Distance Requirement For Fillet Weld And Butt Weld 2

[CATVSDOG]

Is there any requirements for the minimum distance between a fillet weld and butt weld on ASME VIII-1 code?
For example: On pressure vessel, there is a reinforcement Pad locating very close to the shell to shell weld seam. If the pad welded, the weld seam will be lapped on the butt weld. Is it acceptable?

 

[Mr168]

See the following threads:

Thread 127815

Thread 228576

 

[Duwe6]

Agree with the above threads, especially the Long Weld-Neck flanges. For almost all conditions, they calc as 'integrally reinforced' and thus require no repad. Overlapping HAZ's does not seem to be a 'real' problem, as there is no history of failures cauesd by this interaction. CAVEAT: some environvents and material combinations have 'knife-edge' corrosion & 'wasting' of the HAZ. This may be the basis for the Brittish prohibition.

Also beware; ASME requires additional NDE for butt-weld seams that are going to be covered by a repad. So that takes you back to LWN flanges, as the increased cost of the ALW will be covered by not needing to fab and weld a repad and pay for, and schedule the additional NDE.

 

[jte]

I agree that the use of LWN's and heavier forgings can frequently (disagree with "almost all conditions"!) avoid the need for a repad. In many cases it is the better way to go, and I've gone so far as to reword our company (generic, CS) vessel spec to favor integral reinforcement over repads. From an owner-user perspective, a repad makes online determination of thickness impossible, and as noted above, the ability to inspect welds and HAZ can be of substantial value. Finally, the use of integral reinforcement opens the door to the use of the "F" factor which can ease the reinforcement requirement if the designer is a bit clever about it.

One caution before running down the "lose the repad" path: Consider that in some cases I've designed repads to be thicker or wider than would be necessary for simple area replacement. Piping loads can push a design towards requiring repads or insert plates over heavy wall nozzles.

jt