Tube to Tubesheet Weld Procedure Qualification

[Afox88]

Guys,

I am following up on this previous post:

http://www.eng-tips.com/viewthread.cfm?qid=291961

Just to clarify, if we are welding a Section VIII division 1 heat exchanger that has a tube to tubesheet strength weld (partial or full), we do not need to qualify the procedure using a mock tubesheet with 10 tubes. If this is true, all we need to do to qualify this procedure, is to simply make a test coupon with the applicable dimensions and materials as if it was any other weld.

Please advise if my understanding is correct or advise if I am missing something. I could not find any reference to QW-193 in UG-20 and according to the post above, it does not exist.

 

[metengr]

There is indirect reference in UW-28. Any and all welding procedures used in Section VIII fabrication must be qualified using ASME Section IX.

 

[Afox88]

So are you saying that a mockup is required for every tube-tubesheet strength weld procedure? A test coupon is not enough?

 

[metengr]

If you qualify a tube to tube sheet weld procedure specification, only applicable to tube to tube sheet application, yes. If you are using a groove weld procedure, no.

However, most clients including myself will require QW-193 by engineering specification.

 

[Afox88]

Thanks Metengr. My previous company always does the mockup procedure. My current company does not, unless a customer requests QW-193. Our AI does not request it.

 

[fleischfresser]

The key to the question is QW-202.6:

"QW-202.6 Tube‐to‐Tubesheet Qualification. When the applicable Code Section requires the use of QW-193 for tube‐to‐tubesheet demonstration mockup qualification tests, QW-193.1 shall apply. If specific qualification test requirements are not specified by the applicable Code Section, tube‐to‐tubesheet welds shall be qualified with one of the following methods:
(a) groove welds per the requirements of QW-202.2 and QW-202.4
(b) a demonstration mockup per the requirements of QW-193.1
(c) fillet welds per the requirements of QW-202.2(c) (for nonpressure retaining tube‐to‐tubesheet welds only)"

While ASME VIII/1 have no specific requirements for Tube‐to‐Tubesheet Qualification, ASME VIII/2 requires per paragraph 6.3.4 the demonstration mockup (QW-193 is very similar to Article F-3 of the old ASME VIII/2 and was removed from ASME VIII/2 and added in ASME IX with the Edition 2004, Addenda 2006).

That means in your case (design code ASME VIII/1) you have the free choice of QW-202.6 (a), (b) or (c) if applicable.

Hope that helps




Regards - Juergen

 

[Afox88]

Thanks. This clears up a lot.

 

[engfla]

ASME Sec. VIII, Div. 1 also defines a tube to tubesheet seal weld as "used to supplement an expanded tube joint to ensure leak tightness." This "weld" is to provide tightness against leakage, but carry no loads. This type of "weld" can use filler metal or can only fuse the tube wall to the tubesheet face. Does this type of "weld" or fusion require qualification in accordance with Sec. IX? Much of the acceptance criteria of QW-193 do not seem to apply as there is no minimum leak path, no applicable complete fusion and no weld root for penetration.

I appreciate any guidance on this matter.

 

[minibenny]

engfla,

Yes, this weld would require qualification in accordance with one of the (3) options given in paragraph QW-202.6 of ASME Sec. IX. QW-193 is not mandatory for ASME Section VIII Division 1, to my knowledge.