Hydrotest of psv

[Indy]

Hello,
I have a question regarding the hydrotest of a psv. I understand that a hydrotest is usually carried out at 1.5 times the design pressure but if the valve is specified without a test gag then surely it would lift at its set pressure ( lower than 1.5 times the design pressure of the line). How then is the testing usually carried out?

Thanks

 

[The Obturator]

Hydrotest is normally a one time test done by the manufacturer during production.
The body test pressure is based on the outlet pressure rating. The hydrotest is done on the body separately before assembly.
If the nozzle is of cast construction it is also hydro tested separately.
In cases where the hydrotest is to be done on a built valve, then a test cap or if you like, a cap with test gag is used to stop the PRV from opening during test.
Note that PRV's that are in PED mandated applications, the bonnet would also be hydrotested by the manufacturer (cast defined pressure containing parts).

All of these test are ore certified by the manufacturer and any inspector that has witnessed the tests.

Hydrotests are normally not done during overhaul, unless the condition of the components warrants it.

Per ISO-4126, only the term Safety Valve is used regardless of application or design.

 

[Indy]

Thank you for the reply. How would it be decided if the hydrotest was to be carried out on a built valve and not the individual components?

Thanks again.

 

[The Obturator]

Essentially the manufacturer will try to limit the number of visits by a customer appointed inspector. This gets in the way of production. In the old days, the inspector would come in to witness hydrotest on the individual components and then arrange to return for testing of the assembled valve. This meant no main production until the hydro was witnessed and signed off. Still occurs dependant on the purchasers requirements.

To answer your question, these days most manufacturers will get ALL their body, bonnets and nozzles and caps (if cast) done up front individually and certified anyway (most times by an offshore producer that does the casting, machining and hydrotesting). This is what ISO-9001 maintained control allows them to do. Doing it this way allow multi use of all of these parts (ie., it covers most, if not all, offerings).

Typically in this day and age, final physical inspection will consist of;-

*Check of nameplate, casting heat nos., materia certification etc.
*Set pressure test
*Leakage test
*Bellows integrity test if applicable
*Hydro test (nozzle only on built valve using test gag adaptor - only if nozzle cast and not already done)
*Pneumatic shell test - already done by the manufacturer but may be wanted for inspectors that know about it (basically checking the seals of the valves between body/bonnet, cap. nozzle etc.)
Note: May vary between manufacturers and type of PRV.

The key is the Quality Plan that has the scope of inspection defined and agreed between buyer and seller.

Hope that answers.

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Per ISO-4126, only the term Safety Valve is used regardless of application or design.