Overpressure Protection with a Closed Isolating Valve?

[Bambie]

Design rules for valves in ASME B16.34, B31.1, Sections VIII, III etc. require analysis of stem retaining structures or 'a means' to ensure that failure does not result in stem ejection from the valve body.

Analysis is not required to ensure suitable margins exist under pressure and seating preload to prevent loss of seating stress.

Without this analysis, am I permitted to rely on a single closed valve as the only overpressure protection provided for the lower of two interconnected systems?

 

[Bambie]

Put another way...

Would a closed valve used for overpressure protection for which there is no analysis of the yoke sleeve or retaining structure under pressure, thermal or closing loads, require a fully analyzed external stem compression device that prevents the possibility of 'failing open'?

This would be in addition to administrative controls or locks to prevent inadvertent device removal per ASME VIII APPENDIX M.

 

[Bambie]

By the deafening silence, I suspect this is a question better put to the ASME Code Committee.