MDMT calculation

[PBB20]

Hello all,

When i consider fixed Tubesheet (SA 516 70(Normalized)- Curve D) welded with pipe (SA 53-B) (Curve B), for MDMT calculation, governing thickness is based on tubesheet Nominal thickness /4, while MDMT calculation is based on pipe (Curve-B). It's flat tubesheet directly welded to the pipe with fillet and groove joint.
Can anyone explain me code reference for above calculation ?


Thanks

 

[David3399]

See Fig. UCS-66.3 (e) to start.

 

[PBB20]

Thanks David3399 for replying.

The Governing thickness is Tubesheet thickness / 4 as per Fig. UCS-66.3 (e).

But my question is thickness is being governed by the tubesheet (SA 516-70-Curve D), so why MDMT calculation is based on Curve B ?

PV-elite consider governing thickness based on tubesheet (Curve D) and MDMT based on Pipe (curve B).

Here 0.844" is (Tubesheet thickness/4) and 22F is based on Curve B w.r.t 0.844".