ORings-Viton

[Couv]

I spoke with a shop+dive center. They told me the only dive with Nitrox these days, but their O-Rings and rubber parts age very fast, specialy at the high pressure parts.
I asked them why they didn't use Viton instead, as Viton can stay oxygen a lot better. They told me they would like but they have no source for Viton O-Rings. As I work for a hydraulic/pneumatic seal company I would like to ask the community of diver if there is really a need of Viton parts (not only ORings)??
Does it make sense to look into it and offer something or is that simply not true and there is no need or there are already strong companies on that?

Please advise!
Michael

Hello,

Regarding o-ring usage for a Scuba regulator.

As I believe in the "keep it simple, stupid" method, I would like to know if I can use one type o-ring material (FKM or EDPM) with single hardness (shore a 70, 75 or 90) for all of the o-rings in and on my regulator i.e. high pressure and low pressure hose ports, piston head and stem, hose to 2nd stage interface....If not, what would be your recommendations for each application.

Over the last few months I have turned up so much conflicting information I thought I would go to someone in the business. Here are a few examples of what I have found:
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From Dive Rite web site: http://www.diveriteexpress.com/hardware/orings.shtml :

"Hardness -- O-rings are normally available with a hardness rating, as measured by an ASTM type-A durometer, of 70 (the "soft" kind) or more rarely a rating of 90 (the "stiff" kind). The O-rings sold on this page are 90-duro (except for the -003 SPG O-ring), and well suited for the SCUBA applications we describe. The soft O-rings are appropriate for dynamic applications where the O-ring is providing a seal with a constantly moving part, such as inside regulators. The stiff O-rings are more durable in static applications where the O-ring is providing a seal with stationary or occasionally moving parts, such as a valve. "
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From a trusted poster, DA Aquamaster:

"Viton does not seem to hold up as well in dynamic applications where they are subect to wear and are less tolerant of inadeuate lubrication in static applications.

Viton is less susceptible to buring in a high o2 environment but produces phosgene gas when it does. Phosgene was one of the poison gases used in WWI, so an o2 fire while you are brething on the reg would be a very very bad thing with viton o-rings.

I used to use them in O2 regs before SP switched to EPDM o-rings but I now use EPDM o-rings and am much happier with their longevity."

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From oxyhacker- Vance Harlow:

"I use 90s for yoke valve to regulator and tank neck, and 70s for hoses and just about everything else except a few oddballs like piston rings." (did not say what to use)

"Air-Oil has viton 90s and other goodies at very reasonable prices - higher than the ones on the on-line ordering form, but still cheaper than anyone else I've found - but you have to call and ask for them.

That said I am not a big fan of viton for anything except maybe gear that will see 100% for extended periods and equipment that came originally equipped with it."

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So could I impose on you to provide a list of recommended seal material and hardness? I know there are web sites with this technical and usage application data, but I would like the input of a diver/engineer/someone in the business.

Bottom line question, is there a single material and hardness that can be used for:


Port plugs and hoses

1st stage Piston head

1st stage Piston stem

I have most of the o-ring sizes documented, I just need the aforementioned material/hardness recommendations

Thank you,

Couv

 

[JBRES1]

Roakey,
Thanks for the list of o-ring sites.
Don't know if I will use them for Scuba, but I sure will for my company.
I own an industrial valve sales company and we go thru alot of viton o-rings in high pressure ball valves.
Thanks, Jim Breslin

 

[Tom Smedley]

When viton burns it gives off flourine gas. AquaLung for one recommends EPDM over Viton for o'rings.

 

[h90]

viton can not produce a phosgen gas. Flourine gas. But max usable temperatur is 200 Degree Celcius. We run tests at 225 degree Celcius and it was still useable, so I think not possible to reach that temperatur while diving (not even the french fries oil get that hot).
For the hardness: thats an extremly difficult question, consider my answer as generell sealing answer might be a bit different for diving.
For dynamic applications an O-Ring is anyway not recommended, but sometimes there is no other choice, as other solutions might be either expensive or bigger and there are not many strokes when diving (many would be 2 strokes/per minute 24 hours a day for 2 years). A hard O-Ring (90 shore) might not seal good at LP as it might be a bit too hard. While a 70 shore might get squeezed into the gap at HP and beeing broken soon.
At static application both should do the job well if the gap is small the housing smooth.

If we produce O-Ring, we usually use 80 shore (but thats not meant for diving, more for generell hydraulic/pneumatic).

NBR O-Ring age fast with heat/ozone/light, so an O-ring in the showroom in the direct light is broken after 1 year.

Viton (or FPM which is the same, Viton is the trademark of DuPont) does not has the good mechanical properties of NBR, but excellent resistance against nearly everything. But there are also differences. There some mixtures which are a bit better.

In cases where o-ring brake very fast, it might make sense to try a square ring instead.

 

[oxyhacker]

BTW the problem may not be with the compound, but the quality of the O-rings. There are huge differences in quality of O-rings, even among ones that are supposedly the same compound and duro. I've had some nitrile O-rings that will degrade in a few months from exposure to just air, and others that have lasted years in nitrox service. Some of the cheap bulk O-rings from abroad are the worst in this regard, though I've had pretty good luck lately with the ones from Air-Oil. Air-Oil, incidently, can get a lot of sizes duro and compounds that are not on their site, like 90 duro viton.

 

[h90]

BTW the problem may not be with the compound, but the quality of the O-rings. There are huge differences in quality of O-rings, even among ones that are supposedly the same compound and duro. I've had some nitrile O-rings that will degrade in a few months from exposure to just air, and others that have lasted years in nitrox service. Some of the cheap bulk O-rings from abroad are the worst in this regard, though I've had pretty good luck lately with the ones from Air-Oil. Air-Oil, incidently, can get a lot of sizes duro and compounds that are not on their site, like 90 duro viton.

Thats ABSOLUT TRUE.
There are these O-Rings from Chinese/Thai backyard products, which are really not good, but very cheap.
Sometimes companies which repair traktors request them from us and than there are brand name O-Rings.
Very hugh differences.

 

[roakey]

Roakey,
Thanks for the list of o-ring sites.
Don't know if I will use them for Scuba, but I sure will for my company.
I own an industrial valve sales company and we go thru alot of viton o-rings in high pressure ball valves.
Thanks, Jim Breslin

You're welcome. I just reread the original post and realized that I didn't answer the question asked, I thought they were looking for where to buy them. But I'm glad that it helped someone

Roak

 

[pescador775]

About 20 years ago, Scubapro changed O ring compounds for use in regulator applications. They started using something called "hyperthane" for some of their rings. The problem of slow air leaks which had plagued the brand for many years and was one of the reasons for "yearly checkups" had to do with extrusion of an O ring when it bit into a sharp metal shoulder and was riding against a curved surface. I believe this "hyperthane" is a polyurethane compound. In particular, the large O ring on the piston appears to be made of this material. In any case, urethanes, which appear in several types and grades, are tougher than Buna-n with higher tensile strength and so forth. The common polyether urethane is available at reasonable prices and might be a good choice for the Scubapro piston, eg, if it is decided that this item is to be from a generic source. Different material may be required for the stem in an oxygen application. It would seem that 70 duro would be the right hardness for the piston and the stem. OringsUSA and Marco Rubber Co carry urethane in several sizes and grades.

I find it hard to believe that Nitrox would cause problems with Buna-n O rings in general. "Hacker" alluded to O ring quality. IMO a quality neoprene ring will do fine in Nitrox atmospheres. Perhaps not so well in pure oxygen but that has been discussed here and elsewhere. If there are problems with O rings on the valve face including extrusion then perhaps urethane in 90 duro would be an option. These have appeared in the dive industry from time to time. My experience is that they are excellent performers, particularly at higher pressures.

 

[h90]

About 20 years ago, Scubapro changed O ring compounds for use in regulator applications. They started using something called "hyperthane" for some of their rings. The problem of slow air leaks which had plagued the brand for many years and was one of the reasons for "yearly checkups" had to do with extrusion of an O ring when it bit into a sharp metal shoulder and was riding against a curved surface. I believe this "hyperthane" is a polyurethane compound. In particular, the large O ring on the piston appears to be made of this material. In any case, urethanes, which appear in several types and grades, are tougher than Buna-n with higher tensile strength and so forth. The common polyether urethane is available at reasonable prices and might be a good choice for the Scubapro piston, eg, if it is decided that this item is to be from a generic source. Different material may be required for the stem in an oxygen application. It would seem that 70 duro would be the right hardness for the piston and the stem. OringsUSA and Marco Rubber Co carry urethane in several sizes and grades.

I find it hard to believe that Nitrox would cause problems with Buna-n O rings in general. "Hacker" alluded to O ring quality. IMO a quality neoprene ring will do fine in Nitrox atmospheres. Perhaps not so well in pure oxygen but that has been discussed here and elsewhere. If there are problems with O rings on the valve face including extrusion then perhaps urethane in 90 duro would be an option. These have appeared in the dive industry from time to time. My experience is that they are excellent performers, particularly at higher pressures.

Hyperthane, really sounds like a Polyurethane (PU). PU is very wide used for sealing and in most situations it is better than NBR. In my list I have also a higher resistance against Oxygene than NBR has.
To what I know (I may oversee something) it should be better than NBR in nearly all diving applications. Just our PU is a bit harder than the NBR, so at low pressure I would prefer a softer material.

PU is a more expensive raw material, but it can be processed faster and easier than NBR when moulding things so it might be cheaper in some case, more expensive in other cases.

 

[pescador775]

Most of the urethane offerings are made from a material called "millable gum" referring to a milling process, I guess. However, the O rings for paint ball markers (guns) are made from cast urethane and are also more expensive. These O rings are marketed specifically for pressurized carbon dioxide markers. Marco Co offers a regular, low cost urethane O ring and also a "high strength" urethane. These O rings are commonly called "10,000 psi" O rings. So, there are the polyether (millable) and polyester(cast) urethane O rings. I'm not really sure of the differences and the recommended applications and/or why. However, I note that cast/ether (AU/EU) urethanes are rated "high" for ozone resistance and abrasion resistance and are rated very high for dynamic applications, higher than EPDM and much higher than FKM (viton).