Under API 598 the shell is filled with water and held at about 1.5 times its cold rated pressure with the valve partly open so the whole body cavity sees pressure. No visible leakage through the walls or body-bonnet joint is allowed. It is followed by seat tests: a high-pressure hydrostatic closure test at about 1.1 times rating and a low-pressure air test at around 60 to 100 psi.
Repaired valve passed the shell test, but it's bubbling on the low-pressure air seat test, back to lapping.
Also heard as
- body test
- hydrostatic shell test
Related terms
Body
The main pressure-containing shell of a valve, carrying the flow passage and the end connections.
Hydro
A hydrostatic pressure test: filling a valve, piping system or vessel with water and pressurizing it to prove strength.
Bubble-tight
Shut off with no visible seat leakage when tested with air or gas under water.
Shutoff class
A rating of how much seat leakage a closed control valve is allowed, from Class I to Class VI.