Dry testing - losing pressure

[dan the man]

good thread.

 

[Onetap]

Thought about this Hep test some more ... does his pump tester (as pictured) compress the water rather than add air to the pipe work?

Yes. It's a Rothenberger test pump, the most common make. REMs do something similar. They cost about £150 or you may be able to hire them. The hand pump draws water from the attached red tank, which you have to fill up.

Note that the tank doesn't hold much water, but you shouldn't need much. The system under test would be filled up with a hose connection and all the air vented prior to the test.

I once tested a pressure vessel (at 8 or 10 bar, I think) with a cheap car foot pump immersed in a 4 gallon F&E tank. The pump sucked in water instead of air. It worked, though a bit undignified.

PS. The recommended test procedures for systems containing plastic plumbing is here (previously posted by Softus; thanks, Softus)

http://www.hepworthplumbing.co.uk/Hep pdfs/TFSP4Testing-6.pdf

The system is pumped up to pressure and allowed to expand before the test procedure starts. Note that this test method is specified in the Water Regulations, so legally it should be carried out on all new water supply systems. A similar test method should be applied to CH systems with plastic piping.

 

[Monsoon]

Quick update:

I've filled the pipework with main water pressure (>2.5bar) and the fittings and pipe work are fine (read no leaks)

The lose of air I experienced with the hazardous air test has not been replicated in a lose of water during the mains test.

As an aside I thought Id run a small test to feel what 3bar air pressure felt like taking all the necessary safety precautions. I placed my thumb over the open end of a copper 15mm pipe while pumping in air. I was quite surprised to find I could take the pressure up to 3bar. The force against my thumb really wasn't too bad.

 

[doitall]

As an aside I thought Id run a small test to feel what 3bar air pressure felt like taking all the necessary safety precautions. I placed my thumb over the open end of a copper 15mm pipe while pumping in air. I was quite surprised to find I could take the pressure up to 3bar. The force against my thumb really wasn't too bad.

Try putting your thumb on the tap spout to see if you can stop the flow.

If you want to do a proper test, get a 3m length of copper pipe and anchor it down ( a length of timber will do ) fit a lever valve one end and the pump the other, from the lever valve fit a short length of pipe with a compression cap pushed on the end without doing it up.

Blow the pipe up to 3bar and open the valve quickly to see how far the cap travels, warning do point it away from danger or better still at a thin sheet of metal about 3m away.

 

[r.bartlett]

Wow what a bunch of girls!!

In our trade - air conditioning- we pressure test to 30 bar (500 psi) with OFN. Never seen an accident. True we operate at a higher standard re- copper, fittings, braising and joints but it certainly doesn't scare me or anyone else in the industry. I have also seen/had loads and loads of leaks which have never caused an accident.
Dry testing is a great way of checking a system before a wet test and The first time I sAw it being done on a C.H system I though "yes that makes sense, keep it dry till you find/fix the leaks. No mess, no water on the carpet, no chasing steam round the pipes when re-soldering...."

If your work is up to standard I would be surpirised if the pipes of a C.H system couldn't hold easy 5+ BAR.

Cheers

Richard

 

[Onetap]

Wow what a bunch of girls!!

In our trade - air conditioning- we pressure test to 30 bar (500 psi) with OFN. Never seen an accident. True we operate at a higher standard re- copper, fittings, braising and joints but it certainly doesn't scare me or anyone else in the industry.

Ooooooh! What well 'ard chaps you are.

I think there's two possibilities with this

First, there's no hazard, and you have nothing to be scared of;
or;

Second, there is a hazard, you should be scared of it but you're not aware of it..

So, do you know which BS is concerned with pressure testing with air or OFN?

Do you know what it says about air testing?

Do you just use the pressure gauge on the cylinder regulator?

The BSs are compiled by a panel of recognised experts so I'd be inclined to trust them. I'll have to look it up when I get to work, if it doesn't take too long. I'm not certain that the one relevant to CH or water systems applies to refrigeration.

Flared fittings are less liable to come adrift than BS 864 (I think it is?) compression fittings with an olive on a parallel tube.

I found brazing to be far easier than soldering, but my main experience of it was on bench work. Joints didn't leak but they were all tested with water.

You wouldn't wet test a refrigeration system.

I have also seen/had loads and loads of leaks which have never caused an accident.
Dry testing is a great way of checking a system before a wet test and The first time I sAw it being done on a C.H system I though "yes that makes sense, keep it dry till you find/fix the leaks. No mess, no water on the carpet, no chasing steam round the pipes when re-soldering...."

If your work is up to standard I would be surpirised if the pipes of a C.H system couldn't hold easy 5+ BAR.

You've listed the advantages of air testing.

The disadvantages are that it's a bad medium for testing ( a small air leak causes a small pressure drop; a small water leak causes a loss of all the pressure) and it's dangerous. See the Hepworths link above. Most CH systems could go to 9 or 10 bar, I think, but there's usually components in the pumps or boilers that wouldn't tolerate that sort of pressure.

 

[r.bartlett]

Ooooooh! What well 'ard chaps you are.

Or stupid???

I think there's two possibilities with this

First, there's no hazard, and you have nothing to be scared of;
or;

Second, there is a hazard, you should be scared of it but you're not aware of it..

In life there are always risks. However due to a change in refrigerants to R410a we now have had to up the std pressure test from 300 to 500+ psi.

So, do you know which BS is concerned with pressure testing with air or OFN?

Air is PSSR2000. However it must be remembered pretty much every factory, tyre shop etc all have compressed air.

A direct lift-
"Compressed air is a safe and reliable power source that is widely used throughout industry. In fact, approximately 70% of all companies use compressed air for some aspect of their operations."

Do you know what it says about air testing?

Do you just use the pressure gauge on the cylinder regulator?

We use the standard nitrogen regulator onto our refrigeration gauges.

The BSs are compiled by a panel of recognised experts so I'd be inclined to trust them. I'll have to look it up when I get to work, if it doesn't take too long. I'm not certain that the one relevant to CH or water systems applies to refrigeration.

I believe from past learning the main concerns are pressurising containers recievers and vessels with air not pipework due to the volume/surface area equation.

http://www.bcas.org.uk/pdf/factsheets/FCT851 Air receiver selection & conformity.pdf

http://www.bcas.org.uk/pdf/factsheets/FCT105 Compressed air safety.pdf

Flared fittings are less liable to come adrift than BS 864 (I think it is?) compression fittings with an olive on a parallel tube.

Indeed and necessarily so.

I found brazing to be far easier than soldering, but my main experience of it was on bench work. Joints didn't leak but they were all tested with water.

Yes we often wonder why the soft solder vapourises off when we get the copper cherry red...

You wouldn't wet test a refrigeration system.

Not unless you wanted to rip it out and do it all again...

If your work is up to standard I would be surpirised if the pipes of a C.H system couldn't hold easy 5+ BAR.

You've listed the advantages of air testing.

The disadvantages are that it's a bad medium for testing ( a small air leak causes a small pressure drop; a small water leak causes a loss of all the pressure) and it's dangerous. See the Hepworths link above. Most CH systems could go to 9 or 10 bar, I think, but there's usually components in the pumps or boilers that wouldn't tolerate that sort of pressure.

I think as experienced engineers a plumber could use air as a 1st stage test. As I say I saw a plumber doing a big house where he pressurised it to 50 psi and left it an hour. He came back and found it was leaking. Checked over found the 'leak' cured it and re-checked it. Then when he felt confident he filled it with water. -no leaks. No flooding everybody's happy.

Sure I'm not advocating it, as it's for the plumber to make his decession and observe safety regulations et al but if I did a re-pipe of my house I would consider this method myself.(look out for me on Meridian news

Cheers

Richard

 

[Boilerman2]

I am shocked by the number of proffesional people on here that have no idea how dangerous compressed air is!!!

Why do you think that you have to write methos statements, set up no go zones! air testing at the sort of pressures mentioned on this post should always be carried out using water
If a system fails during a Hydralic test, you get a bit wet, no explosion no noise, just water. however a failure a 3-0bar can be as destructive a a small Bomb

 

[Onetap]

I am shocked by the number of proffesional people on here that have no idea how dangerous compressed air is!!!

The thread is 3 years old.