Determining the Optimal Maintenance Strategy for Ammonium Hydroxide ‎Production Unit Using Risk-Based Inspection ‎and Analytic Hierarchy Process

Ammonium Hydroxide production ‎unit (AHPU) is one of the widely ‎used and important units available in ‎many ‎industries such as oil and gas, ‎petrochemical, and power plants. In ‎this research, for the first time, a ‎detailed systematic inspection and ‎maintenance plan for AHPU ‎is ‎determined based on the ‎prioritization of equipment using ‎equipment’s risk analysis. ‎Equipment’s failure risk is ‎calculated ‎based on probability and ‎consequence of failure according to ‎American Petroleum Institute ‎Recommended Practice (API RP) 581. ‎Different ‎maintenance strategies were ‎designed and compared considering ‎several criteria like safety, cost, and ‎feasibility using the analytic hierarchy ‎process. Then risk-based optimal ‎maintenance policy for each group of ‎equipment ‎was identified. Finally ‎results showed that, the equipment ‎identified as high or medium to high ‎risk level such as liquid ‎ammonia ‎storage tank and its related ‎pipes, should has preventive ‎maintenance with an inspection ‎period of 48 months. While for the ‎medium risk equipment such as ‎ammonium hydroxide storage ‎tank ‎and low-risk equipment such as ‎ammonia absorption tank, should ‎have corrective maintenance with ‎inspection period of 72 and 90 ‎months, respectively‎.