Thanks MoverZ, you are right as I can only model the end caps/dished heads as a weight on end nodes. As per B31.1 - 104.1.1 the closures can either be designed as per Standards listed in 126.1 table OR as per ASME Sec I-PG-31 (unstayed flat head and cover).

My main problem is to design them as per Asme Sec I, PG-29 (Dished Heads) because that I can. ASME B 31.1 doesn't restrict use of PG-29 but also doesn't permit it.

[I know this is not a CODE discussion forum but if anybody have any idea or have worked on similar situation...than I'll be glad to hear an opinion]

@Dan. Yes I need to be careful but do I have a dished head option or not is the main thing!. Thanks for your input anyway.

Regards,
Salz