Tube to Tubesheet Welds

[hakkik]

Hi,
I have questions about the Tube To Tubesheet welds. BPVC Sec. VIII Div.1 UHX not specifies the qualification method so i may use either of groove weld, fillet weld PQR's or Mock-up.(Sec. IX QW-193)

My first question is, which one will you prefer for the attached weld detail? As far as i know manufacturer not have single layer fillet or groove weld PQR's(GTAW)

My second question is, if we use mock-up(QW-193)option, after welding 10 tubes and passing all NDE(VT+PT) how many macro sections do we need to evalute? All 10 tube welds with 4 surfces(total 40 macro!) or only one weld on 4 surface.

Thanks in advance,

 

[metengr]

I would qualify a groove weld WPS using Section IX QW-193 tube to tubesheet weld mock-up. In response to your second question, the macro-examination requires cutting each welded tube lengthwise to expose the tube to tubesheet weld region, having a total of four(4)exposed surfaces from one cut. Depending on tube wall thickness, you can have two of the four exposed surfaces in one metallurgical mount for examination. Or, you can prepare each cut surface for individual examination.

 

[hakkik]

Thanks metengr,

When we cut the pipe in to two halves we get 4 weld surfaces, but 2 faces were the same in practical as they mirror images of others. When i say 40 macros i was thinking like cutting each pipe in to quarters to get different sections of the weld. Is my thinking wrong? I hope i'm wrong as this will save me from many specimen prep.

 

[metengr]

hakkik
The code requires examination of four exposed surfaces from sectioning regardless if they are mirror images - you can have buried flaws and this is what the examination is supposed to reveal among verifying the throat dimension, etc. How you choose to prepare the cut surfaces is up to you just make sure the surfaces are smooth enough for proper interpretation.

 

[CWEng]

Yes, the 40 macros are required. I believe there is a Section IX interpretation confirming this as well.

 

[CWEng]

Also, if the mockup qualification method is not required, the groove welding qualification method allows for much more flexibility in tube sheet and tube dimensions without requalifying. I go with the groove weld method when allowed, so no requalification is required if the tube wall, tube diameter, ligament thickness, etc. change.