Logic behind UHX-14.5.9(b)

[jehan17718]

This is wrt ASME S8D1 edition 2007 para UHX-14.5.9(b) which deals with checking the tubes for buckling stress.

Can anybody explain the reasoning/logic behind this para which is relevant for floating head shell and tube heat exchangers?

As this para is valid for FLOATING head heat exchangers, I am unclear as to how compressive stresses and correspondingly how bucking stresses are induced in the tubes.

Thanks in advance to share your perspective.

-jehan

 

[eliebl]

If the shell side pressure was larger than the tube side pressure then there would be some compressive loading on the tubes.

EJL

 

[DG72]

I believe that it results from the tubeside pressure only case. Even though one tubesheet is floating, you can get some localized compressive stresses within the tubefield when the tubesheet deflects due to pressure. It has nothing to do with thermal expansion, just pressure on the tubesheet.

For the record, this is just my explanation on the subject, based on my own observation of the rules. I have never seen any evidence that this explanation is correct. If anyone has any support of this explanation, I would like to see it.