Effective Maintenance Plan Research Articles

Achieved availability importance measure for enhancing reliability-centered maintenance decisions

An effective defense strategy requires aircraft, among other weapons systems, to be available and ready for use when circumstances deem necessary. This article offers a set of importance measures to identify the critical components in a system from their influence on system-achieved availability, a common Department of Defense availability calculation that is a ratio of mean time between maintenance and total system time, including mean maintenance time. With these measures, more effective maintenance plans, including inspection and supply inventory, can focus on those components that more significantly impact achieved availability. A decision-making formulation results from these component importance measures, and an example based on a US Air Force system illustrates the modeling contributions.

Comparison of sensors and methodologies for effective prognostics on railway turnout systems

Railway turnout systems are one of the most important components of a railway’s infrastructure. Their geographically distributed nature makes failure detection, forecasting and maintenance planning extremely important. Prognostics, forecasting the time to failure in order to achieve effective maintenance planning, has attracted increasing attention from industry and researchers in recent years. The prognostic approach has great potential to achieve reduced costs and increased availability. However, the applicability of any engineering model requires economic and practical justifications. This paper presents an analysis of different prognostic methods for railway turnout systems. Five different sensors, installed in a real turnout system used on Turkish State Railways, are individually analysed by applying various prognostic methods. This paper aims to guide practitioners on the application of prognostics and health management technologies to railway turnout systems by discussing the advantages and disadvantages of using different sensors and prognostic methods.

Applications of radio frequency identification (RFID) technology with eMaintenance cloud for railway system

Radio frequency identification (RFID) helps automatic identification of objects using radio waves. This is not a new technology instead decades old and has been used during the World War II, when it was used by allied ground forces to track German bombers. It is a technology for wireless communication between a reader and a transponder/tag. This technology permits the transfer of data to the most diverse objects without the need for physical contact and uses intelligent barcodes to track items and have been successfully applied in military, security, healthcare, real time location tracking, vehicle identification and other areas. This paper is based on applications of RFID technology with eMaintenance cloud for railway system to analyze and visualize data of trains for the cost effective maintenance planning. Further, cloud computing is an emerging research area that can be utilised for acquiring an effective and efficient information logistics. Specifically, the widespread use of RFID will enable wagons to be tracked leading to better resource utilization, lower freight costs, and better maintenance. Therefore, it helps to provide greater control of the train carriages, making it easier to plan resources. However, RFID is a powerful tool that can help to improve industry proficiency, implementing this technology is not easy. Furthermore, operating RFID systems can be a challenging process. Thus, this paper is based on the application of RFID in the context of railway operation.

Measurement of welding residual stresses of reactor vessels by inherent strain method – Diagnosis of inherent strain distribution function

The fundamental objective of this study is to ensure the safety of nuclear reactors. A few accidents involving leaks from welded zones at the pipe penetration part of reactor vessels or at coolant pipes have been reported at home and abroad. One of the main causes is welding residual stress. Therefore, it is very important to know the welding residual stress in order to maintain the high safety of the plant, estimate the plant life cycle and design an effective maintenance plan. Welded joints of nuclear reactor vessels have complex shapes, and the welding residual stresses also have three-dimensional (3D) complex distributions. In this study, inherent strain-based theory and method are applied to measure the welding residual stresses. The inherent strain method is an analytical method as an inverse problem, using the least squares method, based on the finite element method. So the method gives the most probable value and deviation of residual stress. The reliability of the estimated result is discussed. In this method, inherent strains are unknowns. When residual stresses are distributed complexly in a 3D stress-state, the number of unknowns becomes very large. So, the inherent strain distribution is expressed with an appropriate function to decrease largely the number. A mock-up is idealized for a welded joint at the pipe penetration part of an actual reactor vessel. The inherent strain method is applied to the measure the residual stress of the joint. In this paper, the applicability of the inherent strain distribution function is diagnosed. Ten kinds of functions are applied to estimate the residual stress, and the accuracy and reliability of the analysed results are judged from three points of view, i.e. residuals, unbiased estimate of variance of errors and welding mechanics. The most suitable function is selected, which brings the most reliable result.

固有ひずみ法による原子炉溶接継手の残留応力の測定

The objective of this study is to ensure the safety of nuclear reactors. A number of accidents occurred from the welded zones at pipe penetration points of the reactor vessel or in coolant pipes have been reported at sites around the world. One of the main causes of such leaks is welding residual stress. It is therefore very important to know the welding residual stress in order to maintain the safety of the plants, estimate plant life cycle and design an effective maintenance plan. Welded joints in nuclear reactors have complex shapes, and the welding residual stresses have complex three-dimensional distributions.In this study, the mock-up is idealized and manufactured for the welded joint at the pipe penetration part of actual reactor vessel. The inherent strain method is applied to measure the welding residual stress of the joint accurately. The inherent strain method is an analytical method which solves an inverse problem using a least squares method.For more accurate estimation, the robust estimation is applied to the inherent strain method. As one of the robust estimation methods, the least squares method with cut is used. The data of the measured strains are selected, based on the residuals. First, all data are used in the analysis. Some data which have large residuals are cut, and the next analysis is performed, using the rest of the data. Such calculation is repeated until a convergence condition is satisfied. A concrete procedure of the calculation is proposed. The welding residual stress of the joint is analyzed by such robust estimation method. As a result, high-accurate estimation is achieved. The significance of the result is discussed in detail.

Source of Ballast Fouling and Influence Considerations for Condition Assessment Criteria

Railway ballast is a critical element in the railway track support structure. The ballast is often overlooked when inspection tools are developed for track. When ballast is not functioning correctly, the strength of the track structure may be inadequate and thus compromise track stability. Track stability–related failures vary from rapid deterioration with little warning to slow and progressive deterioration with often predictable required maintenance. Ballast-related deterioration is progressive and usually provides visual evidence to warn maintenance personnel of needed rehabilitation. However, the blocked drainage that develops with fouled ballast can result in a saturated roadbed that is not stable and could rapidly deteriorate to an unsafe condition with little warning. Although massive failures are rare, if a side hill fill or embankment deteriorates to the point of becoming susceptible to massive failure, then the challenge becomes evaluation. More detailed knowledge of the track support condition will be needed for a thorough evaluation than can be provided by current track inspections, except for costly detailed visual inspections. The current standard of practice for ballast inspection and maintenance can be improved to reduce the risk of sudden failure. Much of the required technology, knowledge, and resources is already available and being utilized under the current system. A more precise evaluation of ballast condition is essential to identify thresholds related to unsafe track support conditions and to support effective maintenance plans.

Data classification and MTBF prediction with a multivariate analysis approach

The paper presents a multivariate statistical approach that supports the classification of mechanical components, subjected to specific operating conditions, in terms of the Mean Time Between Failure (MTBF). Assessing the influence of working conditions and/or environmental factors on the MTBF is a prerequisite for the development of an effective preventive maintenance plan. However, this task may be demanding and it is generally performed with ad-hoc experimental methods, lacking of statistical rigor. To solve this common problem, a step by step multivariate data classification technique is proposed. Specifically, a set of structured failure data are classified in a meaningful way by means of: (i) cluster analysis, (ii) multivariate analysis of variance, (iii) feature extraction and (iv) predictive discriminant analysis. This makes it possible not only to define the MTBF of the analyzed components, but also to identify the working parameters that explain most of the variability of the observed data. The approach is finally demonstrated on 126 centrifugal pumps installed in an oil refinery plant; obtained results demonstrate the quality of the final discrimination, in terms of data classification and failure prediction.

固有ひずみ法（T-L法新理論）による極厚板平板継手の溶接及び応力除去焼なまし後の残留応力の測定

The objective of this study is to ensure the safety of pressure vessels. It is very important to know the welding residual stress in order to maintain the safety of welded components and design an effective maintenance plan, including the fabrication process. Very thick welded joint is studied in this research, so the welding residual stress has complex distribution in the section. The inherent strain method combined with Finite Element Method (FEM) is applied to measure the welding residual stresses accurately.One more subject is to examine the effect of stress-relief annealing (SR treatment) for the thick welded joint. So, two same mock-ups for a welded joint of pressure vessel were prepared for the study. As a practical measuring procedure of the inherent strain method, TL-method had presented. However, the method gives the determinate value of the residual stress, and does not give the most probable value and the deviation which are estimated by the original inherent strain method. So, the TL-method is improved to give them, allowing the reliability of the estimated results to be discussed.The deviations of the estimated results are small enough for the most probable values. It assures the high reliability of the results. The residual stresses after the SR treatment are small enough, compared with the welding residual stresses. Sufficient effect of the SR treatment is confirmed.

原子炉厚板冷却材配管溶接継手の3次元残留応力分布の固有ひずみ法による測定

The objective of this study is to ensure the safety of nuclear reactors. A number of accidents caused by leaks from welded zones at pipe penetration points of the reactor vessel or in coolant pipes have been reported at sites around the world. One of the main causes of such leaks is welding residual stress. It is therefore very important to know the welding residual stress in order to maintain the safety of the plants, estimate plant life cycle and design an effective maintenance plan. In this study, the inherent strain method combined with Finite Element Method (FEM) is applied to measure the welding residual stress accurately.A mock-up for a welded joint at a coolant pipe of an actual nuclear reactor was manufactured for the study. The inherent strain method is used to measure the three-dimensional residual stress distribution. In this method, the inherent strains are unknowns. When the residual stresses have a complex three-dimensional distribution, the number of unknowns becomes very large. The inherent strain distribution is therefore expressed with an appropriate function, significantly decreasing the number of unknowns.10 kinds of inherent strain distribution functions are applied to estimate the residual stress distribution of the joint. Applicability of each function is diagnosed. Accuracy and reliability of analyzed results are judged from three points of view, that is, residuals, unbiased estimate of variance of errors and necessary conditions from welding mechanics. Most suitable function is selected, which brings most reliable result.The characteristics of the three-dimensional residual stress distribution are cleared. The circumferential stress and axial stress are important, related to stress corrosion cracking (SCC). The circumferential stress is estimated to be large tension near the outer surface of welding finish region. The large tensile axial stress is produced near the outer surface, widely in the circumferential direction. Near the inner surface where SCC may occur, both stresses are small tension or compression.

固有ひずみ法による原子炉溶接継手の残留応力の測定

The objective of this study is to ensure safety of nuclear reactors. A few accidents of leaks from welded zones at pipe penetration parts of reactor vessel or in coolant pipes have been reported around the world. One of the main causes of such leaks is welding residual stress. It is therefore very important to know the welding residual stress in order to maintain the safety of the plants, estimate plant life cycle and design an effective maintenance plan. Welded joints in nuclear reactors have complex shapes, and the welding residual stresses have complex three-dimensional distributions.The inherent strain method is an analytical method that solves an inverse problem using a least squares finite element method. The method gives the most probable value and the deviation of the residual stress, allowing the reliability of the estimated results to be discussed. In this method, the inherent strains are unknowns. When residual stresses have a complex three-dimensional distribution, the number of unknowns becomes very large. The inherent strain distribution is therefore expressed with an appropriate function, significantly decreasing the number of unknowns. In this study, inherent strain theory and method are applied to measure the welding residual stresses for a mock-up of a welded joint at a pipe penetration of reactor vessel.In this paper, applicability of strain measurement region is diagnosed. 5 kinds of regions are applied to estimate the residual stress, and accuracy and reliability of analyzed results are judged from 4 points of view, that is, residuals, unbiased estimate of variance of errors, welding mechanics and economy. Most reliable and economical measurement region is selected, which brings most reasonable result.

Maintenance and spare parts inventories in man‐made humanitarian disasters

PurposeThe purpose of this paper is to determine how a small country's military force and a small country's non‐governmental organization (NGO) plan for and set up equipment maintenance, spare parts inventories in connection with man‐made humanitarian disasters. Additionally, it seeks to determine how the physical context, organizational structure and governance affect the planning and set‐up.Design/methodology/approachA research model that combines organizational theory with spare parts inventory theory is developed. Case study research methodology is used and observations and findings are discussed within the research model in order to answer predefined hypotheses.FindingsRegarding planning procedures, as well as how the maintenance concept and spare parts inventory are set up, the research concludes that the organizational structure and governance of the organization contributing to the humanitarian operation in question are more important than physical context of the operation itself. Further it is concluded that the maturity level, when it comes to inventory control issues, is different for the two cases in question. None of the cases, however, utilize modern optimization methods and tools.Research limitations/implicationsQualitative data from the two case studies give the possibility for in depth analysis of the case study findings. Lack of quantitative data means that it has not been possible to statistically reject or accept the hypotheses. More research is needed to present a template and/or processes based on the findings in the research.Practical implicationsBy applying the research model developed in this study, organizations that contribute to humanitarian disasters could more easily assess their own possibility for effective maintenance and spare parts inventory planning and set up.Originality/valueThe study of the planning and set up of maintenance and spare parts inventories for both military and NGO players in connection with a man‐made humanitarian disaster is new. Further, the development of spare parts inventory theory into organizational theory is relatively new. Limited research is available within this field. The paper should be of interest to both practitioners and researchers within the field of maintenance and spare parts inventories in general, and in connection with humanitarian disasters in particular.

Quantitative HAZOP Analysis for Gas Turbine Compressor based on Fuzzy Information Fusion

Abstract An improved Hazard and Operability (HAZOP) modeling and reasoning method is proposed based on the fuzzy information fusion theory, in order to solve practical safety-related problems in industry, such as quantitative information loss and the difficulty of system safety decision-making during the traditional computer-aid HAZOP analysis. A directed graph knowledge model of systematical HAZOP analysis is first developed, taking advantage of different fuzzy quantitative methods corresponding to various variable nodes with different attributes in the system. Based on the D-S evidence theory, the quantitative deviated information between relevant nodes on the path of hazard propagation is used for the fuzzy information reasoning, which is to indicate the fusion reliability of hazard reasons and consequences of system, respectively, and provides an important foundation in safety decision-making. The results of the proposed method applied on the gas turbine compressor system in “Se-Ning-Lan” pipeline system present the possible hazard reasons and consequences according to the current running states with corresponding sorted fusion reliabilities, based on which the appropriate and effective safety maintenance plans are taken into action to avoid accidents. The comparison with traditional HAZOP analysis shows that the proposed method is able to solve the limitation and the uncertainty of traditional HAZOP qualitative analysis and improve the rationality of maintenance decision-making under the existence of multi hazard sources.

固有ひずみ法による原子炉溶接継手の残留応力の測定

Fundamental objective of this study is to ensure safety of nuclear reactor. A few accidents of leak from welded zones at pipe penetration part of reactor vessel or at coolant pipe are reported at home or abroad. One of the main causes is welding residual stress. Therefore, it is very important to know the welding residual stress in order to maintain high safety of the plant, estimate plant life cycle and design effective maintenance plan. Welded joints of nuclear reactor vessel have complex shapes, and the welding residual stresses also have three-dimensional complex distributions. In this study, inherent strain-based theory and method are applied to measure the welding residual stresses.The inherent strain method is one of analytical method as inverse problem, using least squares method, based on finite element method. So the method gives most probable value and deviation of residual stress. Reliability of estimated result can be discussed. In this method, inherent strains are unknowns. When residual stresses are distributed complexly in 3-dimensional stress-state, the number of unknowns becomes very large. So, inherent strain distribution is expressed with appropriate function to decrease largely the number. A mock-up is idealized for a welded joint at pipe penetration part of actual reactor vessel. The inherent strain method is applied to measure residual stress of the joint.In this paper, applicability of inherent strain distribution function is diagnosed. 10 kinds of functions are applied to estimate the residual stress, and accuracy and reliability of analyzed results are judged from 3 points of view, that is, residuals, unbiased estimate of variance of errors and welding mechanics. Most suitable function is selected, which brings most reliable result.

An investigation into the causes of squats—Correlation analysis and numerical modeling

Nowadays squats are a severe rolling contact problem on some railways. The root causes of it are not yet clear. From railway operation and maintenance points of view, root causes have to be known so that effective maintenance policies and plans can be made based on measurements and prediction. In the present work first a correlation analysis is performed based on measured data and field observations, and then a relation between squat occurrence and some parameters of the vehicle–track system is identified. Subsequently a transient finite element model of vehicle–track interaction is built up to analyze the contact forces and the resulting stresses and strains. The numerical results show good correspondence with observed phenomena at squats, and suggest certain relation between squat development and some eigen frequencies of the coupled vehicle–track system. A squat growth process is accordingly postulated.

X-ray computed tomography and aggregate image system (AIMS) for studying hot mix asphalt and aggregates

Achieving reliable pavement design, durable roadway structures and effective maintenance and rehabilitation plans requires the suitable characterisation of the materials used in pavement construction. This paper describes two nondestructive techniques based on image acquisition and analysis and their successful application in pavement engineering: X-ray computed tomography (X-ray CT) and aggregate imaging system (AIMS). The former has been used for characterising the internal structure of asphalt mixes to analyse and model their performance; it has been particularly used for studying the content, size, distribution and connectivity of air-voids and these variables’ relationship with moisture damage susceptibility, capillarity and permeability within the mixes. AIMS was intended for characterising aggregates’ morphological properties (i.e., form, angularity and texture). This technique provides important advantages regarding the standard methods used for obtaining the same aggregate properties: it is objective, reliable, reproducible and can be carried out quickly. This paper was aimed at describing these two techniques’ theoretical backgrounds, mention some recent applications and provide insight into how existing characterisation of materials used in pavement construction can be improved.

Performance Analysis of an FMS Operating Under Different Failure Rates and Maintenance Policies

Flexible manufacturing Systems (FMSs) typically operate at 70–80% utilization, which is much higher than the utilization of traditional machines that can operate with as low as 20% utilization. A result is that an FMS may incur four times more wear and tear than a traditional system. This requests the execution of effective maintenance plans on FMSs. While maintenance actions can reduce the effects of breakdowns due to wear-outs, random failures are still unavoidable. It is important to understand the implications of a given maintenance plan on an FMS before its implementation. This paper discusses a procedure that combines simulation and analytical models to analyze the effects of corrective, preventive, and opportunistic maintenance policies on the performance of an FMS. The FMS performance is measured by its operational availability index, which is determined using the production output rate of the FMS under a variety of time between failure distributions and different operational conditions. The effects of various maintenance policies on FMS performance are simulated and the results are compared to determine the best policy for a given system.

A neural network application for reliability modelling and condition-based predictive maintenance

Traditionally, decisions on the use of machinery are based on previous experience, historical data and common sense. However, carrying out an effective predictive maintenance plan, information about current machine conditions must be made known to the decision-maker. In this paper, a new method of obtaining maintenance information has been proposed. By integrating traditional reliability modelling techniques with a real-time, online performance estimation model, machine reliability information such as hazard rate and mean time between failures can be calculated. Essentially, this paper presents an innovative method to synthesise low level information (such as vibration signals) with high level information (like reliability statistics) to form a rigorous theoretical base for better machine maintenance.

Analysis of induction motor fault diagnosis with fuzzy neural network

The online diagnosis of an electrical drive is the first step towards the application of an effective predictive maintenance plan on such electrical machines. The analysis of residual features corresponding to instrumentation faults of an induction motor lead to the design of a faults classification system. The training set is obtained by a faulted machine dynamical model as simulator. Two neuro-fuzzy structures will be conceived to learn the exact input-output relation of the fault detection process for induction motor, using measured data. The first neuro-fuzzy architecture maps the residuals into two classes: one of fixed direction residuals and another of faults belonging to velocity sensor. The second adaptive neuro-fuzzy network will provide updated membership functions of the sets of fixed oriented residuals that better describe the fault diagnosis map.

Design and implementation of a maintenance planning and control system

In this paper, a preventive maintenance (PM) planning and control system designed and implemented in a large foundry is presented. The system designed and implemented is part of the measures taken by the top management to increase the scope and effectiveness of PM activities within the production facility. In this paper, first, shortcomings of the previous system are stated. Then, a systematic approach to bring about a well functioning and effective maintenance planning and control system is presented. The heart of the new system is a custom tailored software containing data management, PM task scheduling and performance evaluation modules, and these are discussed in the paper. Furthermore, a priority function developed for the selection of the PM tasks for scheduling is also introduced and discussed.

A Method of Propulsion Plant Performance Evaluation for Marine Applications

A performance evaluation system for a steam-propelled merchant ship is described which utilizes a general-purpose computer for data acquisition and analysis. The performance of the steam plant on the ship's maiden voyage is used as the performance base line, and subsequent evaluations are referenced to this base line. The diagnostic and prognostic capabilities of the system are presented in a description of the graphical display of the historical and real-time data. The operating costs of the vessel are reduced since effective maintenance planning and scheduling can be accomplished, resulting in greater ship availability.