Maintenance strategies affecting equipment performance

  • A.B.M.Z. Kabir

Student thesis: Doctoral ThesisDoctor of Philosophy


Proper maintenance of plant items is crucial for the safe and
profitable operation of process plants, The relevant maintenance
policies fall into the following four categories:
(i) preventivejopportunistic/breakdown replacement policies,
(ii) inspection/inspection-repair-replacernent policies,
(iii) restorative maintenance policies, and
(iv) condition based maintenance policies,

For correlating failure times of component equipnent and complete
systems, the Weibull failure distribution has been used, A new powerful method, SEQLIM, has been proposed for the estimation of the Weibull parameters; particularly, when maintenance records contain very few failures and many successful operation times.
When a system consists of a number of replaceable, ageing components, an opporturistic replacernent policy has been found to be cost-effective, A simple opportunistic rrodel has been developed.
Inspection models with various objective functions have been investigated, It was found that, on the assumption of a negative
exponential failure distribution, all models converge to the same
optimal inspection interval; provided the safety components are very
reliable and the demand rate is low, When deterioration becomes a
contributory factor to same failures, periodic inspections, calculated from above models, are too frequent, A case of safety trip systems has been studied,
A highly effective restorative maintenance policy can be developed if the performance of the equipment under this category can be related to some predictive modelling. A novel fouling model has been proposed to determine cleaning strategies of condensers,
Condition-based maintenance policies have been investigated. A simple gauge has been designed for condition monitoring of relief valve springs.
A typical case of an exothermic inert gas generation plant has
been studied, to demonstrate how various policies can be applied to
devise overall maintenance actions.
Date of AwardOct 1980
Original languageEnglish


  • maintenance
  • reliability
  • process plant
  • safety
  • Weibull distribution

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