There are a few ways to test for leaks in pipes or other pressure vessels. You could use compressed air, but that is not recommended for safety reasons, should it burst, a lot a damage would occur.

A low pressure mix if helium - nitrogen would work with a sniffer, that takes some time and more then a little practice but it's safe.

First thing - From a safety point of view there is no difference between air and any other gas mix as a medium for testing - so beware of that fallacy. There are many factors to be assessed before deciding how to test and you don't provide enough info to make any decisions. Plenty of pipework has been tested with air but such tests are leak tests not strength tests and you should be clear about the difference. Leak testing with a gas is not particularly dangerous but strength testing should never be done except with a hydraulic medium - water or oil for example. 0.2 bar is a very low operating pressure , but what you have not said is what the design 'normal operating pressure' is of the pipe? For various reasons I would be very surprised if it is not 6 Bar. If it is 6 Bar then to test your pipe with air at your plant working pressure - as a leak test - does not pose any appreciable risk and you will not get any catastrophic failure. You may find a leak but that is all. Your pipe manufacturer should be able to give you a test procedure and they should also have a test certificate that show what test pressure the pipe was subject to in the factory before being shipped to you. If it does not you should question your QMS generically.

You are not correct. Pressurizing with a compressible medoum, like air, can be very dangerous because if the vessel breaks the compressed air will propel the fragments at some velocity in some direction. Boilers full of compressed steam(a gas) have been exploded in the past and destroyed the building and often killed many people. These explosions gave rise to boiler test procedures that specify a static water test to the proof pressure of the tank.

http://en.wikipedia.org/wiki/Nondestructive_testing

http://en.wikipedia.org/wiki/Boiler_explosion

lots of images here

http://images.google.com/images?hl=en&q=%22boiler+explosion%22&btnG=Search+Images&gbv=2

I am NOT wrong - read my message again. I have leak tested many pipework systems with compressed air. There are plenty international specifications for doing so. Boilers have exploded in the past but not because some engineer who knew what he was doing was yield or strength testing it using a compressible medium. A LEAK test done in accordance with a proper procedure and following a recognised guideline IS safe and they are carried out using air all the time in the oil and gas industry. A test at 0.2 barg is a LEAK test almost by definition. Boilers typically work at 40 Bar and are hydrostatically tested typically to 1.5 times normal operating pressure - you cannot in reality carry out a static test to such pressures.

Yes, I agree with you. Low pressure tests with gasses are suitable for leak detection, and not for proof of vessel tests, which as you correctly point out, must use an incompressible medium. I am sorry for my hasty reading that glossed over your correct fine points.

Wrong is Wrong and off base is what you are. I am certain that I have been involved in more boiler failures than you have and your attempt to relate boiler failures to this thread is nonsense. FYI when a steam boiler vessel fails the small amount of internally stored steam is not the primary destructive force it is the rapid expansion of all of the "high" temperature water that was formerly contained by the vessel.

If a "high" temperature high pressure hot water boiler were to fail it would even be more dangerous then a steam boiler because it is full of hot water looking for some place to flash all of its steam too. Steam let out to the atmosphere reduces velocity fast and condenses. Hot water flashes to steam and expands rapidly to get there.

Now to settle this as I am a field guy and you are a teacher or a philosophiser, here are the two best choices.

1. Vacuum test the entire pipe system.

OR

2. Fill the system full of water. Remove everyone from the area (this is not a shopping center you know) apply pressure to the completely full and purged of all air piping system. Take the system to projected system pressure and inspect all joints. If I were being paid to make this system safe I would have checked the manufactures data already for allowable pressure V. temperature. I would then increase pressure to the mid point between operating pressure and maximum recommended pressure.

Sorry Alf but I could not stay out of this say hi to aunt Ruth for me.

Mike Robertson

The Boiler Guy

He wants to test pipe with compressed air, and not static pressurized water into an evacuated system. My comments are to dissuade him from this by showing him what happens when high pressure gas induces a failure. As you say the water above 100C will instantly flash off and create a large volume of expanding gas that will propel anything far away with violence. I well know that the water above 100C flashes off when the water spaces is open to atmosphere.The boiler illustrations were to show what can happen to equipment that is not properly pressure tested or is taken beyond it's original limits by wear and tear or component failure.

Mike - the thread got sidetracked I think into boilers, steam etc etc - wrongly as you have pointed out. The original question was clear - that the guy wants to test PN10 PE pipe to 0.2Bar. So he isn't going to be putting steam through that or even boiling water or he is going to see why the material is called 'plastic'. If his operating P is 0.2 bar and he wants to test it at 0.2 bar on pipe with a design operating P of 10 Bar he is actually wanting to do a leak test. I am assuming his design review and risk analysis has determined that he does not have to do a strength test so leak test it is - maybe he has a lot of mechanical joints in the pipe run - who knows! Testing that 'vessel' to 0.2 bar with air won't pose any significant safety issue. He should take it up to pressure with everyone out of the area, wait with the pressure on hold for an hour then do a soapy water test. Nothing could be easier - but as usual with many of these threads really the only correct advice is to tell the guy with the question that he needs to go get an experienced and knowlegable engineer - in this case a test engineer to do it for him. I see you are a Robertson like me - but who is Aunty Ruth??

If the pipe is new, what does the manufacturer's warranty have to say on the subject?

What does the end Client's testing procedures have to say on the subject?

It would be safer to vacuum-test at -0.2Barg than to pressure test at +0.2Barg, if one is only looking for leaks. A pipe that diameter of any significant length will contain a lot of energy when under pressure, and under pressure it has the potential to do a lot of damage in the event of a catastrophic failure.

Why cannot water be used? Curious minds want to know....

we were testing entire submarine with vacuum of 600mm as its impossible to test the an operational submarine has to be pressure tested before sailing and pressure testing the submarine before it sailed ,and when ever we removed and worked on hull valves we were vacuum test to prove the submarines water tight integrity.secondly refrigerant lines are tested with vacuum when ever we work on the refrigerant system so vacuum testing of pipes is the good solution for pressure test of plastic pipes members opinion is welcome.

crm

What is the pipe going to be used for? If it will have a lot of pressure with hot water be careful. If it will have little pressure with cool or cold water your in better shape. The best/safest way to find a problem is to pull a vacume on the pipe. Sorry Del you have to be correct again or could we say "on target".

Let us know what your process is.

Mike

Use Blower air , a very low pressure but conveyable ( but do not use compressed )air mixed with non harmful powder (Telcom powder/ ASH) and pass through the line.This will solve your problem.

Use the concept of "pressure decay" testing.

Fit an accurate pressure gauge to the pipe/system.

Fill the pipe to a relatively low and safe pressure and seal all inlets and outlets and record the pressure in the pipe.

Leave it for 24 hours and read the pressure again. ANY change in pressure represents a leak. (Depending on the precission you need, you may need to compensate for temperature, that's why I suggest 24 hours. Same time of day, probably similar ambient conditions.)

If there's a leak, then the "sniffer" process can be used to assit detection.

Hope this helps.

Using air this way will never give you a satisfactory result and is not the way a leak test is carried out.

It would help if you disclosed what you intend to test for. Leaking, yielding, bursting, etc. If you can not use water you might consider another fluid. Glycerine and fluocarbons have been used. If you must use gas under pressure, consider submeging the unit under test in a fluid for safety reasons. Given more information, we may be able to be of futher assistance.