Crossed Welds

[JGG70]

Hello everybody!

currently I'm reviewing the mechanical design of an ASME III Class 2 Heat exchanger. The designer proposes a fixed tubesheet configuration where the shell and channel are groove welded to the tube-sheet according to the code allowed weld details. Additionally, one of the supports of the equipment (saddle supports) has been placed near the shell-channel-tubesheet joint. The saddle support is attached to the rest of the equipment using a reinforcement pad which takes the whole angle of the saddle support. The pad is planned to be fillet welded in the whole perimeter so this implies that the two horizontal pad welds cross the circumferential welds of the tubesheet. In this scenario I haven't found any provision concerning this question in the code. Could anybody report to me any experience about if this configuration is code allowed or not, and in the case that the configuration would be OK, please send me any comments about the suitability of this design. I'm afraid that the proposed detail could lead to fast fracture failure due to triaxial stress states.

Thanks in advance.

Regards.

 

[gr2vessels]

My interpretation of KD-721 is that the tubesheet welded in the shell/channel is a gross structural discontinuity and as such, the saddle wrapper's fillet weld should be far away from the circular seam of the tubesheet skirt and the shell (assuming the minimal length of the skirt per KD-1112).
Cheers,
gr2vessels