Imperfect Preventive Maintenance Policy Research Articles

An optimal sequential preventive maintenance policy under stochastic maintenance quality

This paper presents a sequential imperfect preventive maintenance policy for a degradation system. Two kinds of activity, called continuous preventive maintenance (PM) and minimal repair, are simultaneously considered when arranging discrete imperfect preventive maintenance schedules. In order to obtain the maximum benefit in a finite lifetime, an expected benefit model is formulated based on maximal/equal cumulative-hazard rate constraints, and the optimal PM intervals are obtained using a genetic algorithm (GA). It is usually difficult to determine fixed maintenance quality after performing maintenance activities. This problem is addressed in the present paper by assuming that the reduction factor is a stochastic variable following probability distributions at fixed times. It is more rational to describe the fluctuation and trend of quality of discrete preventive maintenance during a lifetime; this makes optimisation results more robust and insensitive to the randomness of the crucial parameters in imperfect PM models. A numerical case is presented to illustrate the proposed model and some discussions are summarised.

Imperfect preventive maintenance policies for two-process cumulative damage model of degradation and random shocks

In numerous applications, the system may fail due to multiple competing risks, especially degradation processes and random shocks. In this paper, we develop a two-process combination model for degraded system subject to cumulative effect from random shocks and degradation with two kinds of path function, including additive and multiplicative. Two numerical examples with sensitivity analysis for additive and multiplicative degradation path are discussed separately to illustrate this combination model. Based on the definition of the cumulative damage system, the imperfect preventive maintenance policy (N*, T*) with a common improvement factor is obtained to minimize the expected maintenance cost rate. The uncertainty of the reliability estimation and maintenance optimization is considered in the problem modeling. Also some extensions for this combination model are suggested for further research.

Extended periodic imperfect preventive maintenance model of a system subjected to shocks

This article deals with a periodic imperfect preventive maintenance (PM) model of a system subjected to random shocks. A system is subject to shocks that arrive according to a non-homogeneous Poisson process. As shocks occur, the system experiences one of the two types of failures: type-I failure (minor) and type-II failure (catastrophic). Type-I failures are rectified by minimal repair. The system is maintained following the occurrence of a type-II failure or at age T, whichever takes place first. At the N-th PM, the system is replaced. An approach that generalises the existing works on the periodic imperfect PM policy is proposed. The imperfect PM model adopted is hybrid in the sense that it not only reduces the effective age of the system but also alters the system hazard rate. Taking random minimal repair costs into consideration, the objective consists of finding the optimal PM and replacement schedules that minimise the expected cost per unit time over an infinite time-horizon.

Optimization of Preventive Maintenance Policies for Aging Equipments in Finite Time Horizon

The recursion relationship between the failure rate and the equipment age before and after preventive maintenance (PM) was built up concerning with the concept of improvement factor. The optimal imperfect PM policy model in finite time horizon of the aging equipments following Weibull distribution was proposed, which can minimize the total relative cost of the equipment PM. The optimal maintenance frequency and optimal maintenance interval under imperfect maintenance were determined by the model, and the reliability after each PM of equipments was considered. The model built in this paper can be used the decision supporting the maintenance plan and providing decision supporting for job shop scheduling.

A modified imperfect preventive maintenance policy considering failure replacement

This article is an extension of the periodic imperfect maintenance model in the literature. The purpose of this research is to investigate the influence on the optimal periodic maintenance policy after considering the failure replacement in the last period of preventive maintenance (PM). The specific maintenance decisions for a repairable system are: when to replace the system, when to repair the system; whether to conduct PM or keep the system operating. A partially periodic PM policy is proposed incorporating the costs of minimal repair, PM, failure replacement, and preventive replacement. The average cost rate for the proposed policy is obtained. Finally, the optimal parameters of the maintenance policy can be calculated using the cost rate function and the numerical comparisons of different policies are provided to demonstrate the effect of failure replacement.

Sequential imperfect preventive maintenance policies: A case study

In this paper, two preventive maintenance (PM) policies for the bus engines of a transport network have been considered. Based on the mean time to failure (MTTF) data of the engines of a particular make and model, maintenance policies are developed where the failure rate of the engines does not exceed the pre-determined level of maximum failure rate. In policy I, the system has a different failure distribution (Weibull) between PMs, and in policy II, each PM reduces the effective age of the system. The number of PM interventions and their schedule times, which minimize the expected mean cost rate over an infinite time horizon for both the policies, have been discussed. Finally, numerical illustrations and the effect of cost factors on the number of PM interventions and the expected cost rates have been presented.

Sequential imperfect preventive maintenance policies : Toshio Nakagawa. IEEE Trans. Reliab.R-37, 295 (1988)

Sequential imperfect preventive maintenance policies : Toshio Nakagawa. IEEE Trans. Reliab.R-37, 295 (1988)

Sequential imperfect preventive maintenance policies

Improvement factors in hazard rate and age for a sequential preventative maintenance (PM) policy are introduced. Two imperfect PM models are analyzed: (1) PM reduces the hazard rate while it increases with the number of PMs, and (2) PM reduces the age. The PM is done at intervals x/sub k/ (k=1,2, . . . , N) and is imperfect. The optimal policies to minimize the mean cost rates are discussed. The optimal PM sequences (x/sub k/) are computed for a Weibull distribution.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

小修理を伴う定期取替のまとめ

Several periodic replacement policies with minimal repair at failures are summarized: 1) A policy for a unit with random and wearout failures. 2) Two modified policies where if a failure occurs just before the replacement time, then (i) a unit remains failed, (ii) a unit is replaced by a new one. 3) Three imperfect preventive maintenance (pm) policies where (i) a unit after pm has the same failure rate as before pm with a certain probability, (ii) the age of a unit becomes x units of time younger at pm, (iii) the age of a unit after pm reduces to at at pm. Expected cost rates for each model are obtained and optimum policies are discussed. Some examples for the above models are presented. and the (k - 1) previous failures are corrected with minimal repair. Fur- ther, Tilquin and Cl~roux (17) introduced the adjustment costs which increase with the age of a unit. Tahara and Nishida (15) also introduced the break-· down cost suffered for a failed unit which is replaced at the first failurE~ after some age. In this paper, we summarize the knovm results of the policy, and consider extended and modified models which could be applicable to practical fields. For instance, we consider the policy for a used unit of age x and for a unit

A summary of imperfect preventive maintenance policies with minimal repair

A summary of imperfect preventive maintenance policies with minimal repair