Applications of delay time theory to maintenance practice of complex plant

Lee, C

Abstract

This thesis is concerned with investigating and understanding the role and
consequence of different modelling options and parameter estimation options for
modelling a complex plant. As systems become more complicated and required new
technologies and methodologies, more sophisticated maintenance models and control
policies are need to solve the maintenance problems. The initial chapter introduces the
review of previous work on a single component system and multi-component system.
Although in recent years there has been a shift in the maintenance literature from
consideration of single items to systems composed of several components, so far only a
few papers have tackled the modelling of actual multi-component plant. In the third
chapter, delay time concept and analysis technique have been presented. Of
particularly importance are parameter estimation methods, namely the objective method
and the subjective methods. In the fourth chapter the component PM model and the
system PM model for downtimes and costs based upon various PM policies are
discussed. The key options within maintenance modelling are to determine regular
Minspection periods for the system modelled as a whole, and to determine the periods
for the plant as a set of separate component models. An extension to the downtime
model is presented for the case when the downtime due to failures within system is not
small, and impacts upon the estimate of the number of failures arising over a specified
time zone. In the following chapter, we address parameter estimation methods using
simulated data, and assess the ability of estimation techniques to capture the true
parameter values. Particular attention is paid to the problem arising during the
parameter estimating process because of the inadequate recording of PM data and
implied correlation between model parameters. Finally, a case study is presented of
maintenance modelling of production plant in a local company with view to improving
current practice. The model developed is based upon the delay time concept where
because of an absence of PM data, using the results of earlier chapters, the process
parameters and the delay time distribution were estimated from failure data only using the method of maximum likelihood. The modelling was repeated based upon
subjective assessmentosf parameter,a nd considerablec onsistencyw ith the objectively
based case obtained. For the plant study, modelling indicated the current PM
inspection program was ineffective. A snap-shot approach is then applied to assess
other ways of reducing the downtime, and the possibility of improving the PM
inspection practice. This leads to readily adapted improvements.

Citation

Lee, C. Applications of delay time theory to maintenance practice of complex plant. (Thesis). University of Salford, UK

• Thesis Type: Thesis
• Deposit Date: Jun 29, 2009
• Publicly Available Date: Jun 29, 2009
• Additional Information: Additional Information : PhD supervisor: Professor A. H. Christer
• Award Date: Jan 1, 1999