Author Topic: Hydro-testing  (Read 1653 times)

Jake Parker

« on: July 27, 2018, 10:50:59 AM »
I used to hydrotest gas pipelines 4 high-pressure applications. When I got a used air compressor receiver given to me a hydro tested it as well. I also Hydro tested a friends are receiver while testing my own. I thought I would walk you through the steps that I took to safely make sure that an air compressor tank will hold up to its recommended settings.
To started with you need to plug all holes, and remove the safety pop off valves. You need one bung to be at the highest point of the tank to ensure that all air has been forced out.
 I tapped into the lower drain hole with a half inch ball valve and a garden hose adapter. I used a "T" in one of the pop off valve ports to hook a gauge and a fitting to connect my "porta power's" hydro pump. I filled yhe tank from the bottom pushing the air out of my vent, agin the highest point, until it was full I pkugged off the vent, closed the fill valve and used the "porta power's" hydro pump to pump the tank up to 210psi. I used the pipeline standard of 150 per cent of normal working pressure.
I held the test for 2 hours with no fluctuation in pressure.
I drained all the water back through oil absorbing matts to eliminate the small amount of oil injected from the "porta power".
I let the tank sit in the sunshine open to help evaporate any residual water for a few days.

Jake Parker

Re: Hydro-testing
« Reply #1 on: July 27, 2018, 10:52:17 AM »
The "t" and gauge.

Jake Parker

Re: Hydro-testing
« Reply #2 on: July 27, 2018, 10:54:15 AM »
More random pictures

Jake Parker

Re: Hydro-testing
« Reply #3 on: July 27, 2018, 10:55:01 AM »
If y'all have any questions, please ask.


Re: Hydro-testing
« Reply #4 on: July 27, 2018, 11:55:55 AM »
Jake, thanks for posting.  I will make this a "sticky" so it's there for anyone in the future can reference to.

Have two questions here. 1) how far are you from the tank when applying pressure to the tank?

2) Should a person base the test pressure off of the ASME tag on the vessel or tank?

I think it would be a good idea before applying any pressure, first, look at the ASME tag and see what the tank was originally hydro tested to before applying any pressure.  150% of working pressure is correct for most applications, only if you know the original design working pressure of the vessel. That's why you go off the metal tag that should be affix to the vessel or tank.  If this label is missing, DO NOT PRESSURE TEST, unless you have had a working air pressure applied.  Then follow your advice of a test pressure of 150 psi.

If you have a shop built tank and want to pressure test, your are on your own!  No advice given here.

I am a mechanical engineer, not licensed, but have/do work with high pressure equipment all the time.



Re: Hydro-testing
« Reply #5 on: July 27, 2018, 01:13:19 PM »
Going by the ASME plate would be best if the tank has one. A lot of "homeowner" compressor tanks aren't ASME rated though. All you can really do with those is use the compressor packages pressure as tank MWP.

Jake Parker

Re: Hydro-testing
« Reply #6 on: July 27, 2018, 03:02:29 PM »
Im pretty close to the tank, literally right next to it.
Hydro testing is fairly safe, due to the fact that the pressure comes up very slowly. Plus with the small expansion amount of the water, it will equalize almost instantaniously if there is a rupture.
If theres a a.s.m.e tag, by all means adhere to it, as an overpressure incident can render your test piece usless.


Re: Hydro-testing
« Reply #7 on: July 27, 2018, 04:30:53 PM »
I encourage anyone who wants to try this, to exercise extreme caution and work safe!

Remember, any trapped air can turn a vessel into a bomb, if not bled off properly.

Before you test a vessel, wrap a flat blade tape around the tank and take an accurate measurement and record.  If you like, at test pressure, measure again.  You might be surprised how much bigger the vessel is.  Last, re-measure after all of the pressure is removed.  It should measure the same as it did before the pressure test was performed.  If the tank did change in diameter or length on the measurement, that would indicate it over-stressed the material, it would be best advised to scrap the tank. 

Also, if you keep loosing pressure and can't figure out where it's going, the tank material is stretching and fixing to rupture.  Please be careful!


slip knot

Re: Hydro-testing
« Reply #8 on: July 27, 2018, 04:32:50 PM »
I've done the same thing using a grease gun. it just takes a bit longer.   


Re: Hydro-testing
« Reply #9 on: July 28, 2018, 07:45:11 AM »
Nice write up. Thank you
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Re: Hydro-testing
« Reply #10 on: July 28, 2018, 08:55:11 AM »

it would be best advised to scrap the tank. 

Or make a BBQ pit out of it  ::)


Re: Hydro-testing
« Reply #11 on: August 04, 2018, 05:35:41 PM »
As a quick and easy first step, you could use very low pressure air (careful) and spray the outside with a dish soap/ water mixture.   Any pinhole leaks will produce tell tale bubbles.  Gas molecules will squeeze thru smaller defects and is a more rigorous test as far as leak tests go. 
If it fails this initial test toss it.  If it passes this test then maybe proceed to hydro.
Hydro is safe(er) for the bystander but the downside is you risk turning it into a destructive test to the vessel as it stretches under pressure.  Kind of like the guy at the muffler shop stabbing your exhaust system with a screwdriver to check for holes!! LOL    I get it tho - the whole point of over pressure testing is to check a tank that's presently holding in the operating range but only barely. 
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