MW- 5617- RE: 5606] Tube to tube sheet welding
pgoswami
John,
Thanks for illustrations on EN/ISO design specification for tube to tube sheet weld. ASME Sec-IX does not specify any requirements on Tube to tube sheet weld design. Sec-VIII, DIV-1 covers this aspect under UW-20 with additional guidelines in form of good engineering practices in Appendix-A.
Yes you’re right, there is no straight thumb rule in Sec-VIII, if there were something it would have helped everyone.
However the interpretation of the code is that Minimum Leak Path:- i.e. the shortest distance from the bottom-most point (depth) of the groove shall be at least equal to the thickness of the tube or more.
Dimensions of leak path could change depending on the weld design (i.e. depth of groove, J-radius etc), joint efficiency factor, etc . Thus it should be calculated by the designer and the values should be established through detailed calculation as under UW-20, definitely before fabrication.
I ran a quick illustration on UW-20, i.e. basis for calculation for Tube-Tube sheet weld. T-TS weld is is very subjective to joint design , hence I have seen that the leak path issue is being resolved on a specific joint design basis.
Thanks
Pradip Goswami,
P.Eng.
Welding & Metallurgical Engineer/Specialist
Ontario Power
Generation
Inc.
Email-p...@sympatico.ca,
pgos...@quickclic.net
-----Original Message-----
From: material...@googlegroups.com [mailto:material...@googlegroups.com] On Behalf Of John Henning
Sent: Wednesday, June 16, 2010 11:02 AM
To: material...@googlegroups.com
Subject: [MW:5617] RE: 5606] Tube to tube sheet welding
The attached figure is from EN ISO 15614-8, "Specification and qualification of welding procedure for welding materials - welding procedure test - Part 8: Welding of tubes to tube-plate joints.
Minimum leak path dimension determination for ASME would be similar.
My company routinely manufactures ASME Section VIII heat exchangers and fire tube boilers. What my company routinely does is to measure the smallest distance from the root of the weld to the surface of weld as part of the macro exam. Our acceptance criteria is that this measured minimum distance must be greater than or equal to the wall thickness of the tube. This is conservative but may preclude having to do push/pull out testing. We have demonstrated for some customers that the tube will fail outside of the weld when this criteria is adopted. Our J-groove is always cut deeper than the tube wall thickness dimension.
Let me know if you have any additional questions.
John
-----Original Message-----
From: material...@googlegroups.com
[mailto:material...@googlegroups.com] On Behalf Of Shadab Alam Ansari (Welding Engineer)
Sent: Tuesday, June 15, 2010 3:19 PM
To: Materials & Welding
Subject: [MW:5606] Tube to tube sheet welding
In Tube to tube sheet weld joint what is the minimum leak path distance as per ASME SEC-IX.
Regards
Shadab Alam Ansari
Welding Engineer
Olayan Descon
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John Henning
Pradip,
You are correct.
I was hasty in my comment – however for the particular material and design parameters we employ the result is an over welded joint (more than 50%). As long as QW-193.1.3(d) is met, our joints have been compliant. If tube diameter and/or thickness changes significantly this will have to be revisited.
John