Risk Based Method to Establish Inspection Intervals for Pressure Relief Devices

SUMMARY

This paper describes the API Risk-Based Inspection (RBI) methodology for pressure relieving devices (PRDs) as detailed in the soon to be released 2nd edition of API 581 “Base Resource Document On Risk-Based Inspection” This methodology has been successfully used at several petrochemical facilities to establish risk-based inspection intervals for PRDs.

The API PRD RBI technology provides a system approach (includes the damage state of the pressure vessels, piping and heat exchangers protected by the PRDs) and evaluates the probability (reliability) and the consequence (criticality) of pressure relief valve failure and sets the appropriate inspection frequency based on risk. Results of recent studies have demonstrated the benefits of the new approach. Compared to a typical API 510 (3) approach, the risk based plan can significantly reduce the overall risk in the plant and at the same time, may provide a significant reduction in inspection costs.