Proof Proof / hydrostatic test
Proof / hydrostatic test · Inspección y ensayos · ISO 1101 + ASME Y14.5
Example in plan
How to interpret it
On the drawing, “Hydrostatic test 1.5× design pressure · 30 min” states a proof / hydrostatic test requirement.
What controls
Test in which the part or assembly is subjected to a pressure or load higher than the service value for a defined time to demonstrate its structural integrity without failure or permanent deformation. It is a result requirement on the specific product, not a process check: the part tested is the one that is qualified. In fluid circuits the usual approach is a hydrostatic test with water, which is safer than gas because the liquid stores far less energy.
How to verify
Stepwise pressurization or loading up to the specified value, holding for the stated time and recording the pressure or load versus time curve with a calibrated instrument. The part is inspected during and after for leaks, permanent deformation and cracks, and on demanding parts some dimensions are measured before and after to confirm there is no permanent set. The record with the curve and the part identification is the evidence.
Common mistakes when interpreting it
- Confusing the load or pressure proof test with leak testing: one demonstrates integrity, the other tightness.
- Testing with gas what should have been tested with liquid, multiplying the risk unnecessarily.
- Accepting the test without recording the pressure-time curve with a calibrated instrument.
How to get it in the workshop / if it comes out of tolerance
It is a hazardous test: cordon off the area, bleed the air from the circuit before pressurizing and stay clear while it is under load. Check that the part is in the appropriate condition (heat treated, welded, with no pending machining that would reduce section), because testing before it is finished proves nothing. After a hydrostatic test the part usually needs drying and, on sensitive materials, checking for residual water.
Pressure drop during the hold: first rule out trapped air and fixture leaks, then look at the part. Permanent deformation after the test: the part does not comply and is not accepted even if it did not leak. If the test has to be repeated, bear in mind that overloading a part several times is not harmless and must be allowed for. And do not confuse this test with leak testing: they are different requirements and both are often specified.
Alternative symbol:Hydro
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