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Hydrostatic testing

A place to ask general spud cannon related questions.
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Unread postAuthor: Gippeto » Wed Dec 10, 2008 2:21 am

As long as the joint dimensions remain the same, yes.

Might vary somewhat if you try to epoxy to teflon though. :wink:
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Unread postAuthor: daccel » Wed Dec 10, 2008 10:28 pm

I completed an initial test today.

4"x3/4" type L copper pipe, fitting and valve epoxied ~1/2" in either end with JB KWIK . 15 hour cure time.

This is the sprayer used: http://www.graco.com/Internet/T_PDB.nsf/SearchView/Ultra395. Specs say 3300 psi, but I don't have a gauge, so I don't know the exact pressure reached. The hose fitting is 1/4" npsm, but I had a broken spray gun on hand to borrow a compatible part from.

All air was removed by closing the valve on the end of the pipe while water was running through. Pressure was slowly raised to max. No visual deformation was apparent.

After about 30s there was a brief hissing sound and then the plug blew out. It was pretty loud and the hose shot out of the bucket at a good rate.

In retrospect, I should have had the foresight to fix the hose in place. I know the reason you get a consistent spray is that the hose acts as a pressure reservoir, so the test part isn't going to fail the same as on a solid test rig. Duh.

This will be addressed in any future tests, possibly with the addition of a hardline off the sprayer.

Sorry, no video! Pictures will have to suffice.
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Unread postAuthor: D_Hall » Wed Dec 10, 2008 11:35 pm

Looks like I'm a little late to the thread, but as a data point....

At the office we have a number of pressure vessels that must be anually hydrostated. The test rig of choice by those who actually do this for a living? A power washer.

Not too different than a paint sprayer. 8)
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Unread postAuthor: Gippeto » Wed Dec 10, 2008 11:39 pm

I use one of the dead weight testers at work. Accuracy at it's finest. :D
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Unread postAuthor: daccel » Wed Dec 10, 2008 11:56 pm

Well you know what they say about good ideas..

Although with this, if I had a gauge, it has the advantage of variable pressure to test lower pressure things.

Yeah, I really should look at finding a job with more spud-relevant equipment, sprayers and pressure washers aside. :lol:
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Unread postAuthor: ALIHISGREAT » Thu Dec 11, 2008 2:49 am

wait.... what was the actual pressure it held?

edit: oops i just noticed the fact you don't have a gauge LOL you should really get one LOL
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Unread postAuthor: Hotwired » Thu Dec 11, 2008 12:40 pm

Well, on the plus side the copper still looks in pristine condition.

You should try using something other than pure epoxy for a plug fully exposed to pressure. I know Jack likes the stuff a lot but it's a brittle bugger and high pressure can cause things to flex somewhat.

Interesting revelation about using pressure washers for hydro. Vastly less hassle than getting some professionals along to fiddle with your cannon.
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Unread postAuthor: ALIHISGREAT » Thu Dec 11, 2008 12:53 pm

Surely using something fibrous in a similar way to pykrete would strengthen the epoxy?
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Unread postAuthor: daccel » Thu Dec 11, 2008 8:42 pm

Yes, a gauge would be useful but I think it's safe to say it reached at least 3000 psi, because the regulator is factory set to 3300 and the pump was just serviced so it's in good shape.

Yeah, the copper seemed unfazed, a straight edge against it pressurized showed no visible deformation.

I think for reinforcement I'll go with crimping the end, and see if I can get some small screws to sit flush with the outside of the pipe. Or could make pins out of wire or steel rod instead of screws, and drill shallow holes in the fitting to seat them in
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