Question on Flange To Shell Weld Stress

[sixgpipewelder]

Hi,
I am a newbie 6G pressure vessel welder and have a question. I backwelded a flange onto a carbon steel separator shell (GMAW Root, FCAW Fill & Cap). My superviser told me that because I didn't weld the OD right away that I run the risk of cracking the back weld when I go to weld the outside. Is this true? Wouldn't preheating both sides avoid this event? I would appreciate any tips on this as I have to finish this weld Tuesday and there are a few internals I would have to remove to fix this if it fails. I have looked everywhere for info and this is the only site I have faith in. Thanks. Stanley

 

[metengr]

Not true for welding carbon steel pipe materials (see B31.1 and interruption of welding). For low alloy steels, like P-No 3, 4 and 5A, yes, there is a risk of cracking, which is why a minimum deposit thickness is required and visual examination (before welding begins again) should welding be interrupted (loss of preheat).

 

[bernoullies123]

Can't say I've ever heard of it. We just qualified some procedures with a delay (> 8 hours) to cover those welds where a few runs were completed prior to knock off time. These are pipe welds and not your design but same principle.

 

[sixgpipewelder]

Thanks for the responses. I never had any issues with cracking as long as I pre-heated when restarting any welding. I appreciate the info without getting "flamed" for my lack of knowledge. Thanks again. Stanley