Title:
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Maintenance strategies affecting equipment performance
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Proper maintenance of plant i terns is crucial for the safe and
profi table operation of process plants, The relevant maintenance
policies fall into the following four categories:
(i)
(ii)
(iii)
(iv)
preventivejopportunistic/breakdown replacement policies,
inspectionjinspection-repair-replacernent policies, -
restorative maintenance policies, and
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 fomd 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 rrodels, 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,
Condi tion-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.
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