Fig UW 13.1

[weldtek]

These sketches show how we are to design a head to shell joint, when, as is often the case, the head and shell have different thicknesses. I'm sure all fabricators order the heads so the centerline offset falls into that allowed by this Code section.( </= 1/2 (th-ts)) Our practice is to wait until we have received the heads to cut and roll shell plates so that we can closely match them up, but, I've talked with others that say the 'design' aspect ends with the order for the heads, after that they apply UW 33 tolerances to the edges at fit up. I'd be interested in your opinions.

 

[JoeTank]

My shop experience was also that the shells were cut and rolled AFTER the formed heads were received and taped.


Joe Tank

 

[vesselfab]

We order ours to the ID or OD of the vessel

Our head manufacturers hold tight tolerances and they match up very well.

Any small deviation is handled in the weld seam for a smooth transition.

Our schedules are too tight to wait on heads to roll and weld shell cans.

We have not experienced any problem whatsoever meeting/exceeding code/customer expectations in these joints.

 

[SnTMan]

My experience has been similar to vesselfab's. I don't normally see a very large difference in thickness between shell and head anyway.

Regards,

Mike