Reinforcement calculation as per UG-37(c) & (d) of ASME Sec VIII Div.1 2

[jai2705]

Hi,
A vessel is designed for internal pressure of 4bar(g) and an external pressure of Full Vacuum (1 bar(g) as per ASME Sec VIII Div.1.

There are two formula available for reinforcement calculation based on internal and external pressure in UG-37(c)&(d)of ASME Sec VIII Div.1.

Wherein the reinforcement requirement of vessel subject to external pressure is only 50% of that required for internal pressure.

Does it mean that the calculation shall be performed for both internal and external pressure and if nozzle required reinforcement based on the internal pressure calculation has to to be provided with reinforcement though external pressure calculation showing reinforcement not required?

 

[TGS4]

Yes

 

[GenB]

Yes...

 

[jai2705]

Thanks TGS4 and GenB for your view on this.

 

[TomBarsh]

It's worth pointing out that although the Code requires only "50% of the area" for external pressure using the rules for internal pressure, the required thickness of the shell, tr, is to be that for external pressure.

If the same numerical value of pressure is applied for both internal and external pressure (as well as temperature), the required shell thickness tr will very likely be greater for the external pressure than for internal pressure. Thus the actual numerical value of required area for external pressure will likely not be 50% of that for internal pressure, and could actually govern over the internal pressure design.