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>These Viton material are much harder than regular Nitril. If the regular >rings tends to mush maybe the Viton material is the answer. Viton, like nitrile, comes in many different hardnesses - that's what the durometer number is about. So one can't really say one is harder or softer than the other. I was talking to a tech rep at Parker the other day, who told me, when I asked about viton, "Oh, I really hate to recommend viton, when there is anything else that will do the job". I asked why, and she said because the wear characteristics were so bad. I note that SCUBA suppliers like Global, who supply generic Orings, supply 70 duro in nitrile for general purposes,, but 90 (harder) in viton. And we've had posts here about soft green viton rings that don't hold up. All this suggests to me that viton does not hold up as well as nitrile, and that common practice is to substitute a harder grade to compensate. The catch to this is, the harder grade may have other disadvantages, especially in dynamic seals in regs where they directly effect performance. If I'm using O2 in a reg, and the manufacturer has a O2 kit, I figure why not use it, since the manuf. has probably made sure the parts will work at least fairly well. Otherwise, I'd rather go with the manufacturers choice of Orings than to try and reengineer the thing myself based on a single parameter. If people were having trouble using nitrile with O2, I might do reconsider, but since they don't seem to be, why worry? BTW, aviation practice is to use nitrile with O2. -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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