Short answer: more often than most people think, and it isn’t ASME who decides.
ASME doesn’t set the interval. Your inspector does.
This surprises people. ASME writes the construction code that the valve is stamped to. The National Board certifies capacity and maintains the inspection code. Neither publishes a rule saying “test every valve every X months.”
What actually governs you is:
- Your state or local jurisdiction. Boiler and pressure vessel laws are state-level in the US, and many set inspection intervals in law.
- Your insurance inspector. In practice this is the one most facilities work to. Insurers carry the risk, so they set the schedule, and large plants generally build their programs around what the inspector asks for.
If you want a definitive answer for your site, ask your jurisdictional or insurance inspector. Everything below is a starting point, not a substitute for that.
A practical rule of thumb
| Service | Typical interval |
|---|---|
| Boiler valves | Annually |
| Process valves | Every 3–5 years |
| Steam service | Annually at minimum |
Published guidance lines up with this. The National Board Inspection Code generally recommends annual testing for power boiler safety relief valves, and industry guidance suggests an initial inspection interval of no longer than 12 months, tightened or relaxed after that based on service conditions and how the valve is actually performing.
Why steam valves in particular
Steam valves should be tested at least once a year, without exception. The reason is simple: seats stick. A valve that sits closed on steam service for years can corrode or bind to the point where it won’t lift when it’s needed — and the one time it’s needed is the time it has to work.
Annual testing on steam isn’t about paperwork. It’s about confirming the valve still moves.
What drives the interval shorter
- Dirty, corrosive or scaling media
- High cycle counts, or a valve that has relieved
- High temperature service
- Any valve that has leaked, simmered or failed to reseat since the last test
Where to start
If you don’t have a schedule at all, start by asking your inspector what they require, then put boiler and steam valves on an annual cycle and process valves on three to five years. Tighten from there based on what the tests actually show.
Need replacements or spares while valves are out for testing? Send us the part numbers and we’ll quote them. Requests received before 3 PM ET are typically quoted the same business day.
For information only. This article is general technical guidance, not a specification or a recommendation for any particular installation. Valve selection, sizing, set pressure and inspection intervals depend on the equipment’s design data and the code it was built to. Always confirm with a qualified engineer and your jurisdiction’s boiler or pressure vessel inspector before specifying, changing or relying on a relief device.