UG-19 Combination Unit?

[SleepyFather]

I have a large pressure vessel with a smaller chamber inside it. The smaller chamber is spherical with a small hole (5/32") drilled into it. The chamber is in constant communication with the larger vessel through the small hole. Upon testing it was found that during rapid filling of the large pressure vessel there was ~225 PSI differential pressure between the pressure vessel and the smaller chamber (external to the smaller chamber).

The large pressure vessel is a ASME Sec 8 div 1 vessel, and if the smaller chamber were to collapse it would not damage the large pressure vessel.

Dose the smaller chamber need to be designed to ASME Sec 8 div 1?

 

[GenB]

i would design to Code , it may not need stamping.

 

[SleepyFather]

Does anyone know if my case would be an exception to UG-19 (a) because of the constant communication to the larger pressure vessel?

Please note, if the small chamber were to collapse it would not pose a safety concern nor affect the larger pressure vessel.

 

[SnTMan]

SleepyFather I would say you do not have a true combination unit as no differential can be maintaned across the two chambers. However you do have a transient condition where the inner chamber is exposed to external pressure. You have to design it somehow, why not Sec VIII, Div 1, unless there is too much conservatism in it for your particular case.

Since the outer vessel is a Code vessel you should maybe confer with your AI as well.

Regards,

Mike