Welding Pipe to Pipe instead 2.6 Deg from 45 Elbow 1

[Opensource]

Hi all


I would like to ask if is possible or is not recomended to weld pipe to pipe a 12" line ( Ventline for Drillship)instead of cutting a 45 Deg elbow for a 2.6 Deg. In my opinian since the service is not for high pressure, high temperature or cycling, vibrating but the 12” line can been subjected to high dynamic loads associated at shallow gas blowouts, and there is a high resulting failure probability and one of the associated effects is due to cavitation, impingement of fluid and solid particles from blowouts which contributes in the overall pressure of the well, adding the risk of formation fracturing and possible seabed cratering.
I think weld pipe to pipe instead of cutting a 45 Deg fitting will be a non-standard weld because it will increase the thickness of the weld (there is a maximum and a minimum of the weld thickness) and will not be able to withstand the dynamic load and flow erosion hazards associated with shallow-gas flow unless we apply PWHT (Post-Weld Heat Treatment) this weld and with 100 RX with a conservative NDT testing .
This is god question to Inspection Part, normally is them who approve this.

The pipe is ASTM A106-B 323.9 OD x 9.52

Thank you in advance!

 

[LittleInch]

ASME B 31.3 section 302.4.3 allows alignment of up to 3 degrees without calling it a miter bend. I can't see how you would chop a 45 fitting to get 2 point six degrees, especially for a 12" pipe. This would only leave a very small ring of pipe and hence two welds in very close proximity. If you cut the pipe with the 2.6 degree angle, then the weld will be the same as any other. The pipe will look a little odd, but should be OK. Difficult for anyone to recomend based on your description, but if the service is vital or seen as hazardous and subject to erosion then should be Ok, but very difficult to judge.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[Opensource]

Hi LittleInch

We think it is better to weld pipe to pipe and avoid two welds so close to each other due to very high heat input to the material between the two welds like you said. Thanks for your help to see in B31.3 something about it.

Regards

 

[stanweld]

Opensource,
Your current reasoning is correct but also add the difficult fit-up of pipe to a cut fitting.