sensitive leak check 1

[Ebyate]

Our client is requesting to carry out sensitive leak check for fluid category M as per section B31.3 section 300.2 and appendix M after hydrotest of the line.

The line is hydrotested at 100 bar while the sensitive leak check is carried pneumatic at 2 bar . Could anyone explain what is the purpose and benefit of this since at 100 bar there is no leak then what is expected to be revealed by bubble test of the test at 2 bar sensitive check.

 

[Dhurjati Sen]

Dear Ebyate,

It seems the sensitive requirement exists in the Client's QA Procedure / Manual / etc.

Find out if you have agreed to carry it out in your contract with the client.

If yes, then go ahead. If no, then don't do it.

After necessary invoicing and all, tell them politely to remove it from their QA Procedure.

Regards.

DHURJATI SEN
Kolkata, India

 

[Ebyate]

Even if it is in the procedure, we can request for waiver. Is there was any technical justification required to be carried out for the weld joints in a piping system

 

[LittleInch]

Well it depends if there is any break in containment or jointing after the hydro?

If there is then the leak test is to certify tightness of the joints versus the strength test of the hydro.

Also one drop of water is difficult to find, especially if its raining....

Bubbles represent a much lower leak quantity.

Cat M is for stuff " so highly toxic that a very small quantity .. can produce serious irreversible harm to persons.."

That's pretty dangerous stuff to me.

Why would you not do everything humanly possible to ensure that there is no leak??

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

 

[DekDee]

Agree 100% with LI.
A single drop or two of water will not show on any pressure gauge during hydrotest and if it is not picked up visually then the test is deemed a success.
What happens when the piping system is put into production and that single drop or two then becomes a toxic liquid ?

 

[Ebyate]

I do agree that all safety measures needs to be checked before putting the system in service. Normally in the plant system, we carry out hydrotest and then as part of pre commissioning a leak check of the system is carried out at operating pressure ie combination of many hydrotest packs to ensure the flange integrity is maintained.

But in the above case, the client is requesting for sensitive leak immediately after hydrotest of a test pack to check if there are any leaks in the weld joints . That too at 2 bar when the line is hydrotested at 100 bar. As part of pre commissioning, again a leak check will be done at operating pressure to check the flange integrity.

Hence I am trying to understand if the sensitive leak check (2 bar) requested is a misinterpretation of the codes

 

[DekDee]

Not sure how this can be a " misinterpretation" of the code ?

M345 TESTING
Paragraph 345 applies, except that
(a) a sensitive leak test in accordance with para. 345.8
shall be included in the required leak test (para. 345.1)
(b) the initial service leak test (para. 345.7) does not
apply.

So you have to do a hydrostatic or pneumatic test as per 345.1 plus a Sensitive Leak Test

 

[DekDee]

Interpretation: 20-47
Subject: ASME B31.3-2004 Edition, Hydrostatic Testing
Date Issued: October 18, 2005
File: 631-05-1223
Question: In accordance with ASME B31.3-2004 Edition, are both a sensitive leak test and a
hydrostatic, pneumatic, or hydrostatic-pneumatic leak test required for Category M piping?
Reply: Yes; see para. M345.

 

[IRstuff]

Wouldn't one rationale for doing a fine leak test is that a high pressure hydrotest could actually seal small leaks, much like the way the SR-71 leaked av fuel until its joints got hot enough from aerodynamic heating to close up from the material thermal expansion?

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[EdStainless]

How are they going to dry it after the hydro?
We have done this with tubing and we were required to force dry the tubes between so that water could not block a small defect.
Give that water has 100 time the viscosity of air, you can put air through a leak that water will not pass.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[Ebyate]

My understanding of service leak check is with product and not air/nitrogen. As mentioned, during pre commissioning we are anyhow carrying out leak check with bubble check for the whole system.

Doesn't that meet the criteria of sensitive leak criteria . Currently we carrying out so called sensitive (2 bar pneumatic ) and later leak check ( at operating pressure) before commissioning the system. Is then 2 pneumatic test after hydro required as per Code as it does not classify between construction and pre commissioning stage activities .

Hence I was asking if the code is misinterpreted

 

[DekDee]

Ebyate,
You are the one who seems to be misinterpreting.
Read M345 which you should be working to:
(b) the initial service leak test (para. 345.7) does not
apply.
So forget your service leak test !

Question: In accordance with ASME B31.3-2004 Edition, are both a sensitive leak test and a
hydrostatic, pneumatic, or hydrostatic-pneumatic leak test required for Category M piping?
Reply: Yes; see para. M345.

Which part of that interpretation is hard to understand ?

 

[weldstan]

Well said DekDee; a star for you.