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Article
Publication date: 22 March 2013

Xufeng Zhao, Syouji Nakamura and Toshio Nakagawa

The purpose of this paper is to consider maintenance policies for an operating system which works at random times for jobs. Each job causes some damage to the system and these…

311

Abstract

Purpose

The purpose of this paper is to consider maintenance policies for an operating system which works at random times for jobs. Each job causes some damage to the system and these damages are additive, and the system fails when the total damage has exceeded a failure level K.

Design/methodology/approach

Using techniques of cumulative damage models, the maintenance is made at the N‐th completion of working time for the first model and at a damage level Z with a limit number of working times N for the second model.

Findings

The system is maintained at the first completion of the working time over time T for the third model. The system fails with probability p(x) when the total damage is x and undergoes minimal repair at failure for the fourth model. The expected cost rates are obtained and optimal maintenance policies are discussed analytically and computed numerically.

Originality/value

The paper discusses four maintenance policies for an operating system which works at successive random times for jobs, where the system fails due to damage that can be additive caused by jobs.

Details

Journal of Quality in Maintenance Engineering, vol. 19 no. 1
Type: Research Article
ISSN: 1355-2511

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Article
Publication date: 1 September 2005

Cun Hua Qian, Kodo Ito and Toshio Nakagawa

This paper considers and discusses analytically the optimal preventive maintenance (PM) policies of aged plants such as fossil‐fired power plants.

725

Abstract

Purpose

This paper considers and discusses analytically the optimal preventive maintenance (PM) policies of aged plants such as fossil‐fired power plants.

Design/methodology/approach

Shocks are assumed to occur at a nonhomogeneous Poisson process and the total damage due to each shock is additive. The system undergoes the PM at a certain time or the total damage exceeds a managerial level. The expected cost rate until PM is derived and optimal policies which minimizes it are discussed.

Findings

There exists a unique optimal time (T*) or managerial level (k*) which minimizes the expected cost rate. But there does not exist a positive pair (T*, k*), simultaneously.

Research limitations/implications

The damage occurrence distribution is assumed to be nonhomogeneous Poisson one.

Practical implications

Useful methods to consider the optimal PM policies for power plant engineers.

Originality/value

This paper contributes to users of aged power plants economically and practically.

Details

Journal of Quality in Maintenance Engineering, vol. 11 no. 3
Type: Research Article
ISSN: 1355-2511

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Article
Publication date: 1 March 2005

Toshio Nakagawa and Kazumi Yasui

The reliabilities of systems are generally improved as units of redundancy increase. This paper aims to summarize the authors' results.

916

Abstract

Purpose

The reliabilities of systems are generally improved as units of redundancy increase. This paper aims to summarize the authors' results.

Design/methodology/approach

A conceptual discussion and approach are taken.

Findings

Focuses on the optimal number of units and replacement times of parallel systems, two modified replacement policies and two maintenance policies where a system is replaced at Nth repair and Nth failure. Further, as some examples of redundancy, five redundant models of data transmission, checkpoint, network and copy are given, and optimal policies for each model are analytically discussed.

Originality/value

Presents the number of units and replacement times of parallel systems, and other modified replacement and preventive maintenance policies.

Details

Journal of Quality in Maintenance Engineering, vol. 11 no. 1
Type: Research Article
ISSN: 1355-2511

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Article
Publication date: 1 December 1998

Hiroaki Sandoh, Hiroyuki Hirakoshi and Toshio Nakagawa

This study proposes a new modified discrete preventive maintenance policy where failures of a system can be detected only by inspections and be fixed by minimal repairs. The…

211

Abstract

This study proposes a new modified discrete preventive maintenance policy where failures of a system can be detected only by inspections and be fixed by minimal repairs. The maximum number of minimal repairs allowed to the system is, however, a prespecified integer, N. Under the proposed policy, inspections are conducted at times T, 2T, ...(T>0) to detect and fix failures by minimal repairs, and the whole system is preventively replaced by a new one when the cumulative number of failures detected becomes equal to an integer, k or more. The expected cost per unit time is formulated under the proposed maintenance policy. The existence of an optimal integer k=k* which minimizes the expected cost is then shown. Numerical examples are also presented to illustrate the theoretical underpinnings of the proposed formulation.

Details

Journal of Quality in Maintenance Engineering, vol. 4 no. 4
Type: Research Article
ISSN: 1355-2511

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Article
Publication date: 1 December 1998

Mitsuhiro Imaizumi, Kazumi Yasui and Toshio Nakagawa

A large number of microprocessors (μPs) have been widely used in many practical fields and the demand for improvement of their reliabilities have recently increased. Watchdog…

376

Abstract

A large number of microprocessors (μPs) have been widely used in many practical fields and the demand for improvement of their reliabilities have recently increased. Watchdog processors (WDPs) are small and simple coprocessors that can detect errors by monitoring the behavior of μPs. This paper formulates three reliability models of μP systems with WDPs: model 1 considers the system where a main processor (MPu) has n WDPs with self checking. Next, model 2 considers the system with upper limit number of resets. Further, model 3 discusses the system with limit processing time. The expected costs of each model are derived and the optimal policies which minimize them are discussed analytically. Finally, the numerical examples are given.

Details

Journal of Quality in Maintenance Engineering, vol. 4 no. 4
Type: Research Article
ISSN: 1355-2511

Keywords

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Article
Publication date: 1 December 2004

Toshio Nakagawa, Kazumi Yasui and Hiroaki Sandoh

There exist some reliability models whose performances increase by partitioning them into parts. Such a typical model is the basic inspection policy in which an operating unit is…

377

Abstract

There exist some reliability models whose performances increase by partitioning them into parts. Such a typical model is the basic inspection policy in which an operating unit is checked at suitable times for a finite time span and its failure is detected. This paper applies the concept of the basic inspection policy to five models: back‐up for hard disk, checkpoint for double modular redundancy, job partition, garbage collection, and network partition. The performances of each model are analytically evaluated.

Details

Journal of Quality in Maintenance Engineering, vol. 10 no. 4
Type: Research Article
ISSN: 1355-2511

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Article
Publication date: 1 September 2002

Toshio Nakagawa and Qian Cun Hua

This paper considers a series‐parallel and a parallel‐series system, and investigates theoretically their fundamental characteristics: it is shown that the reliability of the…

434

Abstract

This paper considers a series‐parallel and a parallel‐series system, and investigates theoretically their fundamental characteristics: it is shown that the reliability of the series‐parallel system with the same number of series and parallel tends to one as its number goes to infinity. It would be of great interest that the golden ratio plays a role in analyzing two systems. Further, an optimal number of units for a series‐parallel system with complexity is derived.

Details

Journal of Quality in Maintenance Engineering, vol. 8 no. 3
Type: Research Article
ISSN: 1355-2511

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Article
Publication date: 1 June 2004

Hiroaki Sandoh, Nobuko Igaki and Toshio Nakagawa

The present study deals with an optimal inspection policy for a scale where the inspection for a scale is conducted when the elapsed time since the previous inspection or…

189

Abstract

The present study deals with an optimal inspection policy for a scale where the inspection for a scale is conducted when the elapsed time since the previous inspection or adjustment reaches T (> 0) for the purpose of detecting its uncalibrated or inaccurate state and where its uncalibrated state can also be detected empirically or accidentally. The design variable under such a policy is T (> 0). The expected cost per unit of time is formulated as an objective function to be minimized. The conditions under which an optimal inspection scheduled time T exists are then clarified. Numerical examples are presented to illustrate the theoretical underpinnings of the proposed formulation. The proposed model is also compared with the conventional one to show that the proposed model can reduce the cost.

Details

Journal of Quality in Maintenance Engineering, vol. 10 no. 2
Type: Research Article
ISSN: 1355-2511

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Article
Publication date: 1 March 2003

Toshio Nakagawa and Kazumi Yasui

Large‐scale systems have been developed with increasing requirements of high quality and performance. It would be indispensable to define the reliability of more complex systems…

662

Abstract

Large‐scale systems have been developed with increasing requirements of high quality and performance. It would be indispensable to define the reliability of more complex systems, considering their complexity. This paper defines a complexity of redundant systems as a logarithmic function of paths, using the concept of an entropy. Further, a reliability function of complexity is given, and the reliabilities of series and parallel systems with complexity are computed. As one of typical redundant systems, a majority voting system is analyzed, and an optimal number of components is derived. Finally, a complexity of network systems is also proposed.

Details

Journal of Quality in Maintenance Engineering, vol. 9 no. 1
Type: Research Article
ISSN: 1355-2511

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Article
Publication date: 25 September 2009

Sophie Hennequin, Gabriel Arango and Nidhal Rezg

This paper aims to propose an approach for the optimization of imperfect preventive maintenance and corrective actions performed on a single machine. After maintenance, the…

831

Abstract

Purpose

This paper aims to propose an approach for the optimization of imperfect preventive maintenance and corrective actions performed on a single machine. After maintenance, the machine returns to an age between “as good as new” and “as bad as old”.

Design/methodology/approach

The approach is based on fuzzy logic and simulation‐based optimization. Fuzzy logic is preferred over crisp logic because it is relatively easy to implement in this situation considering that the human factor is hardly interpreted by analytical methods because of its unpredictable nature. Simulation‐based optimization is used to have a more reactive and accurate tool for practitioners.

Findings

Taking into account the impact of the imperfections due to human factors, the period for preventive maintenance, which minimizes the expected cost rate per unit of time or maximizes the availability of the system, is evaluated by the simulation‐based optimization.

Research limitations/implications

Different and more realistic maintenance levels must be considered and the traceability of a specific system could be used to determine the most appropriate failure law. For this study, cost reduction was considered as the priority, but the model can be adjusted according to the user's preferences.

Practical implications

This paper considers a single repairable machine as a system that undergoes periodic preventive and corrective maintenance actions. Considering maintenance imperfections, rule‐based fuzzy logic can be integrated into the maintenance program to determine the times for the periodic preventive maintenance actions.

Originality/value

Considering human factors in maintenance programs is indispensable to assure more accurate and realistic results. However, due to the difficulty engendered by their modeling, most theoretical maintenance models do not consider these factors. Therefore, the proposed fuzzy model in the paper can be an important tool to include them.

Details

Journal of Quality in Maintenance Engineering, vol. 15 no. 4
Type: Research Article
ISSN: 1355-2511

Keywords

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