THE PERIODIC MAINTENANCE POLICY FOR A WEIBULL LIFE-TIME SYSTEM WITH DEGRADATION RATE REDUCTION UNDER RELIABILITY LIMIT

2008 ◽  
Vol 25 (06) ◽  
pp. 793-805 ◽  
Author(s):  
CHUN-YUAN CHENG ◽  
MINGCHIH CHEN
Keyword(s):  
Failure Rate ◽  
Degradation Rate ◽  
Life Time ◽  
Repairable Systems ◽  
Maintenance Policy ◽  
Rate Reduction ◽  
Expected Cost ◽  
Cost Rate ◽  
Special Cases ◽  
Reduction Effect

From the literature, it is known that preventive maintenance (PM) can reduce the deterioration of system or equipment to a younger level. Researchers usually develop optimal PM policies based on the assumption that the PM can reduce system's age or failure rate. However, the PM actions, such as cleaning, adjustment, alignment, and lubrication work, may not always reduce system's age or failure rate. Instead, it may only reduce the degradation rate of the system to a certain level. In addition, most of the existing optimal PM policies are developed by minimizing the expected cost rate only. Yet, as demonstrated in this paper, the system will have very low reliability at the time of preventive replacement if the reliability limit is not considered. Hence, this paper is to develop an optimal periodic PM model by minimizing the expected cost rate per unit time with the consideration of reliability limit for repairable systems with degradation rate reduction after each PM. The improvement factor method is used to measure the reduction effect of the degradation rate. The algorithm for searching the optimal solutions for this PM model is developed. Examples are also presented with discussions of parameter sensitivity and special cases.

Sequential imperfect preventive maintenance policy with random maintenance quality under reliability limit

2011 ◽  
Vol 225 (8) ◽  
pp. 1926-1935 ◽  
Author(s):  
Z Wang ◽  
J Yang ◽  
G Wang ◽  
G Zhang
Keyword(s):  
Failure Rate ◽  
Preventive Maintenance ◽  
Average Cost ◽  
Numerical Control ◽  
Maintenance Policy ◽  
Cost Rate ◽  
Proposed Model ◽  
Optimal Maintenance ◽  
Average Cost Rate ◽  
Optimal Maintenance Policy

To determine the optimal maintenance number for a system with random maintenance quality in infinite time horizon, a sequential imperfect preventive maintenance model considering reliability limit is proposed. The proposed model is derived from the combination of the Kijima type virtual age model and the failure rate adjustment model. Maintenance intervals of the proposed model are obtained through an iteration method when both failure rate increase factor and maintenance restoration factor are random variables with a uniform distribution. The optimal maintenance policy is presented by minimizing the long-run average cost rate. A real numerical example for the failures of numerical control equipment is given to demonstrate the proposed model. Finally, a discussion is presented to show how the optimal average cost rate depends on the different cost parameters. The results show that in order to satisfy the practical requirements of high reliability, it is necessary and worthwhile to consider the system's reliability limit in preventive maintenance practice.

OPTIMAL PERIODIC PREVENTIVE MAINTENANCE SCHEDULES WITH IMPROVEMENT FACTORS DEPENDING ON NUMBER OF PREVENTIVE MAINTENANCES

2007 ◽  
Vol 24 (01) ◽  
pp. 111-124 ◽  
Author(s):  
JAE-HAK LIM ◽  
DONG HO PARK
Keyword(s):  
Preventive Maintenance ◽  
Hazard Rate ◽  
Optimal Schedule ◽  
Maintenance Policy ◽  
Expected Cost ◽  
Cost Rate ◽  
Mathematical Formulas ◽  
Periodic Preventive Maintenance ◽  
Maintenance Schedules ◽  
Preventive Maintenance Policy

This paper considers a periodic preventive maintenance policy under which each preventive maintenance (PM) reduces the hazard rate of the repairable system, while keeping the pattern of hazard rate unchanged. For this model, the hazard rate at a given time t is affected by the improvement factor which depends on the number of PMs conducted until t. In addition to the periodic preventive maintenance, the system undergoes the minimal repair at each failure between the preventive maintenances. We derive mathematical formulas to evaluate the expected cost rate per unit time by computing the expected number of failures depending on the hazard rate of the underlying life distribution of the system. Assuming that the system is replaced by a new one at the N-th preventive maintenance, the optimal values of N and the preventive maintenance period, which minimize the expected cost rate, are solved and thus the best schedules for the periodic preventive maintenance policy are established. Explicit solutions for the optimal schedule for the periodic preventive maintenance are presented when the failure times follow the Weibull distribution.

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