We purchased an "off the shelf" stock item cryogenic nitrogen vessel that is stamped for a MAWP of 250 psig. The rupture disk is stamped 365 psig at 68F and also stamped 263 psig at 740F. When contacted, the manufacturer referenced CGA S-1.3 paragraph 5.1.2.3 as allowing this rupture disk set point.
I guess the theory is the disk is only for the fire case, where the temperature will lower the actual burst pressure of the disk material. I get the physics (or metallurgy), but does ASME BPVC Section VIII, Div. 1 allow this?
Obviously the Authorized Inspector who signed the U-1A agrees that it is ok, but is there an interpretation out there? Non-Mandatory Appendix M, paragraph M-13 references CGA S-1.3, but it does so in the context of determining the required flow capacity. Can this be extended to include the allowances for setpoint of CGA S-1.3? It seems a bit of a stretch to me, but if there were an interpretation that allowed it, I would feel a lot better.
Thanks!
I guess the theory is the disk is only for the fire case, where the temperature will lower the actual burst pressure of the disk material. I get the physics (or metallurgy), but does ASME BPVC Section VIII, Div. 1 allow this?
Obviously the Authorized Inspector who signed the U-1A agrees that it is ok, but is there an interpretation out there? Non-Mandatory Appendix M, paragraph M-13 references CGA S-1.3, but it does so in the context of determining the required flow capacity. Can this be extended to include the allowances for setpoint of CGA S-1.3? It seems a bit of a stretch to me, but if there were an interpretation that allowed it, I would feel a lot better.
Thanks!
