Relief Valve Replacement vs. Bench Testing (IIAR 6, Part 15)

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Replacement of pressure relief valves (PRVs) every five (5) years has long been established as RAGAGEP in industry documents (IIAR Bulletin No. 109 and No. 110) and manufacturer literature. ANSI/IIAR 6-2019 §13.1.2 introduces an alternative for owners that desire to increase the service life of their PRVs. The alternate test method can extend the service life of PRVs to ten (10) years and works as follows:

  • After five (5) years of service, a representative sample of relief valves must be removed from service and bench tested;
    • The representative sample must not be less than seven (7) PRVs or 5% of the total number of PRVs installed, whichever is greater;
    • The representative sample must be comprised of the PRVs experiencing the harshest environment and have been installed for the longest period of time;
    • The representative sample must be replaced with new PRVs;
  • The bench test must verify the following:
    • The PRV does not leak before reaching 90% of its set pressure;
    • The PRV activates at ±3% of the PRV set pressure;
    • The PRV is fully open by 110% of the PRV set pressure;
  • Where all of the tested PRVs pass the bench test, the remaining installed PRVs may continue in service for another year until the next representative sample of PRVs are removed and tested;
  • Where any of the tested PRVs fail the bench test, all PRVs that have been in service for a time period equal to or greater than the failed valve must be replaced, bench tested, or recertified within 6 months;
  • The maximum allowable service life for all PRVs must be decreased to one year less than the actual service life of the failed PRV;
  • If no PRVs fail a bench test after five (5) consecutive years, all remaining PRVs must still be replaced. The maximum service allowable service life for a PRV is ten (10) years even with 100% pass rate on bench testing.
  • A.13.1.2 includes two helpful examples which demonstrate how the alternate test method might look at a facility. In Example #1, a system with 100 PRVs successfully passes each bench test and achieves the maximum allowable service life of ten years for 65 of their PRVs. In this example, the facility would replace 328 PRVs over a twenty-year span, compared to 500 PRVs if time based PRV replacement were followed.

Example #2 is a more complex scenario in which the PRVs were installed in different years and at least one PRV failed the bench test in the 9th year after installation. The example illustrates the complexity involved in accounting for PRVs at large facilities with various PRV installation dates.

The alternate test method will not be a cost-effective solution for every facility. For systems with less than 50 PRVs, there simply will not be enough valves eligible for extended service life due to the requirement to test at least seven (7) PRVs annually. As an example, if a system has forty (40) PRVs and seven (7) are successfully bench tested each year, only five (5) PRVs would benefit from ten years of service without being bench tested.

This is Part 15 of a series on IIAR 6. You can access previous blogs in this series below:

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