KernOily, I've not actually seen such, but, if working to Sec VIII, Div 1, Appendix 13, 13-14 would appear to be applicable. Nozzle reinforcing and any other relevant features would be addressed thru other Code methods.
Regards,
Mike
The problem with sloppy work is that the supply FAR EXCEEDS the demand
I've yet to see a case on a typical welded box header air cooled heat exchanger where 14.7 PSIG external pressure would come anywhere close to being the governing design case, but if you have to show calcs proving it, follow Appendix 13, section 13-14 "VESSELS OF NONCIRCULAR CROSS SECTION SUBJECT TO EXTERNAL PRESSURE". There are three requirements: A) perform the same internal pressure calculations substituting internal pressure for external pressure, B) perform stability calculations per 13-14(b) and C) perform buckling calculations 13-14(c).
UG-28 would also apply to the tubes.
Just for kicks I did some scratch calculations on typical ACHE tubes (5/8 16BWG typical up to 1-1/2 18BWG worst case)and found the external MAWP came out to roughly 2/3 of the internal MAWP, so nowhere close to 14.7 PSIG.
Appendix 23 has special external pressure requirements for heat exchanger tubes that are Copper, Copper Alloy, Titanium Alloy, with integral fins.
