrical sub-systems of draglines. The boom, hoist rope and attachments, swing, drag and hoist machineries have been identified as priority components for mechanical sub-systems. Likewise the drag, hoist, swing and propel motor and generator sets have been identified as priority components for the electrical sub-system.
Key Words: Dragline maintenance, data analysis, logarithmic scatterplots
Number of pages 7; References 21
Importance of Measure based Ranking and Maintenance Scheduling for Heavy Duty Belt Conveyors: A Case Study from underground Coal Mine
Abstracts: This paper focuses on the maintenance scheduling for production equipment keeping cost control as the primary objective. It highlights prioritization of resources and the importance of the measure based ranking of components and sub-systems. A cost-effective measure has been proposed for scheduling various maintenance tasks.
Key Words: Underground Coal mines, Heavy duty conveyors, measure based ranking procedure
Number of pages 8; References 44
Establishing a Dragline Monitoring System at Kleinkopje Colliery
Abstract: This paper discusses the process undertaken by the Kleinkopje Colliery to establish a reliable and effective monitoring system on its fleet of walking draglines. The paper highlights the process of monitoring system selection, site establishment, commissioning and also gives an outline of current and future uses of the monitoring system. It also focuses on the background, setting up details, results and future perspectives of an efficient monitoring system in a large and prestigious opencast colliery.
Key Words: Opencast colliery, walking draglines monitoring
Number of pages 7; References 6
Productivity Diagnostic study of Draglines operating in Horizontal Tandem
Abstract: This paper reports the investigation undertaken in a large Indian opencast coal mine to critically investigate the horizontal tandem operation of draglines for removing moderately hard and blasted sandstone bench. The paper outlines a methodology to determine the efficiency of dragline operations and to diagnose the key operating parameter that influences its efficiency.
Key Words: Indian opencast coal mines, failure diagnosis of draglines
Number of pages 6; References 11
Volume 14, Number 2, April 2011
Special Feature Issue on Failure Diagnosis and Prognosis of Swedish Mining Assets
Evaluation of Abrasive Wear Measurement Devices of Mill Liners
R. Dandotiya, J. Lundberg and A.R. Wijaya
Abstract: Measurement of the liner wear in the mill of an ore dressing plant is one of the critical parameters in the context of mill downtime and production performance. Due to the different quality attributes of a measuring device, e.g. cost, accuracy, reliability and accessibility, it is necessary to select an important performance measure for the service quality of the device. This paper provides an approach to customer satisfaction with special reference to quality attributes. The primary aim of this investigation is to provide unified measure or quality index which corresponds to the total predicted usability of the particular measurement method. The paper also proposes a new concept of an indirect measurement method to reduce downtime during inspection.
Key Words: Mill liner abrasive wear, diagnosis and prognosis
Number of pages 15; References 26
Non-Destructive Testing methods for Detection and Monitoring of Fatigue Cracks in Mining Mills
F. Berglund, J. Nordstrom and A. Parida
Abstract: The mining industry is striving for higher production and to maximize the availability of its machinery. Smart diagnosis and prognosis of mill machinery operations is vital to minimise unplanned stops, expensive failures, production loss and breakdowns due to fatigue cracks, especially in the mill shell. The aim of this paper is to highlight the scopes and limitations of the different crack detection methods. The authors have applied analytical hierarchical process (AHP) to determine the rank or unified measure for the selected crack detection methods.
Key Words: Mining mills machinery, condition monitoring and diagnosis
Number of pages 9; References 25
Condition Monitoring and Maintenance Performance Assessment issues for Mining Industry
Abstract: Maintenance performance assessment of mining industry is a complex issue as it involves various stakeholders both internal and external. In this paper the author discuss various condition monitoring and maintenance management issues relating to mining industry.
Key Words: Mining industry, issues and challenges, condition monitoring, performance assessment
Number of pages 8; References 31
Enhancement of Mining Machinery Performance through Supportability
B. Ghodrati, T. Markeset and A. Ahmadi
Abstract: Cost analysis of mining operations in general shows that 30 to 50 percent of direct mining costs are related to maintenance and losses related to lost production during equipment downtime. To reduce these losses one first needs to improve the equipment reliability and thereafter to reduce the downtime losses through improved maintainability and supportability. The mining operational environment is often harsh and may severely impact all three of these abilities. In this paper the authors focus on how to improve the estimation of spare parts by taking into account the operating environment in the estimation models. In this investigation the authors have developed an improved statistical-reliability (S-R) analysis approach that takes into account the system/machine operating environment. This analytical approach is based on multiple regression based on Cox’s proportional hazards modelling (PHM).
Key Words: Mining machinery, performance monitoring, proportional hazards modelling
Number of pages 9; References 16
Rock Mass Characterisation using Drill and Crushability Monitoring: A Case Study
H. Schunnesson and T. Kristoffersson
Abstract: This paper presents the application of drill and crushability monitoring to predict detailed rock mass characterisation in the Swedish surface copper mine (Aitik). Both monitoring methods can provide relevant rock mass information to support production and production planning. Furthermore the necessary geometrical connection between drill hole position, loading position and the related crushing activities later in the process can be solved by the mine planning system, MineStarTM
Key Words: Copper mining operation, drill and crushability monitoring
Number of pages 9; References 15
Volume 14, Number 3, July 2011
Lean, Clean, Green and Intelligent infrastructure for Sustainable Cities
Abstract: The UN estimate that 30% - 40% of the world’s energy use arises out of the operation of buildings, resulting in the release of many millions of tonnes of CO2 into the atmosphere either directly through the burning of fossil fuels or indirectly through the use of electricity produced at power stations. This current model of power generation and supply and ever growing demand is unsustainable and will need to adapt. The design and management of energy infrastructure for new and existing cities must change in order to make better use of resources through a combination of energy efficiency, application of new and emerging technologies and a shift to renewable sources of energy. The future of city energy infrastructure lies in an holistic approach to supply, demand and distribution. Securithy of supply and intermittency considerations need energy systems that can expand to changes in energy source availability and changes in demand whilst ensuring resources are not wasted. Buildings and cities must be designed to work sympathetically with renewable energy supply systems requiring buildings that are not only designed to minimise energy use but be capable of responding to the condition of the supply network through short term dynamic control and storage. This paper will consider the interrelated nature of a city wide sustainable energy system in the context of the GCC states, identifying the key policy, design and operational principles required to achieve a successful outcome.
Key Words: Sustainable cities, energy policies, operational principles
Number of pages 7; References 5
Automatic maximum Power Point Tracker for Solar PV Modules using D-Space Software
M.F. Ansari, S. Chatterji and A. Iqbal
Abstract: Maximization of power from a solar photo voltaic module (SPV) is of special interest as the efficiency of the SPV module is very low. A peak power tracker is used for extracting the maximum power from the SPV module. The present work describes the Maximum Power Point Tracker (MPPT) for the SPV module connected to a resistive load. A personal computer is used for control of the MPPT algorithm. The power tracker is developed and tested successfully in the laboratory. The simulation studies are carried out in MATLAB/SIMULINK. Data acquisition, monitoring and control are done by dSPACE software and digital signal processor card on PC.
Key Words: Solar PV module, maximum power point tracker (MPPT), dSPACE software
Number of pages 8; References 12
Heavy machineries in Classified Zone 22 Dusty Atmosphere: A Case Study
Singh, A.K. R.K. Vishwakarma, B. Ahirwal, N. Kumar, A. Kumar and A. Sinha
Abstract: Fire and explosion is the biggest problems in any industry that deals with explosive gases. Other than gas explosion dust ignition is also a major concern during selection of an electrical apparatus. Keeping in view of this Larson and Toubro Ltd. in Vadodara and Macnell Engineering Ltd, in Kalkata submitted design documents for development of battery operated fork-lift truck and requested Central Institute of Mining and Fuel Research (CIMFR) to take up the necessary examination, investigation and advice on the development of complete fork-lift truck for in Zone 22 hazardous area associated with Purified Terephathalic Acid (PTA) planr of IOCL in Panipat. In this paper the authors describe the suggestion and advice given by them for development of Battery Operated Fork-Lift truck for Zone 22 hazardous atmosphere.
Key Words: Industrial fire and explosion, heavy machineries, dusty atmosphere, Zone 22
Number of pages 6; References 7
Numerical analysis of Aircraft Wing Leading Edge of Glare (Glass Reinforced) materials
P.G. Mukunda, P.B. Shetty and V.K.Basalalli
Abstract: Numerical methods provide solutions about the integrity of the structure that is being examined with reasonable levels of confidence. GLAss Reinforced (GLARE) material is fibre metal laminate, built up of laminates of thin layers of aluminium alloy and glass fibre/epoxy are mechanically bonded together. Wing leading edge in technologically the most critical structural part and forms the front portion of the main wing of an aircraft. The present work is an attempt to examine the structural integrity of the wing leading edge of a typical commercial aircraft using GLARE as a test material through numerical and Finite Element Analysis to establish its candidature in aerospace applications. The results are experimentally validated.
Key Words: Aircraft wing leading edge, structural health monitoring, glass reinforced material
Number of pages 6; References 5
Simultaneous independent measurement of Pressure and Temperature using Two Embedded Fiber Bragg Gratings
S.C. Tjin, R. Suresh and S. Bhalla
Abstract: This paper presents a technique of simultaneous measurement of temperature and pressure using uniform Fiber Bragg Grating (FBG) with inherent property of temperature independent measurement of pressure. This sensor measures magnitude as well as the direction of the application of the pressure. In this sensor two FBGs are embedded within layers of carbon composite material (CCM) in such a way that the separation of the two FBG wavelengths is a function of the applied pressure and its direction of application, whereas the shift of individual peak wavelength shows sensitivity with temperature.
Key Words: Monitoring pressure and temperature, FBGs
Number of pages 5; References 9
Utilization of Solar Energy in degrading Organic Pollutant: A Case Study
S. Feroz, N.B. Raut and R. Al Maimani
Abstract: UV photo catalytic oxidation uses solar energy to activate a catalyst to physically decompose the pollutant into non-toxic components. An experimental study was carried out on photo-oxidation of Benzoic Acid over Titanium Dioxide immobilized catalyst in pipe reactors to investigate the effectiveness of natural solar energy and the energy from UV lamp in mineralization of the organic compound. Plug flow reactors with different diameters are used to study the effect of the diameter versus the reaction rate constant. The results showed that in the case of pipes exposed to natural solar radiation the reaction rate constant was higher and increases with the increase in the flow rate.
Key Words: Solar energy, degradation of organic pollutant, pipe reactor, photocatalytic oxidation
Number of pages 5; References 10
Volume 14, Number 4, October 2011
Ultrasonic measurements of Internal Flaws in Manganese Crossings. Part 1: Capacity Test of Ultrasonic Equipment
J. Lundberg, A. Bohlim and M. Syk
Abstract: Manganese crossings are widely used in the railway sector because of their self-hardening properties. However, Manganese is a coarse grained material with internal reflections and it is difficult to detect internal flaws. In this paper the authors have investigated the behaviour of this material using spike and square pulsed ultrasonic device. The knowledge gained by using this technology will be further explored in Part 2 of this investigation.
Key Words: Detection of internal flaws in Manganese crossings, ultrasonic measurement
Number of pages 7; References 7
Ultrasonic measurements of Internal Flaws in Manganese Crossings. Part 2: Blindfold tests on a Manganese Crossing
J. Lundberg, A. Bohlim and M. Syk
Abstract: In this paper measurements of internal flaws on a real Manganese Crossing using the ultrasonic equipment described in part 1 is reported and the results discussed.
Key Words: Condition monitoring of Manganese Crossings, Rail Research, ultrasonic method
Number of pages 13; References 10
Studies on Packaged Fiber Bragg Grating sensor for Health Monitoring of Concrete Structures
K. Kesavan, B. Arun Sundaram, S. Parivallal, A.K. Farvaze Ahmed, P. Biswas, S. Bandyopadhyay, K. Ravisankar and K. Dasgupta
Abstract: Fibre Bragg Grating (FBG) sensors possess good qualities for applications in Civil Engineering Structures. This paper presents development and performance evaluation of packaged FBG sensor. By employing this sensor strain transfer characteristics have been gathered through static and dynamic loading of concrete specimens embedded with FBG sensors. Numerical investigation was carried out to validate the experimental results and optimisation of the package was also carried out.
Key Words: Structural health monitoring, concrete structures, FBG sensors
Number of pages 8; References 6
Neural Network approach for multidisciplinary Health Monitoring of a Gas Turbine Engine
S.G. Barad, P.V. Ramiah, G. Krishnaiah and R.K. Giridhar
Abstract: A discipline that has emerged in recent years is to apply data fusion techniques to diagnose and prognose overall system performance and effectiveness. The present paper investigates a neural network approach to assess the health of gas turbine engines. Through an integrated approach the authors are convinced to derive maximum benefits in terms of accuracy and reliability.
Key Words: Machine health monitoring, gas turbine engine, artificial neural networks
Number of pages 10; References 8
Model-based Fault Detection and Isolation applied to a Pneumatic Actuation System
K.S. Grewal, R. Dixon and J. Pearson
Abstract: This paper discusses research carried out on the development and validation of a parity equation and Kalman-Bucy filter based fault detection and isolation system for a pneumatic actuator. These equations are formulated and used to generate residuals that, in turn, are analysed to determine whether faults are present in the system. Details of the design process are given and the experimental results are discussed.
Key Words: Pneumatic actuation system, fault diagnosis, modelling, control, design
Number of pages 12; References 24
Volume 15, Number 1, January 2012
Special Feature Issue on Remaining Useful Life Estimation of Industrial Assets
Estimation and Residual Life Prediction in a CBM Model
R. Jiang, M.J. Kim and V. Makis
Abstract: In this paper the authors present a parameter estimation and residual life prediction problem for condition based maintenance. The authors presume that system deterioration evolves according to a three-state continuous time homogeneous Markov Chain with unobservable healthy state 0, unobservable warning state 1 and observable failure state 2. Multivariate observations that are stochastically related to the system state are collected at equidistant sampling epochs through condition monitoring. The state and observation processes are modelled in the hidden Markov process framework, and the model parameters are estimated using the EM algorithm. Formulae for the mean residual life and the distribution function of the system residual life are derived in explicit forms as functions of a posterior probability statistic. A numerical example is provided to illustrate the entire computational procedure.
Key Words: Condition based maintenance model, residual life prediction, hidden Markov process
Number of pages 10; References 30
Condition-based Recursive Estimation of Proportional Hazards Model for Equipment Remaining Useful Life Prediction
Lin Li, Xinwei Xu and Yong Lei
Abstract: One of the most popular models that reflect equipment condition monitoring is Proportional Hazards Model (PHM) originally introduced by Cos in 1972. This model uses condition monitoring data as covariates and finds their effect on the equipment lifetime. Conventional modelling process of PHM is only based on historical data, and the model regression parameters are fixed for on-line implementation. In this paper a methodology is developed to recursively diagnose component operation and integrate reliability and prognostics to predict component remaining useful life (RUL). The results illustrate that the recursive estimation of PHM effectively monitors the equipment status change and leads to a more accurate RUL prediction comparing with traditional PHM.
Key Words: Condition-based recursive estimation, proportional hazards model, remaining useful life
Number of pages 10; References 22
An outline of the Monte Carlo-based (Particle) Filtering method for Failure Prognostics
M. Marseguerra and E. Zio
Abstract: In this paper the main concepts underlying the Monte Carlo Simulation (MCS)-based for state estimation and prediction, called particle filtering are outlined with reference to the prognostics of the stochastic failure behaviour of engineered structures, systems and components (SSC). In general, the model-based approaches to the estimation and prediction of the state of SSC build a posterior distribution of the unknown state by combining the distribution assigned a priori with the likelihood of the observations of measurements of parameters or variables related to the SSC state. The MCS based particle filtering method approximates the state distributions of interest by discrete sets of weights are estimates of the probabilities of the trajectories. For illustrative purposes, a mathematical example of literature concerning a highly nonlinear dynamic system is considered and extended to the case of unknown, time-varying model parameters.
Key Words: Engineered structures, systems, components, Monte Carlo Simulation, particle filtering, diagnosis and prognosis
Number of pages 10; References 22
Prognostics and Health Management for Next Generation LED Lighting Systems
G. Niu, D. Lau and M. Pecht
Abstracts: Modern lighting requires efficient and economical alternatives in order to decrease power consumption, lengthen the lifetime of lights, make maintenance easier, and decrease lifetime costs of lighting systems. Light-emitting diode (LED) systems have been developed to meet these requirements. However, the current high life cycle cost of LED lighting systems is a significant obstacle that confronts the LED lighting industry in seeking to expand market share. In this paper prognostics and health management is proposed as an effective technology strategy for next generation LED lighting systems, which can achieve improved reliability, maintainability, supportability, and affordability.
Key Words: LEDs, economic alternatives, improved reliability, maintainability, supportability, affordability
Number of pages 12; References 21
Online Health Condition Prognosis for Dynamically Tuned Gyroscope using Evidential Reasoning-based Prediction Method with Expert Judgements
X-S. Si, C-H. Hu and Q. Zhang
Abstract: In this paper a new scheme is proposed for the online prognosis of the health condition of a Dynamically Tuned Gyroscope (DTG) and the estimation of the residual useful life of the DTG using the Evidential Reasoning (ER) based prediction method. This new method is different from the others that have been used in the past, in which it makes use of both expert judgments on health condition and measurable condition monitoring parameters. Since expert judgements on health condition may be in the form of belief distributions, we directly use the distributions to represent expert judgments, in which the subjective uncertainty can be reduced and represented by applying the ER approach. Based on the judgments and the condition monitoring parameters, a health condition prognosis model is established using the ER-based prediction method and further a residual life estimation method is presented. To build an effective forecasting model, a recursive parameter estimation algorithm based on Expectation Maximization (EM) algorithm is investigated for online updating the health condition prognosis model. The main feature of this algorithm is that only partial input and output information is required, and the health prediction model can be recursively updated once new information becomes available. This is very important in the case when real-time applications are considered. The model established and the algorithms investigated are validated using real data of the DTG monitored, and the predicted results are satisfactory and provide a basis for further studies. It is noted that although the model itself is established for the DTG concerned, it can be generalized to modelling similar health condition prognosis problems to some extent.
Key Words: Dynamically Tuned Gyroscope, on-line health condition, evidential reasoning, expectation minimization, residual life, diagnosis, prognosis
Number of pages 13; References 35
An overview for Prognostics Based Maintenance (PBM) of New and used Aero-engines in China: Theory and Methods
Z. Hongfu, R. Xiang, B. Fang and R. Shubong
Abstract: This paper outlines an overview of the study of prognostic maintenance problems for newly manufactured and used aero-engines in China. The authors seek to study the following four issues with a goal to develop new theory and methods of the whole system life-cyclic prognostic maintenance. The first issue is to research the formation mechanism of charged particles resulting from the failure of the critical components and establish the principle and methods of the electrostatic monitoring sensors. The second issue is to establish failure trending models based on sensor data, the combination of sensor information and physical models to predict the performance degradation of the whole system and the time and the distribution of component functional failures. The third issue is to establish aero-engine maintenance decision-making models and methods based on multi-agent co-operative diagnosis and failure trending predictions. The fourth issue is develop a prototype of a predictive maintenance decision support system. A case study is shown to demonstrate these issues.
Key Words: Prognostics based maintenance, new and old aero-engines, predictive maintenance decision support system
Number of pages 13; References 24
Volume 15, Number 2, April 2012
Special Feature Issue on Failure Diagnosis and Prognosis of Railway Assets
Failure Diagnosis of Railway Assets using Support Vector Machine and Ant Colony Optimization method
Y. Fuqing, Uday Kumar and D. Galar
Abstract: Support Vector Machine (SVM) is an excellent pattern recognition technique. This paper reports a diagnostic application of a multi-class SVM as a classifier to solve a multi-class classification problem. The authors have used the heuristic Ant Colony Optimization (ACO) algorithm and multi-class SVM to diagnose failures in electric motors used in a railway system. The results indicate that the accuracy of performed diagnosis on the electric motor is found to be highest.
Key Words: Railway assets, failure diagnosis, support vector machine, ant colony organization
Number of pages 8; References 24
Evaluation of Track Geometry Degradation in Swedish Heavy Haul Railroad: A Case Study
I.A. Khouy, H. Schunnesson, A. Nissen and U. Juntti
Abstract: The measurement and improvement of track quality are key issues in determining both the time and cost of railway maintenance. Efficient track geometry maintenance ensures optimum allocation of limited maintenance resources and has an enormous effect on maintenance efficiency. In this paper track geometry data from the iron ore line in northern Sweden which handles both passenger and freight trains are used to calculate track quality degradation trend in a cold climate. The paper also describes Trafikverket’s (Swedish Transport Administration) tamping strategy and illustrates the distribution of safety failures in different seasons. It also analyses the track geometry degradation and discuss about the possible reasons for distribution of failures over a year and along the track.
Key Words: Swedish railway, track geometry degradation, maintenance, tamping
Number of pages 6; References 16
Enhanced Condition Monitoring of Railway Vehicles using Rail-mounted Sensors
Abstract: Rail-mounted sensors such as strain gauges have been used for several years in systems like train scales and wheel flat detectors, and in systems that are often named Truck Performance Detectors (TPDs). This paper presents some main guidelines for using such sensors and it demonstrates an extended use of sensor information for condition monitoring of railway vehicles.
Key Words: Railway vehicles, condition monitoring, rail-mounted sensors
Number of pages 9; References 14
Condition Monitoring of Wheel Wear on Iron Ore Wagons
M.Palo and H. Schunnesson
Abstract: Keeping wheel profiles in an acceptable condition is a major concern for both railway operators and infrastructure owners. This paper studies the correlation of the wear rate and the wheel force to temperature and seasonal differences by monitoring eight identical wheel axles of different ages for a full life cycle. The study notes differences in wheel wear and wheel/rail forces while operating with a 30 tonne axle load and in temperatures ranging from -300C to +300C. At a research station near Lulea in Sweden, measurements have been performed of the speed and the vertical and lateral forces for every train passage, and the significantly greater at lower temperatures. The magnitude and variation of the lateral forces are strongly dependent on the bogie position with the highest peak value recorded for the leading low rail. The L/V ratio is strongly seasonally dependent, with large differences within a month due to changes in friction.
Key Words: Wheel wear, condition monitoring, iron ore wagons
Number of pages 8; References 29
Managing Rail Integrity in Heavy Axle Load Regime in Mixed Traffic Scenario: Experience of Indian Railway
Madan Sen and P. Funkwal
Abstract: The paper outlines Indian Railway’s experience in running heavy axle loads in a mixed traffic scenario. Results of field studies for assessment of key parameters influencing track stresses namely track modulus and dynamic augment factors for present day track structure and rolling stocks and track forces imparted by upgraded rolling stocks are presented. Specific studies pertaining to defect generation in rails and welds suggest that Indian Railway has so far been able to increase axle loads without compromising safety and integrity of rails with slew of preventive measures and a highly effective monitoring regime. The monitoring has provided valuable insight into challenges faced by Indian Railway in sustaining the operation. Actions initiated to effectively meet these challenges are also covered.
Key Words: Rail integrity, heavy axle loads, defect generation in rails and welds
Number of pages 9; References 13
Study of an Instrumented Diagnostic Cleat for Diagnosing Vehicle Mechanical Faults using Off-board Dynamic Response Measurements
T. DiPetta, D. Koester, D. Adams, P. Doherty and K. Fisher
Abstract: Current maintenance schedules for ground vehicles are determined largely based on reliability predictions of a population of vehicles under anticipated operational loads. This approach leads to unnecessary maintenance and, in some cases, in-field failures depending on differences in the usage of individual vehicles. Condition-based maintenance is scheduled instead according to the condition of each vehicle to reduce the risk of failure and maintenance costs. However, on-board instrumentation for acquiring, processing, and storing operational data is expensive, and this data is also difficult to analyse due to variation in loading. An instrumented diagnostic cleat for diagnosing mechanical faults in ground vehicle wheel ends and suspensions is studied in this paper. The cleat excites the vehicle’s dynamic response through an impulse delivered to the vehicle’s front and back tires. The response of the instrumented segment of the cleat is then recorded while in contact with the vehicle’s tires using accelerometers. The measured dynamic response is compared to a reference response, and anomalies that correspond to vehicle faults are then detected. This paper demonstrates that the measured response spectrum from the instrumented diagnostic cleat can be attributed to vehicle chassis modes of vibration in the frequency range below 10 Hz and natural frequencies in the free dynamic response of the cleat above 10 Hz. Tire and suspension faults are simulated in a high mobility multi-purpose wheeled vehicle and the faults are detected. Tire faults are simulated by decreasing the pressure within each tire below the manufacturer recommended level, whereas suspension faults are simulated by disconnecting each damper to mimic the effects of broken damper. The data indicates that the faults and locations of the faults are identified with 90% confidence in 7 out of 8 fault cases. Errors in the measurements are modelled to compensate for changes in vehicle speed.
Key Words: Ground vehicles, mechanical faults, diagnostic cleat, off-board dynamic measurements
Number of pages 13; References 19
Volume 15, Number 3, July 2012
Remaining Useful Life Estimation using Time Trajectory Tracking and Support Vector Machines
D. Galar, Uday Kumar, J. Lee and W. Zhao
Abstract: In this paper a novel remaining useful life (RUL) prediction method inspired by feature maps and support vector machine (SVM) classifiers is proposed. The historical instances of a system with life-time condition data are used to create a classification by SVM hyper places. T test the system’s RUL, degradation speed is evaluated by computing the minimal distance based on the degradation trajectories, i.e. the approach of the system to the hyper place that segregates good and bad condition data on a different time horizon. The final RUL of a specific component can be estimated and global RUL information can be obtained by aggregating the multiple RUL estimations using a density estimation method.
Key Words: Remaining useful life, time trajectory tracking, support vector machine, bearing failures
Number of pages 7; References 8
Formulation of Maintenance Strategies – A simplified process
Abstract: Research studies shows that as much as one third of the maintenance cost is unnecessarily spend due to bad planning, overtime costs, bad use of preventive maintenance procedures, etc. However, studies have revealed that few manufacturing companies consider maintenance to be of strategic importance. Even among those firms that do have a maintenance strategy, it is not evident that their strategies are clearly linked to their business strategies. Many companies in the manufacturing industry seem to find formulation of maintenance strategies to be difficult. To some extent this is due to lack of formal competence in maintenance management. Also, companies often find the formulation process too resource demanding. Hence, maintenance strategies are not widely used in manufacturing industry today. In addition, there seems to be no clear picture of what components a maintenance strategy could or should include. With this in mind, this paper aims to present a process for the formulation of maintenance strategies in discrete item manufacturing organizations. Important criteria for the formulation process are that it is easy to follow and that it does not require vast amount of resources. The results show that the formulation process developed and tested in this study has been easy to use and understand. The three case companies have found that their new maintenance strategies have given them a good picture of the present situation, as well as good guidance in their necessary work improvement.
Key Words: Maintenance strategies, formulation process, case studies
Number of pages 10; References 28
Analysis of Composite Prosthetic Energy-Storing-and-Returning (ESR) Feet: A Comparison between FEA and Experimental Analyis
J. Vinney, S. Noroozi, A.G.A. Rahman, P. Sewell, O.Z. Chao, K.K. Kuan and M. Dupac
Abstract: Current methods of evaluating the performance of a runner using Energy Storing and Returning (ESR) prosthesis rely heavily on metabolic and biological factors. This makes it difficult to differentiate between the contributions made by the athlete and prosthesis to the act of walking or running. Static tests show these feet to have non-linear stiffness, making the prediction of dynamic response, based on static data unreliable. A methodical approach has been developed that allows complete determination of the dynamic characteristics (natural frequency, mode shapes, damping and energy efficiency) of a running prosthesis system. This data is needed to inform the design of such system in order to improve the overall athlete performance. Previous study show that there are suitable self selected frequency and mode shapes that if synchronised with the running step frequency can result in better interaction between the amputee and his prosthetic. However, these composite feet are expensive and their designs are complex. Making and testing prostheses is costly and time consuming. Finite Element Analysis (FEA) is a powerful design tool capable of performing complex dynamic analysis of structures. FEA has successfully been used to predict the natural modes of vibration of structures. This paper examines the suitability of FEA as a design and analysis tool for studying a highly non-linear and anisotropic thick composite system with dynamic boundary conditions.
Key Words: ESR prosthesis, finite element analysis, composites
Number of pages 10; References 27
The Envelope Shock Detection: A New method for Processing Impulsive Signals
B. Badri, M. Thomas and S. Sassi
Abstract: This paper describes a new signal processing method called Envelope Shock Detector (ESD). Acting exactly like a filter, the ESD is designed to track shocks in the time domain and to isolate them from any other random or harmonic components. This innovative tool could be used in the time domain, to estimate the proportion of the total signal energy caused by the shocks. In the frequency domain, the same tool could be used through spectral, envelope or time-frequency analyses to recognize if the source of the shocks is from defective bearings or gears. The applicability and efficiency of this new method has been discussed using real cases.
Key Words: Rolling element bearing failures, impulsive signal analysis, Envelope Shock Detector
Number of pages 10; References 40
Structural Health Monitoring of a Prestressed Concrete Bridge with recent Advancement in Measurement Technology
S. Parivalla, K. Kesavan, B. Arun Sundaram, A.K. Farvaze Ahmed and K. Ravisankar
Abstract: Structural health monitoring of a prestressed concrete bride has been carried out to study the long-term performances of the bridge and to estimate the long-term prestess losses. The bridge was instrumented with fibre optic and vibrating wire sensors which have in-built temperature sensors for strain and temperature measurements. The bridge was monitored for a period o about five years. The bridge was also remotely monitored using the latest communication technologies and data acquisition systems. In this paper, the importance and potential of fibre optic sensors for monitoring of bridge structures have been highlighted. The details of the bridge instrumentation, data acquisition and long-term monitoring of the bridge prestessing tendoms is evaluated. Details of remote monitoring of the bridge with the latest communication technologies and data acquisition systems are briefly explained. Prediction of prestress losses from the short-term measured data is also presented.
Key Words: Prestressed concrete bride, structural health monitoring, remote monitoring
Number of pages 8; References 17
Volume 15, Number 4, October 2012
Special Issue on Advances in e-Maintenance Technology
Study of Aspects of Data Quality in e-Maintenance
M. Ajumaili, P. Tretten, R. Karim and Uday Kumar
Abstract: Data quality (DQ) concerns all the phases of maintenance activities. The purpose of this paper is to explore and identify the aspects of DQ in e-Maintenance. Seven case studies from three industries are covered. The empirical data was collected through interviews, observations, archival records and workshop sessions. One of the main findings of this paper shows that the organizations do not often implement maintenance solutions whole-heartedly with the result that the full potential benefits are not realised.
Key Words: e-Maintenance, data quality, case studies
Number of pages 12; References 46
Maturity-based Evaluation of IT Systems for Maintenance Management
Abstract: Research shows that investments in IT have a positive correlation to company profitability and competitiveness. It is also known that IT projects often fail to deliver the expected benefits. One of the main reasons for this is the increased complexity both with respect to the project management and the poorly implemented IT solutions. e-Maintenance is a concept developed for dealing with this complexity by securing effective information logistics for the maintenance. The quality of the implemented IT system is a function of the procurement. This paper addresses this issue in some depth.
Key Words: IT systems, complexity, e-Maintenance, quality of procurement
Number of pages 11; References 29
Model-based Security System for Data Acquisition in e-Maintenance using Artificial Immune System and Cloud Computing
Y.K. Al-Douri, R. Karim, A. Parida and Uday Kumar
Abstract: This paper suggests a new security model-based security for Supervisory Control and Data Acquisition (SCADA) systems through Cloud Computing and Artificial Immune System (AIS). It provides AIS which is based on Decision Tree (C4.5 Algorithm) using clustered features set. The features set are selected from NSL-KDD cup. It is new version of KDD dataset. As a result two Antibodies are generated that could recognize Normal and Antigen. This has produced a high level of accuracy.
Key Words: Security system, data acquisition, e-Maintenance, Artificial immune system, Cloud computing,
Number of pages 12; References 62
Functionality gaps in IT Systems for Maintenance Management
Mirka Kans and A. Ingwald
Abstract: e-Maintenance is an information intensive concept highly dependent upon relevant and reliable information technology support. One important prerequisite is IT Functionality that fits the demands of maintenance organization. The purpose of this paper is to investigate the existence of functionality gaps in the IT applications used in the field of maintenance. A questionnaire survey has been undertaken by asking the end users to estimate the misalignments/gaps in their current IT support. The generated data is analysed using statistical methods.
Key Words: IT systems, functionality gaps, questionnaire survey, analysis
Number of pages 13; Reference 13
Data Collection Process driven by Components Health Assessment based on Coloured Stochastic Petri Nets for e-Maintenance Decision Support
Z. Wang, M. Atli and K.H. Adjallah
Abstract: This paper investigates a scalable process of data collection driven by performances evaluated at levels of components and system, for the health condition monitoring and e-Maintenance decision support. The authors propose a reduced size state model of performance assessment of a repairable multi-state multi-component system, using stochastic coloured Petri Nets (CSPN), The successive states of the system may then be studied, while overcoming the combinatorial expansion problem encountered when one uses Markov models. Hence, the system degradation may be predicted with the Monte Carlo simulation, based on the condensed model. The data collection strategy considers the degradations of components in the system, evaluated using both actual available data and simulated results to decide the next steps of the data collection. Data include operating statuses, inspection data, tests data, diagnosis results, e-Maintenance log data, etc/
Key Words: Multi-unit multi-state system, data collection process, components and systems health assessment, coloured stochastic Petri Nets, e-Maintenance
Number of pages 9; References 24
Volume 16, Number 1, January 2013
Special Feature Issue on Advances in Tribology Applications in COMADEM
Condition Monitoring and Diagnostic Engineering Management (COMADEM) of Modern Tribological Systems: A State-of-the-Art Review
Abstract: Modern triblogical systems have moving parts of one type or another and are becoming increasingly complex, sophisticated and expensive. Keeping such systems fit-for-use conditions in hazardous operational environments is a challenging task. Various failure modes have been identified and these are known to influence its useful life-cycles thus adversely affecting their reliability, availability, safety and maintainability. Tribology has played a significant role in reducing friction, wear and extending the remaining useful life of such systems. In the past few decades, system engineers and designers are increasingly becoming convinced that the proactive concept of condition monitoring and diagnostic engineering management is the way forward to continuously improve the health, safety and performance of their valuable assets. In this state-of-the-art review paper, some well known tools, techniques and strategies are identified with specific reference to modern tribological systems.
Key Words: COMADEM, tribological systems
Number of pages 18; References 154
Diagnostic approach for Electrical Pitting of Grease-lubricated Rolling Element Bearings: Utilization of Wear Debris Analysis
S. Raadnui and S. Kleesuwan
Abstract: The generated electrical pitting wear debris from grease lubricated rolling element bearings has been previously investigated. In this paper the authors assessed both statistically and physically the effects of electrical current and mechanical parameters of the test conditions on the wear debris characteristics of electrical pitting on grease lubricated rolling element bearings under the AC field. The authors have established typical characteristics and morphology of electrical pitting wear particles. The authors also propose electrical pitting wear regimes corresponding to physical responses such as bearing housing temperature, worn surfaces, corrugated length, corrugated width and wear debris morphology.
Key Words: Grease lubricated roller element bearings, electrical pitting, wear debris analysis
Number of pages 5; References 23
Condition Monitoring through Oil Analysis – Expert System approach
M. Gopalakrishnan, B.V.A. Rao and K.V. Ramana
Abstract: Condition monitoring of moving parts in various components and machinery continues to be an effective and cost effective strategy to prolong the remaining useful life. Lubrication oils have been classified and standardised based on their physical, chemical, operational and application environment. The present paper describes an expert system approach by considering the viscosities of the oils for health assessment of machinery.
Key Words: Oil analysis, expert system approach
Number of pages 6; References 31
“Filtersonicgram” for Filter Debris Analysis (FDA)
Abstract: Due to the increasing fineness of filter elements in high precision machinery lubricating oil systems, monitoring of Filter Debris Analysis is gaining increased significance for the early failure detection of moving parts. These considerations led to the development of a new method to recover filtered debris particles efficiently, productively and economically. “Filtersonicgram” is a novel method to recover solid particles trapped in filter elements with the utilization of ultrasonic wave and conventional filtration approach simultaneously in a single shot. The recovered particles on the multi-patch filters can be assessed with the aid of a microscope. Careful examination of the “debris” can give specific information about the condition of the moving parts precision machine elements from which they were generated, the wear mode or wear mechanism in operation in the system from which they were filtered.
Key Words: Lubricating systems, filter debris analysis, Filtersonicgram
Number of pages 5; References 2
Centrifiltergram Maker – A Novel approach for Separation of Solid Particles in Used Lubricants
Abstract: It is a well known fact that every lubricating oil sample contains soled particles. They come in different types, shapes, sizes and numbers. The growing interest in “wear debris morphologicial analysis” is due to the fact that wear debris can be used to elucidate wear modes and wear mechanisms. This paper introduces a new approach for soled debris separation utilization of “conventional” centrifugation and filtration techniques in combination.
Key Words: Solid particles, wear debris monitoring, solid debris separation, novel method
Number of pages 4; References 4
Volume 16, Number 2, April 2013
Failure Diagnosis and Prognosis of Rolling-Element Bearings using Artificial Neural Networks: A Critical Review
B.K.N. Rao, P. Srinivasa Pai and T.N. Nagabhushana
Abstract: Rolling-element bearings are extensively used in almost global industries. Any critical failures in these vitally important components would not only affect the overall systems performance but also its reliability, safety, availability and cost-effectiveness. Proactive strategies do exist to minimise impending failures in real time and at a minimum cost. Continuous innovative developments are taking place in the field of Artificial Neural Networks (ANNs) technology. Significant research and development are taking place in many universities, private and public organizations and a wealth of published literature is available highlighting the potential benefits of employing ANNs in intelligently monitoring, diagnosing, prognosing and managing rolling-element bearing failures. This paper attempts to critically review the recent trends in this topical area of interest.
Key Words: Rolling-element bearings, failure diagnosis and prognosis, Artificial neural networks
Number of pages 12; References 65
A different approach to Economic Load Dispatch of Thermal Power Plants using an Exponential Cost Function
M. Mohatram, P. Dhyani and P. Tiwari
Abstract: In this paper, the problem of Economic Load Dispatch (ELD) in power systems is solved by considering the operating cost of a thermal power plant as an exponential function. Equality constraints of power balance and inequality plant generation capacity constraints are taken into consideration. The problem is formulated with the transmission losses in the lines and is solved by Lagrangian approach of equal incremental cost. The results of the proposed method are tested for a system consisting of six generating units and the results are compared with a similar problem having quadratic cost functions. Finally, the significance of the proposed method is highlighted. It may be concluded that the proposed method can be considered as a replacement for the conventional practices presently being used in different central load dispatch centres across the globe.
Key Words: Economic load dispatch, exponential cost function, Lagrangian approach, quadratic cost function
Number of pages 6; References 15
A method for analyzing Rotating Machinery Faults using Time-Frequency Applications
Oulmane, A., A. A. Lakis and N. Mureithi
Abstract: The diagnosis of machines was the subject of some works in the domains of time and frequency. The conventional methods of signal processing present numerous inconveniences in resolving this type of problems. In this paper, the authors have characterized defects as non-stationary or cyclo-stationary phenomena. Considering the difficulty in finding the defects in the temporal or frequency domains, the authors have treated them as mixed representation of time-frequency. In this paper, the limits of the methodologies mentioned are presented. Also, the limitations of the conventional methods are outlined.
Key Words: Time-frequency analysis, failure diagnosis, rotating machinery, vibration analysis
Number of pages 14; References 26
An experimental study on Angular Misalignment Detection in Rotor Bearing System using Welch Power Spectral Density
G. Baskaran and M. Nataraj
Abstract: The paper describes Welch Power Spectrum Density, a technique that monitors the functioning of rotor bearing system and the faults occurrence in its operation environment. Vibrations in rotor bearing system have been measured to detect faults with and without angular misalignment. It is difficult to predict in each mode of vibration and hence investigations on the vibration characteristics for the misalignment have to be determined so that down time can be eliminated. This study reveals that the changed dynamic force induced at the bearing depends on the localization and the magnitude of angular misalignment.
Key Words: Rotor bearing system, angular misalignment detection, vibration monitoring, angular misalignment
Number of pages 7; References 16
Asset Management Overview focusing on Fault Detection in Industrial Processes: A State-of-the-Art
J.A. Garcia-Matos, M.A. Sanz-Bobi and A. Munoz
Abstract: The current energy related economic context brings the need for a proper asset management of power generation facilities. This paper is intended to provide a wide view of the state-of-the-art in asset management, with a special focus on fault detection and diagnosis. The different stages involved in this field are defined and arranged in the following order; Acquisition and pre-processing of data, fault detection, fault diagnosis and maintenance policies. Fault detection approaches are analysed in-depth, highlighting the main characteristics, the advantages and the drawbacks of each approach. Fault diagnosis techniques and maintenance policies are also described and analysed.
Key Words: Industrial processes, fault detection and diagnosis, asset management
Number of pages 12; References 104
Volume 16, Number 3, July 2013
Generalized Teager Kaiser Energy Operator-based Bearing Fault Diagnosis
M. Bubathi, S.A.V. Satya Murthy and T. Jayakumar
Abstract: The bearing fault vibration signals are amplitude and frequency modulated. The quality of demodulation achieved determines the efficiency of the vibration spectrum analysis used for the bearing fault diagnosis. Recently, a parameter free demodulation method based on Teager Kaiser Energy operator (TKEO) was shown to be very efficient in bearing fault diagnosis. In this paper, it is shown that TKEO underperforms in case of vibration signals with very low signal to noise ratio (SNR). A simple method which overcomes the aforementioned problem is also presented. It is based on the application of Generalized Teager Kaiser Operator (GTKEO) and it is demonstrated using two experimentally generated data: one is bearing fault vibration signal with additive noise, another is mixture of bearing fault vibration signals and vibration interference from gear awith additive noise. The efficiency of the proposed approach to detect fault in presence of very low SNR is shown in comparison with TKEO.
Key Words: Bearing fault diagnosis, vibration analysis, Teager Kaiser Energy Operator
Number of pages 13; References 29
Application of Wavelet Analysis in Multi-class Fault Diagnosis of Gear using SVM
R. Tiwari, D.J. Bordoloi, S. Bansal and S. Sahu
Abstract: In this paper, a novel technique of speed interpolation has been proposed that helps the SVM classifier to carry out multi-class gear fault diagnosis with appreciable accuracy even in the absence of training data at the given running speed. Utilising this concept of speed interpolation, the multi-class fault diagnosis capability of SVM has been study when the gear vibration data in time-frequency domain is used. The time-frequency domain data is obtained from time domain data using the wavelet analysis. Two different feature extraction approaches are used that utilise the continuous and discrete wavelet transforms followed by the statistical feature extraction. As a further application of the wavelet analysis, an optimum level noise reduction technique on the vibration data has also been developed and finally the improvement of prediction accuracies after the noise reduction procedure on time domain has been demonstrated.
Key Words: Gear fault diagnosis, multi-class diagnosis, Wavelet analysis
Number of pages 8; References 19
Exchange Rate Prediction using Neural-Genetic Model
M. Raihane and T. A. Nacer
Abstract: Neural network have successfully used for exchange rate forecasting. However, due to a large number of parameters to be estimated empirically, it is not a simple task to select the appropriate neural network architecture for exchange rate forecasting problem. Researchers often overlook the effect of neural network parameters on the performance of neural network forecasting. The performance of neural network is critically dependent on the learning algorithms, the network architecture and the choice of the control parameters. .Even when a suitable setting of parameters can be found, the ability of the resulting network to generalize the data not seen during learning may be far from optimal. For these reasons it seems logical and attractive to apply generic algorithms. Genetic algorithms may provide a useful tool for automating the design of neural network. The empirical results on foreign exchange rate prediction indicate that the proposed hybrid model exhibits effectively improved accuracy, when it is compared with some other time series forecasting models.
Key Words: Neural-Genetic model, exchange rate prediction
Number of pages 6; References 15
Experimental Evaluation and ANN-based Prediction Model for Dynamic Properties of Epoxy Glass Fabric Composites with Natural Rubber Particle Inclusions
H. Ravi Sankar, R.R. Srikant, P. Vamsi Krishna, V. Bhujanga Rao, P. Bangaru Babu and G. Bhanu Kiran
Abstract: Conventional materials are being replaced by composite materials due their tailored and high specific properties. In almost all the fields these materials are to be found in some form or another. Damping is one of inherent properties of materials used in structures to reduce damaging vibrations to minimum. In the present paper improvement in material damping of glass fabric epoxy composites with particle rubber inclusions is explored. The results reveal considerable enhancement in damping without significant reduction in stiffness. ANN-based prediction model is developed to predict these properties.
Key Words: Epoxy Glass Fabric Composites, ANN-based Prediction Model
Number of pages 6; References 19
Maintenance Audit and some Maintenance Management Improvements – A School Building Case Study
Ana C.V. Vieira and A.J. Marques Cardoso
Abstract: The paper contains the identification of the maintenance requirements for a specific educational institution, and its influence on the preventive maintenance plan resulting from a previous maintenance management audit. The paper reports the results of the analysis of those factors influencing the maintenance management audit performed. Among them are equipment inventory and codification, database implementation, information circuits and maintenance documents. The aim of this project was to establish a cost effective maintenance plan in order to support the administration, adding value to its assets.
Key Words: School buildings, Maintenance management improvements, maintenance audit
Number of pages 11; References 32
Volume 16, Number 4, October 2013
Special Issue on e-Maintenance
A Case Study on Railway Wheel Maintenance Management with several layers of Contractors
M. Palo, I. Lindsund and P-O. Larsson-Kraik
Abstract: The purpose of this paper is to discuss holistic maintenance management for railway wheels in an environment where there are several layers of contractors. To make this work in a system with many stakeholders, good information flow is crucial. With a holistic computerised information system, each stakeholder can assess maintenance effectiveness, including availability, reliability and maintainability. This paper uses a vehicle wheel axle as a case study.
Key Words: Railway wheel maintenance management, e-Maintenance, case study
Number of pages 7; References 29
The use of a Laser-based Trolley for Railway Switch and Crossing Inspection
M. Rusu, C. Roberts and S. Kent
Abstract: Railway turnouts are used to guide trains from one track to another and they are usually formed of a switch and crossing (S&C). They pose both economic and safety issues since they need to be maintained, which is costly, and if in a good state they can cause fatal railway accidents. The purpose of this research is to improve the inspection process for S&C, which is accomplished by : (1) identification of areas where research in needed and (2) research and development of a laser based trolley for the inspection of railway switches and crossings. The first stage was carried out systematically and is described in second section of the paper. With the output of the first step, as well as the help of Network Rail, it has been concluded that in Great Britain there is a need for a lightweight device that can carry out inspection for specific derailment hazards on switches and crossings as well as advise the welders on how they should be repaired. This research proposes a new approach for this issue by considering a lightweight laser based trolley system. The system is based on the ability to scan and record 2D slices of the parts that need to be inspected and calculate different wear indicators and derailment hazards in accordance with the Network Rail inspection standards. The work and findings of this research will also feed into the European Project AUTOMAIN, Augmented Usage of Track by Optimisation of Maintenance, Allocation and Inspection of railway Networks, http://www.automain.eu/.
Key Words: Railway turnout, switch and crossing, automatic inspection, laser profile measurement, derailment hazard
Number of pages 11; References 9
Case-based Reasoning supports Fault Diagnosis using Sensor Information
N. Xiong, T. Olsson and P. Funk
Abstract: This paper advocates that computer-based diagnosis systems can be built based on sensor information and by using case-based reasoning technology. The authors justify how case-based reasoning can be employed to support diagnosis tasks by giving four applications to illustrate their view point. The authors also discuss how case-based reasoning (CBR) can be integrated with machine learning techniques to enhance its performance.
Key Words: Fault diagnosis, case-based reasoning, signal processing, crack detection, process monitoring, artificial intelligence, knowledge discovery
Number of pages 6; References 39
Dependability Improvement through Configuration Management: A Study of Railway Signalling System
Morant, A., R. Karim, P. Tretten and P-O. Larsson-Kraik
Abstract: The purpose of this paper is to investigate how the process of configuration management can improve the dependability of the railway system. It presents a model for the configuration management of railway signalling systems. The model is based on the results of company surveys and interviews, data analysis and literature review. This model provides better control and visibility of the information related to the system and any changes made to it. Faster and better failure diagnostics man be performed, thus improving maintenance performance. This, in turn, provides better availability of the system by reducing the downtime of the railway network; hence, an improvement in maintainability is also achieved.
Key Words: Railway maintenance, information logistics, configuration management, capability maturity model integrated (CMMI)
Number of pages 10; References 51
Framework for Designing Effective Condition Monitoring and Maintenance Systems
R. Farahani and M. Lipsett
Abstract: In this paper, a framework has been developed that extends current information system design methods for effective design and evaluation of machine condition monitoring and maintenance management systems, as a method for more concretely demonstrating the value of system features prior to system design, and for assessing system performance after implementation for continuous system improvement. An effective system from the framework’s perspective is first, performance-based, i.e. benefits due to the system are balanced with associated costs. Second, it is fit for the system owner’s purpose, i.e. it has been designed with respect to organizational business strategy, objectives and constraints. And third, it is holistic, i.e. it addresses various performance criteria that are important to the system stakeholders, e.g. operational excellence, financial, safety and environmental. This paper describes the framework and its high-level application using an example case related to the maintenance management of mobile machines in oilsands mining operations.
Key Words: Machine condition monitoring, maintenance systems, system stakeholders, mobile machines in oilsands mining operations
Number of pages 14; References 53
Volume 17, Number 1, January 2014
Quick Acquisition of Major Parameters of Moiré Sensing Technique by an Image Processing Approach
Md. Tawhidul Islam Khan; Japan
Abstract: Moiré fringe structures generated by the superposition of two optical grating patterns can be applied in different metrological applications for precise measurements of surface profilometry as well as structural deformations. As these typical structures are exaggerated from their original gratings, this technique can be widely implemented in measurements for getting the apparent enlargements of minute deformations in structure or in motion of an object. Although in many smart sensing this technique is useful, due to complications in dimensioning, particularly in generalizing its particular parametric calculations, this method suffers from aversion in many advanced applications. In this paper, a processing algorithm for quick scanning of major parameters used in the moiré sensing technique is presented. The proposed technique is simple, quick and easy in its practical applications.
Keywords: Moiré fringe analysis; Moiré parameters acquisition; Single grating system; Precise angular measurement
Number of References cited: 12
Wavelet Transform for Bearing Condition Monitoring and Fault Diagnosis: A Review
Kumar, H.S., Srinivasa Pai, P., Vijay, G.S. & Raj B.K.N. Rao; India & UK
Abstract: Condition monitoring and fault diagnosis of rolling element bearings is essential for smooth and safe running of rotating machinery. Signal analysis is an important component of condition monitoring and diagnostic engineering management. Wavelet Transform (WT) has been widely used for signal analysis, particularly in condition monitoring over a number of years. WT and its applications in this proactive discipline is increasing at a rapid rate. It is therefore important to review the literature to understand the current trends in this new and emerging area of signal processing. This review will cover some broad areas of research like; time-frequency analysis; fault feature extraction, singularity detection, denoising and various pattern recognition techniques such as artificial neural network(ANN), support vector machine (SVM) and fuzzy logic. A summary of some major developments in this field is also presented.
Keywords: Bearing condition monitoring; Failure diagnosis; Wavelet transform
Number of References cited: 100
Vibration Analysis of a Cylindrical Roller Bearing considering Multiple Localized Surface Defect on Races
Jing Liu, Yimin Shao, Jianji Zhou & Yuong Fan; PRC
Abstract: Cylindrical roller bearings are vital components in rotating machinery. The main failure modes such as localized surface defects (pits and spalls) are induced on the surfaces of the races and rollers due to periodic loads. It is therefore important to investigate the dynamic characteristics of cylindrical roller bearing with localized surface defects in order to gain some understanding of this failure mode. In this paper, a new dynamic model is proposed to investigate the vibrations of a cylindrical roller bearing with multiple localized surface defects on its inner and outer races. The time varying excitations cause by the multiple localized surface defects and non-Hertzian contact relationship between the logarithmic profile rollers and races of the bearing are considered. The dynamic model is described as a two-degree-of-freedom lumped spring-mass system, which includes the effects of the damping, time-varying compliance of the bearing, time-varying deflection excitations and time-varying contact stiffness excitations caused by the defects on its inner or outer races and profile of the rollers. The effects of the width, angular position and number of defects are investigated. The results show that the proposed method provides new ways to simulate the effects of multiple localized surface defects due to vibrations induced on cylindrical roller bearings.
Keywords: Cylindrical roller bearings; Vibration analysis; Multiple localized surface defects; Time-varying excitations
Number of References cited: 21
Identification of Faulty Ball Bearings using Singular Value Ratio: A Case Study
Bubathi, M., Satya Murty, S.A.V. & Jayakumar, T.; India
Abstract: This work investigates the possibility of using the ratio of singular value for bearing fault detection. The existing simple time domain methods are affected by variation of sample points. Also, they have not been shown to be effective in the presence of noise. The present work overcomes the above issues. Singular value decomposition on the bearing vibration signal is obtained under healthy and different fault conditions. The dominant singular values are selected based on the singular value plot. The ratio of these singular values is used as fault index which is found to be having a constant value for faulty bearing and another range of values for healthy bearing. The method is tested with experimental data obtained for different bearing fault types, with increasing fault severity and at various load. The effect of load, fault size, sample points and noise are studied on the fault index. The advantage of the proposed method are shown in comparison with the existing sample time domain techniques.
Keywords: Bearing fault; Vibration analysis; Singular value ratio; Energy operator; Time domain method
Number of References cited: 13
Effective Operational Excellence through Reliability Centred Maintenance
Browne, E.R. & Godkar, R.: Sultanate of Oman
Abstract: In many industries maintenance policies are implemented for failures which are either preventable or predictable. This paper is based on the experience gained by the authors who have successfully applied reliability centred maintenance (RCM) strategies in various industries. For the analysis a modern industrial system consisting of an electrical distribution system and selective rotating equipment expected to be maintained for an availability of 96% has been considered for given operating conditions. This paper compares the outcome of RCM analysis with usual preventive maintenance practices otherwise would have been followed on the selected system and equipment. Results are discussed in terms of changes in selected task and savings in resources.
Keywords: Reliability; Availability; Reliability Centred Maintenance
Number of References cited: 5
Observations on Bladed Disk Vibrations of an Aero-Engine – Experiences during Testing
Giridhar, R.K., Ramaiah, P.V., Sanjay, G.B. & Krishnaiah, G.: India
Abstract: A major task in the development program of a gas turbine engine is to ensure that the blades and bladed disc assemblies have no serious vibration problems. These blades are subjected to variety of excitations that influence their response characteristics. Any high oscillatory response of the blade is not acceptable as it has direct influence on the blade’s life. The challenge to designers is to ensure that these responses are well contained within the endurance limits. In addition, the design should ensure that the system is free from phenomena that set in uncontrollable increase in amplitude (self-excitation). Al these will drastically influence the bladed disc vibration. This paper detail the occurrence of various phenomena that are encountered during a developmental phase of a gas turbine engine program. Understanding these phenomena will definitely help the designers in arriving at a healthy design of a bladed disc. This paper discusses the mechanism, instrumentation, data acquisition/storage/and processing required and ways to control them.
Keywords: Bladed disc vibrations; Flutter; Non-synchronous vibration; Separated flow vibration
Number of References cited: 18
Volume 17, Number 2, April 2014
Integrated Network Topology Control and Key Management for Wireless Sensor Networks
Satish Kumar, D. & Nagarajan, N.: India
Abstract: At present, wireless sensor network (WSN) have appeared as one of the important fields due to their low-cost, self-organizing behaviour, sensing ability in hazardous environment, and its popularity. One of the most challenging topics is in relay network security. The existing Network Topology Acquisition (NTA) is not effective in providing the security features. It is critical to provide privacy and validation. In this paper, Incorporated Network Topological Control (INTC) and key management concepts are proposed to provide privacy and validation.
Keywords: Wireless sensor network; Relay nodes; Network topology acquisition; Multi-cluster routing protocol; Multiple intensity keying; Communication energy; Non-transparent mode relay network.
Number of References cited: 15
Digital Image Processing Technique for Microstructure Analysis of Spheroidal Graphite Iron
Shetty, P.B., Shetty, A., Murthy, A.K., Sarojadevi, H. & Mukunda, P.G.; India
Abstract: In this paper a microstructure analysis is carried out by employing the digital image processing (DIP) technique. This is a tool that permits a fast, complete and accurate acquisition of information. The processing of microstructure images sharpens the microstructure before carrying out quantitative analysis. In previous studies the analysis was carried out manually, which was time consuming. This problem is avoided by implementing DIP. In this paper the main emphasis is given to the analysis of microstructure grain boundary, which is detected using various edge detection operators. Here the digital image is converted into a binary image using a threshold value to segment the image. Using this procedure it is possible to change the intensity of the image to investigate the properties of grains more accurately. This also helps in counting the spheroids in the microstructure. Also, the image can be enhanced by apply the filtering technique. The results obtained are in the form of new microstructure image with smoothed grain areas with precisely detected grain boundary. Such effect allows optimizing further analysis of material structure to perform statistical calculations of average grain size or prepare material model for Finite Element Method simulations. The results of the analysis of microstructure images helps to correlate certain mechanical properties like ductility, malleability, brittleness, etc.
Keywords: Material microstructure; Grain boundary Digital image; Edge detection; Filtering
Number of References cited: 5
Numerical Simulation and Experimental Study on Plate Valve Transient Motion and Fatigue Fracture Principles
Zhang, J., Jiang, Z., Wang, Y. & Xu, F.; PRC
Abstract: Valves are used extensively in refining, pipeline and metallurgical enterprises. They are the most frequently damaged components of reciprocating compressors. Most of the research efforts are focused on faults features extraction and signal processing methods. Very few deals with the root cause failure mechanisms. In this paper, the transient movements of plate valve under different conditions have been simulated by establishing a modified thermodynamic and dynamic models with higher accuracy.
Keywords: Plate valve; Thermodynamic and dynamic models; Transient movement; Numerical simulation; Finite element analysis
Number of References cited: 20
Condition Monitoring of Combined Fault Scenarios in Rotating Machinery by Integrating Vibration based analysis & Design of Experiments
Majumdar, J. & Naikan, V.N.A.; India
Abstract: This paper aims to quantify the effects of combined faults in rotating machinery using vibration based condition monitoring using design of experiments (DOE) approach. The quantified contribution of faults and their interactions to overall severity in multiple defect scenarios creates better understanding of the dynamics of faults. Practically, it helps to improve the design as well as guide the maintenance decisions by the user of any rotating machinery. This paper presents a sample investigation and demonstration into the quantification of the effects for the combination of two most common but critical defects of rotating machinery: Static unbalance and parallel misalignment. Besides the quantification the DOE approach is also utilized to analyse the effects of combined fault scenarios in rotating machinery.
Keywords: Rotating machinery; Combined fault scenario; Vibration based monitoring; Design of experiments
Number of References cited: 21
Development of an Advanced Diagnostic System for Automotive Mechanical Transmissions
Mohamed, H., Onsy, A., Husseinand, M. & El Sherif, I.A.: Egypt
Abstract: Automotive transmission is one of the most important parts of any vehicle power train system, and in order to achieve reliable operation, effective health monitoring must be used. Predictive health monitoring (PHM) systems are currently gaining in popularity due to their effectiveness in reducing maintenance costs. However, reliable monitoring techniques are required such as the analysis of vibration, acoustic emission and oil debris. In this paper different monitoring techniques and their features are studied in order to develop an advanced monitoring system able to track the condition of an operating transmission system, classify faults and detect the onset of failure. The study presents an online PHM system utilizing autoregressive (AR) parametric algorithms, time and frequency analysis based on wireless transmission of vibration data. The online monitoring algorithms can support CBM and PHM of automotive multistage manual transmissions. The design, operation and validation of the online system are described and demonstrated. The results of the experimental test prove the system’s capability and support the recent trend of using CBM and PHM strategies.
Keywords: Mechanical transmission; CBM; PHM; Vibration analysis
Number of References cited: 24
Volume 17, Number 3, July 2014
A General Model for Reliability Analysis of a Domestic Waste Water Treatment Plant
Rizwan, S.M. Thanikal, J.V. & Torrijos, M.; Sultanate of Oman & France
Abstract: This paper presents a general model for analysing a domestic wastewater treatment plant from reliability perspective. The plant operates at a minimum capacity during the non-touristic months and at full capacity during touristic months, which is roughly for about 6 months in a year. The main components of the plant are pumps used for pumping at various stages. The pumps for pumping from the primary settling tank for pre-treatment are of 6 in numbers. With a capacity of 168 cu.m/hr where one is always kept as standby pump. There are 4 pumps for supply of ferric chloride, works at intervals and 5 pumps used for back washing and to pump out the treated effluent. The reliability of these pumps/components is useful from maintenance perspective in order to carry on the whole process without the component failures of tolerable limits and there is no alternative wa as well to store the waste water other thus treating the effluents and rejecting to the sea. Three years of maintenance data for this treatment plant have been analysed and important reliability indices are obtained. The semi Markov process and regenerative point techniques are used in the entire analysis.
Keywords: Wastewater treatment; Reliability; Semi Markov regenerative process
Number of References cited: 3
Optimization of the Reliability of Seawater Desalination Plant Systems through Maintenance Modelling
Alkali, B.M.I., Al Hinai, A., Zhou, C. & Farrag, M.; UK
Abstract: The adequacy of reliability and maintenance is an important factor in water desalination plants. Desalination plant energy recovery system deteriorates due to the accumulation of solid particles on the internal surfaces of membranes. Scaling and fouling of the membrane are considered to be one of the main reasons for reduction in plant performance and large numbers of breakdown events. This study focuses on investigating the operating costs of the excessive use of energy as a result of inadequate maintenance strategies on selected critical equipment in a water desalination plant. A comprehensive failure mode and effect analysis is conducted on the plant critical equipment to identify their failure modes and impacts on the plant’s overall efficiency. A reliability analysis of 5 years historical failure data of the reverse osmosis plant is conducted and the results are compared against the competing failure modes identified. The framework of a classical competing risk model is presented and conditional independent multiple competing risk models are proposed. A simulation example using the failure data collected is proposed and simulated results of the models cost curve show optimisation of cost effective maintenance schedules for the plant critical equipment.
Keywords: Seawater desalination; Plant systems; Optimisation; Reliability; Maintenance modelling; Scaling and fouling; Risk models
Number of References cited: 19
Gear Fault Diagnosis based on Central Tendency Measure of Intrinsic Mode Functions
Anand Parey & Ram Bilas Pachori; India
Abstract: Fault detection of gear is very crucial to avoid unexpected breakdown of machinery. Vibration signal coming out of gearbox can be used for analysis in order to find gear fault at an early stage. Various analytical methods based on empirical mode decomposition (EMD) have been used for diagnosing gear failures. The EMD method represents an original signal as a linear combination of finite band-limited signals in time domain. These band limited signals are known as intrinsic mode functions (IMFs). The analytic signal representation of IMFs exhibits circular pattern in complex plane. The central tendency measure (CTM) quantifies the degree of variability in IMFs of vibration signal. The CTM parameter has been used to measure the variability present in IMFs in order to detect fault in the early stage. The experimental results illustrate the effectiveness of the proposed method for diagnosing gear failures.
Keywords: Gear faults diagnosis; Vibration signal analysis; Intrinsic mode functions; Central tendency measure
Number of References cited: 27
Technology Innovations for Aircraft ‘Hard Landing’ Events
Paul Phillips; UK
Abstract: This paper provides an objective review of a range of literature and technology inventions relating to aircraft landing systems. More specifically, this paper deals with innovations that have been proposed by determining the occurrence and severity of non-normal landing events such as ‘hard landings’. The main findings of the paper indicate that the current method for determining a harr landing event, based upon the calculation of the aircraft sink rate and flight crew judgement result in overly conservative declarations, resultngin costly and unnecessary maintenance inspections. Methods based upon kinetic conditions of the aircraft are not accurately reliable as they are only ancillary to flight parameters and not the cause of any structural damage. Forces are applied to the landing gear structure from a multitude of causes that include arresting the vertical descent, wing lift at touchdown less than the weight of the aircraft, momentum of the aircraft about its roll axis, spin up of the wheels and tires with the associated spring back and side forces due to the aircraft yaw on touchdown. Methods based upon measurements of these forces using accelerometers, strain gauges, pressure, stress/strain indicators do not measure the effect of many of these forces and also rely on adding increased complexity and weight to the structure itself. The capability to accurately and reliably identify hard landings and make a quantitative assessment on the scale of such events has not yet been fully realized within commercial aircraft.
Keywords: Aircraft landing gears; Hard landings, Aircraft maintenance; Failure diagnosis; Fault indicators
Number of References cited: 30
Fault Diagnosis of Deep Groove Ball Bearing through Discrete Wavelet Features using Support Vector Machine
Kiren Vernekar, Hemantha Kumar & Gangadharan, K.V.; India
Abstract: Bearings are the most important and frequently used machine components in most of the rotating machinery. In industries, breakdown of such crucial components causes heavy losses. Hence prevention of failures of such critical components is very essential. This paper presents an online fault detection of a bearing used in an internal combustion engine through machine learning approach using vibration signals of bearing in healthy and simulated faulty conditions. Vibration signals are acquired from bearing in healthy as well as different simulated fault conditions of bearing. The Discrete Wavelet Transform (DWT) features were extracted from vibration signals using MATLAB program. Decision tree technique (J48 algorithm) has been used for important feature selection out of extracted DWT features. Support vector machine is being used as a classifier and obtained results found with classification accuracy of 98.67%. The advantage of machine learning technique for fault diagnosis over conventional vibration analysis approach has been demonstrated in this paper.
Keywords: Bearing fault diagnosis; Discrete wavelet features; Decision tree technique; Support vector machine
Number of References cited: 23
Unification of Multi-class Fault Classification from Diverse Domain Features of Gear using SVM Algorithms
Tiwari, R. & Bordoloi, D.J.; India
Abstract: In this paper, the health monitoring of a gear has been attempted by the support vector machine (SVM) learning technique with the help of time, frequency and time-frequency (wavelet) vibration data. Four fault conditions in the gear were considered including the no defect case. The multi-fault classification capability of the SVM has been suitable demonstrated and is based on the selection of SVM parameters. Different optimization methods (i.e. the grid search method (GSM), the genetic algorithm (GA) and the artificial bee colony algorithm (ABCA)) have been performed for optimizing SVM parameters. Time domain vibration signals were measured from the gearbox casing operated in s suitable sped range and was transformed in frequency domain. The continuous wavelet transform (CWT) and the wavelet packet transform (WPT) are extracted from time domain signals. A set of statistical features are extracted from signals in three domains. The prediction of fault classification has been attempted at the same angular speed as the measured data as well as innovatively at the intermediate and extrapolated angular speed conditions, since it is not feasible to have measurement of data at all speed of interest. The classification ability has been noted and compared among all domains, and in general these show excellent overall prediction performances especially with time-frequency domain data. Classifications so obtained are unified for a more reliable prediction by a voting technique. A fault for a particular data point is assigned according to the majority in voting of the fault defined by different methods and by using different domain data. The unified prediction is compared first with the best accuracies obtained using the time, frequency and time-frequency domain data and subsequently with the average of all accuracies obtained using three domains. It is observed that this technique is better than the average predictions obtained from different domains and classification methods, and many times they are competitive with the best fault prediction results.
Keywords: Gear; Multi-fault classification; Support vector machine; Optimization; Wavelets; Unified prediction accuracy
Number of References cited: 27
Volume 17, Number 4, October 2014; Special Feature Issue on Machinery Failure Prevention Technology
Application of Adaptive Filtering in Bearing Fault Detection in Wind Turbine Gear Transmission System
Ruoyu Li, Mark Frogley, Michael Messerschmidt & Johnny A Simmons; USA
Abstract: In this paper, an adaptive filtering technique will be applied for bearing fault detection in wind turbine gear transmission systems. The periodic components are removed from the original vibration signal to enhance the bearing fault signal-to-noise ratio. Statistical feature of the processed signal are extracted to quantify the bearing states. Simple linear classifier is trained to classify the healthy gearbox form the gearbox with bearing damage. Real wind turbine vibration signals were used to demonstrate the effectiveness of the presented method.
Keywords: Adaptive filtering; Bearing fault diagnosis; Condition monitoring; Gear transmission system; Wind turbine
Number of References cited: 15
Optical Torque Sensor Design enables new opportunities for Machinery Diagnostics and Failure Prevention
Fred M Discenzo; USA
Abstract: Commercial torque transducers are available today and widely used for industrial and commercial applications. While currently available sensors provide torque information for process monitoring and control their use is frequently limited to high value or critical applications due to the cost, size, reliability and performance limitations of commercial torque sensors. This paper presents the operating principle of the optical torque sensor along with several enhancements that provide for increased accuracy, self-powered operation and remotely located electronics and active optical elements. These enhancements provide unique opportunities for machinery health assessment and failure prevention.
Keywords: Optical torque sensor; Birefringence; Photo-elasticity; Torque sensor.
Number of References cited: 6
Reconfigurable Informatics Platform for Rapid Prognostic Design and Implementation: Tools and Case Studies
David Siegel & Jay Lee; USA
Abstract: This paper presents a methodology and suite of algorithms to explain the time and reduce the trial and error methods used in developing predictive health monitoring systems. The methodology highlights the key aspects in prognostics and health management system development, including data preparation and cleaning, feature extraction, health assessment, diagnosis, and health prediction. A discussion of the algorithms for each of these processing modules is provided, including a tabular summary of the relative merits of each of the algorithms. A case study on anemometer sensor health assessment is presented that highlights the various processing modules and the use of a residual clustering health model. An additional case study for aircraft engine remaining useful life prediction using a similarity based prediction method is also included. Overall, the outcomes using the proposed methodology resulted in quickly developed and accurate health monitoring models. Future work is looking at enhancing the suite of prediction algorithms for situations with sparse amount training data.
Keywords: Algorithm selection; Health monitoring; Remaining useful life; Prognostics
Number of References cited: 26
Rotating Machinery Diagnosis using Synchro-Squeezing Transform based Condition Indicators
Budhaditya Hazra & Sriram Narasimhan; Canada
Abstract: This paper utilizes the decomposing power of synchro-squeezing transform to extract the intrinsic mode functions (IMFs) from gear and bearing signals, followed by the application of standard rotating machinery condition indicators. This approach promises improved prognostic power than that can be achieved by applying condition indicators directly to the inherently complex data. The efficacy and the robustness of the algorithm are demonstrated with the aid of practical experimental data obtained from a helicopter gearbox test facility in Trenton, New Jersey, and also from seeded bearing fault tests, called the helicopter integrated diagnostic system (HIDS), carried out using iron bird test stand (SH – 60) at Naval Air Warfare Centre (NAWC) – Trenton and SH – 60B/F flight vehicles at NAWC Patuxent river.
Keywords: Time-frequency analysis; Diagnostics in rotating machinery; Synchro-squeezing transform (SST); Condition indicators
Number of References cited: 13
Signal Processing Techniques to Improve Acoustic Emission Sensing
Eric Bechhoefer, Yongzhi Qu & David He; USA
Abstract: This paper hypothesizes that the AE signature is the result of some forcing function (e.g. periodic motion in the case of rotating machinery). As such, by demodulating the AE signature, one can reconstruct the information carried by the AE signature and provide improved diagnostics. As most on-line condition monitoring systems are embedded system, both analogue and digital processing techniques are proposed which reduce the effective sample rate needed to operate on the AE signal to those similarly found in traditional vibration processing systems. This hypothesis is tested on a split torque gearbox and results are presented.
Keywords: Acoustic emissions, Condition indicators, Analogue signal processing, Demodulation heterodyne
Number of References cited: 16
The use of Minimum Entropy Deconvolution Filter in Valve Response Speed Study
Hiroaki Endo & Tim Chapman; USA
Abstract: This paper presents an application of the Minimum Entropy Deconvolution (MED) technique to enhance the clarity of impulse caused by opening and closing of actuated mechanical valves. The response speed and consistency of the response delay in valve opening and closing have significant influence on the overall performance of an air motor of interest. Acceleration signals were measured in non-intrusive manner on the valve casing. The impulses caused by the valve opening and closing were monitored to measure the speed and consistency of the valve response. Some of the impulses in the original accelerometer signals were masked by significant noise from the flow of compressed air passing through the valve. The impulse which correlated to the closing of the valve was masked by the noise from the air flow. The MED filter, tuned to give the optimum impulse enhancement was used to successfully separate the impulses from the noise and allowed precise assessment of the valve performances.
Keywords: Minimum entropy deconvolution (MED); Valves
Number of References cited: 9
Waveguide Vibration Sensor for Aerospace Health Monitoring
Chris Larsen, Nathan Branch & Richard Roth; USA
Abstract: This paper presents results from a new waveguide vibration sensor as used in two turbine engine main shaft bearing seeded defect tests. It provides background information on waveguides and the waveguide vibration sensor used for these tests. The results from seeded defect testing aa performed on T63 engine at the Air Force Research Laboratory (AFRL) are presented. The results from seeded defect testing on a Rolls Royce 501 – KB5+ (industrial version of the T56) are presented. Finally the paper summarizes the conclusions and recommendations for further testing.
Keywords: Aerospace; Bearings; Diagnostics in rotating machinery, Turbine engine, Vibration analyses
Number of References cited: 6
Volume 18, No. 1, January 2015: Special Issue on Condition Monitoring & Measurement
Strategic Maintenance Management: Formulating Maintenance Strategy
Ali Rastegari & Antti Salonen; Sweden
Abstract: In recent decades, by introducing lean manufacturing the vulnerability to system disturbances has increased and so, the demand for dependable production equipment. The need for having high production equipment availability causes companies to need a more effective and efficient maintenance strategy in order to stay competitive. Despite the increasing demand on reliable production equipment, few manufacturing companies work with strategic maintenance development and a large part of the manufacturing industry lack clear maintenance strategies. It is therefore difficult to develop the maintenance work in accordance with the strategic goals of the manufacturing companies. The main objectives of this paper is to define a process for formulating maintenance strategy in order to facilitate further development in a strategic way. The problem has been studied by literature review and through case study at one major manufacturing site in Sweden to investigate the company’s view on strategic maintenance development. The company’s overall goals were considered and translated to the strategic objective of maintenance. Balanced score card is used as a tool to make a framework of the maintenance strategy. As a result of this study, the company could easily formulate a maintenance strategy by using a simple process based on the tools that they have already used. In addition to this, the result indicated how a maintenance strategy can contribute to the company’s business goals.
Key words: Maintenance strategy; Maintenance management;
Number of References cited: 20
Towards a Fault Tolerant Railway System
Claudia Fecarotti, John Andrews & Rasa Remenyte-Prescott; UK
Abstract: The railway transport system is experiencing an increasing level of traffic demand in terms of both passengers and freight. The 24/7 railway has been stated as a possible solution to satisfy the future growth in demand. However a greater utilization of the network will accelerate deterioration processes and reduce the time slots for maintenance. In this context the ability of the system to continue operating properly in case of failure is a key factor to provide a safe and reliable service, but the railway system is not currently designed to be fault tolerant. This work is a first attempt to investigate options for exploiting and optimizing the potential of the current infrastructure to provide alternative paths to trains when failure occur or sections of track are taken out for maintenance, thus improving service reliability. This paper presents a methodology based on a whole system approach aiming at evaluating ways in which features of the design, operation and maintenance strategies can provide a fault tolerant railway system. Simulation, optimization and failure modelling techniques will be combined for an integrated assessment of different solutions in order to reveal the most effective railway system. A discrete-event simulation model has been developed to simulate railway operation according to a given time table and assess system performance for different system designs and failure scenarios. The railway system is modelled as a timed colour Petri net which implements safety, control and dispatching rules in order to manage trains movements through the network. Performance requirements are defined in terms of total delay. Rail operations in a section of the UK network have been simulated for a number of infrastructure and failure scenarios, and results show a positive effect of additional switches on service reliability.
Keywords; Railways; Fault tolerance; Holistic approach; Discrete-event simulation; Petri nets
Number of References Cited: 18
Alleviating the Challenges of Manual Data Collection with Field Force Management Integration Interface
Juha Tiihonen, Jukka Borgman & Johanne Lehtinen; Finland
Abstract: Product manufacturers can gain significant competitive advantage to their service business by utilizing detailed information about the individual products that formed the installed base or are under service contracts. This Service Base Information includes details on failures and maintenance, location and site, computational structure, operation and environment and data on key performance indicators. Information can be collected manually or by automated means. However, 8 cases from Finnish machine building and telecommunication industries indicate that the state-of-the-practice still has significant room for improvement. Quality of manually collected information is often insufficient for many analyses and scope is often too narrow. In this paper, the authors identify the information needs and describe a proposed OASIS standard - Field Force Management Integration Interface (FFMII). When FFMII is applied with appropriate data content, coding systems, and user interfaces, it is possible to increase the scope and quality of service base information without excessive reporting burden on field engineers. The paper also reveal how FFMII can be applied to collect the necessary information. This, in turn enables fact-based adaptation of preventive maintenance programmes to be more efficient field operations resulting in more accurate pricing of service sales and analysis of field reliability.
Keywords: Data collection; Field force management; Field-force management integration interface
Number of References Cited: 12
A New Technique for Torsional Vibration Measurements with Digital Image Correlation
Mikko Hasanen, Juha Miettinen, Pentti Saarenrinne & Voitto Kokko; Finland
Abstract: Strain measurements are essential in experimental vibration analysis in many areas of machinery research and development field. Generally strain fields have been determined by measuring the time series at a point, where the strain gauges are widely employed. Although this method is accurate enough in many cases, the installation of sensors and data analyses are time consuming. In this paper, a new way of measuring the static and dynamic measurements of a rotating shaft in industrial environment is investigated. The method is based on high speed digital imaging of two spots separated by two meters, while using only camera. This is done with the help of mirrors so that the resulting pictures includes images of both spots on the shaft recorded simultaneously with a pulsed diode laser illumination. The target is the drive shaft of a 26.5 MW Francis turbine of hydro-electric power plant, in a position where the circumstances for imaging measurements with more than one camera be very challenging. Because of the camera’s memory restrictions (16 Gb), the sampling rate was decided to be 1000 Hz to avoid aliasing and to get long enough record length. Speed of the shaft surface was about 4 meters/second, which causes a requirement to use pulsed laser light for illumination to freeze the surface pattern at used sampling rate. The local surface displacement between pictures is calculated for both the upper and lower spot. With these time series it is possible to study the torsional vibration of shaft in time and frequency domains. The results obtained are compared with the theoretical model and also to reference measurements made with strain gauges. The results obtained are promising.
Keywords: Torsional vibration; Digital image correlation; Diagnosis of rotating machinery
Number of References cited: 12
Tacholess Computed Order Tracking Method via STFT and Vold-Kalman Filtering
Ming Zhao, Jing Lin, Xiufeng Wang & Yaguo Lei; China
Abstract: Order Tracking (OT) is considered as a classic and effective technique for the non-stationary vibration analysis of rotating machinery. Traditionally, additional hardware such as a tachometer is required to provide a reference signal. To extend the applications of the OT technique, some tacholess OT methods were proposed recently. However, they are only applicable to those with small sped fluctuations. A new tacholess OT method is established in this paper, which is applicable to the cases with large speed variation such as in the run up/down processes. In this method, the instantaneous frequency of one harmonic of rotation frequency is first estimated by time-frequency analysis. Vold-Kalman filtering is then employed to extract the harmonic from the overall signal. Finally, the original signal is resampled by using the instantaneous phase of the extracted harmonic. In this way, the OT method can be carried out without a tachometer. Simulations and experiments show that the results obtained through this method are almost the same good as those obtained from a tachometer under large speed variation. Furthermore, as incipient fault of gear is detected efficiently for a gearbox by using this method under large speed variation.
Keywords: Order Tracking (OR); Vold-Kalman filter; Time-frequency representation; Hilbert transform
Number of References cited: 13
Application of Maintenance Performance Measurement for Continuous Improvement in Railway Infrastructure Management
Stephen M. Famurewa, Aditya Parida and Uday Kumar; Sweden
Abstract: Railway transport infrastructure is a linearly distributed asset that requires an effective performance management system to meet sectional and overall business objective. In particular, an effective performance management system with relevant analysis technique in an ongoing manner is necessary to facilitate continuous improvement. Maintenance Performance Measurement (MPM) is essential to quantify the impact of past maintenance decisions and actions and also to support new decisions. This paper presents the challenges of implementing and using MPM systems for maintenance decisions in the railway industry. Also, a risk matrix with maintenance performance indicators is introduced as a complementary analysis tool to identify weak links on a railway line. A case study of a section on the heavy haul line of the Swedish Transport Administration railway network is presented to demonstrate the application of the risk matrix tool continuous improvement.
Keywords: Railway infrastructure; Maintenance performance measurement; Risk matrix
Number of References cited: 28
Volume 18, Number 2, April 2015. Special Issues on eMaintenance
Control Charts supporting Condition Based Maintenance of Linear Railway Infrastructure Assets
Bjarne Bergquist & Peter Soderholm; Sweden
Abstract: This paper presents a control chart approach for monitoring, diagnosis and prognosis to support condition based maintenance using condition data on linear railway infrastructure assets. The condition data were obtained from regular inspections conducted using a railway track measurement wagon. The data were statistically analysed using two control charts to evaluate the possibility of improved detection of derailment-hazardous faults using both temporal and spatial information. The findings of this investigation reveal that the two proposed control charts give earlier fault warnings than does the traditional approach.
Keywords: Railway track failure diagnostics; Control charts; Spatiotemporal analysis
Number of References cited: 34
Investigation of the Top-of-Rail Friction by Field Measurements on Swedish Iron Ore Line
Yonas Lemma, Mathias Asplund & Matti Rantatalo; Sweden
Abstract: Friction management in the railway industry is a wee established technology with the aim of optimizing the friction between the wheel and the rail. Determining the friction coefficient (µ) at the wheel-rail interface is therefore important especially for heavy haul lines with higher axle loads. This paper presents an initial study of the top-of-rail friction condition of a line with 30 ton axle load, the Iron Ore Line in the northern part of Sweden. The friction coefficient between the rail and the metal wheel of a portable tribometer was measured at different geographical locations and in different environmental conditions. The effects of precipitation are studies and compared with the effects of top-of-rail friction modifiers. The measurements of non-lubricated line section showed values of µ=0.3 for areas with, for example, top-of-rail lubrication. In snowy conditions a decrease in friction could also be detected.
Keywords: Friction management; Heavy load railway line Swedish Iron Ore line; Friction monitoring
Number of References cited: 12.
Using Coloured Petri Nets to investigate Fleet Cannibalisation
Jingyu Sheng & Darren Prescott; UK
Abstract: Cannibalisation is a maintenance activity that involves removing serviceable parts from inoperative platforms to replace unserviceable parts of the same type in other platforms. It can provide a significant benefit to fleet readiness, particularly if spare parts are in short supply. However, cannibalisation also has drawbacks. It brings an increased workload for maintenance crews and parts can be damaged during the cannibalisation process. For this reason, it is important to have a clear understanding of the effects that cannibalisation will have on fleet operation and maintenance. Accurate models are needed to predict the effects if cannibalisation on fleet performance and to provide fleet managers with trustworthy information on which to base maintenance decisions relating to cannibalisation and spare parts provision. This paper presents a coloured Petri Net (CPN) model of fleet cannibalisation that takes account of fleet operation and a number of factors relating to maintenance. An example fleet is modelled and measures of average fleet readiness and maintenance cost are used to evaluate the effects of cannibalisation on fleet performance. The model is used to assess the impact of a number of maintenance factors and fleet size on the use of cannibalisation and fleet performance.
Keywords: Fleet; Cannibalisation; Coloured Petri Nets (CPN)
Number of References cited: 8
Natural Language Processing of Maintenance Records Data
Christer Stenstrom, Mustafa Aljumaili & Aditya Parida; Sweden
Abstract: Enterprise resource planning systems and maintenance management systems are commonly used by organisations for handling of maintenance records through a graphical user interface. A maintenance record consists of a number of data fields, such as drop-down lists, list boxes, check boxes and text entry fields. In contrast to the other data fields, the operator has the freedom to type in any text in the text entry fields, to complement and make the maintenance record as complete as possible. Accordingly, the text entry fields of maintenance records can contain any words, in any number. Data quality is crucial in statistical analysis of maintenance records, and therefore manual analysis of maintenance records’ text entry fields is often necessary before any decision making. However, this may be a very tedious and resource consuming process. In this paper, natural language processing is applied to text entry fields of maintenance records in a case study, to show how it bring further value in the assessment of technical assets’ performance.
Keywords: Natural language processing; Rail infrastructure; Maintenance records; Data quality
Number of References cited: 12
Safety and Security in eMaintenance: The need for integration
Tim Tinney, Anders Adlemo, Ulf Seigerroth & Olov Candell; Sweden
Abstract: eMaintenance provides many new possibilities and opportunities to increase the productivity of industrial systems, yet decrease resources and administration costs. To accomplish this though, it is often required to rely on some network connectivity with the system of interest. It is this network connectivity capability that runs the risk of being interdicted, thereby providing a window of opportunity, commonly referred to as a vulnerability, for a threat to exploit. This in itself is not necessarily new, but the applicability to eMaintenance is not well understood. To this end, this paper answers the question of whether or not the integration of safety and security is of value to the eMaintenance domain by first providing a number of comparisons and contrasts between safety and security. This paper also introduces a pragmatic way to integrate safety and security called the harmonized protection conceptualization, which helps to assist with visualizing and organizing safety and security is a viable and necessary consideration within the eMaintenance domain. Besides addressing the question of the practicality and usefulness of integrating safety and security, this paper will also address past research and noteworthy projects that have previously attempted this endeavour. Some general safety and security aspects of eMaintenance have also been addressed.
Keywords: eMaintenance; Network connectivity; System safety and security; Harmonization
Number of References cited: 60
Volume 18, Number 3, July 2015
Numerical Investigations on the Effect of Blade Angles of a Vertical Axis Wind Turbine on its Performance Output
Kyoo-Seon Park, Taimoor Asim & Rakesh Mishra; UK
Abstract: There are many social, political and environmental issues associated with the use of fossil fuels. For this reason, there are numerous investigations currently being carried out to develop newer and renewable sources of energy to alleviate energy demand. Wind is one source of energy that can be harnessed using wind turbines. In this study, numerical investigations using Computational Fluid Dynamics (CFD) solver have been carried out to determine the optimum blade angles of a wind turbine used in urban environment. The effect of these blade angles have been considered to be within the normal operating range (α from 1.689 to 21.689 , ¥ from 18.2 to 38.2 and ö from 22.357 to 42.357 ) while β was kept constant at 90 due to design requirements. The results show that as α increases average torque output increases to a certain point after which it remains constant. On the contrary, as ¥ and ð increase, average torque output decreases. From the results, it can be concluded that the ideal blade angles, for optimum torque output are α = 11.689 , ¥ = 18.2 and ð = 22.357 ,
Keywords: Vertical axis wind turbine; Computational flued dynamics; Torque; Tip speed ratio
Number of References cited: 19
Life Cycle Oriented Analysis and Evaluation of Active Flow Control in Wind Turbines
Uwe Gotze, Christina Symmank, Maria Dressel, Martin Schuller, Anja Schmidt, Mathias Lipwoski, Thomas Gessner & Thomas Otto; Germany
Abstract: Active Flow Control (AFC) devices in rotor blades offer a high potential to improve the efficiency of wind turbines, e.g. by increasing rotor blade life, improving load control or reducing acoustic emission. Thus, the energy yield can be increased and/or the rotor blades be downsized – both implying positive economic consequences. However, since AFC devices also cause additional costs in different phases of their life cycle, a life cycle related evaluation of their probability is necessary. This paper presents a decision theory-based procedure model, which enables not only a sophisticated evaluation of AFC concepts and devices but also the identification of needs and potentials for improvement.
Keywords: Wind turbines; Active flow control; Life cycle analysis; Economic evaluation
Number of References cited: 42
Radial Basis Function Neural Network for Effective Condition Monitoring of Rolling Element Bearing
Vijay G.S., Srinivasa Pai, P., Sriram, N.S. & Raj B.K.N. Rao; India & UK
Abstract: The performance of Radial Basis Function Neural Network (RBFNN) in the defect classification of a Rolling Element Bearing has been investigated in this paper. The input features required for training the RBFNN have been extracted from the non-overlapping segments of the raw and denoised bearing vibration signals. A kurtosis-based wavelet denoising method has been used to reduce the noise components in the vibration signals. The Fisher’s Criterion (FC) has been used to select a few sensitive features and form a reduced feature set. The centers of the RBF units have been optimized using a modified Fuzzy C-Means (FCM) algorithm, viz, Cluster Dependent Weighted FCM (CDWFCM). The performance of the RBFNN has been compared for four training strategies; two types of feature sets (all features and FC selected features) and two types of RBF centers selection method \9centers selected randomly and centers selected using CDWFCM). These strategies have also been tested for the bearing vibration signals provided by the Case Western Reserve University Database.
Keywords: Rolling element bearings; Radial basis function neural network; Wavelet denoising; Dimensionality reduction; Fuzzy C-Means; Fisher’s criterion
Number of References cited: 52
Monitoring of Upper-Limb EMG Signal Activities using a Low Cost System: Towards a Power-Assist Robotic Arm
Ahmed Azab, Ahmed Onsy & Mohamed El-Mahlway; Egypt & UK
Abstract: Many human activities depend upon upper limb motion, which can be characterized and estimated using the activation levels of the Electromyography (EMG) signal of the upper limb muscles. Researchers are devoting much effort to investigating these activities during elbow extension and flexion. Also, a few studies have concluded with the development of a power-assisted arm. However, the systems introduced so far are expensive and there are long waiting lists of people requesting such systems. The aim of this paper is to develop a power-assist arm based on the EMG signal activities of the upper limb, and this paper describes the first part of this study focusing on the monitoring of EMG signals during upper limb activities based on the development of a low-cost system. The relationship between elbow motion and the activity level of the biceps muscle is characterised and different relevant features are logged. The new low-cost system is then validated against the Biopak specialized biomedical measurement system.
Keywords: Biceps muscle; Exoskeleton system; Electromyography; Low-cost controller, Power-assisted robotic arm
Number of References cited: 16
Fire Safety Analysis of a Railway Compartment using Computational Fluid Dynamics
Anwar Embaya, Taimoor Asim, Rakesh Mishra and Raj B.K.N. Rao; UK
Abstract: Trains are considered to be the safest on land transportation for both passengers and cargo. Train accidents have been disastrous especially in case of fire, where the consequences results in loss of life and goods. The fire would generate smoke and heat which would spread quickly inside the railway compartments. Both heat and smoke are the primary reasons for causalities in a train. This study has been carried out to perform numerical analysis of fire characteristics in a railway compartment using commercial Computational Fluid Dynamics code ANSYS. Non-premixed combustion model has been used to simulate a fire scenario within a railway compartment, while Shear Stress Transport k-ω turbulence model has been used to accurately predict the hot air turbulence parameters within the compartment. The walls of the compartment have been modelled as no-slip stationary adiabatic walls, as is observed in real-life conditions. Carbon dioxide concentration, temperature distribution and air flow velocity within the railway compartment has been monitored. It has been observed that the smoke above the fire source flows to both sides of the compartment. The highest temperature zone is located downstream the fire source, and gradually decreases with the increase in the distance from the fire source. It can be seen that the CFD can be used as an effective tool in order to analyse the evolution of fire in railway compartments with reasonable accuracy. This paper also briefly discussed the topical reliability issues.
Keywords: Railway compartment; Fire modelling; Computational Fluid Dynamis; ANSYS
Number of References cited: 18
Optimum Inspection Interval for Hidden Functions during Extended Life
Alireza Ahmadi, Behzad Ghodrati, Amir. H.S.Garmabaki & Uday Kumar; Sweden
Abstract: The methodology proposed in this paper aims to provide a mathematical model for defining optimal Failure Finding Inspection (FFI) interval during the extended period of the replacement life. It considers the maintenance strategy of “a combination of FFI and a discard action after a series of FFI”. A Cost Function (CF) is developed to identify the cost per unit of time associated with different FFI intervals, for the proposed extended period of life, i.e. postponement period. The Mean Fractional Dead Time (MFDT) concept is used to estimate the unavailability of the hidden function within the FFI intervals. The proposed method concerns as-bad-as- old (ABAO) inspection and repairs (due to failures found by inspection). This means that the unit keeps the state, which it was in just before the failure that occurred prior to inspection and repair. It also considers inspection and repair times and takes into account the costs associated with inspection and repair, the opportunity cost of lost production due to maintenance downtime created by inspection and repair actions, and also the cost of accidents due to the occurrence of multiple failures.
Keywords: Hidden functions; Optimum interval; Extended life; Failure finding inspection; Reliability centered maintenance
Number of References cited: 21
Volume 18, Number 4, October 2015
Enhancing the Product Life of Automobiles by Managing Maintenance Crisis in Developing Countries
Rajeev Namdeo & Smita Manepatil; India
Abstract: This paper is based on maintenance management planning, organization and control aspects of automobile service sector in developing countries. The vehicle sale in developing countries is ever growing over the last decade. It leads to global warming and uneven fuel consumption, which puts pressure on after sales service of vehicles. An automobile service sector is still untouched for computer aided vehicle maintenance management (CAVMM). After sale service of an automobile can be effectively managed by using CAVMM software. CAVMM comprises three-tier management information system in which server (first tier) act as brain by interacting with its executive bodies named Authorised Service Centre (ASC) (second tier) to serve the customers (third tier). In this system, the main focus is maintenance cost which will be optimized by using a scientific approach for maintenance actions.
Keywords: Computer aided vehicle maintenance management; Authorized service centre; Unique identification number
Number of References cited: 12
Enhanced Detection of Rolling Element Bearing Fault based on Averaged Stochastic Resonance
Niaoqing Hu, Lei Hu, Lun Zhang, Weiyu Hou & Fengshou Gu; PRC & UK
Abstract: Bearing localized faults generate a series of impact vibrations at bearing characteristic frequencies, which often contain very little energy, and are usually overwhelmed by noise and periodic components generated from other parts, such as gear and shaft. In the past decades, classical stochastic resonance (CSR) method is presented to enhance the fault detection of rolling element bearing. Aiming at identifying the bearing characteristic frequencies in the spectra, SR normalized scale transform has been proposed based on parameter-tuning bistable SR model by the authors. Based on the authors’ former work, this paper presents a new method via averaged stochastic resonance (ASR) to enhance the result of rolling element bearing fault detection. Simulations are carried out to validate the effect of the weak signal detection method of ASR. Moreover, two bearing fault enhanced detection strategies of CSR and ASR are investigated. Normal and seeded outer race fault bearings vibration signals from a test rig are processed and analysed using the two methods, and the results are compared.
Keywords: Rolling element bearing fault diagnosis; Averaged stochastic resonance; equip
Number of References cited: 14
Quantifying the Economic Benefits of Online Monitoring
Neil Davies, Paul Blackmore & Ying Wang; Australia
Abstract: Online condition monitoring equipment with the capability to detect a wide range of failure mechanisms in power systems equipment is now widely available at affordable prices. Online monitoring with its near continuous sampling can dramatically improve the effectiveness of condition monitoring as a risk mitigation tool by reducing the possibility for a failure to develop undetected between inspection periods. This type of system however carries significant up-front implementation as well on-going operating costs associated with system maintenance and the management and interpretation of condition data. In this paper the authors discuss the economics of implementing on-line monitoring by comparing estimates of the reduction of risk against the cost to install and operate a typical on-line partial discharge condition monitoring system. Risk estimates are calculated im monetary terms using EA Technology’s Condition Based Risk Management (CBRM) methodology taking into consideration network performance, safety, cost and environmental consequences. Through the analysis of aggregated distribution company CBRM data, the authors present examples where online monitoring is clearly justified as well as statistics indicating the proposition of typical circuit breaker populations where continuous monitoring is likely to be cost justified on a risk mitigation basis.
Keywords: Rotating machinery diagnostics; Time-frequency analysis; Vibration analysis
Number of References cited: 9
Laser Scanning for complete Wear History Capture and Life Cycle Data Analysis in the Mining Industry
Peter Clarke, Igor Elias & Juha Kautto; Australia & Finland
Abstract: Laser scanning has become an accepted and common technology for collecting spatial data on a wide range of objects. This new technology has been developed to capture the entire wear history inside grinding mills and gyratory crushers using laser scanners for data collection. Sacrificial wear liners are installed in mills and crushers and form the working components in breaking ore down to the required size. It is critical that these wear liners do not run to failure and expose the structural members behind them to damage. However, it is equally important to extract as much life as possible from the liners before it shutdown which is expensive both in cost and downtime. Detailed analysis of the life cycle is hampered by the fact that with conventional manual data acquisition methods. Only a limited subset of the thickness measurements required for this analysis can be collected due to practical constraints. The introduction of laser scanning technology removes this constraint and instead of 10 to 20 measurements being made inside a 13 meter diameter vessel. 10 million data points can now be collected. This paper will describe the data collection methodology, how the data is processed and some case studies.
Keywords: Grinding mill liner life; Laser scanning; Asset management
Number of References cited: 2
Monitoring the Fatigue Damage in Ductile Cast Iron by AE Technique
Md. T. Islam Khan, Nagao, T., Kondo, Y., Teramoto, K. & Hattori, N.: Japan
Abstract: Damage initiation and propagation characteristics of ductile cast iron due to crack, micro-crack have been investigated by acoustic emission (AE) technique. As spherical graphite cast iron has high strength as well as excellent workability and damping capacity, it has been used in automobile as well as in many other engineering applications. However, the damage initiation of the spheroidal graphite cast iron might depend not only on the graphite size but also on the distribution of the graphite nodules. The fatigue failures of this spheroidal graphite cast iron caused by cracks and micro-cracks have been investigated sequentially by AE technique. AE events during the initiation of cracks and micro-cracks have been characterized by comparing the microstructural images of the specimen. The result shows good acquisition performance in the evaluation process.
Keywords: Ductile cast iron Crack initiation; Fatigue damage evaluation; AE technique; Non-destructive evaluation
Number of References cited: 21
Classification of Railway Vehicles and their contribution to the Track Degradation
Dan Larsson; Sweden
Abstract: This paper presents a method to use real time force data from enhanced wayside monitoring stations to classify railway vehicles contribution to the overall track degradation. The wayside force monitoring station was installed on the western main line near Gothenberg in Sweden in May 2009. The examples provided with three different train types shows how data can be used.
Keywords: Railway vehicles; Classification; Track degradation; Wayside monitoring
Number of References cited: 15
Volume 19, Number 1, January 2016
Importance of maintenance data quality in extended warranty simulation Katrine
Mahlamäkia , Arto Niemib, Juuso Jokinenb , Jukka Borgmana; Finland
Abstract: As manufacturing industries are transforming towards service orientation, predicting the costs of product-service systems is becoming essential. Simulation is one possibility for evaluating the costs and risks involved in product-service systems, such as extended warranty agreements. We conducted a case study with a globally operating manufacturer of industrial goods who also provides services for the equipment. We created equipment performance simulation (EPSi) models and a tool, EPSitor, for using the models in predicting extended warranty costs. However, reliable simulation results require good quality maintenance and operation data from existing installations. We discovered that it is difficult to collect the data needed for simulations and there were many challenges with data quality. Quality problems were mainly observed in manually collected data. Insufficient data quality leads to a wider margin of error in the simulation models, which increases business risk. Identifying these challenges is the first step in transforming the data collection routines to support equipment performance simulations. The key to long-term business benefits of simulation is to acknowledge the importance of data quality and to establish efficient data collection routines. Future research should find ways to motivate maintenance technicians to collect good quality data. This would contribute to more accurate cost analysis and thus to better profitability of extended warranty contracts.
Keywords: Asset management, Human factors, Data quality
Number of References cited: 27
An Economic Lightweight Concept for the evaluation of thermoplastic foams for aerodynamic lightweight structures
Marco Walthera, Michael Heinricha, Christina Symmankb, Anja Schmidtb, Martin Schüllerc, Uwe Götzeb, Thomas Geßnerc and Lothar Krolla; Germany
Abstract: Thermoplastic foams offer a high potential to increase the efficiency of aerodynamic lightweight structures such as rotor blades of wind turbines. In this paper, a mathematical model which allows for improving the production of thermoplastic foams simultaneously from an economic and mechanical point of view is presented. The model can be used for the assessment of individual process parameters regarding the incurring costs and the resulting mechanical properties of the components produced this way. The results of the economic and the mechanical evaluation are integrated in a common target figure, the Economic Lightweight Index, which serves as a means for decision support. A transfer to other material systems is possible and feasible without major adaptations.
Keywords: injection moulding; lightweight structure; mechanical properties; economic evaluation; Economic Lightweight Index
Number of References cited: 14
Effect of gear tooth faults on time varying mesh stiffness of spur gear pair
Ankur Saxena, Anand Parey, and Manoj Chouksey; India
Abstract: This paper presents, a computer simulation based analytical approach to quantify the time varying mesh stiffness (TVMS) reduction of gear pair due to various gear tooth faults. Gear faults affecting transmission of gear pair are always accompanied by a stiffness reduction. TVMS is an important parameter in condition monitoring and to understand the dynamics of meshing gear pair. Potential energy method is one of the most widely used analytical methods to calculate TVMS. In this paper, reduction of gear mesh stiffness has been studied for three gear faults: cracked tooth, chipped tooth and spalled tooth using potential energy method. The results show that due to presence of gear faults the TVMS reduces which will affect the vibration response of spur gear pair.
Keywords: Gear tooth faults, mesh stiffness, stiffness reduction
Number of References Cited: 8
A hybrid feature selection method for hidden Markov model based bearing performance assessment
Hui-ming Jiang, Jin Chen, Guang-ming Dong, Tao Liu, Gang Chen and Ran Wang; PRC
Abstract: Bearing performance assessment as an advance warning of defects has received considerable attentions in industrial maintenance. Hidden Markov model (HMM) has been widely utilized in bearing fault diagnosis and performance assessment recently. The likelihood probability is the key index for HMM-based performance assessment which is called PI. And the scatter of PI between different degradation stages is quite important for performance assessment, so the PI is also can be called as likelihood distance (LD). In this paper, a hybrid feature selection method is proposed for HMM-based bearing performance assessment. The LD from HMM is combined with distance evaluation method to build a new feature selection method considering the basis theory of HMM-based performance assessment. The hybrid feature selection method is called likelihood distance based distance evaluation (LDDE) method. Through a bearing accelerated life test experiment, the effectiveness of the proposed feature selection is validated.
Keywords: Bearing, Performance assessment, Feature selection, diagnosis, hidden Markov model, Distance evaluation.
Number of References cited: 27
Effects of Surface Roughness in Squeeze Film Lubrication of Two Circular Plates
Vijaya Kumar.J., and Raghavendra Rao.R; India
Abstract: A generalized form of Reynolds equation for two symmetrical surfaces is taken by considering surface roughness at the bearing surfaces. This equation is applied to study the effects of surface roughness for the lubrication of squeeze films of two circular plates. Expressions for the load capacity and squeezing time obtained are studied theoretically for various parameters. The load capacity and squeeze time increases with the increase in the value of ‘k’ i.e; due to high viscous lubricant layer near the surfaces the load capacity and squeezing time increase which enhances the lubrication process. In the case of transverse roughness the load capacity and squeezing time increases as the mean height of surface asperities increases and the load capacity and the squeezing time decreases as the mean height of surface asperities increases in the case of longitudinal roughness. Hence the effect of roughness is more pronounced in the case of transverse roughness.
Keywords: Reynolds equation; Surface roughness; Squeeze film lubrication; Load capacity; Squeezing time.
Number of References cited: 45
Volume 19, Number 2, April 2016
Degradation assessment study for bearings with outer race fault
Patricia Henríqueza, Jesús B. Alonso, Miguel A. Ferrera and Carlos M. Travieso; Spain
Abstract: This paper presents a new methodology for degradation assessment in bearings with outer race fault. The novelty of the paper is the application of the Lempel-Ziv complexity (LZC) to the node of maximal energy from the wavelet package transform of the raw vibration signal. The objective of the paper is to develop a methodology for outer race fault bearing severity assessment and to show how the extracted feature LZC follows monotonically the bearing degradation. The proposed methodology is compared with LZC and kurtosis extracted from the raw vibration signal and with kurtosis extracted from the node with maximal energy.
Keywords: Bearing, Lempel-Ziv complexity, Wavelet Packet Transform
Number of References cited: 23
Finite element prediction of the stress state of a rail underhead radius under high axle load conditions
Sagheer Abbas Ranjhaa, Ambarish Kulkarni, Palaneeswaran Ekambaram, Peter Mutton Ajay Kapoor; Australia
Abstract: The stress state at the rail underhead radius (UHR) has been parametrically analysed in this paper under high axle load conditions. A finite element method (FEM) was used to undertake the analyses with respect to head wear (HW) and the operational / track support conditions. The wheel load was simulated as a Hertizan contact pressure applied to an elliptical patch on the rail head, assuming fully slipping conditions. The results reveal that the longitudinal tensile stress at the rail underhead radius is highly dependent on the rail head wear (HW), the wheel contact load eccentricity, and the L/V ratio of lateral (L) to vertical (V) loads. The magnitude of tension spike increases, as a result of an increase in the contact patch offset, the L/V ratio, and HW. This stress is further enhanced by residual and thermally induced stresses. This may result in fatigue cracking and risk of material failure at the underhead radius (UHR).
Keywords: Head wear; Longitudinal bending stress; Finite element method; Rail-wheel contact; Contact patch position; Stress state; Railway
Number of References cited: 20
Assessment of Tensile and Electrical Characteristics of Pultruded Glass Fiber Reinforced Polymer Rods with Carbon Nanotubes
Venkatesh M K, Sudhakar K G, and Kumar R K; India
Abstract: Tensile and electrical characteristics of glass fiber reinforced polymer rods, containing epoxy as resin and carbon nanotubes as filler material - the test material produced through pultrusion process - have been examined as influenced by the amount of filler material added to it. Tensile tests are carried out on test samples employing typical test facilities, revealed that the tensile strength of GFRP enhanced by 6% with an addition of 0.2% of CNT whereas 12% improvement in tensile strength is possible with 0.4% CNT addition to GFRP. Further electrical resistivity is found to decrease by 36% and 57% with 0.2% and 0.4% CNT additions to GFRP respectively. Pultruded GFRP rods with carbon nanotubes as a filler material can be a viable alternative to conventional ACSR materials to achieve techno economic benefits with respect to their maintenance aspects in the long run..
Keywords: Polymer composites, glass fiber, epoxy, tensile test, CNT
Number of References cited: 16
Bio-fuel crop: Jatropha plantation in Oman
Ahmed Al-Busaidi and Mushtaque Ahmed; Oman
Abstract: A preliminary study was done to evaluate the ability of Jatropha plant to grow and survive under saline irrigation (3 & 6 dS/m) and heat stresses conditions. The study was done under three different metrological conditions: in a glasshouse with controlled temperature, in a shade house and in an open area. The results showed that glasshouse plants were the best even if the plants were irrigated by saline water up to 6 dS/m. Whereas the worst growth was found in the open field where the temperature was very high (average = 40 oC) and salts were accumulated in the soil surface. It was difficult for the young Jatropha plants to grow under heat and salinity stress conditions. However, the plants showed some strength and they did not die completely. It was concluded that Jatropha plant can grow well under saline and drought stress conditions but the plant should be transplanted when the average temperature is around 30 oC. The best plants from this study were transplanted in plots. They are growing very well and producing seeds that can be used for bio-fuel production.
Keywords: Glasshouse, Shade house, Open area, Saline irrigation, Heat stress.
Number of References cited: 17
Making bio-fuel from used cooking oil for generation of electricity
Shubber E.K, Waffa Al-Hosini, Assma Al Bahri, Majda Al Ismail y and N.S. Biju kumar; Oman
Abstract: It is common that used vegetable oil ends up at landfills or gets poured down the drain. It is widely reported that used cooking oil can be recycled into bio-fuel. This study attempts to work on conversion of used cooking oil collected from households and local restaurants. Collected used cooking oil was filtered and heated at 100 °C for 60 minutes to remove the water content before chemical treatments. The conversion of dried used cooking oil into bio fuel is achieved by alkali catalyzed (Methanol+ NaOH) chemical reaction known as a transesterification, American Standard Tests Methods (ASTM 6751). The product was then treated chemically and separated completely from the by product, glycerol. From the results it was clear that the products bio-fuel was within the recommended standard of bio-fuel/ petro-fuel. A small generator of a capacity [Fireman SPG950], 900 watts/hour, process used for generation of electricity. Petro-fuel mixed with 2% lubricated oil was used to test the potency for electric generation. For bio-fuel samples test for generation of electricity: prepared bio-fuel samples were mixed with petro-fuel in ratios of 10%, 20%, and 30% (V/V) in a total volume of 2 liters for generation of a fixed 580 watts/hr light for 90 minutes. Current and voltage (amperes), fuel combustion quantity, and CO2 emission were measured. A stable power was achieved during these tests. Bio-fuel was blended with petro fuel at a ratio of 10, 20, and 30%. Significant reduction in fuel consumption (14.7%) and level of emitted CO2 (27.9%) were observed using bio-petro-fuel mixture. Similar results were achieved using previously prepared bio-fuels using the same procedure and stored under laboratory conditions as an indication of bio-fuel shelf life. These results are considered as the key for recycling of used cooking oil into clean renewable source of energy and for protection of the environment.
Keywords: Bio-fuel, Cooking oil, Generation of electricity
Number of References cited: 45
Energy Conserved Fault Tolerance Relay nodes in Wireless Networks
D.Satish kumar & N.Nagarajan; India
Abstract: The rapid development of wireless communications has permitted to improve low-cost, low-energy sensor nodes, each accomplished of sensing, processing, and communicating with neighbouring nodes by means of wireless links. A dual tired network model are planned to be proposed for relay placement problem. Energy-alert and Fault tolerance are two important design goals of large scale wireless sensor network. Dual tired network model formulate a constrained multi-inconsistent linear programming to determine the location of the sensor nodes and data transmission pattern. Initial tier, a linear network finds optimal placement strategies algebraically using Consistent Assignment (CA) scheme. Through algebraic results, the optimal node placement strategies provide a significant benefit to minimize the energy alert total cost. In dual tired network model, second tier develops a Level Self-sufficient (LS) scheme to create a solution for fault tolerance mechanism. It also analysis the fake information sources that acted as storage nodes during the failure of links to minimize the delay time. The two objectives studied in the paper are to minimize the energy consumption total cost and to develop fault tolerant mechanism. A finite number of sensor or aggregation nodes in a region with certain coverage requirement are provided to perform the experimental evaluation. Various statistical parameters computed are compared with the existing Mobile Multi-hop Relay (MMR) networks to obtain better results with 8.166 % minimized energy consumption in terms of cost, effective fault tolerant and minimal delay occurrence during network re-entry.
Keywords: Wireless Network, Two-tier Network model, Energy alert, Fault tolerance, Level Self sufficient scheme
Number of References cited: 26
Application Of Renewable Energy In Health Care Industries In Sultanate Of Oman
Ali Alawi, M. Ramaswamy, Holger Gutgesell and Farooq Al Jahwari; Oman
Abstract: In Sultanate of Oman, Ministry of Health, (MOH) which is responsible for providing comprehensive health services to the people of Oman, has achieved substantial progress during the last three decades. All hospitals are equipped with latest available technology in the world. A typical hospital consists of many-sophisticated equipment ranging from syringe pumps to CT scan. Hospital needs strict indoor environment and falls in the high-energy consumption industry category. It is a known fact that buildings are responsible for around a third of energy consumption and all hospitals in Oman use conventional energy. A hospital of approximately 250-bed capacity needs 3000 to 3500 KW of electrical load in addition to the fuels used for boilers and medical waste treatment plants. Energy consumption for a typical hospital in Oman accounts for 10% of the running budget of the hospital. Therefore there is great potential to use renewable energy in health care industries at Oman. In this paper feasibility study to use renewable energy in health care industries is discussed in detail with few case studies and conclusions based on the studies are reported. Methodology to implement the proposal, subject of the availability of funds, is summarized. Conclusions based on the study are listed in this paper.
Keywords: MOH, Renewable and Non Renewable Energy, Environment, Green House Gases, Medical equipment, solar energy, Medical waste treatment, Solar cooling.
Number of References cited: 32
Volume 19, Number 3, July 2016
Special Issue on Improving Reliability of Industrial Processes through Innovative Technologies
Modern envelope analysis for bearing diagnostics
Robert Randall; Australia
Abstract: Envelope analysis, sometimes known as the “high frequency resonance technique” (HFRT) is by far the most successful method for rolling element bearing diagnostics. It was first developed in the 1970s, using analogue processing to extract the envelope and frequency analyse it. The most efficient way of obtaining the (squared) envelope of an optimally band-pass filtered signal now uses the so-called “Hilbert” process, by inverse transforming a reduced bandwidth 1-sided frequency spectrum. The benefits include the fact that the bandpass filtration is by an ideal filter, able to exclude large discrete frequency components immediately adjacent to the filtered band, and that the signal is automatically down-sampled, without aliasing, to a rate corresponding to the range of the modulating frequencies, and that the squared envelope is superior to the envelope. Moreover, the “Hilbert” envelope hugs the signal optimally, without the requirement to decide on a time constant for the RC smoothing, which limits the rate of decay of the envelope. The paper compares the Hilbert technique with some new alternatives, including the proprietary “PeakVue” method, and the Teager Kaiser Energy Operator (TKEO), which is shown to be simply the squared envelope of the derivative of a time signal.
Keywords: Bearing diagnostics; envelope analysis; Hilbert method; PeakVue method; Teager Kaiser Energy Operator (TKEO).
Number of References cited: 10
Fault detection and diagnosis of gear transmission systems with sensorless variable speed drives
Samieh Abusaad, Fengshou Gu, Riliang Zhang, Ahamed Benghozzi and Andrew D. Ball; UK & PRC
Abstract: Observer based approaches are commonly embedded in sensorless variable speed drives for the purpose of speed control. It estimates system variables to produce errors or residual signals in conjunction with corresponding measurements. The residual signals then are relied to tune control parameters to maintain operational performance even if there are considerable disturbances such as noises and component faults. Obviously, this control strategy outcomes robust control performances. However, it may produce adverse consequences to the system when faults progress to high severity. To prevent the occurrences of such consequences, this research proposes the utilisation of residual signals as detection features to raise alerts for incipient faults on mechanical systems. Based on a gear transmission system with a sensorless variable speed drive (VSD), observers for speed, flux and torque are developed for examining their residuals under two mechanical faults: tooth breakage with different degrees of severities and lubricant shortage at different levels are investigated. It shows that power residual signals can be based on to indicate different faults, showing that the observer based approaches are effective for monitoring VSD based mechanical systems. Moreover, it also shows that these two types fault can be separated based on the dynamic components in the voltage signals.
Keywords: Gearbox, Observer based fault detection, Lubricant quality, Motor electrical signature analysis, Sensorless VSD.
Number of References cited: 22
Assessment of the data quality of wayside wheel profile measurements
Matthias Asplund, Jing Lin and Matti Rantatalo; Sweden
Abstract: To evaluate the behaviour and the condition of a railway wheel in relation to performance and safety criteria, the wheel profile can be measured. This can be achieved using manual methods or automatic systems mounted along the railway track. Such systems have the advantage that they can measure a vast number of profiles, enabling new possibilities of performing statistical analyses of the results and pinpointing bad wheels at an early stage. These wayside measurement systems are, however, subjected to different conditions that can affect the data quality of the measurement. If one is to be able to use automatic wheel profile measurements, the data quality has to be controlled in order to facilitate maintenance decisions. This paper proposes a method for the data quality assessment of an automatic wayside condition monitoring system measuring railway rolling stock wheels. The purpose of the assessment method proposed in this paper is to validate individual wheel profile measurements to ensure the accuracy of the wheel profile measurement data and hence the following data analysis. The method consists of a check routine based on the paired t-test, which uses a hypothesis test to verify if the null hypotheses are true. The check routine compares measurements of passing wheels rolling to a certain destination with measurements of the same wheels returning from that destination. The cause-and-effect diagram is used to identify the error sources where the difference between the two measurement units is significant. The routine of comparing measurements of the same wheel, which is performed by four sensors (one on each side of each rail), will ensure that the sensors generate the same data for the same sample. The case study presented shows how the method can detect a faulty setup of the measurement system and prevent incorrect interpretations of the data from different measurement units in the same system. The paper ends with a discussion and conclusions concerning the improvements that are presented.
Keywords: Data quality; Railway; Condition monitoring; Wheel profile measurement system; Paired T-test
Number of References cited: 27
Towards comprehensive value management in inter-organizational industrial maintenance
Salla Marttonen-Arolaa, Maaren Ali-Marttila, Antti Ylä-Kujala, Minna Saunila, Sanna Pekkola, Tiina Sinkkonen, Timo Kärria, Olli Pekkarinen, Tero Rantala, and Juhani Ukko; Finland
Abstract: Business environments have changed during the last decades, posing new kind of challenges and yet offering new possibilities for industrial maintenance and asset management. As a result there are novel decision-making needs in both strategic and operational maintenance management, calling for identifying, modelling and managing the value of maintenance in inter-organizational business contexts. This paper contributes to exploiting the value potential of maintenance by describing a range of maintenance management tools constructed in collaboration with case networks from mining and energy industries. The paper results in a framework for managing the value of maintenance. The framework can be applied in comprehensive decision making in maintenance management ranging from operational to strategic issues in modern inter-organizational contexts. The created tools are aligned with an exemplary sample of existing maintenance decision-making tools, the perspective of which is often more technical. Previous research has mostly discussed individual management tools used by single companies. In this paper we argue that due to its business context and multidisciplinary nature, industrial maintenance and asset management would benefit from integrating the use of different management tools in various decision-making situations and developing maintenance management together with other companies in the business network, e.g. service providers and original equipment manufacturers.
Keywords: Maintenance management, Value, Decision-making tools, Maintenance services, Framework, Strategic maintenance, Operational maintenance, Business network.
Number of References cited: 22
Implementation of Non-Destructive Techniques for the Monitoring of Rebar Corrosion of Concretes Developed for Nuclear Applications
Damián Vazquez and Gustavo Duffó; Argentina
Abstract: There are many mechanisms associated to the degradation of reinforced concrete and, among them; the corrosion of the reinforcing bars is the most frequently degradation mechanism found. It is worth mentioning that the annual worldwide cost of maintaining and repairing of reinforced concrete structures is approximately eight thousand million dollars. So, the monitoring of the corrosion state of a reinforcing concrete structure is mandatory for economical (among others) reasons.
In the present work, the rebar corrosion was studied by mean of different parameters such as: corrosion potential, corrosion rate, electrical resistivity, oxygen availability and temperature of the concrete and environment. The measurements were carried out by non-destructive electrochemical techniques, implemented with corrosion sensors embedded in the concrete. The sensor design involves an appropriate electrodes system. Besides, some of these parameters were measured directly from the structure by mean of a commercial instrument, which allows the confinement of the electrochemical signals in a selected zone. Two different reinforced concretes, designed for nuclear applications and whose durability must be higher than three hundred years, where compared from the rebar corrosion point of view. The work was carried out on prototypes, but focuses in the implementation of these techniques in real structures.
Keywords: Reinforced concrete corrosion; durability of reinforced concrete; nuclear materials.
Number of References cited: 10
Special measurements in Atucha II nuclear power plant
Federico Elfi, Andrés Bello, and Pablo Tabla; Argentina
Abstract: During the commissioning of Nuclear Power Plant Atucha II, a number of tests are required with the objective of demonstrating the reliability and safety of equipment and facilities. Throughout those tests, a series of measurements were taken in order to determine the stress states of different components of the primary and secondary systems, with the objective of verifying the calculation models used during the design stage. In this work we present, in particular, results of the strain measurements in pipes of the primary system connected to the steam generator during ramps of temperature and pressure. We describe the instrumentation used, the details of the measurement point, the acquisition system, and the entire process applied to the signals, including filters and corrections. Finally, we discuss some of the results obtained. With those results, the calculation models were verified correctly.
Keywords: Special measurements, Commissioning, Nuclear Power Plant, Strain measurements.
Number of References cited: 5
Structured light laser scanning. Application to the inspection of railway components
Rodrigo Romero Rosero, Guillermo Cosarinsky, and M. Fernanda Ruiz Gale; Argentina
Abstract: A laser scanner device is used to obtain a 3D digital representation of an object. The method uses a laser with a refractive element in order to generate a laser light plane. The intersection of the light plane with the object delineates a cross section of it; the image of that curve is acquired by a digital camera, stored and processed by a program developed by the authors. The displacement of the light plane with respect to the object allows obtaining several cross sections of its surface which are combined to produce the 3D representation.
The laser scanning system uses two sensors to record parts that would remain otherwise hidden when using a single sensor. Calibration of the sensors is described for a single frame of reference, as well as the algorithms to correct for geometric distortion and obtain the laser line representing the profile of the object studied. This paper presents an experimental system of inspection of geometrical defects to assess the main components involved in the running of trains: rails and wheels. This system may be suitable for operation either in the workshop or on the railways.
Keywords: Laser Scanning; 3D representation; geometrical defects; railway components.
Number of References cited: 10
Designing optimal parameter combination for abrasive water jet cutting process
R.M. Chandima Ratnayakea and Felix Santhiapillaia; Norway
Abstract: Machining parameter design is vital for old and/or new machine tools in small- and medium-scale manufacturing firms as they operate under tight profit margins. The concept of ‘parameter design’ and related computations proposed in the engineering robust design (ERD) approach enables the design of parameter combinations under the noise. It is vital to investigate the optimal machining parameter combination, especially when the existing machinery becomes mature or when machining a metal, whose machining parameters are unknown. This manuscript proposes a mathematical framework, which it is possible to utilize for the investigation of the optimal combination of parameters in metalworking or engineering processes. A case study has been performed to investigate the optimal parameter combination of the abrasive water jet cutting (AWJC) process. Experimentation has been performed to establish the initial machining parameters and their levels, with the expert knowledge of machinists. The optimal parameter combination is identified using experiments and subsequent computations. Using the additive model proposed in the ERD approach, the theoretical value of target output performance under the optimal parameter combination is calculated. A verification experiment has been performed to verify the optimal parameter combination.
Keywords: Time-frequency analysis, Failure diagnosis, Diagnostics in rotating machinery, Vibration analysis.
Number of References cited: 21
Fault detection of parallel hydraulic pumps in non-stationary operation
Alexander Rose, Dustin Helm, and Markus Timusk; Canada
Abstract: There is a current demand to advance condition monitoring research for non-stationary systems since a significant proportion of industrial equipment are required to function under variable speeds and loads. This work investigates a fault detection technique for such equipment. The approach presented here compares the dynamic pressure and vibration signals of two identical gear pumps subjected to synchronized duty cycles. The premise of the proposed technique is that a developing fault will cause a change in the calculated residual between signal features from both pumps while in stationary and non-stationary operation. Pump thrust plates at several progressions of deterioration were interchanged within a pump and were examined under various duty cycles. This paper evaluates the proposed fault detection methodology and the results of this approach are discussed with respect to the advantages and drawbacks over conventional systems. This study validates that this technique provides sufficient information to detect faults in parallel hydraulic pumps under non-stationary operation
Keywords: Condition monitoring, fault detection, hydraulic pump, gear pump, non-stationary operation, parallel system
Number of References cited: 9
Condition monitoring of rolling-element bearings in parallel operating belt drive systems
Dustin M. Helm, Alexander M. Rose, and Markus Timusk; Canada
Abstract: Condition monitoring of non-stationary machines is an important area of research as current techniques often have difficulty detecting faults with a high degree of accuracy when subject to changing speed and loading conditions. This work will present a method for condition monitoring of parallel machinery (a class of machinery with two or more identical subsystems that simultaneously experience identical duty cycles) operating under non-stationary conditions (variable speed and load). The purposed method aims to detect faults in the machinery by comparing the vibration signals from either subsystem and then classifying them as either faulted or healthy based on signal residuals. Tests were performed on rolling-element bearings mounted in idler pulleys in two identical belt drive systems operating on the same duty cycle and the faults detected include outer race, inner race and rolling-element faults of varying degrees of severity. Preliminary results show that this is a promising approach for applications where it was previously difficult to use standard fault detection methods due to their sensitivity to speed and loading conditions.
Keywords: Condition monitoring, fault detection, parallel system, rolling-element bearing
Number of References cited: 4
Volume 19, Number 4, October 2016
Special Issue on Condition Monitoring and Machinery Failure Prevention Technologies, from sensors through diagnostics and prognostics to maintenance
High-accuracy diagnostics from HUMS in noisy environments
Rodrigo E. Teixeira, Kari E. Morris, F. Christian Sautter, Daniel S. Sillivant; USA
Abstract: Condition Based Maintenance (CBM) of military helicopters are tracked by Condition Indicators (CI) calculated from Health Usage and Monitoring Systems (HUMS) vibration sensors. Many CIs have been developed and implemented, yet success has been partial at best, owing to their sensitivity to noises and artifacts that invariably corrupt measurements under real-life operations. Here we report a sequential Monte Carlo algorithm operating a stochastic non-linear model that includes a description of fault evolution. This algorithm estimates fault magnitudes and probabilities, which were compared to component removals validated by tear down analyses. We obtained a high accuracy rate (~95%) over all available data. Data encompassed a 6-year operational history of an entire US military helicopter fleet. These results demonstrate the excellent artifact rejection enabled by this approach, which handles probabilities rigorously to detect fault processes from noise-limited signals. Consequently, our decision support tool could detect faults early and accurately. This technology could drive a significant reduction in maintenance costs by making faults evident and reducing NEOFs (false positives).
Keywords: Diagnostics; Health Usage and Monitoring Systems (HUMS); Condition Based Maintenance
Number of References cited: 2
Pattern tracking for predicting unscheduled maintenance actions of military vehicles
James D. Kozlowski; USA
Abstract: As part of an effort to analyse available sensor data collected on military vehicles, such as the Heavy Equipment Transporters (HET), some tasking was dedicated to establishing if a prediction of the next unscheduled maintenance action of a vehicle could be estimated based on the available sensor data of that vehicle and other vehicles in the fleet. The approach essentially mapped multiple channels of the sensor data into a subspace that produced more distinct characteristics to the changing behaviour of the vehicle. The subspace data was compared to data from other vehicles that have been mapped to this same subspace. When two vehicles had a series of consecutive similar subspace mappings, the two vehicles were considered to be experiencing similar activity or potentially similar degradation of the physical health of the vehicles. This chain of consecutive subspace similarities triggered a maintenance log scan for each of the vehicles to determine the last maintenance actions. The vehicle that had the most recent maintenance action from the consecutive subspace trend was considered the impending event for the second vehicle. Next, the amount of engine load time was estimated from the first vehicle and established as the likely available engine load time of the second vehicle until the same maintenance action was required. To help prevent false positives, some filtering of the maintenance logs was required to exclude those records not likely to be associated with the collected sensor data. Overall, within the available sensor data provided there were not a large number of same maintenance actions (associated with the sensor data) across multiple vehicles. However, despite the limited data sets some trending was identified and represents anecdotal evidence that this approach to estimating the next potential maintenance action of a vehicle has promise for improving fleet logistics and maintenance.
Keywords: Prognostics; Health management; Data-driven processing; Military vehicle monitoring; Classifier-based mapping; Limited data set processing; Multi-vehicle data sharing
Number of References cited: 2
Proactive shop strategy for a successful turbine-generator rotor outage
Zlatan Racica, Marin Racic; USA
Abstract: Standard power generation industry practices of inspection, machining, balancing, assembly and alignment have been developed by OEMs for newly manufactured rotors, and implicitly assume that rotors are within ideal dimensional specifications. However, applying these standard practices in the service industry can fall short for rotors with eccentricities outside such specifications, and by design do not catch the errors that cause true dynamic problems, because they are assumed not to exist, or their effects are unrecognized by traditional industry practice with regard to real rotordynamic behavior. This misunderstanding leads to costly problems, like reinstalling a “balanced” rotor from the shop only to experience high vibrations upon installation, often followed by days or weeks of lost production while field balancing in an effort to salvage the situation. A “successful” start up following a planned outage means that there will be no need for field balancing following the restart of the unit. Since most causes of dynamic problems on turbine-generator rotors are present (in the form of rotor and coupling eccentricities) even prior to starting the unit, almost any such problem can also be identified and fully prevented during the outage if only a few key, improved steps of measurement and analysis and the proper balancing method are included into an outage scope. Specifically, this must include collection and evaluation of total indicator runout (TIR) readings to identify any coupling defects and any excessive rotor bow or distributed eccentricity, and utilization of a new balancing method (using 2N+1) planes if the rotor body exceeds runout limits of ~0.002" eccentricity.
Keywords: Balancing; eccentricity; outage; rotordynamics; runout; TIR; turbine-generator; 2N+1 balancing method.
Number of References cited: 8
Bearing Diagnostics Waveguide for Gas Turbine Engines
Richard Roth, Ryan Matthews, Erik Henderson and Oleg Lobkis; USA
Abstract: Failure in turbine engine main shaft bearings is one of the major causes of catastrophic failures. The traditional approach for determining bearing faults, measuring acceleration on the case of the engine, is unreliable due to the complex and changing transfer path from the bearing to the housing as well as the large number of masking noise sources within the engine. Etegent has developed a new waveguide-based vibration sensor which is able to directly measure the bearing vibration signature, bypassing the complex transfer path and masking vibration seen in traditional techniques. The sensor operates by transmitting the bearing vibration energy from the bearing housing to a location external to the engine, where the sensing element can be easily serviced and can utilize traditional piezoelectric materials with higher sensitivity than specialty high temperature piezoelectric materials. Etegent has successfully shown the utility of this sensor in a number of engine tests to date. The sensor has shown improved performance over case mounted accelerometers in both 250 SHP and 5000 SHP class engines with seeded defects on the thrust bearings.This paper presents the preparations and test setup for an upcoming test on a 5000 SHP turbine engine instrumented with waveguide vibration sensors at each of the 4 main engine bearings as well as case mounted accelerometers and an oil debris monitoring system.
Keywords: Diagnostics; prognostics; health management; gas turbine; bearings; turbine
Number of References cited: 5
Detection of spiral bevel gear damage modes using oil debris particle distributions
Paula J. Dempsey and Robert F. Handschuh; USA
Abstract: Damage progression tests were performed in the NASA Glenn Spiral Bevel Gear Fatigue Rig. During testing, debris generated were measured with an inductance type oil debris sensor, while different classes, modes and degrees of damage occurred on the gear teeth. Debris particle counts, their approximate size and mass were measured by the oil debris sensor. Tooth damage was documented with photographs at the start of the test, when damage occurred on one gear or pinion tooth and when damage transferred to two or more teeth. American Gear Manufacturers Association (AGMA) and American Society for Testing (ASTM) standards were used to describe gear tooth damage. Discrete thresholds based on counts and mass were defined for three gear set states: Healthy, Inspect and Damage. Histograms of particle size distributions were plotted for eight tests at the three gear states. Methods to predict particle size based on gear design and operating conditions were also presented. Results found monitoring oil debris mass provided a good indication of damage progression for slow progressing fatigue failures, while monitoring counts alone did not provide a good indication. The oil debris sensor could not be used to detect scuffing failure modes. Scuffing transfers material between the meshing gears and is less likely to generate debris. If historical data is unavailable, gear geometry and operational conditions could be used to estimate a threshold on mass and average particle size for indicating a contact fatigue damage state.
Keywords: Diagnostics; health management; spiral bevel gears; oil debris, failure modes
Number of References cited: 15
Development of an Advanced Gas Emissions Monitoring System
For Oil and Gas Production Sites
Sara Saleem Al Bulushi & Ahmed Onsy; UK
Abstract: The oil and gas industry involves an extensive variety of operations and supplies, and is a major source of gas emissions. Gases emitted from oil and natural gas extraction operations may be extremely toxic, and include Carbon Dioxide (CO2), Methane (CH4), Propane (C3H8), Hydrogen Sulphide (H2S), Hydrogen (H2) and Ethyl Alcohol (C2H5OH). The proliferation of these gases in air creates an unsatisfactory and risky working environment for crew at rig sites, and prolonged exposure may lead to serious long-term health problems. Therefore environmental condition monitoring systems in engineering plants have increased in significance because they provide a primary safeguard by employing condition-monitoring algorithms to monitor gas emissions. This paper discusses gas emissions during oil extraction operations, where gas emissions begin at the early stages of the exploration phase and continue during the development and oil production phases. The paper also describes the development of a low-cost advanced gas emissions monitoring system (GEMS) capable of monitoring hazardous gases at oil and gas production sites, including the measurement of H2S, CH4, C3H8, CO2, C2H5OH and H2. The system output utilizes Wi-Fi, GPRS and GSM data transmission to provide information to control rooms and other monitoring sites using the Cloud space concept. The validation of the advanced GEMS has been conducted in the laboratory by testing its capability to monitor gases similar to those found at oil and gas production sites.
Keywords: Oil and Gas Monitoring System; Gas Emissions Monitoring System; Cloud space concept; Environmental Monitoring; Health and Safety
Number of References cited: 20
Toxic metal reduction and life extension of gun barrel liners through cold sprayed refractory metals
Blake Barnett, Matthew Trexler, Victor Champagne and Marc Pepi; USA
Abstract: Modern gun barrel technology faces a number of challenges related to the use of chromium-plated steel on the interior bore surface. The amount of allowable chromium has been significantly reduced due to environmental, health, and safety concerns. Furthermore, improved munitions and propellants lead to erosion and condemnation of gun barrels well before their 10,000 round expected lifetime. This has precipitated a search for longer-lasting bore liners, such as refractory metals deposited by explosive bonding. The cost and difficulty associated with shaping these materials have made them impractical choices to date. However, Gas Dynamic Cold Spray consolidation of refractory metals and alloys was selected as an alternative to extrusion for additive manufacture of donor tubes. Tantalum and tantalum-tungsten alloy donor tubes have been produced by Cold Spray and tested for wear resistance and compatibility with the cladding process. A 1-meter (3-foot) long tube was produced to test scalability.
Keywords: Chrome replacement, Supersonic particle deposition, Gun barrel performances.
Number of References cited: 15
Volume 20, Issue 1, January 2017
Multi-class Fault Diagnosis in Gears Using Machine Learning Algorithms Based on Time Domain Data
- Tiwaria, D J Bordoloi , S Bansal and S Sahu; India
Abstract: The support vector machine, as a powerful machine learning algorithm, is recognized to have good generalization ability in its application to multiclass machinefault classification problems. In this paper, an application of the SVM in the multiclass gearfault diagnosis has been performed based on the gear vibration data in time domain. From time domain data the statistical features are extracted and fed to the SVM for the training/testing. When the training and testing data are at the same running speed, it is found that the SVM classifier has excellent multiclass classification accuracy. Though, this approach relies on the availability of both the training and testing data at that particular speed of the machine operation; it is expected that features of time domain data would change with operating speeds. Moreover, the training data may not always be available continuously at all operating speeds of gears, especially for variabledrive systems. Thus, a novel technique of interpolation/extrapolation has been proposed in the present work that helps the SVM classifier to carryout multiclass gearfault diagnosis with appreciable accuracy even in the absence of the training data at a given running speed. It also investigates the speed bandwidth of the training data for which interpolation/extrapolation predictions are reasonably good. The similar analysis is also extended to artificial neural networks (ANN) as the classifier and predictions are noted, and compared with the SVM.
Keywords: Vibration signature; Support vector machines; Gear faults; Fault diagnostics.
Number of References cited: 21
Case-Based Reasoning (CBR) in Condition Monitoring & Diagnostic Engineering Management (COMADEM): A Literature Survey
B.K.N. Rao; UK
Abstract: It is the universal truth that experience is the best teacher. All civilizations have evolved by learning from past experiences of many previous generations from different cultural backgrounds. The primary sources of these past experiences are to be found in many historical, mythological, literary, cultural and spiritual documents. Past experiences still remain the primary source of reference from which the new knowledge/wisdom is generated, discovered, disseminated & from which civilized societies are constantly evolving. It is a basic human survival instinct to learn from the past to resolve day-to-day socio-economic problems and to continuously improve the quality of life. It is embedded in our genes. As a scientific quest, Case-Based Reasoning (CBR) was introduced as a powerful diagnostic and prognostic pro-active management strategy in its own right. Its philosophy is that all reasoning is based on past cases personally experienced. As a scientific endeavour CBR is based on the hypothesis that similar problems have similar solutions & new problems can be solved by revisiting or adapting solutions of past problems. If used judiciously, it can be a powerful method for computer reasoning and for better decision making. There are several potential advantages of fully exploring & exploiting CBR in the proactive and holistic discipline of Condition Monitoring and Diagnostic Engineering Management (COMADEM). This paper reviews this aspect through a brief literature survey.
Keywords: case-based reasoning, artificial intelligence, condition monitoring, diagnostic engineering, proactive management
Number of references cited: 53
Condition-based Maintenance Effectiveness from Material Efficiency Perspective
Ali Rastegari, Sasha Shahbazi and Marcus Bengtsson; Sweden
Abstract: This paper addresses the controversial gap between the environmental perspective and the cost perspective in a manufacturing context. The results of an empirical study on the heat treatment and phosphating processes performed by a manufacturing company indicate that implementing condition-based maintenance contributes not only to cost savings by preventing production losses and reducing equipment downtime but also to a more efficient use of resources by avoiding the generation of scraps and material wastage.
Keywords: Condition-based maintenance, Material efficiency, Manufacturing.
Number of references cited: 16
Prediction of Gear Tooth Crack Propagation Path Based on Pseudo Evolutionary Structural Optimization
Birahima GUEYE, Yimin SHAO, Zaigang CHEN; PRC
Abstract: In an attempt to reduce the computational requirements on gear crack path prediction an efficient alternative method based on pseudo evolutionary structural optimization (ESO) is proposed in this paper. The novel method is self-evolutionary and does not require prior estimation of stress intensity factors neither initial crack location. During the evolutionary process, instead of removing materials with minimum stress in the design domain as in ESO, elements with maximum tensile stress are progressively eliminated and consequently a crack path is defined. The two-dimensional static analysis involves four finite element models of three successive teeth of a gear section with different backup ratios. The results have shown that the proposed method successfully predicts crack growth direction, which is into the gear rim for backup ratio less than unity or through the tooth foot for back up ratio equal to or greater than unity. The simulated results agree remarkably well with solutions, experimentally and analytically, proposed by previous rigorous procedures.
Keywords: Crack Path Prediction, Tensile Stress, Pseudo Evolutionary Structural Optimization, Finite Element Analysis.
Number of references cited: 26
Condition Monitoring and Diagnosis of Modern Dynamic Complex Systems using Criticality aspect of Key Performance Indicators
Aditya Parida; Sweden
Abstract: -Proactive condition monitoring, diagnosis and prognosis of modern complex engineering systems are becoming an increasingly challenging issue. This is mainly attributed to the dynamic global scenario and the ever increasing stakeholders conflicting interests. One of the most important missing links that is often given a low priority while assessing the health of a complex dynamic system is the key criticality of the system in question. This paper discusses some of the challenging issues facing the Asset Management personnel and highlights the importance of incorporating criticality aspect of the key performance indicator in the diagnosis and prognosis of all modern complex systems.
Keywords: Asset Management; Condition Monitoting, Key Performance Indicators, diagnosis, prognosis
Number of references cited: 14
Orbital TIG Welding and Evaluating Methods of Propulsion Feed Lines for Satellites
Karthikeyan M,, Naikan V.N.A., and Narayan R; India
Abstract: Propulsion system meant for Remote Sensing and Communication applications in satellites have built in them propulsion systems for reaction control, attitude control, orbit raising and station keeping purposes. These propulsion systems have propellant feed lines carrying propellants from tankages to thrusters. Orbital Tungsten Inert Gas (OTIG) welding is widely employed for the welding of the feed lines made up of 6mm and 10mm diameter stainless steel tubes of 0.7mm thickness. These welds need to be leak proof and strong and any defect in them will lead to propellant leakage resulting in the failure of the whole mission which means wastage of lot of efforts and Millions of dollars. Such failures seriously offset the programmatic goals and the nation’s need for remote sensing and transponders for communication. To ensure perfect weld joints, systematic process optimization and rigorous testing and qualification are essential. This paper outlines the criticalities of these weld joints and focuses on the various testing methods such as Visual inspection, Dye penetrant test, Hydrostatic tests, Helium mass spectrometer leak detection test, Pressure hold or Condition Monitoring test, X-ray Radiographic tests in addition to destructive tests such as tensile test and bend tests for this particular application of OTIG welding for satellite propulsion systems.
Keywords: OTIG welding, Propellant feed lines, Visual inspection, Tensile test, MSLD, Leak test.
Number of references cited: 22
Volume 20, Issue 2, April 2017
Harmonic and Inter-harmonic Analysis on Power Signal from Railway Traction Systems
Fuqing Yuan and Diego Galar: Norway & Sweden
Abstract: The railway traction system is a non-linear system including a large number of electrical facilities. Analyzing the signal emitted from the system can facilitate the failure diagnosis and evaluate the power supply system’s performance. The power supply system’s electric signal contains a wide range of unintended harmonics and inter-harmonics, which degrades the system’s performance. This paper develops methods to identify the harmonic and inter-harmonic components hiding in the power signal by considering it as a regression problem. It derives explicit expressions to represent the signals collected in the field. That expression can be used for further failure diagnosis. Simulations are proposed to investigate the significance of transmitting line’s mutual interference and use of autotransformers to the performance of the traction power system. .
Keywords: Railway traction system; frequency domain; harmonics; inter-harmonics; simulation.
Number of References cited: 16
Effect of wave velocity in two-dimensional AE damage location on a steel plate
Md. Tawhidul Isalam Khan, Md. Mehedi Hassan & R. Takata; Japan
Abstract: Effects of wave velocity in AE source location of 2D algorithm is presented in the present paper with the experimental validations on a steel plate (SS400). Source location is successfully performed in a wider sensor distances with less than 2% calculation errors. However, the source location algorithm reflects the results with significantly increased calculation errors due to the near field effects of sensor positions as well as the AE wave reflections to the end surface of the steel plate. Therefore, further challenges are necessary to solve the depicted problems in AE source location techniques
Keywords: Acoustic emission; wave velocity; steel plate; source location algorithm
Number of References cited: 9
Flexible Simulator for the Vibration Analysis of Rolling Element Bearings
Jarno Kansanahoa, Kari Saarinen and Tommi Kärkkäinen; Finland
Abstract: The detection of incipient faults as early as possible has great economic value in the monitoring of the rolling element bearings in industrial applications. In the early stage, a local fault in the bearing element produces a series of weak impacts at a rate dependent on the bearing geometry. These impacts in turn excite a special type of vibration that is, in principle, possible to detect using various condition monitoring methods. However, the analysis of vibration measurements taken from a real industrial environment can be challenging because measurements are noisy and periodic phenomena from other external, known and unknown sources may overlap the known behavior of interest, for example, in the spectral representation.
In this paper, we present a flexible simulator for advancing early bearing fault detection. In the simulator, the vibration signals are generated by parametric models of the impulse responses for different vibrating components, with adjustable noise and jitter effects included. The possibility to adjust models and parameters during the simulation allows a more realistic exploration of changes, for example, in different operating conditions. This includes the generation of non-stationary components into the vibration signals, which are not suitable per se for frequency domain methods. It is possible to load measured vibration signals to verify the simulation model.
The main purpose of the versatile simulation environment is to enable the rigorous testing of analysis tools consisting of digital filters, frequency domain methods (FFT, HFRT), time-frequency methods (STFT, WT) etc. In turn, improved knowledge on the behavior of analysis methods and approaches can be reflected back to the simulation when searching the limits of the early fault detection methods.
Keywords: Rolling element bearings, Early fault detection, Vibration measurements, Spectral analysis, Simulation model
Number of References cited: 21
Reliability Enhancement of Centrifugal Pumps by Genetic Algorithm Optimization
Mohammad Pourgol-Mohammad, Peymaan Makarachi, Morteza Soleimani and Alireza Ahmadi; Iran & Sweden
Abstract: In this research, a methodology is presented to optimize the life performance of mechanical systems using multiple objective evolutionary algorithm. Conflicting objectives are encountered (e.g. low costs and longer service life) here along with significant number of constraints (e.g. technological limitations, weight and volume). To solve the design optimization problems, the objective function is weighted with a combination of the targets. The evolutionary algorithm (i.e. GA) is applied for minimization of the system failure rates, reliability allocation optimization. The failure rates are optimally estimated for the system’s critical components. Reliability allocation technique is utilized to determine the optimum reliability of the constituent components with higher failure rates. The reliability targets are determined for the components through the minimized failure rates. The methodology is demonstrated through a case study, on a centrifugal pump. The pump design requires consideration of several targets and requirements with different weight factors for satisfaction (e.g., availability, capability, efficiency and weight) along the pump life. Analytical Hierarchy Process (AHP) is utilized to determine the weights of the objectives. As a result of this research, the equipment design is improved, costly over-designs options are prevented and development tests are optimized.
Keywords: Design for Reliability, Centrifugal Pumps, multi-objective, optimization, Genetic Algorithm (GA), Analytical Hierarchy Process (AHP)
Number of References cited: 27
Stochastic lifetime estimation of pressurized gas pipeline; Case study of the urban gas pipeline
Bahman Modiri, Mohammad Pourgol-Mohammad *, Mojtaba Yazdani, Hossein Salimi, Farzin Salehpour-Oskouei, and Alireza Ahmadi’ Iran & Sweden
Abstract: Corrosion is a major contributor in gas pipeline degradation and failure. Due to significant sources of uncertainties in corrosion progression modelling, non-deterministic approaches are more promising in recent researches. Several researches were conducted about probabilistic assessment of corrosion and its effects in practical models. However, in these studies, either internal or external corrosion individually were separately evaluated, without taking into account their correlated effects. In this study, a reliability analysis method is proposed for pressurized bare gas pipeline buried in soil by taking into account both corrosion effects from inside and the outside of the pipe. Environment effects are also studied on pipe’s corrosion by considering different soil types. It was observed that soil grain size has significant impact in corrosion occurrence. Consequently, sandy clay loam has the highest reliability index while clay and clay loam have the lowest values among these soil types.
Keywords: Pipeline lifetime, Reliability, Uniform corrosion, Pitting corrosion
Number of References cited: 33
Condition Indicators for Centrifugal Compressor – A Review
Xiaoxia Liang, Fang Duan, David Mba and Bennett Ian; UK & Netherlands
Abstract: Centrifugal compressors have been widely applied and acted as a crucial component in gas and oil industries, due to their excellent performance in providing high pressure ratios, large operating ranges with relatively high efficiencies etc. Breakdowns or deteriorated performance can bring significant economic loss to the companies. Given the importance and the crucial role played by these machines, monitoring their status and performing fault diagnosis have become increasingly important. This paper provides a systematical review of condition monitoring and fault diagnosis techniques for centrifugal compressor. Some unique fault types of centrifugal compressors are also investigated, like stall, surge, fouling and impeller fault, which are not usually seen on other rotating machinery. In terms of fault diagnosis, condition indicators which are calculated from multiple signals, can effectively reflect the health status of the machinery. This paper reviewed the common faults and the related state-of-the-art fault diagnostic techniques of a centrifugal compressor. Some condition indicators that are extracted from performance, vibration, acoustic emission and other measurements for centrifugal compressor incipient diagnosis are recommend. Furthermore, several currently used machinery fault diagnostic systems for the centrifugal compressor are investigated.
Keywords: Condition indicators, Centrifugal compressor, Condition based monitoring, Vibration monitoring technique, Performance monitoring technique.
Number of References cited: 87
Thermal Energy Harvesting In Wireless Temperature Sensor Nodes for
Badradin Elforjani, Guojin Feng, Fengshou Gu, and Andrew Ball; UK
Abstract: Monitoring the temperature is an effective mean to collect useful information about the healthy conditions of machines such as a gearbox. This paper presents a novel wireless temperature sensor node powered by a thermal harvester for monitoring the healthy status of gearboxes. A thermoelectric generator module (TEG) is optimised to harvest sufficient electrical power from the heat source of the gearbox undergoing such monitoring. The power generation from this novel method is obtained based on temperature gradients emanated by sandwiching the TEG between the two aluminium plates. One plate is exposed to the heat source and has the role of a heat collector, whereas the other plate, mounted with a low profile heat-sink, acts as a heat spreader. The harvested power is then used to drive a wireless temperature node for condition monitoring. This combination allows a true powerless and wireless system to be realised. To evaluate the system, an industrial gearbox is monitored by the designed temperature node. The node is fabricated using a TEG module; an LTC3108 DC-DC converter for boosting the voltage, a super-capacitor for energy storage and a CC2650 sensor tag for measuring the temperature of the gearbox. The temperature data which is transferred via a Bluetooth low energy module and then monitored using portable monitoring devices, such as a mobile phones. The results obtained show the system can provide a continuous monitoring of the gear temperature and give an online indication of gearbox conditions.
Keywords: energy harvesting; wireless sensor networks; condition monitoring; temperature; thermoelectric generator.
Number of References cited: 23
Vibration signal model for fault diagnosis of sun gear in epicyclical gearboxes
Lun Zhanga,b, Niaoqing Hua,b, Lei Hua, and Fengshou Gu; PRC & UK
Abstract: Signal models of machinery components are helpful to understand influence and character of various fault modes without conducting costly and time-consuming experiments; it also brings convenience to validate new fault diagnosis methods for scientist and engineers. Researchers have built models such as lumped parameter model and finite element model to study problem of interest. However, these models are time-consuming to simulate faults in epicyclical gearbox, some of them could not implant fault on specified gear tooth. In this paper, a simplified fault implantable signal model is established considering meshing regularity between given sun gear tooth and planet gear, as well as amplitude modulation effect caused by rotating of carrier. Theoretical derivations are validated through spectrum analysis of simulation signal, moreover, experimental data collected from fault-seeded and baseline experiments are analyzed to validate the model, computing time of new model and lumped parameter model are compared to show computational efficiency of the model. According to signal analysis and computing time comparison, the signal model proposed in this paper is effective and efficient.
Keywords: Signal Model, Epicyclical Gear, Sun Gear, Fault Diagnosis
Number of References cited: 16
Predicting Oil Film performance in a Journal Bearing based on Modulation
Signal Bispectrum analysis of Vibration Signals
Khaldoon F. Brethee, Ruiliang Zhang, Naima Hamad, Fengshou Gu &
Andrew Ball; PRC & UK
Abstract: This paper presents a study of the lubricant starvation of a journal bearing based on vibration signal analysis by modulation bispectrum. A vibration model is modified to includes conventional hydrodynamic effects, asperity churns and collisions excitations and shaft unbalance. It has been found by modulation signal bispectrum analysis of vibration responses from different levels of lubricant oil in the bearing reservoir shows that vibration characteristics are different in terms of frequency bands and magnitudes, which can be based on to differentiate between degrees of oil film thickness. The instable oil whirls can affect the measured vibration responses in the frequency range from 3.5kHz to 5.5kHz. This can be a good indication for detecting the instability of the rotor system supported by the bearing. Moreover, the structural resonances in the high frequency range of from 5.5kHz to 11kHz can better reflect the effect of the excitations and result in a more agreeable separation of different levels under wide operating conditions.
Keywords: Journal bearing, vibration, oil leakage, modulation signal bispectrum.
Number of References cited: 17
Acoustic Feature Extraction for monitoring the Combustion Process of Diesel
Engines based on EMD and Wavelet Analysis
Shunting Fang, Si-chang Li, Dong Zhen, Zhanqun Shi, Fengshou Gu and
Andrew Ball; China & UK
Abstract: In order to analyze the combustion characteristic of the internal-combustion engine, combustion noise signal was collected, replacing the cylinder pressure signal in this paper. An acoustic signal feature extraction method using empirical mode decomposition (EMD) and wavelet analysis (WA) was proposed. Time synchronous average (TSA) is used for filtering interference noise to enhance the signal-to-noise ratio (SNR) of the measured acoustic signal as noise will affect the decomposition process resulting in over decomposition. The processed acoustic signals were decomposed into a series of intrinsic mode functions (IMF) using the method of empirical mode decomposition (EMD) in the time domain. Then wavelet analysis which has good time-frequency localization feature was applied on useful IMFs containing the information of diesel engine combustion. The root mean square (RMS) value of wavelet analysis results was calculated to achieve linear state monitoring.
Keywords: Diesel engine, Feature extraction, EMD, Wavelet analysis.
Number of References cited: 12
Motor Current Signature Analysis for the Compound Fault Diagnosis of
Usama Haba, Guojin Feng, Abdulkarim Shaeboub, Xinyu Peng, Fengshou Gu
and Andrew D. Ball; UK & China
Abstract: Induction motors as a primer driver, are the most widely electric component in the industry which consume tremendous energy each year. The influence of stator winding asymmetry combined with discharge valve leakage (DVL) significantly increases the temperature and reduces the motor efficiency and shorten the motor life. Monitoring the condition of these machines and their downstream equipment on time not only provides valuable information about the machine conditions but also maintaining their efficiency, avoids severe damage to systems and excessive energy consumption. This paper studies the use of motor current signals information to detect and diagnose the effect of the stator winding on different common reciprocating compressor (RC) faults which create varying load to the induction motor. The motor is applied by the RC with an oscillator torque which induces additional components in measured current signals. Moreover, the current signatures contain changes with the torque profiles due to different types of faults. Based on these analytical studies, the experimental studies examine different common RC faults, such as valve leakage, intercooler leakage, stator asymmetries and the compounds of them. The envelope analysis of current signals allows accurate demodulation of the torque profiles and thereby it can be combined with overall current levels for implementing model-based detections and diagnosis. The results show these simulated faults can be separated under all operating pressures
Keywords: Induction motor, reciprocating compressor, stator winding asymmetry, discharge valve fault, envelope analysis, motor current signatures analysis.
Number of References cited: 25
A Study of the Diagnostic Amplitude of Rolling Bearing under increasing
Radial Clearance using Modulation Signal Bispectrum
Ibrahim Rehab, Xiange Tian, Ruiliang Zhang, Fengshou Gu and
Andrew D. Ball; UK & China
Abstract: The rolling element bearing is a key part of machines. The accurate and timely diagnosis of its faults is critical for predictive maintenance. Most researches have focused on the fault location identification. To estimate the fault severity accurately, this paper focuses on the study of roller bearing vibration amplitude under increasing radial clearances due to inevitable wear using the modulation signal bispectrum (MSB). The experiment is carried out for bearings with two different clearances for the inner race fault and the outer race fault cases. The results show that the vibration amplitudes at fault characteristic frequencies exhibit significant changes with increasing clearances. However, the amplitudes of vibrations tend to increase with the severity of the outer race fault and decrease with the severity of the inner race fault. Therefore, it is necessary to take into account these effects in diagnosing the size of defect.
Keywords: condition monitoring; radial clearance; nonlinear contact deformation; bearing defects, MSB.
Number of References cited: 13
Condition Monitoring of Lubricant Starvation Based on Gearbox Vibration Signatures
Khaldoon F. Brethee, Fengshou Gu, Andrew D. Ball; UK & Iraq
Abstract: Different gear failure modes are strongly correlated with lubricant status, for example low oil level or starved lubrication leads to significant gear damages. In order to develop an early detection and accurate diagnosis of gearbox lubricant serving conditions based on online vibration measurements, this study will investigate the effect of lubricant starvation on the gearbox vibration responses. A two-stage helical industrial gearbox was tested under different lubricant shortage conditions. Any shortages in the oil service volume reduce the consumption power of the driving motor due to the decreasing of dipping oil churning losses and the submerge depth of gears. However, breakdown in the oil film and increasing in the sliding friction between the contact tooth surfaces are more expected, which affect the vibration characteristics of the gear system.The test was carried out with normal oil quantity and two lubricant shortages under different operating conditions. The results show that the gearbox vibration signature changes significantly with lubricant starvation, which includes more consistent increase in the amplitudes of vibration responses at meshing frequency harmonics and their associated sideband components. These changes correspond that vibration signal can be considered to normalise condition indicator of gearbox lubricant starvations.
Keywords: Gearbox ; Diagnostics ; Lubricant starvations ; Vibration response ; Power losses.
Number of References cited: 26
Local fault diagnosis of non-stationary gearbox based on order envelope analysis
Liming Wang, Yimin Shao, Pan Sun , Chaokun Gu and Ben Zhou; PRChina
Abstract: Gear tooth local fault is usually observed in gear system, it’s of significance to detect the gear tooth local fault during the operation process of the gearbox. However, the gearbox usually working in a non-stationary condition, namely the rotating speed or load are time varying, which increases the difficulty of fault diagnosis since the statistic features and spectrum vary by time. In this paper, an order envelope analysis method is proposed for fault diagnosis of a two-stage gearbox with local spalling fault and crack fault under non-stationary working conditions. Firstly, an accelerometer and an encoder are mounted on the gearbox to acquire non-stationary vibration data and rotating speed, respectively. After that, the angular resampling method is applied to convert the non-stationary time domain signal to angle domain signal by interpolation algorithm. Then envelope analysis is employed for the angle domain signals to detect the local fault characteristic frequency components in envelope spectrum. Finally, a new health inductor is proposed to detect spalling faults and crack faults in different working conditions. The fault diagnosis results show that the new method can effectively detect the gear local fault in various non-stationary working conditions.
Keywords: Fault diagnosis; non-stationary; angular resampling; order envelope analysis; tooth fault.
Number of References cited: 12
Enhanced safety management through robust helicopter flight data monitoring
Eric Bechhoefer and Michael Augustin; USA
Abstract: Helicopter Flight Data Monitoring (HFDM) can be a central and very effective component of an operator’s safety management system. By capturing operational information about aircraft operations, the operator/owner can identify safety hazards, facilitate monitoring and assessment of the interaction between the pilot and the aircraft, initiate remedial actions, and support continuous improvement of the safety management system. The Robust HFDM system described in this paper provides improved results via automation of data download and reporting. Automation is achieved by formalizing the
concept of a flight operation, adding exceedance reporting, and improving the HFDM architectural design to allow for the immediate transfer of data to secure ground based storage. In the extreme, robust HFDM also provides protection of data in the event of a mishap event that would usually only be available via a crash survivable memory. This paper discusses the formalized concept of a flight operation, how regime recognition is used to support the function of an operation, and exceedance monitoring, in order to improve the robustness of a HFDM program.
Keywords: automated data logging; flight safety; health and usage monitoring system
Number of References cited: 16
Atypical cases of pinion vibration in parallel shaft turbo gear units
Mantosh Bhattacharya; UAE
Abstract: Speed increasing parallel shaft double helical turbo gear units are commonly used in centrifugal compressors and high energy pump applications. Such turbo-gears are API 613 compliant (Titled as -Special Purpose Gear Units for Petroleum, Chemical, and Gas Industry Services) and have horizontal offset transmission line, with journal bearings on the high speed shaft and low speed shaft. When a full load full speed complete unit test is carried out, pinion dynamic behaviour is found to be different than what observed during full speed no load condition as mandated in API 613. During this test, gear box high speed pinion may show up with high vibration or combination of both during certain load and speed combination in spite of proper balancing and alignment. Since full load full speed test is kept as an option in API 613 , hence these type of vibration may not be detected during a no load test in gear box manufacturer’s premises. These types of vibration patterns are not explicitly addressed in API 613. The first objective of this paper is to cover analytical, design and diagnostic aspects which can be helpful to mitigate above issues before it is towed out from manufacturer’s premises. The second objective of the paper is to suggest installation /innovation / design modification on high speed pinion as a pre-emptive approach which can save time to mitigate if encountered during any certain speed –load combination.
Keywords: Spectrum, Sub -synchronous, relief, Gear mesh frequency, super-synchronous, tuning, nodes, FEM analysis
Number of References cited: 16
Failure, modal, and vibration analysis of a reactor pool cooling pump
Thomas J. Hazelwood, Larry D. Phillips, and Blake W. Van Hoy; USA
Abstract: Two 75 HP pumps redundantly supply cooling water to the reactor pool of the High Flux Isotope Reactor (HFIR) at the Oak Ridge National Laboratory (ORNL). Due to a recent history of premature bearing failures, one of these pumps has undergone maintenance to deal with possible issues of misalignment and base looseness. Vibration analysis and modal analysis including steady state spectrum, operational deflection shape, run up and down order tracking, and modal impact have been utilized to verify the effectiveness of the maintenance and identify possible remaining failure modes. The studies conclude that the pump is, after the maintenance, in an overall good conditional state as per ISO 10816, but a few failure modes remain. These modes consist of some shaft unbalance, considerable shaft misalignment intensified by piping movement, possible motor ground fault, hydrodynamic issues such as cavitation with modal interaction, and base looseness. These failure modes and their supporting data have been used to make suggestions for future maintenance, to verify the effectiveness of the previous maintenance, and to provide a base on which to check future data. This report will cover the testing setup, methodology, analysis results, and maintenance suggestions.
Keywords: Condition monitoring ; diagnostics ; failure prevention; fault analysis; signal analysis.
Fault detection in bearings using autocorrelation
Rushit N. Shaha, Michael H. Azariana, and Michael G. Pecht; USA
Abstract: Autocorrelation is a special case of cross-correlation wherein a signal is correlated with a time-lagged version of itself – the resulting signal comprises only the periodic information from the original signal whilst reducing noise. This property of autocorrelation can be particularly useful in analysing bearing faults since vibration data from a bearing, with local faults/defects, consists of cyclostationary acceleration signals usually contaminated with noise from sensors and other environmental factors. This study introduces a method which provides early failure warning in rolling element bearings by applying an autocorrelation operation to vibration data. The Sequential Probability Ratio Test (SPRT) is used to detect anomalies indicative of incipient failure. The results from the autocorrelation analysis are compared with results from a simple moving-RMS analysis of the acceleration data. The developed method is shown to provide an earlier warning of failure than the RMS-based method. This method can detect early stages of degradation in bearings – which in turn allows earlier scheduling of maintenance and the avoidance of system failures.
Keywords: Autocorrelation; bearings; diagnostics; health management; prognostics; SPRT; anomaly detection
Number of References cited: 21
Prediction of Sensor System Reliability
Shan Guan, Christopher Taylor and Narasi Sridhar; USA
Abstract: This paper summarized influencing factors to the sensor system reliability used in Oil and Gas. A management plan based on criticalities of influencing factors to the overall system is proposed. Prediction of sensor system reliability will be especially useful in the situation where sensor systems can degrade over time in service. A modeling approach has been carried out in this paper to combine the Bayesian network modeling and “Analytical Redundancy relations” Methodology for assessing sensor reliability in a digital downhole application
Keywords: Sensors; Reliability; FMECA; Bayesian network
Number of References cited: 8
Comparison between Two Very Efficient Signal Processing approaches
for Vibration-based Condition Monitoring of Rolling Element Bearings
Dany Abboud, Mohammed Elbadaoui; USA
Abstract: This paper compares two of the most efficient signal processing approaches used nowadays for vibration-based condition monitoring of rolling element bearings. The first is based on pre-processing the vibration signal through the minimum entropy deconvolution method (MED) followed by the spectral kurtosis (SK), before analysing the spectrum of the signal envelope. The MED aims at maximizing the signal impulsivity by deconvolving the system transfer function through an optimization approach that maximizes the kurtosis of the output. Then, the spectral kurtosis (SK) is applied to conceive the optimal filter to be applied before computing the envelope spectrum. The second approach is based on a cyclostationary modelling of the bearing signal. It applies the spectral coherence to the signal with a special attention on setting the estimation parameters. The spectral coherence is a bi-variable map of the cyclic frequency, α, and the spectral frequency, f. The former variable describes the cyclic content of the modulations, while the former describes the properties of the carrier. The improved envelope spectrum is then computed by simply projecting its squared-magnitude with respect to the f-variable. These methods are evaluated according to their potentiality to detect the fault in its earliest stage. The comparison is be made on real bearing vibration signals in run-to-failure tests.
Keywords: Vibration analysis, bearing diagnosis, Cyclostationarity, Minimum entropy decomposition, Spectral kurtosis.
Number of References cited: 9