Dumb question #92 - Oring question

[Landlocked123]

So I have purchased a few tanks (HP 100 and HP 133 and a handful 2 bony bottles) over the years. Every time I go to change the Orings (lost or damaged/worn) I notice that the O rings my local lds gives me are somewhat softer and different looking than the ones that came with the tanks. The ones I get appear to be same size but are noticeably softer. Yesterday I got in the mail some VIton orings which I understand are made for Nitrox. They are way stiffer and seem thicker (not larger) than the ones my LDS sells me. What is the deal? Is there not a standard scuba Oring ? So should I use the larger stiffer ones ?

 

[runsongas]

the viton orings are most likely just higher duro than the NBR duro 70 rings from your lds (which are the cheapest / most widely available orings). i only bother to replace with viton because in bulk amounts of 100+, the difference comes down to a difference of pennies.

 

[The Chairman]

Exposure to air will cause old buna o-rings to harden considerably. This won't happen with Viton.

 

[tbone1004]

they should be 214 o-rings, 90 durometer. If they feel softer, they're being lazy and buying 70 or 75 duro. Not cool. If they are different thickness, then they're giving you the wrong one entirely.

 

[Landlocked123]

Ok thanks all so sounds to me cant go wrong with the Viton Orings. They just seem beefier and better quality and Nitrox ready. I am switching the ones I had replaced with the VIton ones. Got I love this board....

 

[Scubagaskets]

Regarding the Shore,( Duro) the recommendations from my consultants is that the hardness of the o-rings are determined by the pressure and level of friction at the point of use. For applications of high pressure (over 100 bars) is recommended the use of hard o-rings (Sh 90) since they can handle pressure much better than the soft ones (Sh70) Nevertheless soft o-rings (Sh70-Sh75) are used for static applications with pressures, (over 100 bars) without recorded problems. I have wideness of a shreated soft o-ring (sh70) when it was mistakenly used on a scuba the tank valve due to high pressure and probably over tightening first stage to the tank valve, but i also have customers that prefer soft o-rings for all their applications. In respect of manufacturing is more difficult to make hard o-rings due to technical factors and thus the availability of soft o-rings in the market is much more than the hard garde.
Very soon at scuba gaskets one will be able to find a variety of Hard grade (Duro 90 -Sh90) scuba o-rings in viton and EPDM on top of the existing hard o-rings of NBR (Nitrile) and Polyurethane that we already have, that was specially developed and manufactured for scuba application.