The governing MAWP shall be applied for the multiple loads cases analysis

[mechengineer]

Hello everyone,
My understanding is that the governing MAWP plus the external load (nozzle external load, wind load...) shall be applied to analyze for the area of nozzle and the vessel support on the vessel to ensure anywhere of the pressure vessel is safety under the governing MAWP. (some people are not agreed with my opinionc above)
Secondly, as I know, the current softwares have no such option to use the governing MAWP plus the external loads to analysis the nozzle and the vessel support except using the governing MAWP to replce the design pressure to recalculate one more time. This became one reason that some people disagree with my opinion.
How do you treat such issue in your experience?
Thank you.

 

[SnTMan]

mechengineer, in my experience in my class of work, shell & tube exchangers, this was just about never done. I had one checker long ago that insisted nozzle loads be run at MAWP, but nobody else, including the clients ever asked for it on any kind of consistent basis.

As you note there can be practical problems in doing so. If you have stand alone program modules, fine, but if your software is making design decisions, then you have to lock everything down before running at the MAWP, else your design may change. If you can't lock everything down, then you are stuck with re-checking every single dimension and calculation output...

Given that nozzle loads especially are generally works of fiction, hardly seems worth the trouble. My opinion.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[mechengineer]

SnTMan,
Happy to see your comment and thank you.
It is worth mentioning that the saddle support & the skirt calculation has the same issue without checking by the governing MAWP. In such case, I think, the better way may use the design pressure as the MAWP (UG 99 note 36).

 

[SnTMan]

Saddles, skirts, legs, clips, lugs, what have you, yeah, strictly speaking any external loadings would be run at MAWP. Didn't ever get into skirts, HX's usually horizontal, so the Zick calcs were relevant, but...

Again, they are a mess when applied to the normal shell & tube exchanger, not especially accurate at any pressure. My opinion.

And yeah, if you can get away with assigning DP as the MAWP, that's an obvious solution

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand