Performance Of Repair Systems Research Articles

Importance measure-based maintenance strategy considering maintenance costs

Maintenance is an important way to ensure the best performance of repairable systems. This paper considers how to reduce system maintenance cost while ensuring consistent system performance. Due to budget constraints, preventive maintenance (PM) can be done on only some of the system components. Also, different selections of components to be maintained can have markedly different effects on system performance. On the basis of the above issues, this paper proposes an importance-based maintenance priority (IBMP) model to guide the selection of PM components. Then the model is extended to find the degree of correlation between two components to be maintained and a joint importance-based maintenance priority (JIBMP) model to guide the selection of opportunistic maintenance (OM) components is proposed. Also, optimization strategies under various conditions are proposed. Finally, a case of 2H2E architecture is used to demonstrate the proposed method. The results show that generators in the 2E layout have the highest maintenance priority, which further explains the difference in the importance of each component in PM.

Cost Benefit Analysis of a k-out-of-n: G Type Warm Standby Series System Under Catastrophic Failure Using Copula Linguistics

This paper deals with the study of reliability measures of a complex engineering system consisting three subsystems namely L, M, and N in series configuration. The subsystem-L has three units working under 1-out-of-3: G; policy, the subsystem-M has two units working under 1-out-of-2: G policy and the subsystem-N has one unit working under 1-out-of-1: G; policy. Moreover, the system may face catastrophic failure at any time t. The failure rates of units of all subsystems are constant and assumed to follow the exponential distribution however, their repair supports two types of distribution namely general distribution and Gumbel-Hougaard family copula distribution. The system is analyzed by using the supplementary variable technique, Laplace transformation and Gumbel-Hougaard family of copula to derive the differential equations and to obtain important reliability characteristics such as availability of the system, reliability of the system, MTTF, and profit analysis. The numerical results for reliability, availability, MTTF, and profit function are obtained by taking particular values of various parameters and repair cost using maple. Tables and figures demonstrate the computed results and conclude that copula repair is more effective repair policy for better performance of repairable systems. It gives a new aspect to scientific community to adopt multi-dimension repair in form of copula. Furthermore, the results of the model are beneficial for system engineers and designers, reliability and maintenance managers.

Safety Risk Management in Production Process: A case study in the automotive supplier industry

This paper deals with the study of reliability measures of a complex engineering system consisting three subsystems namely L, M, and N in series configuration. The subsystem-L has three units working under 1-out-of-3: G; policy, the subsystem-M has two units working under 1-out-of-2: G policy and the subsystem-N has one unit working under 1-out-of-1: G; policy. Moreover, the system may face catastrophic failure at any time t. The failure rates of units of all subsystems are constant and assumed to follow the exponential distribution however, their repair supports two types of distribution namely general distribution and Gumbel-Hougaard family copula distribution. The system is analyzed by using the supplementary variable technique, Laplace transformation and Gumbel-Hougaard family of copula to derive the differential equations and to obtain important reliability characteristics such as availability of the system, reliability of the system, MTTF, and profit analysis. The numerical results for reliability, availability, MTTF, and profit function are obtained by taking particular values of various parameters and repair cost using maple. Tables and figures demonstrate the computed results and conclude that copula repair is more effective repair policy for better performance of repairable systems. It gives a new aspect to scientific community to adopt multi-dimension repair in form of copula. Furthermore, the results of the model are beneficial for system engineers and designers, reliability and maintenance managers.

A 3D Lattice Modelling Study of Drying Shrinkage Damage in Concrete Repair Systems.

Differential shrinkage between repair material and concrete substrate is considered to be the main cause of premature failure of repair systems. The magnitude of induced stresses depends on many factors, for example the degree of restraint, moisture gradients caused by curing and drying conditions, type of repair material, etc. Numerical simulations combined with experimental observations can be of great use when determining the influence of these parameters on the performance of repair systems. In this work, a lattice type model was used to simulate first the moisture transport inside a repair system and then the resulting damage as a function of time. 3D simulations were performed, and damage patterns were qualitatively verified with experimental results and cracking tendencies in different brittle and ductile materials. The influence of substrate surface preparation, bond strength between the two materials, and thickness of the repair material were investigated. Benefits of using a specially tailored fibre reinforced material, namely strain hardening cementitious composite (SHCC), for controlling the damage development due to drying shrinkage in concrete repairs was also examined.

Reliability evaluation of a Semi-Markov repairable system under alternative environments

ABSTRACTTo accurately describe the performance of repairable systems operating under alternative environments, for example, mild/harsh, working/idling, maximum/minimum level demand etc., a Semi-Markov process with a finite state space and two different Semi-Markov kernels is introduced. The state set of the system which is regarded as acceptable might depend on the environments. Two important reliability indices, the availability and time to the first system failure, are obtained via Markov renewal theory, transform and matrix methods. The results and numerical examples are also provided for two special cases: (1) when sojourn times under alternative environments are constants and (2) when sojourn times under environments have exponential distributions.

Optimizing the Reliability and Performance of Remote Vehicle-to-Grid Systems Using a Minimal Set of Metrics

Vehicles connected to electric systems are considered “plug-in” vehicles. They can be an integral part of a microgrid. Ground vehicles have become more electrified over time, providing electrical power for the propulsion system (hybrid) and a complex suite of auxiliary power systems, enhancing their use in microgrids. Optimizing the microgrid system for performance and reliability considering many external loads and sources is a challenging problem. This is especially true when the plug-in vehicles may enter and leave the microgrid randomly becoming either sources or loads. The microgrid is a repairable system. Recent work has shown that multiple metrics are needed to fully account for the performance of repairable systems under uncertainty. In this paper, we propose a decision-based framework to design and maintain repairable systems for optimal performance and reliability using a set of metrics such as minimum failure free period (MFFP), number of failures in planning horizon, and cost. Optimal tradeoffs among a minimal set of metrics (MSOM) can be used in the design and maintenance of these systems. The optimal solution includes the initial design, the system maintenance throughout the planning horizon, and the protocol to operate the system. Critical remote military installations with plug-in vehicles connected to the microgrids require careful consideration of cost and repair strategies because of logistical challenges in performing repairs and supplying necessary spare parts in unsafe locations. We show how a MSOM helps to solve the complex optimization problem of finding the best microgrid power management strategy considering performance, reliability, and cost.

Refurbishment of steel tubular pipes using composite materials

This paper describes a glass fibre based composite repair system for steel tubular pipes that can cope with internal and external corrosion, as well as mechanical damage. The original objective, to develop a rehabilitation technique for pressures up to 40 bar, has been achieved and significantly higher pressures seem viable. The most critical parameter for tubes subject to internal corrosion, was identified as the ability of a bonded repair system to resist the formation of pressurised blisters. It is shown that, for bonded repairs, the key parameter determining blistering resistance is the fracture toughness of the metal/composite interface in the presence of pressurised fluid. The effective value of this parameter was found to be lower than might be expected on the basis of published fracture toughness values of laminates. This was attributed to the presence of pressurised water at the metal/composite interface. A fracture mechanics based criterion is proposed to enable the performance of repair systems to be assessed and compared.To address different repair scenarios, especially for higher pressures and when surface preparation may be difficult, a novel version of the rehabilitation system has been developed, which does not depend on achieving a bond at the metal/composite interface.