Valve Pressure and Tightness Testing: Shell, Seat and Air Tightness
The question we get most often about valve pressure testing is “what pressure should we apply?” But the acceptance decision rests on three independent things: shell strength, seat tightness and micro-leakage (air tightness). Their multipliers, media and criteria differ, and a report that says only “hydrostatic test passed” will not survive a third-party retest.
This cluster collects the methods, standards, criteria and bench configuration for that line of work. Every section links to the article that carries the clause structure and the numbers you can check.
1. Three kinds of “no leak”
| Test | Pressure | What it looks for | Typical mistake |
|---|---|---|---|
| Shell strength | 1.5× rating, higher under some standards | Leakage or permanent distortion at body and joints | Rejecting a whole batch for a seat leak |
| Seat tightness | 1.1× rating | Leakage past the closure, judged by rate letter | Writing “passed” without the rate letter |
| Air tightness | Atmospheric or a low tier (6 mbar, 0.5 bar) | Bubbles, pressure decay or tracer concentration at low pressure | Running the high tier only, where pressure itself seats the seal |
The third row is the one that gets skipped. EN 1074 for water supply valves requires a 0.5 bar low tier in addition to 1.1×PFA; EN 13774 for gas distribution requires 6 mbar alongside 1.1×pmax. Six millibar is about 60 mm of water column — a valve that leaks there often shows nothing at 1.1×, because the pressure has pressed the sealing faces shut.
2. Find the article by question
How much pressure
- PN or CWP? Five things to settle before pressing a PN16 valve to 2.4 MPa — nominal pressure is not test pressure
- ASME B16.34: Class 150 is not 150 psi — rating at 38 °C × 1.5, then rounded up to 25 psi
- API 6D pipeline valves: pressure, seat and special tests in the 25th edition
- EN 12266-1: P10, P11, P12 and leakage rates A to G
Hold time and criteria
- How long should a pressure test hold? Three bases for the answer
- ISO 5208 leakage classes: ten rates on one table, soft and metal seats judged differently
- API 598 versus GB/T 13927: why the same valve gives two results
- GB/T 13927-2022: shell, seat and the judgement method
Air tightness and micro-leak hunting
- Air tightness tests that keep failing? Five leak paths to check first
- Seven reasons air tightness results drift, and how to trace them
- Choosing a leak test method: pressure decay, flow, tracer gas, vacuum
- Pressure testing in practice: clamping, conditions and the pressure curve record
- Hydrostatic and air tightness benches: separate strength, leakage and burst first
Benches and fixtures
- Choosing a valve test bench: settle pressure, size and acceptance rules first
- Custom pressure test benches: fixtures, medium, pressure envelope and guarding
- Accepting an intelligent valve test bench: method, traceability, safety functions
3. Three mistakes that cost acceptances
Treating the rating as the test pressure. A PN16 valve needs 2.4 MPa at the shell. That is right for EN — but the same valve on a US order needs 3.45 MPa, because AWWA C515 asks for 2.5×. Confirm which standard governs before you book the bench.
Reporting a result without its conditions. The same valve at 5 °C and 50 °C, held 15 s or 300 s, can pass one way and fail the other. A usable report carries medium, temperature, pressure, hold time, the clause the criterion comes from, and the measured leak rate.
Applying a soft-seat rate to a metal seat. Soft seats usually reach rate A (no visible leakage); metal-seated butterfly valves typically land around D under ISO 5208. Demanding A from a metal seat is not a stricter spec, it is the wrong criterion.
4. Configuring the bench
Every test on this line is one clamping system, one pressure source and one criterion. Covering DN15 to DN1200 and 6 mbar to 640 bar on a single machine usually means being inaccurate at both ends. In practice:
- Valve pressure test machine — shell at 1.5×, seat at 1.1×, report per valve, built for line takt
- Pipe and connection leak test bench — pressure decay and helium, for the 6 mbar and 0.5 bar tiers
- Valve comprehensive test bench — pressure, tightness, flow, torque and life on one frame
If you are unsure where to start, read how to choose valve testing equipment, or send us your valve types and standard list and we will map the bench.
Continue by test item
These clusters are grouped by test item rather than by standard number. The other four:
- Flow and control performance — Cv/Kv, PRVs and TMVs
- Life, torque and fatigue — fix the conditions first
- Special and safety tests — fire, cryogenic, emissions, type test
- Certification and market access — EU, US and China
Not sure about the test pressure yet? Use the valve test scope configurator — pick valve, size, class and standard, and it returns shell and seat pressures, hold time and a bench list you can email.
Related test equipment
Each test above maps to a bench. Pick by valve type and by the item you need to prove:
- Valve pressure test machine — shell at 1.5x and seat at 1.1x, with a report per valve
- Pipe and connection leak test bench — pressure-decay and helium methods, judged against a leak-rate limit
- Valve comprehensive test bench — pressure, tightness, flow, torque and life cycling on one clamping system
- Valve testing equipment range — browse all models by valve type and test item