Optimization of Multilayer Standby Mechanisms in Continuous Chemical Processes

Every
critical online unit in a continuous process must always
function normally, and one or more identical units are usually put
on standby to sustain the uninterrupted operation. Although a few
related studies have been reported in the literature, a comprehensive
analysis of the standby mechanism still has not been carried out.
The objective of this research is to construct a generalized mathematical
model to synthesize the multilayer standby mechanisms for any given
processes by minimizing the total expected life cycle expenditure.
A Matlab code can be developed accordingly to perform the required
optimization tasks via a genetic algorithm. The feasibility and effectiveness
of the proposed approach have been demonstrated with the case studies
concerning the pump system in a typical chemical plant. From the optimization
results, one can obtain the optimal design specifications of the multilayer
standby mechanism, which include (1) the number of layers, (2) the
numbers of both online and spare sensors in each measurement channel,
(3) the corresponding voting-gate logic in each channel, (4) the inspection
interval of a switch, (5) the number of spares for a switch, (6) the
inspection intervals for warm standbys, and (7) the number of cold
standbys.