A data deficiency based parameter estimating problem and case study in delay time PM modeling

This paper describes a modeling study of preventive maintenance (PM) policy of production plant in a local companywith a view to improving current practice. The model developed is based upon the delay time concept where because ofan absence of PM data, the process parameters and the delay time distribution were estimated from failure data onlyusing the method of maximum likelihood. Particular attention is paid to the problem arising during the parameterestimating process because of the inadequate recording of PM data and the implied correlation between modelparameters. An objective estimation process has been adopted here as far as possible. The case of data de"ciency exploredin the study is important because it is a relatively general situation in practice. An inspection model is "nally proposed toidentify the best inspection policy based upon the estimated model parameters and the delay time distribution. It isconcluded that the company has other problems to attend to before the inspection problem is "nally solved, anda structured review of maintenance engineering practice is recommended. ( 2000 Elsevier Science B.V. All rightsreserved