Welding Tips and Tricks

Hello all, I'm a new member here, and I was wondering if someone could advise on if there is a code specific to pressure testing of aluminum pressure vessels. I'm an engineer (I know, we are the worst), with a part that needs to be leak checked, and I was wondering if there were standards before I wrote up a procedure.


Thanks!

For repair work you typically need to test to 80% of the max name plate pressure. I believe that for a new tank it has to be tested at the rated pressure on the paperwork before the name plate is affixed. I would recommend testing with hydro and not air.

Thanks Poland308, do you know if that comes from an AWS code? I flipped through AWS D1.2 and could not find anything on pressure testing. I assume testing with water is better because it is in-compressible and leaks are more apparent? This is a new part that I am designing and doesn't really see high pressures.

I don’t know for sure what part of the code it’s under but I’ve seen lots of tanks from different manufacturers that are made from different materials they all seem to have the nameplate. Aluminum vessels seem to be more common in food production. But I’ve seen aluminum water tanks as well. Hydro testing is primarily for safety, but also it’s easier to slowly hit a pressure. It’s less likely to have a pressure swing due to temp changes during the test period. Perhaps this is a topic Otto /Steve could comment on. I think much of the stuff he works on is aluminum and SS pressure vessels.

helfires688 wrote:Thanks Poland308, do you know if that comes from an AWS code? I flipped through AWS D1.2 and could not find anything on pressure testing. I assume testing with water is better because it is in-compressible and leaks are more apparent? This is a new part that I am designing and doesn't really see high pressures.

helfires,

What kind of max working pressure is this thing suppose to operate at? And is it being used with a liquid or a gas? Also are you just looking for a way to "proof test" your design or do you need to set up a method you can test ever one you build as part of your QC inspection program?

Don't know of any AWS codes that address pressure testing but ASME sec VII and ANSI B31.3 have something to say on the subject that may or may not be relevant to what you're doing.

ASME SEC VIII is the code in the US for pressure vessels. For vessels that are in service and requiring repair, the National Board Inspection Code (NBIC) has rules for testing.

Pressure testing is usually performed at 1.3 times the design pressure but options exist for other methods. Welded Repairs to pressure vessels are required to be performed by NBIC "R" Stampholders.

First and foremost, water is and always has been compressable. It requires a hell of a lot of energy to do it.

Water is not as elastic as air, and less energy is stored in a vessel under test. Ergo, water testing is "safer".

A vessel full of air at 200psi will turn itself inside out in failure as the energy is released. The same vessel filled with water experiencing the same failure will squirt a couple quarts of water out and be back to zero pressure.

If you go into hydrostatic testing, the vessel is submerged in a tank of water and the tank manometers are zeroed to display the volume occupied by the vessel being tested. When the vessel under test is at pressure, the manometers indicate how much if any expansion has occurred in the vessel.

Unfortunately, due to an excess of matriculated meatballs running around in 2018, pressure testing and hydrostatic tend to be misused interchangably.

HT2-4956 wrote:

helfires688 wrote:Thanks Poland308, do you know if that comes from an AWS code? I flipped through AWS D1.2 and could not find anything on pressure testing. I assume testing with water is better because it is in-compressible and leaks are more apparent? This is a new part that I am designing and doesn't really see high pressures.

helfires,

What kind of max working pressure is this thing suppose to operate at? And is it being used with a liquid or a gas? Also are you just looking for a way to "proof test" your design or do you need to set up a method you can test ever one you build as part of your QC inspection program?

Don't know of any AWS codes that address pressure testing but ASME sec VII and ANSI B31.3 have something to say on the subject that may or may not be relevant to what you're doing.

Franz,
I can't share the specific working pressure but lets just say its pretty low (<100psi). This is more for a proof of concept, but I am also looking to develop a process for long term QC should this end up working out. Our vendor is struggling to get a leak proof part, and I think I may try a cut an etch to look at the weld profile, as I suspect we are getting lack of fusion at the toes of the weld.

Thanks for the heads up on pressure testing vs. hydrostatic testing, I care less about deformation under pressure, and more about zero leaks.

Thanks everyone for the help and info on this topic!