B31.3 Fitting Hydrotest

[loilfan]

I am designing a fitting to B31.3 that is a cored bar material NPT threaded on both ends with a 1/4" bleed in the middle of it. Is a hydrotest still required if no welding is performed? I think it does, but couldn't find anything in the Code that says one way or the other. Thanks!

 

[pennpiper]

I think you should be using ASME B16.11 Forged Steel Fittings, Socket-Welding and Threaded

Sometimes its possible to do all the right things and still get bad results

 

[loilfan]

pennpiper, ASME B16.11 is not a design code. The fitting that we are designing does not fall entirely under any of the categories in B16.11.

 

[LittleInch]

"cored bar material" with a hole in the middle of it and another hole half way along.

Sounds like a strange bit of pipe to me so test it as part of the system test.

a drawing, photo or sketch might help, but if it can see pressurized fluid then it's part of the system.

345.1 says" Prior to initial operation, and after completion of the
applicable examinations required by para. 341, each piping
system shall be tested to ensure tightness. The test
shall be a hydrostatic leak test in accordance with
para. 345.4 except as provided herein."

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

 

[TGS4]

I agree with littleinch. It may not be required that the individual fitting be hydrotested separately, but it will certainly be subject to hydrotest pressures during the system hydrotest.

 

[loilfan]

It's a fitting used to bleed the pressure when doing coupon extractions. Unfortunately I can't post the drawing of it for proprietary reasons at this point. Think of a thick pipe with a 1/4" hole tapped in the middle of it.

The fitting is owned by a services company and wouldn't be hydrotested with the original piping system since it will get moved from site to site. I suppose it would be considered its own "system" in that case.

 

[LittleInch]

Correct. I wouldn't let some one connect an untested thing to any pressurised system so I hope no one else would.

Just imagine what would happen if it failed in service?

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

 

[DekDee]

In addition to LI's response

Interpretation: 20-24
Subject: ASME B31.3-1998 Addenda to 1996 Edition, and B31.3-2002 Edition, Para. 345.2.3, Piping Subassemblies
Date Issued: May 20, 2005
File: B31-oS-1S7 and B31-oS-319
Question (1): Does ASME B31.3-2002 Edition define "subassemblies" the same way as it defines "piping components"?
Reply (1): No.
Question (2): In accordance with ASME B31.3c-1998 Addenda and ASME B31.3-2002 Edition, does para. 34S.2.3(a) allow piping components to be independently tested as required by para. 345.1, and then assembled and placed into service with no additional leak testing?
Reply (2): No, unless the system is assembled with flanged joints or closure welds as described in paras. 34S.2.3(b) and (c).


Hope that helps,
Regards,
DD

 

[loilfan]

LittleInch, I agree. That's what I was thinking too but couldn't find a good Code reference in case the client questioned it.

DekDee, That interpretation makes it sound like we won't be able to install a threaded fitting onto a piping system after the system hydrotest. It sounds like threaded instrumentation gauges would also not be allowed to be installed post-system hydro since they aren't closure welds or flanged connections...

 

[LittleInch]

That's probably covered in section 345.2.6 - Repairs or additions after leak testing -

If repairs or additions are made following the leak test, the
affected piping shall be retested, except that for minor
repairs or additions the owner may waive retest requirements
when precautionary measures are taken to assure
sound construction.

So you need to convince the Owner that sufficient "precautionary measures" are taken, one of which is almost certainly that the particular item has itself been pressure tested to a pressure at least similar or higher than the piping system to which it is becoming attached to, even if for a short time.

I hate the word "temporary" when it comes to anything to do with pressurized systems as the implication is that testing, operation and systems can somehow be magically reduced compared to "permanent" piping for no particular reason.

Many many failures have occurred on "temporary" connections, especially where this operation is undertaken infrequently or by inexperienced or inadequately trained operators and supervisors.

Of course frequent make / break connections are also much more at risk of incorrect assembly, no or inadequate testing which then fail in practice.

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

 

[KevinNZ]

The B31.3 hydro test is a leak test. This is only looking for leaks in treads, welds etc. It is not a proof test for a manufactured fitting. It does not prove the design of the fitting.

 

[loilfan]

KevinNZ, you are correct. Since these are cylindrical components, I used 304 of B31.3 to design it. I do not intend on using the hydrotest as a proof test under UG-101 of ASME VIII.

LittleInch, considering this as a minor addition is probably the way to go. My client has Job Risk Assessments and Installation Procedures for this task in place already so we should have the sound construction portion covered. Doing a leak test of that threaded connection is complete overkill if the original system and our fitting were tested independently. Thanks for your help!