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.