Butt-weld thickness

[CloudNine1]

Hi guys,
I would like to calculate the thickness (and the other parameters needed) of butt weld that connects between a pipe and a weld neck flange:

I couldn't find any thumb rule, or even better: an analytic formula (which involves working pressure, temperature, etc) that allows calculating the required sizes for the welding.
I also need such formula for fillet weldings.

Thanks.

 

[MJCronin]

You will not find any rules or calculation formulas regarding piping butt welds...... ASME/EN piping welding rules are different than structural welding.

The basic piping code assumption is that: If the butt weld is properly configured AND of proper materials AND using proper weld procedure THEN the weld is stronger than the pipe..... and, it is !!!

The ASME B16.25 Standard covers the preparation of buttwelding ends of piping components to be joined into a piping system by welding. It includes requirements for welding bevels, for external and internal shaping of heavy-wall components, and for preparation of internal ends (including dimensions and dimensional tolerances).

In the USA, American Welding Society requirements also apply ...

Hope that this helps !!!

MJCronin
Sr. Process Engineer

 

[racookpe1978]

And, note that "properly prepared" = "Full penetration butt weld" for most joints.
(When needed, the fillet welds for socket joints are also defined in the AWS and ASME spec's below.).)

See the AWS Certified Welding Inspector training (and documents) for ASME 31.1 and 31.3 piping, ASME IX for certification and selection of material (filler metal), certification of each company's weld inspection and weld training/operations programs, and individual certification of each welders as well.

The thickness and root gap and weld cover requirements are clear. Source of filler material and final NDE also.

What is your experience with pipe design and fabrication?

 

[LittleInch]

Maybe I'm missing something here, but what "thickness" are you trying to calculate.

Like my fellow posters above, a butt weld needs to be the thickness of the pipe, which is calculated base don design code, design pressure & temperature, material strength and other factors applicable to the pipe. The weld should be of a higher strength than the pipe material.

Bevel shape is determined by welding code and Weld Procedure Specification.

Fillet welding is more difficult as there are different factors, but again thickness of the material is key.

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