Vacuum Vessel Flange Design

I am designing a vessel for use in pressures that range from full vacuum to 150 psig. Our flange design is flat faced and o-ring sealed providing metal-to-metal contact across the face when assembled. The o-ring resides in the "door" flange (we are using a swinging door design) while the sealing surface is the stationary vessel flange. The o-ring groove is machined as close as possible to the inside diameter of the flange. My question is this: Is this an Appendix 2 or an Appendix "Y" flange design. I have looked at appendix Y and it seems to illustrate an o-ring seal design in the latest version of the B&PV code book making me think that this should be an Appendix Y design.

The next question is this: in either case of App 2 or App Y, are there any sources for the design of flanges which are externally pressurized. I don't believe the code covers this (for sure in App Y) except to say use "good engineering judgment", true?

Thanks,
rjw

Hi RJW,

You may refer to ASME VIII-1, Appendix-2, section 2-11 "Flanges subject to external pressures".

HT for external pressure only, can refer to UG-99 (f).

Wish it helps.

S K Tan