Thread: Hydrostatic testing a compressor receiver

Hi all,

A workmate and j recently swapped air compressors. Mine was a newer but smaller belt driven unit and his was older but larger (too big for his shed) unit made by Clisby.

His unit spent a good part of its life in Darwin. I looked like it has had a hard life but I'm confident that with some TLC it will still be a good unit.

One thing that did concern me was any potential for the receiver to be badly rusted given it's working environment in Darwin. So I decided to do my own hydrostatic testing.

Turns out it's pretty easy to do with a pressure washer. Plenty of YouTube videos including one by Keith Rucker which was very informative.

The plate on the side says the TP is 1650 Kpa and WP is 1100 Kpa that's about 239 psi and 160 psi respectively in the old scale.


Given that my WP will be around 120 psi max and the fact that it is old, I decided to de-rate the test and test only to approx. 220 psi.

I want to know it's reasonably safe but I also don't want to destroy it either.

Process was straight forward. Remove all fittings (I left the non return valve in place as I didn't have a spare 3/4" blank) Fill it with water making sure there is no air left inside and blank off all except for a place for a pressure gauge and the wand attachment.

Start up the pressure washer and adjust the pressure relief valve slightly above the test pressure. Not a huge amount of work for a pressure washer that can do over 3000 psi. Squeeze the trigger on the wand and watch the pressure gauge. The pressure rises very quickly and you need to be on the ball or you will go above your intended pressure and destroy a perfectly good receiver!

When you achieve the test pressure, release the gun trigger, turn pressure washer off and wait about 5 mins.

Look for leaks....

No leaks and no loss of pressure!

Happy with that. Happy myself nor one of my kids will end up wearing it. While it's not a certified test, it gives me some peace of mind.

Simon






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Good move testing an old tank. You just never know.

I don`t know what the current standards are (specially as wall thickness on tanks seems to be getting thinner) but it use to be three time rated pressure.
I test anything I make, pneumatic or hydraulic to three times pressure.
Tony

Hi Tony,

I think it may depend on type of use. For example, one of my LPG bottles has a test pressure (according to the stamp on the neck) of 3.3 Mpa. That's about 2.7 times it's working pressure of 1183 Kpa (pressure to keep LPG a liquid)

Test pressures for air compressor receivers seems to be 1.5 time working pressure. That's certainly the case on the receiver I tested according to the compliance plate.

At work our breathing apparatus cylinders have a working pressure of 3000 bar and often get abused, exposed to heat, chemical attack and mechanical abuse. I'll have to have a look but I suspect that their test pressure is a much higher percentage of work pressure than above examples.

Simon

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Good work on doing the test. I've seen references to filling the receiver with water then using a grease gun as the pressure source, but hadn't seen or thought of using a pressure washer as the source.

FWIW - my vertical receiver test pressure is about 1.7x - WP is 958kpa and TP is 1650.

Steve

I've seen the grease gun method too. Both that method and the use of pressure washer are featured on YouTube. Another reason to love having a pressure washer!

Wrt your receiver, it appears that regardless of the working pressure, the test pressure seems to be around the 1600 Kpa mark.

Simon

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Originally Posted by bts

Good move testing an old tank. You just never know.

I don`t know what the current standards are (specially as wall thickness on tanks seems to be getting thinner) but it use to be three time rated pressure.
I test anything I make, pneumatic or hydraulic to three times pressure.
Tony

All the oil and gas pipework and pumps we do at work is tested to 1.5 Maximum Allowable Working Pressure.

I borrowed the local Boiler Makers water pump box (can't remember the proper name, but same one that plumbers use) years ago when my brother and I were building a Sandblaster. I distinctly remember being told to test the vessel to 1.5 times what I wanted the working pressure to be (WP 120psi TP 180psi). I would have to ask him again as it was a long time ago, but I think the test time was 1 hour. I'd never heard of a pressure washer or grease gun being used, but how does the grease gun work?.

Grease guns can develop very high pressures in order to force grease through small spaces and voids.

The process involves filling the grease gun with water, connecting it to the vessel to be tested and pump away.

Simon

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The ones I recall looking at didn’t mention water in the grease gun, just prefilling the tank with water first. My assumption was that you just used whatever grease was in the gun. Any residual grease wouldn’t be as bad as the oily gunge that I’ve seen come out of some old receivers!!
Must try it sometime - I’m dubious any of my guns would be good enough to actually pump water to a reasonable pressure...

Steve

Hi Stewart, Guys,

Originally Posted by steran50

I borrowed the local Boiler Makers water pump box (can't remember the proper name, but same one that plumbers use) years ago when my brother and I were building a Sandblaster. I distinctly remember being told to test the vessel to 1.5 times what I wanted the working pressure to be (WP 120psi TP 180psi). I would have to ask him again as it was a long time ago, but I think the test time was 1 hour. I'd never heard of a pressure washer or grease gun being used, but how does the grease gun work?.

Somewhere I have a drawing of a pressure test water pump if anybody wants it I'll find it and post it. Its not particularly complicated to build.

I use a hydraulic hand pump for testing. With the receiver tank full of water it only takes a couple of pumps and your there. Not a lot of oil to waste.


The reason I go to 3 x pressure is that years ago I was at a company picking up parts and they made receiver tanks. They tested to 3 x pressure, had x-rays done and did measurements under pressure to gauge tank expansion. Most of their work was for off shore rig work.
My thoughts being that if 3 x pressure was good enough for them its good enough for my. At least for the stuff I build for home.
I would not go this high if it had a tag on it stating test pressures.

Tony

Hello to all.
I'm involved in model steam and boiler building. On Ebay I found a plumbers test pump, new , for $170.00 about 5 years ago. O cheap knock off the real thing. The quality is good and it has a hold valve as well.
Today I would build instead of buy as I'm over the place it was made.
Regards
BC

Interesting idea, I like it.

I tend not to worry about it though.
A workshop type 120psi working compressor is very unlikely to fail by explosive decompression. Failure mode of an old tank is far more likely to be one or more small pin holes caused by rust that will bleed off under pressure.

Originally Posted by steran50

I borrowed the local Boiler Makers water pump box (can't remember the proper name, but same one that plumbers use) years ago when my brother and I were building a Sandblaster. I distinctly remember being told to test the vessel to 1.5 times what I wanted the working pressure to be (WP 120psi TP 180psi). I would have to ask him again as it was a long time ago, but I think the test time was 1 hour. I'd never heard of a pressure washer or grease gun being used, but how does the grease gun work?.

Was it something similar to this?

https://www.totaltools.com.au/36907-...YaAlcSEALw_wcB

Originally Posted by simonl

Grease guns can develop very high pressures in order to force grease through small spaces and voids.

The process involves filling the grease gun with water, connecting it to the vessel to be tested and pump away.

Simon

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Yes grease guns certainly can develop very high pressures. I understand now, the grease gun in this instance is actually only be used as a water pump and there's no reason why that wouldn't work providing the grease gun was in good order.
I actually do have a Test Bucket pump here somewhere, but I've never tried it so I don't know if it works or not it might even be buggered for all I know. I actually would be interested in that drawing BaronJ even though you can buy one off eBay quite cheap but what the quality is like is anyone's guess https://www.ebay.com.au/itm/5000kpa-...5.c10#viTabs_0 .
The pump set up that I borrowed Com_VC which was about 18 years ago was simply a square galvanised box (approx. 250mm square by 250mm high) with a handpump mounted inside. The pump set up was quite old then and was probably something like you would see in an old Mcpherson's Catalogue.
Racingtadpole you might want to check these links on Air Compressor Explosion https://sites.google.com/site/metrop...mpressor-tanks and https://www.compressorwale.com/air- .compressor-explosion-caught-on-a-cctv-footage.html