Optimum Maintenance Interval Determination for Field Instrument Devices in Oil and Gas Industries Based on Expected Utility Theory

Abstract

With the increasing demand for complicated control and monitoring systems in chemical process plants based on tremendous improvements in the digital world, the number of devices for monitoring and controlling the plants has risen dramatically. In such huge networks of a myriad of instrument devices, determination of an optimum proactive maintenance interval (PMI) has become vital for enhancing plant safety and reducing maintenance costs. PMI optimization is a matter of considerable benefit variation, process reliability, personnel safety, and environmental concerns. In this paper, a comprehensive formula and a concise formula are developed and applied for obtaining the optimum PMI based on the expected utility theory. The proposed formulas are applicable for determining the most affordable and effective maintenance plan providing the lowest cost and acceptable reliability, availability, and safety in oil and gas industries in terms of an optimal decision-making problem. By considering variable failure rates and components' wear and tear, a comprehensive formula has been developed. Moreover, for constant failure rate and returning to the “as-new” condition after each proactive maintenance, a concise and “easy-to-use” formula has been obtained. Finally, it has been shown through practical implementation of the presented methodology in a typical gas refinery that about 41% benefit is achieved in one year, compared with the previous heuristic maintenance strategy in the same duration.