Shall the operating static pressure include within the design pressure? 2

[mechengineer]

My understanding is that according to Code UG-21 & Appendix 3-2, the operating static pressure shall include within the design pressure from user mechanical data sheet . No need manufacturer to consider one more time again. Am I correct?

 

[Geoff13]

In my experience the design pressure on the Owner's data sheet is at the top of the vessel. Sometimes it is even stated that way.

The designer of the vessel then needs to add the static head of any product to arrive at the component (element) design pressure as defined in UG-21.

 

[mechengineer]

However, I think that if the static pressure is less than 0.5 bar (5 m H2O), for all horizontal vessel & heat exchangers, the static pressure shall be included in the design pressure that is simple, conservative and will not lead to increase the thickness due to the 0.5 bar of static pressure. Except for tall column (H/D>5 or >10), it shall be necessary to consider the static pressure separately for the bottom portion components of the column. Because it may increase the wall thickness of top portion of the column unnecessarily if put the static pressure into the design pressure.
As for if the design pressure include the operating static pressure that shall clarify with client if it is not specified in datasheet.

 

[prex]

The design pressure is defined in 3-2 as the "pressure used in the design of a vessel component", so it is conceptually local and must include the static head, if applicable. However the 'design pressure' as intended by UG-21 and customarily used for pressure vessels and marked on the nameplate, is conceptually global, and applicable to the whole vessel. So it can't include the static head, as this one is varying on the different parts of the vessel. This is very similar to the definition of MAWP, that, in UG-98, is clearly stated as defined at top of the vessel.
The fact that for horizontal vessels the static head is often negligible doesn't change the concept (and 0.5 bar of static head is not necessarily negligible!): the 'design pressure' as stated in vessel data sheets should always be intended as defined at top of vessel.

prex
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