Welding Olets to B31.3

By A.BUDD Date 02-27-2002 02:52

I have come across a conflick in the weld of olets on a run pipe. The olets are 3-inch and the run pipe is 8-inch. The new olets we are using have a large bevel to fill with weld. Production wants to weld the bevel of the olet only to the wall thickness of the pipe. Inspection is requesting that the bevel be filled all the way as a branch conection is detailed in the B31.3. This increases the welding time and thus is not liked by production. The 31.1 addresses the issue, but the I can not find a referance to welding olets in the B31.3. Does any one know the requirements of weld olets to met B31.3 requirements?? Any help would be welcome.

By Benjie Santos Date 02-27-2002 06:25

Refer to ANSI B31.3 Section 328.5.4 and Figure 328.5.4D. The designer is the final arbiter on the size of the weld. I have seen instances where the weldolet bevel area is incompletely welded but still acceptable based on the design. There are cases where the header thickness is much less than the throat thickness of the weldolet and welding the full thickness is not only unrealistic but would cause unnecessary distortion.

By Brad_J

Date 03-02-2002 01:05

I agree that the designer is the final arbiter. My logic tells me that the wall thickness of the 8" pipe is the correct throat thickness on the weld. This is due to the fact that the 3" diameter will have a much higher burst strength than the 8". The weld size should not be determined by the bevel supplied on the o-let. The designer may want it over welded due to some stress not known by us. Dynamic loadings can often times dictate a larger weld or a concave smooth radiused face such as required to prevent stress risers. I'd consult the designer before anyone comits to a bad decision. Note: the drawings should always state the weld size and profile so these questions don't come up.