Quote:
Originally posted by unregistered
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After designing and doing failure analysis of o-ring joints for many years (in both static and cyclic pressure service),
there are several useful guidlines:
- when the component surfaces make contact, as they must, there should be 30 to 40% compression of the crossection
- the o-ring's volume should be between 60 and 70% of the groove's
- using a 30 to 50 Shore A durometer (hardness) material will make the surface finish less critical
- the o-ring's (centerline) length should match the groove's (do NOT stretch)
- the groove must have an outer containment ring to 'capture' the o-ring, else it is functioning as a gasket (different design basis)
do not use a sealant with the o-ring (no need if properly designed, will overfill the groove, make disassembly a pain, etc)
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Utabintarbo had mentionned o-rings from McMaster (
www.msmaster.com ). I looked through their selection, and it seems that all they have, are o-rings with a shore-A durometer rating of 65 to 90 (55 in shore D, Teflon). We were shooting for a 1/16 round cross-section.
The material selection that they have includes: Polyurethane, Neoprene, Buna-N, Viton, Teflon, Kalrez, Ethylene propylene (EPDM) and silicone.
There's also a slightly different shaped o-ring, but still not within Shore A 30 to 50.
Until I find a supplier, here's a cutsy anecdotal story:
Finding a Shore A durometer