ASME 31.3 Hydrotesting "tester" and "witness" 6

[cleanerstateofconfidence]

Hi all,

Normally my role is testing DOT 4B vessels via hydrostatic expansion, water jacket method. We are looking into a project where we would be hydrostatic leak testing piping at the fabricator's shop. Specifically, about 150 different blanked off sections of sch 40 - 160 pipe. We will be following ASME 31.3 code to perform this testing. We would only be doing the hydrostatic testing, a CWI will inspect welds before testing. We plan on using a hydrorex test cart with 3 pressure ranges (w/calibrated gauges) and a digital card recorder. Do we still need to put any gauges on the weldment itself? Are the pressure readings from the test cart chart recorder sufficient? Are there any special qualifications needed to perform the hydrotest or be a witness to the test? Does the tester need to be an ASME certified inspector? Does the witness? What responsibilities do we have as the tester, and what falls on the owner, fabricator? Thanks in advance!

 

[akpipelineengr]

Read and follow the Code and the owner's specifications. Many of your questions are answered by what is (and isn't) in B31.3 section 345. You've got a good start on the equipment. Not certifications are required for hydrotesting B31.3 piping.

A normal pressure gage should be used in addition to the recorder, so the operator can easily see the pressure. I do like to see another gage on the pipe, particularly when you string multiple spools together, a gage at the end is a good practice.

Filling pipe spools is more complex than the vessels you are used to, as you need to bleed air off at all high points. This gets complex when you bolt up multiple spools to reduce the number of tests.

Note that 345.2.2(a) requires examination of all welds and joints *after* the initial 10 min hold. A lot of folks will try to do a 10 min test and be done, but it needs to be 10 min and then a full inspection of the system.

I assume the fabricator will set up the spools for test? You'll need to inspect their setup, make sure you have barriers and clearance around the test so nobody gets too close, set up your equipment, document everything, and maintain records after the test. Lots of owners will have specifications on water quality, temperature, etc. that you need to plan for or coordinate with the fabricator.

 

[cleanerstateofconfidence]

Thank you for the response akpiplineengr. Very helpful. We are aware of the challenges with bleeding air at high points, and the added challenges of daisy chaining the weldments together. We will be holding for 1 hour at the owners request (US Navy), then lowering to design pressure to conduct thorough leak exam. The fabricator will be setting up spools inside a 20 ft connex container. We will be monitoring the test with live cameras to avoid people being near the spool at test pressure. A few more questions, I believe I know the answers to, but would like conformation. The only acceptance criteria is the presence or absence of a leak at a joint being tested. correct? Pressure only needs to be maintained above the prescribed test pressure during 1 hour hold time, correct? During the 1 hour hold time, would it be acceptable to run the pump to maintain test pressure or should the pump be isolated after test pressures are reached? We are concerned about an unacceptable pressure drop with no weldment leaks during the hold time. I've read that pass thru on valves and valve packing is possible even likely and would not result in a failed test, but would result in pressure drop. Thank you again!

 

[EdStainless]

We used to use vacuum to assist fill for complex systems.
If you actually have all of the air out of the system (using de-aerated water) then there is no risk to standing right next to the test pieces.
For shorter holds we always isolated the test from the pressure system.
For a 1 hour hold I would suppose that they intend for you to keep it pressurized.
Their documents should explicitly state which is the actual case.

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P.E. Metallurgy, consulting work welcomed

 

[LittleInch]

I think though that you will need to put inspectors in there once you've dropped the pressure for the leak test part. Realistically if the piping is good at test pressure and you've dropped down to design pressure, it is no different to what will happen when it is installed, so risk is sufficiently low to be acceptable. Cameras just won't cut it.

Section 340.4 I think answers your question about the qualifications and experience required for the inspector.

Generally you isolate the main pressurising pump and start using a manual one to maintain pressure, measuring the volume of water you put in.

You should really have no leaks or only minor drips. If you need to use the main pump then you'll be spraying water around everywhere and couldn't find a weep on weld if you tried....

B31.3 is actually only a 10 minute hold at 1.5 times design pressure, but most people extend it to an hour and it makes life much easier if there is no pressure drop or water added in that period. Temperature stabilisation / avoiding any solar gain is the key issue, hence why it is often done at night or inside as you seem to be doing.

Some people remove valves during testing to avoid stem leaks and you should not test against closed valves where the test pressure exceeds the valve design pressure.





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[cleanerstateofconfidence]

Thank you for the response LittleInch. Yes, We would still be "manually" examining at design pressure- not relying on the camera for examination. Camera is there to mitigate job hazard per request of fabricator. Does the leak testing examination at design pressure have to be done by a "Qualified Inspector" (ie CWI or ASME engineer) or should this be considered visual "examination" that can be done by us non CWI, ASME folks. The way I interpret B31.3 sec 345.2.2a is this would fall under "examination" not inspection. The fabricator will have all weldments inspected by CWI before hydrotesting. Very helpful tips about pressure pump and valves.

 

[LittleInch]

I think section 340.4 b 1) or 2) should cover you and visual inspection / examination of a hydrostatic leak test can be done by anyone covered by items 1 or 2 as it is one of, not all of them.

The terms inspection and examination are a bit loose for me, but for pressure testing you just need to know what you're doing and what to look for and be prepared to sign on the dotted line that there are no leaks from any of the joints (welds) or components other than valve seats etc.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.