[PSUBS-MAILIST] Pressure Test Chamber

Thu Jun 22 18:38:33 EDT 2017

From: Personal_Submersibles [mailto:personal_submersibles-bounces at psubs.org] On Behalf Of James Frankland via Personal_Submersibles
Sent: Friday, 23 June 2017 3:14 AM
To: Personal Submersibles General Discussion
Subject: Re: [PSUBS-MAILIST] Pressure Test Chamber

I think ive got some of those DK-lok fittings somewhere.  I don't think on the HP system as I used parker and Swagelok for those, but im going to track them down now.

On 22 June 2017 at 00:15, Hugh Fulton via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

Alan,

We have a pressure tester that goes up to 40,000 psi.  If you need to do a high pressure test we can assist.

We had an explosion with a 1” line that was pressurised with 3,500 psi air but there was oil left in the line after hydrotesting with oil.

The explosion blew out the side of the shed  and reached an estimated 25,000 psi in the pipes which ended up looking like Spaghetti.

I had explained in detail to the guy who did the fitting of the pipes that everything had to be taken apart after the hydrotest and cleaned using solvent, then soapy water etc. as well as telling him stories of explosions.

The guy, an aircraft engineer, did not do it properly and left oil in a branch tube, and I did not do a check on it.  Very lucky my son did not get killed as he opened the valve  doing tests.  These things do not just go pop when they fail and this forum needs to hear of these dangers.  The explosion was heard all round Clevedon. That was our first accident of that nature in 40 years of high pressure involvement. We only use water now for testing and make sure there is no air present.  We did have another incident when we hired out our tester to another company who tested a tank to 1500 psi and the sight glass was held in with a very fine thread.  The sight glass went through the roof iron along with the fittings and we never found the parts.  The inspector had looked in the sight glass about 20 seconds before it let go.  If you are using tube fittings always disassemble after swaging and check the ferrules are in the right way and that a proper joint has been achieved.  There are some fittings which are copies and not up to the job.  We had issues with “DK-lok” (from Korea) with NPT threads where the taper was ½ the required taper but the thread gauge said it was OK. They were also not full form threads.   Also had some fittings called “Tubefit”  from I don’t know where and they were poor copies of “Swagelok”.  

We use SSP fittings out of USA which are fully interchangeable with Swagelok but in my opinion they are better quality.  

Air from a scuba tank over water is OK but make sure you have a concrete wall between you and the thing to be tested.  Also you should have an excess flow valve in the line.  You can get those from  Swagelok etc.

Hugh

From: Personal_Submersibles [mailto:personal_submersibles-bounces at psubs.org] On Behalf Of Alan via Personal_Submersibles
Sent: Wednesday, 21 June 2017 5:58 PM
To: Personal Submersibles General Discussion
Subject: Re: [PSUBS-MAILIST] Pressure Test Chamber

Thanks Greg & Hugh,

there was a bit of doubt in my mind about it so mentioned my

intended process. I have just googled accumulators in hydraulic systems

& the danger of high pressure air! Yikes just as well I've got you guys

looking out for me.

What about air from the scuba tank pressurising water?

I can get all the air out of the test chamber apart from the air in

the line pressurising it!

Other than that I have done some previous tests with the water blaster

& may have to suffice with it's pressure!

Cheers Alan

Sent from my iPad

On 21/06/2017, at 3:33 PM, james cottrell via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

Alan,

Pressure testing that high needs to be done with liquid not gas. High pressure air is VERY dangerous. A pressure washer pump using water would be a safer choice.

Greg

  _____  

From: Alan via Personal_Submersibles <personal_submersibles at psubs.org>
To: personal_submersibles at psubs.org 
Sent: Tuesday, June 20, 2017 9:01 PM
Subject: [PSUBS-MAILIST] Pressure Test Chamber

I am making a plastic container to fill with water & stand inside my

pressure chamber. There is a gap between the wall of the container

& the chamber which I intend to fill with oil. There will be about an

inch of air at the top of the chamber & I'm using a scuba tank to

pressurise the unit up to 3000psi.

Will car engine oil do to fill the gap between my plastic container &

the chamber wall, or do I need to go with a hydraulic fluid.

Am using the plastic container to keep water from rusting my test

chamber. (Aussie Steve's idea)

Cheers Alan

Sent from my iPad

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