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High pressure questions

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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High pressure questions

Unread postAuthor: skyjive » Tue Dec 30, 2008 10:39 pm

How much pressure can copper pipe up to 1" diameter safely hold? What about blowguns and QEVs? I know the 3/4" McMaster variety are only rated to like 150 or something but they are very solidly built and I bet someone has taken them much higher.

Also, how do I safely pressure test things? I gather that hydro testing involves filling the item in question mostly with water and adding a little bit of high pressure gas, is that correct? And how long should I leave it for?

Thanks and sorry for the barrage of questions.
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Re: High pressure questions

Unread postAuthor: MrCrowley » Tue Dec 30, 2008 10:47 pm

skyjive wrote:How much pressure can copper pipe up to 1" diameter safely hold? What about blowguns and QEVs? I know the 3/4" McMaster variety are only rated to like 150 or something but they are very solidly built and I bet someone has taken them much higher.

Also, how do I safely pressure test things? I gather that hydro testing involves filling the item in question mostly with water and adding a little bit of high pressure gas, is that correct? And how long should I leave it for?

Depends on the type of copper. I believe there are different types such as 'type L' and 'type M', which all have different ratings.

I'd imagine it could take over 500psi safely though.

Same with the QEV, rated for 150psi, people have taken them to 700psi. I'd imagine 450psi would be a safe constant operating pressure though (i.e, pressurizing the QEV to 450psi more then a few times, unlike 700psi which may just be a one off).

Yes I believe that is how you hyrdo-test things. As for how to leave it for, a few hours will probably do.
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Unread postAuthor: Gippeto » Tue Dec 30, 2008 11:01 pm

For all your copper questions;

http://www.copper.org/publications/pub_ ... ndbook.pdf

I've used a blowgun to 450psi, I'm not sure I would trust them much further without hydrotesting.

To do hydro testing, you can use oil, water, or any non flammable fluid. Fill as much of the part and system with fluid as possible.

I suppose you could pressurize with gas, but using hydraulic (fluid) pressure is MUCH safer.

Have an enerpac or something similar?

http://www.drillspot.com/pimages/332/33229_300.jpg

Whatever you use, try to keep the stored energy to an absolute minimum.

ie. anything the least bit flexible WILL store energy, this includes any pressure gauges.

If it is a proof test, I would leave it for at least 3 hours. More is better.

Some things have already been tested.

http://www.spudfiles.com/forums/the-fai ... 15393.html
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