ASME B31 circumferential weld factor

[IFRs]

When determining allowable pipe spans, are there any guidelines for what to use for the joint efficientcy of a circumferential butt weld? I found a table for longitudinal weld "quality factors" but nothing for the joints between sections of pipe sections that make up a long pipeline.

 

[davefitz]

I think the weld quality factors you referenced deal with the pressure integrity of the pipe, and not the structural integrity due to pipeline forces. Circumferential butt welds experience only 50% of the stress that longitudinal welds are exposed to , due to internal pressure of fluid, thus it is not neccesary to apply a weld quality factor to butt welds when considering only fluid pressure integrity.

The only exception to the above statement is the case of a butt weld of new alloy P112 at operating temps above 1100F; the weld creep strength reduction factor drops below 50% in that one case.

 

[IFRs]

I agree that the longitudinal stress from pressure is half the hoop stress from pressure. I'm looking for any factors for the circumferential joint when 40' randoms are welded together and placed on discreet pipe supports. I'm calculating allowable pipe spans (stress and deflection limited) and adding the longitudinal stress from pressure to that from the pipe as a beam.

 

[unclesyd]

I haven't seen any code based reduction factors for circumferential welds.

I have seen several studies on flaw size in circ welds by fracture mechanics, mainly incomplete penetration where there was no reduction for any conditions that the pipe would see. The allowable flaw size was quite large in all cases, up to 25% in the case incomplete penetration.