UG-44(b) External Moment & Nozzle Projections

[Impostor]

Can someone please explain how nozzle projection factors into external moment calculation for UG-44(b)? I have noticed that terms “VL x Projection” and “Vc x Projection” are subtracted from moments ML and Mc respectively, when calculating for external moment but don’t fully understand the logic. Let’s say the external loads are per API 660 (so both VL and Vc are non-zero).
And a closely related follow-on question: are the loads considered at nozzle-shell junction or at the flange itself?

 

[DriveMeNuts]

I don't see any mention of VL or VC in UG-44(b).
I am looking at he 2021 edition of the code.

 

[TGS4]

The criteria is related to the flange. Therefore any calculations should be referenced to the flange, not the nozzle-shell junction.

Beyond that, the Code does not (nor will not) provide further guidance - you need to be engineer and use your engineering judgement. Just be aware that any calculation that supposedly shows "removal" of moment based on the offset of forces likely doesn't consider the situation when the force is reversed and adds to the moment.

 

[Cobra17]

Here is how Compress handles it.

M = 300 lbf-in (Pr)
W = -250 lbf (ML)
G = 9.3 in (gasket reaction diameter)


Pm = 16*M / (PI()*G^3) = 16*300 / (3.14*9.3^3) = 1.9 psi
Pr = -4*W / (PI()*G^2) = -4*-250 / (3.14*9.3^2) = 3.68 psi
MAWP reduction = max[Pm + Pr , 0] = max[1.9 + 3.68 , 0] = 5.58 psi
Table UG-44-1 Moment Factor, FM = 1.2
MAWP = min[MAWP , MAWP*(1 + FM) - MAW Preduction] - Ps
= min[260 , 260*(1 + 1.2) - 5.58] - 0 = 260 psi

Note that the loads are entered at the end of the nozzle, aka the flange, but if WRC calcs are performed, they convert the loads to the connection between the shell and nozzle for those calculations, which is where the length comes into play. And re-read UG-44 and let me know where you see nozzle projection mentioned.