Are viton o-rings really necessary?

[halocline]

Nitrile O-rings will work reasonably well in captive locations (say a tank valve O-ring), but nitrile when exposed to O2 turns into a sort of nasty paste, so for safety, avoiding nitrile is a very good idea.

The guy took 20 dives with 32% O2. If that little bit of O2 exposure melted the o-rings, then thousands of regulators would be falling apart from nitrox use. Even regulator manufacturers with lawyers allow nitrox to 40% with virtually all of their regulators, of which only a very small minority have viton o-rings. Come on, let's try and stay in the real world here.

 

[Puffer Fish]

Except for the exception of tank o-rings that see high pressure gas for long periods of time I doubt if viton v. nitrile v. EPDM makes much difference. But then this is not like some immutable unknowable subject. Take some o-rings out after a while and look at them and decide if there is much difference. I do not see much.

They actually use a "swell" test for this... I picked a time where it will go way past that, so it would be easy to see the issue. An O-ring may look ok, long after it is not usable in any dynamic situation.

Aviation, by the way, does not use nitrile for O2 service.. not sure where that silly rumor comes from...pick any company you want and check their specifications.

Here is one of them:

http://www.lockheedmartin.com/data/assets/service_news_magazines/V22N04-V23N01.pdf

Lockheed is rather famous for not using expensive O-rings (just read the intro), but then go look for what they spec for 02... and it is not nitrile.

 

[Puffer Fish]

The guy took 20 dives with 32% O2. If that little bit of O2 exposure melted the o-rings, then thousands of regulators would be falling apart from nitrox use. Even regulator manufacturers with lawyers allow nitrox to 40% with virtually all of their regulators, of which only a very small minority have viton o-rings. Come on, let's try and stay in the real world here.

I've seen it after around 100 hours of diving...but only in dynamic applications. At that point, most of the o-rings were mush. But 100 dives = around 300 hours of actual exposure (or just under 2 weeks of continous exposure) and add in some mechanical.

How old was the regulator (rather how old were the o-rings)...what temperature was it stored at? Was it used on say boat dives, where one puts the regulator on, tests it and then leaves in with high 02 for the rest of the day?

Silly conversation though, because it is pretty obvious that chemical degradation and how O2 effects materials is some kind of witch craft and magic.

If you wish to believe that all the dynamic seals in modern regulators are made with nitrile...reality is not going to get in your way.

 

[Mr Carcharodon]

They actually use a "swell" test for this... Ihttp://www.lockheedmartin.com/data/assets/service_news_magazines/V22N04-V23N01.pdf

Lockheed is rather famous for not using expensive O-rings (just read the intro), but then go look for what they spec for 02... and it is not nitrile.

I'm not sure who "everyone" is but it surely is not the whole of the industry. Lockheed is rather famous for not getting it right.

 

[grouchyturtle]

Wow! This is getting interesting.

I'd assume my regs, all Apeks, are viton. And the shop that did my last rebuild I can't imagine using anything but viton. Also all din valves, 300bar Sea elite manifold, considering they come O2 cleaned I'd say all viton.

But really I was just asking because I have a bunch of spare o-rings sitting around. And based on one of the earlier posts...and a few strays I found, I now have my doubts as to if the ones marked viton really are viton.

BTW - What's all this talk of aviation? Seems a little irrelevant since we're talking diving here. Kind of like when people on cruisers forum suggest something because, "works on an RV or in a house."

 

[Bubbletrubble]

I'd assume my regs, all Apeks, are viton.

Bad assumption. The o-rings in your Apeks regs are almost certainly EPDM. At least that's the composition of o-rings in the official Apeks service kits.

A convenient side benefit of using EPDM or Viton o-rings is that their shelf-life is very long. BunaN (nitrile) o-rings seem to degrade rather quickly (or at least faster than EPDM and Viton o-rings).

 

[fppf]

Huh, worth its weight in gold? I would argue that point, many comments here are by arm chair quarterbacks that really don't have any true formal education, just giving there opinions, with nothing to back them up.

As for aviation and oxygen, the aviation industry really does not use oxygen in aircraft. Really the only place you will find oxygen in an aircraft is the emergency breathing systems. So, most o-ring material choices in aviation are driven by fluid compatibility of the various hydraulic oils and fuels.

Now, in Aerospace, there are lots of oxygen systems and other oxidizers. And I can tell you that there is not a single Nitrile oring anywhere in those systems.

With new materials coming out all the time almost no one uses Nitrile anymore.

And if your charging $3 for a tank neck viton oring, I will sell them for $2, who wants some?

 

[redacted]

Huh, worth its weight in gold? I would argue that point, many comments here are by arm chair quarterbacks that really don't have any true FORMAL EDUCATION, just giving there opinions, with nothing to back them up.

If the only way to advance knowledge were FORMAL EDUCATION, the earth would still be flat.

 

[JB]

As I understand it all regulators, tanks and nitrile o-rings are good for 40% nitrox. All tanks are good for 40% oxygen if filled by a membrane system. Tanks have to be specially oxygen cleaned only if the partial fill method of blending nitrox is used (the most common way), because they are then initially partially filled with 100% oxygen, and topped up with air to achieve the end mix.
I suspect viton rings in the tank are necessary for filling with 100% oxygen. Regs have to be Oxygen cleaned only if they are to be used with mixes higher than 40% oxygen.
The good news is Viton doesn't have to be exorbitant. Here's a link to VITON tank size O-rings at about 15 cents each. O-rings Online Frameset so get a few people to share the order, and save heaps.

 

[Mike Boswell]

I really haven't paid much attention to what my various o-rings are made of. I don't read many stories about equipment failure, let alone o-ring failures. I figure after 60 years of experience, the various manufacturers and maintenance shops have o-ring chemistry pretty well figured out.

I DO know that maintenance is a critical element, and I make very sure that my tank valves and regulators are serviced annually.