Welded attachments to Annular plate 1

[BJaffa]

In an 80 ft. diam tank we are installing a heating coil. Can a standoff be welded with fillet welds to the A516-70 annular plate, without performing MT. What NDE would be required? The plate stands will be 4" from the shell (beyond the critical zone). The tank is designed for minus 60 deg. F but will operate at 350 deg. F

 

[JoeTank]

API-650 does not address that specific case. Good practice would suggest MT of the welds, especially for a high temp tank.

Joe Tank

 

[BJaffa]

We will MT the weld. We are considering welding a repad of the same material as the annular ring prior to the attachment. Is the material suitablity of attachments to the annular plate or other primary plates addressed in API 650. If not what practical guidance would be followed?

 

[JoeTank]

Although API650 does not address the compatibility of miscellaneous attachments, I would follow common practice and use materials that are obviously of weldable quality. ASME VIII mentions this situation and indicates the material should be of weldable quality and have a carbon content not exceeding 0.35%. API-650 requires use of qualifioed procedures and welding by qualified welders, so it seem clear that it should be one of the acceptable materials of API-650. Low-hydrogen electrodes are required, depending on shell plate thjickness and grade. Further, if you are in a cold climate and the attachments are subject to loads, I'd select the pad material for the design metal temperature.

Joe Tank