API 527 Safety & Relief Valves
What API 527 requires for safety & relief valves — applicability, key and testing requirements, the alternative standards, and compliant supply with full certification.
What does API 527 require for safety & relief valves?
API 527 (Seat Tightness of Pressure Relief Valves, American Petroleum Institute (API)) sets the design, material and testing requirements for safety & relief valves in its scope. API 527 defines the acceptable seat tightness (leakage limits) for pressure relief valves (PRVs) and safety relief valves at inlet pressure conditions below the set pressure. It provides maximum permissible leakage rates as a function of set pressure for both gas and liquid service. API 527 test procedures are required during manufacturing, and repeat testing is used to qualify a PRV after maintenance. A valve passing API 527 criteria is said to have 'API 527 seat tightness'.
Applicable Pressure Classes
Key Requirements
- Test pressure: 90% of set pressure for metal-seated valves
- Maximum leakage at 90% of set pressure per API 527 bubble test chart
- Bubble test method: discharge submerged in water, count bubbles per minute
- Gas service: maximum leakage expressed in bubbles per minute per orifice area
- Liquid service: maximum leakage expressed in drops per minute
- Re-test after maintenance before return to service
- Test conducted with the valve connected to seat tightness test stand, not in-line
Testing Requirements
- Seat tightness test at 90% of set pressure
- Bubble count or drop count per API 527 acceptance table
- Test conducted before shipment and after maintenance
Alternative Standards for Safety & Relief Valves
Other standards that also govern safety & relief valves — useful for spec cross-acceptance.
Related Standards
Connected Engineering
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