Selection of suppliers of repairable equipment with the aim of minimizing costs in the construction and operation phases

Abstract

Objective: Selecting suppliers of industrial systems equipment to minimize the total construction and operation costs and implement it for Feed Water Multi-state System (FWS) of Heat Recovery Steam Generator (HRSG) boilers in Mapna Company. Methods: Using the Markov chain model results in a mathematical programming model and then analyzing the sensitivity of this model. First, using the Markov chain, different system states are drawn. Then, using the state transfer rate (failure rate and repair rate) of the equipment, the probability of the system being in any of these states is determined parametrically. Then, the Markov chain model results are added to the other constraints of a mathematical model the problem and solved by GAMS software. The effect of cost parameter changes on the optimal solution is calculated individually and then compared in a general graph. Results: The highest construction and operation costs are in ascending order: 1- the equipment purchasing price, 2- the production capacity reduction cost, 3- the system construction delay penalty, and 4- the system shutdown cost. Also, the relationship between the optimal solution to these parameters is linear in a wide range of changes. Conclusion: All costs have a direct effect on the design of the Feed Water System (purchase, delay, capacity reduction, and shutdown), but the cost of purchasing equipment has the most significant effect on the total cost. It is therefore recommended to focus entirely on reducing this cost.

Keywords

• block diagram model
• availability
• reliability
• markov chain
• repairable equipment