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?
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Bolt Spacing Requirements for Flange w/O-Ring seal in VACUUM
- Thread starter Speckworm
- Start date
Compositepro
Chemical
The minimum number of bolts required is zero. My preference would be to use more for when there is no vacuum.
Speckworm,
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.
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.
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