Hydrotesting Instrumentation Tubing

[fidds]

Hey guys,
I am a new member, my job is Instrumentation/Electrical, and I am going through an ABSA approval for our company right now. I have a question about hydrotesting instrumentation tubing. It says to test to 1.5X the MAOP, which is no big deal. So I have a vessel that can handle say 2000 PSI, PRV is set to 1800 PSI, so Ill go to 3000 PSI, to be safe. I can't seem to find many handpumps that can do that high of pressure using water. According to ASME B31.3, section 345.4.1, it has to be water unless water will damage the process, which in my situation it won't. But can I still use a non-toxic mineral oil for all my tests?? Then I can use a hydraulic test pump, which can pressure up to 10,000 PSI, and not have to use water. Does all this make sense?? I may be looking into this too far, but to use water would be the easiest, but I just can't seem to find a good option for a hydrostatic test pumpthat can do around 5000 PSI, which I think is the max I'll ever need. Any help is appreciated.
Thanks!!

 

[bimr]

Sarum Hydraulics manufactures a modular range of pressure and hydraulic test pumps covering the range 1 bar to 1000 bar on a range of fluids including water, mineral oil, kerosene, glycols and skydrol.

http://www.sarum-hydraulics.co.uk/pressure-testing-pump.html

You can use a water or mineral oil-based fluid.


See the link for testing of tubing:

http://www.eng-tips.com/viewthread.cfm?qid=175629

 

[moltenmetal]

They're not hand pumps, but a MAXP or Haskell air-driven piston pump will reach 10,000 psig and will happily pump water or white mineral oil.

You can also safely test tubing systems by means of a properly designed pneumatic test at 1.1x the design pressure. The test can definitely be hazardous if done wrong, but such tests ARE done safely every day so it can be done. You have to weigh the hazard of the pneumatic test against the benefits and disadvantages of the hydrostatic test:

a) An instrumentation tubing system which is not evacuated prior to filling or bled thoroughly like a brake line prior to the test is going to have quite a lot of trapped air in it anyway, which will affect both the safety and sensitivity of the test

b) The test fluid will be very difficult to remove from the system post test for the very same reasons, which may lead to a premature failure of the line in service if the fluid it normally carries is different

c) If compression fittings and threaded joints are used to make the connections, the risk of a brittle failure of a component is actually very small. The tubing itself is likely nowhere near its MAWP during the test, and leakage rather than failure is what you're trying to find and eliminate. A pneumatic test is inherently more sensitive to locate and repair leakage than a hydrostatic test is

d) The limited volume and favourable aspect ratio of a tubing system limit both the stored energy and likelihood and the effectiveness with which that energy can be directed to injure someone during a failure.

People doing the test should be at a safe distance from the components such that a total failure, i.e. a tube with ferrules swaged too close to the end of the tube, which slips out of the ferrules and allows the tube to suddenly come loose like a whip, will not injure someone. Pressure needs to be increased in stages with holds between stages to watch for leaks. The fittings must not be manipulated (i.e. tightened with a wrench) while the system is under the test pressure. An excess flow check valve on the test gas line is a very good idea. If something is leaking, the pressure should be reduced at the cylinder/regulator prior to trying to find the leak. Using a little commonsense the test can be done safely and effectively and the results will be a leak-tight system.

 

[fidds]

Hey guys,
Thanks for all the responses, and they all make sense to me. I will look into these pumps and see which one suit our needs. As for pneumatic tests, ABSA here in Alberta will only permit Pneumatic testing if you can prove that hydrostatic testing will not work or damage your system, which for our line of work, we will never really need to. We do mostly chemical lines, gas lines that are full of liquids anyways. You also have to get written consent from them, so its a big pain in the ass to do pneumatic testing, thats why we are doing hydrostatic. What really gets me is that we have to test these lines out of service on a bench usually, if we can, test it, then put it back in and leak test the joints. Thats kind of useless, IMO, as I would like to test all the fittings and the compression ends, but that will mean I will need a TEE somewhere in line to do that, and thats another leak point. I can see when you are hydrotesting piping, as all joints are threaded, so you are testing those, but for our tubing, its pretty much endless until your starting joint and your finishing joint. So you plug the end with a gauge and a valve to bleed air, hook up your hand pump, pump it up to 1.5X your MAOP, pressure test it with water for minimum 10 Minutes,and the water will never stay steady because of the entrained air in it, then you are done. Then you put it back in-situ, tighten all joints, then slowly open your valves and SNOOP your joints, make sure there is no leaks, then call it good. It just seems like you never really test your joints, where you threaded your compression fittings in to, and thats the spot where it is likely to leak the most. I know you leak test, but really never test to 1.5X the MAOP. Sorry for the rant, Im just trying to make sense of all this.

 

[moltenmetal]

You're giving ABSA too much credit I think. ABSA can't force you to do a hydrotest on tubing when the governing code permits a pneumatic test. It's tubing- hydrotesting is not impossible, but it is impractical.

If you have to test the pipe in order to test the tubing in a meaningful way, you're in a hydrotest regime anyway due to the very real hazard of high pressure pneumatic testing of systems with a large volume of compressed gas. Then, it's just a matter of figuring out how to get the tubing FULL during the test and EMPTY again afterward- if indeed it isn't handling the same fluid as you're testing with which is usually the case.

 

[fidds]

Hey there. Sorry for taking so long to respond. I totally forgot about this as ABSA hasn't even responded to our application yet. I know I am giving ABSA too much credit, I just don't want them to come down here, do our audit, and have us do a mock pressure test, and forget something stupid and not pass the test. All of mus workers have hand pumps that we use for calibrations, but then they don't hold much volume, so I think what we might do is we will fill the tubing line with water first, then hook up the pump, and do the test. That way we don't have to worry about volume. Then pressure up to our MAWP, hold for 10 min or so, then call it good. We will be using a Fluke gauge and our cal eq. pressure cells as calibrated gauges for the test. Sound about right? Thanks guys.

 

[Duwe6]

Sounds just right. Only tubing I've has to hydro was instrument racks at Nuke plant. Took 2-2½ strokes of the handpump to get to the 3000 psi minimum pressure. But it took a fatboy to get that last half-pump. Fitters weighing under 200# couldn't get that much out of that little pump.

 

[dcasto]

You are never required to do a hydrotest on piping, you only are required to do a leak check that could mean using water, if you so see fit.

 

[moltenmetal]

Again, ABSA cannot require you to do a hydrotest when the applicable code (B31.3/CSA B51) permits a pneumatic test. Unless you don't care that your tubing will contain water that will be difficult to completely remove, don't use water- do a properly designed pneumatic test instead. If the system must be tested in a way that includes a vessel or other large volume of high pressure gas during a pneumatic test, fill this portion of the tested system with water for safety reasons.

 

[racookpe1978]

So I have a vessel that can handle say 2000 PSI, PRV is set to 1800 PSI, so Ill go to 3000 PSI, to be safe. I can't seem to find many handpumps that can do that high of pressure using water. According to ASME B31.3, section 345.4.1, it has to be water unless water will damage the process, which in my situation it won't. But can I still use a non-toxic mineral oil for all my tests?? Then I can use a hydraulic test pump, which can pressure up to 10,000 PSI, and not have to use water. Does all this make sense??

Your handpump will not reasonably be able to pressurize the "vessel" . It is too small a volume. IF the entire vessel and ALL of its piping and ALL of its instrumentation were perfectly filled AND perfectly vented, then you "might" be able to raise system pressure with a handpump (good muscles there buddy!) IF there were absolutely zero.zerozerozero leakage from anything and any valve. Good luck meeting all of those "if" statements.

Use a test pump - hydraulically powered! - not pumping hydraulic fluids! - or an air powered or an electric driven pumps - pumping pure water (or as pure as you need for your operations later.)

 

[fidds]

Thanks guys for all the tips. There is definitely alot to take in. Basically, I have to hydrostatically LEAK test my tubing. Just to make sure there is no leaks. To do a pneumatic test would be the way to go, but then I have to put in line PSV's , apply for a new permit through ABSA proving why I can't do hydrostatic, and its more dangerous. We aren't going to be doing crazy amounts of this so testing with water should be okay. We will build the tubing price, then test it in a shop, then re-install, test for leaks, then call it good. At least that's my understanding of it, and what every other company up here is doing.

 

[lsone]

moltenmetal you are wrong on a couple points.

Jurisdiction trumps the code.. Anything over and above 31.3 that is a "shall do" item from ABSA HAS to be met! There is no deviation. Yes you can do pneumatic tests in Alberta according to 31.3, However being in Alberta the only way you can complete a pneumatic test without ABSAs approval is to follow this document.

http://www.absa.ca/forms/AB-522 Standard Pneumatic Test Procedure Requirements.pdf

Method B is the easiest method IMO. Essentially... the higher the pressure the smaller the volume of piping you can test.

People easily over look jurisdictional rules. Just because piping is built to B31.3, does not mean that is the only code to follow.

 

[moltenmetal]

Isone: you are right and my statement, "ABSA cannot require you to do a hydrotest when the applicable code (B31.3/CSA B51) permits a pneumatic test", when interpreted on its face and out of the context of the overall conversation, is in fact WRONG. The AHJ can and does sometimes set rules that go beyond the code minimums- I do not contest that. So, for instance, just because B31.3 permits a pneumatic test, doesn't mean that a pneumatic test of a huge piping system at a high pressure would be a) possible to design and carry out safely or b)will be permitted by the AHJ.

That said: the ABSA document you posted has an Appendix V which says that pneumatic testing per their (rather commonsense) rules as set out in Appendix IV is permitted for testing instrumentation tubing systems constructed of tubing and compression fittings. So it's important to actually read and understand the rules set by the AHJ rather than following the blanket advice given by someone at ABSA who may, or may not, actually know what they're doing. That was my advice to the OP and I stand by it. Code rules are meant to augment engineering judgment, not to supplant it. Obviously, following the advice of anonymous people on an Internet forum, especially when their statements are taken out of context, would be even dumber!

 

[lsone]

I never once said you couldn't test instrument tubing using a pneumatic method. Not sure where you saw that. I was simply stating that to cover ones self, its best to fully understand the code AND your jurisdictional requirements.
ABSA can 100% force you to do a hydrotest if your AQP doesn't have a pneumatic testing procedure,... Then it looks like you have 2 options to keep ABSA happy. Hydrotest or create and apply with your newly added testing procedure

To the OP... for higher pressure hydrotests many places use a 2" trash pump to fill the system, Once full leave the trash pump running and start a car wash pump. That will bring you up to your required pressure.