Failure Assessment of Spring-Operated Pressure Relief Valve Proof Test Data for Extending Time-in-Service

Abstract The proof test results of 1669 Spring-Operated Pressure Relief Valves (SOPRV), which were previously installed in active processes, were analyzed with respect to proof test ratio (R), time-in-service (TIS), set pressure (SP), working fluid (WF), material composition of the SOPRV and, if an SOPRV failed-to-open (FTO), the root cause of failure in the FTO failure mode if available. Many of these SOPRV had accumulated TIS in excess of the normal maximum of five years yet proof testing indicated that most would have functioned properly. This paper examines the results of the analysis and provides guidelines under which it is appropriate to consider extending TIS for individual SOPRV.