Effect of airlock in hydrostatic test

guest,

it should'nt,

but depending on the size of air pocket, it could amount to a safety issue, because of the energy that would be stored.

phoenix911

Trapped air absolutely will affect a hydro test over time. The test gage will show a slow decrease in pressure value.

Sorry guest, I should elaborate more with just a yes and no answer.

I do not know what the volume of the air lock is.

Air is compressable, but pressure is pressure on a sealed unit you cannot gain or lose pressure, after the pressure is established.

As I stated earlier, it's a safety issue. heres a few links

http://www.cheresources.com/airleaktest.shtml

http://www.answers.com/topic/hydrostatic-test

http://www.buchen.com/pdf/safetyinstructionmanual2.pdf

Is this a certified ASME shop, refer toyour WPS or ask you AI for his opinion.

good luck,

phoenix911

The safety issue is a potentially lethal one. 200' of 8" diameter PVDF was being tested in the sub fab at a major chip plant I was working at in Colorado Springs when it ruptured (catastrophic failure). Not good.

Over time you will see a pressure drop at the gage. As to how much of a drop depends on what test equip/sensitivity you are using.

TexasCharley,

Correct,

I should of carried out my reasoning more, than just a yes/no answer. with not only the compressibility of the air, but the deformation of the shell.

It depending the volume of the air lock.

Shipyard I was working, had to design hatches with minimal weight to due weight limitations of aircraft for deploying. This hatch had to hold 4 PSI and a 24" x 48" hatch would have potential of 4608 lbs of energy stored.

And with the weight restrictions, this hatched literally ballooned, but held to specifications.

failure can happen very quick.

phoenix911