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Bolt Spacing Requirements for Flange w/O-Ring seal in VACUUM

Bolt Spacing Requirements for Flange w/O-Ring seal in VACUUM

Bolt Spacing Requirements for Flange w/O-Ring seal in VACUUM

I'm searching for any information regarding BOLT SPACING on large custom mating flanges (48"-120") that seal a VACUUM vessel with an O-RING.  I cannot find any literature with this combination to determine minimum # of bolts. Appendix 2 and Appendix Y only seem to account for positive pressure.  Configuration matches App.Y-5.2 Category 3 with an o-ring groove and no hubs.  (Bolted flanged door to a vacuum chamber.)  I don't see where B16.5 rates for external pressure and Taylor Forge eq. seems to apply for leakage and/or bending between bolts which I do not believe are the same for vacuum.  Is there ANY published guidance for this?   

RE: Bolt Spacing Requirements for Flange w/O-Ring seal in VACUUM

The minimum number of bolts required is zero. My preference would be to use more for when there is no vacuum.

RE: Bolt Spacing Requirements for Flange w/O-Ring seal in VACUUM


You need enough bolts to provide sufficient preload to obtain the required compression on the o-ring(s) - usually 20-30%.  If it is a vertical joint, the weight of the top assembly may well be sufficient to obtain the compression, meaning Compositepro is correct and no bolts are needed.  As far as bolt spacing, I would say it depends on the gravity loading on the joint and flatness of the two mating surfaces.

RE: Bolt Spacing Requirements for Flange w/O-Ring seal in VACUUM

There are standard types of couplings for vacuum service.  Look up Nor-Cal, MDC Vacuum, A&N Corp., etc.

-handleman, CSWP (The new, easy test)

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