dinogep
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As far as I know nor viton, nor epdm or nitrile contains chlorine in its main composition. So phosgene is probably out, too.
Viton vs Nitrile O-rings...
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As far as I know nor viton, nor epdm or nitrile contains chlorine in its main composition. So phosgene is probably out, too.
Couv, You are way too kind. Your knowledge of oxygen and O-rings is rapidly exceeding mine.
It was Phosgene...and degradation of any Chlorine containing compound, in the presence of Oxygen can produce it, as well as several similar nasty compounds. The floride version of that compound is also not any fun.
Is it a danger in SCUBA? Well, no. First because Viton is a fluoropolymer and second because the rate it degrades is so slow. if I was in the plant that made viton, and there was a fire, I would try to leave very quickly.
Also, I know you know this, but Viton is not a single compound, it is a family of them, and they have lots of different properties.
The down side to Viton has been that it is just an ok elastamer...repeated compression and release will damage the material much faster than say EPDM...the upside is that it is far more O2 resistant. That down side happens to make it much better for things like tank valve O-rings and not as good for valve O-ring (although replacement is easy). When talking different materials, durometer numbers do not tell the whole story regarding extrusion issues, as viton is much harder to extrude versus EPDM of the same durometer.
Aircraft, by the way, have very different requirements for their static O2 delivery systems, and one would be advised to not try and copy them. (although the military view makes more sense to me, but the materials are very difficult to get in our world)
Due to the dynamic nature of SCUBA equipment and the need for frequent replacement, I don't see any reason to not use a good Viton O-ring, but people sure to like to play with their equipment.
It was Phosgene...and degradation of any Chlorine containing compound, in the presence of Oxygen can produce it, as well as several similar nasty compounds. The floride version of that compound is also not any fun.
Is it a danger in SCUBA? Well, no. First because Viton is a fluoropolymer and second because the rate it degrades is so slow. if I was in the plant that made viton, and there was a fire, I would try to leave very quickly.
Also, I know you know this, but Viton is not a single compound, it is a family of them, and they have lots of different properties.
The down side to Viton has been that it is just an ok elastamer...repeated compression and release will damage the material much faster than say EPDM...the upside is that it is far more O2 resistant. That down side happens to make it much better for things like tank valve O-rings and not as good for valve O-ring (although replacement is easy). When talking different materials, durometer numbers do not tell the whole story regarding extrusion issues, as viton is much harder to extrude versus EPDM of the same durometer.
Aircraft, by the way, have very different requirements for their static O2 delivery systems, and one would be advised to not try and copy them. (although the military view makes more sense to me, but the materials are very difficult to get in our world)
Due to the dynamic nature of SCUBA equipment and the need for frequent replacement, I don't see any reason to not use a good Viton O-ring, but people sure to like to play with their equipment.
What is your deffinition of reasonable? Phosgene gas is one of the chemical weapons that was used in WWI. Had a great track record for battlefield casualties.
I believe "reasonable" in this case refers to what compound could by made by degrading O-rings. Under the right conditions, they could degrade to make some Carbonyl difluoride (the fluoride version of Phosgene)..but not from normal room temperature use.
Phosgene was also used (when I was a kid, a very long time ago) to kill insects for collections. Some rubber bands, some carbon Tetrachloride and you get phosgene. Why it was important for grade school kids to learn how to make Phosgene is still unclear to me, but it was a very common practice.
Red River Scuba
New
If I'm not mistaken NASA uses liquid oxygen and the stability is a little bit different. Nuff said there. There is however a reason bulk O2 tanks (welding or any other use) is limited to 2200 psi. Combustibility increases with the pressure. The physics of this relates in several areas here and includes p.p. blending in tank. Different scenarios create issues, basically the higher the pressure, the more combustible. A bend in the line, curved or 90° or any combination there of creates greater friction with increased pressures. Can you think of anything like this in a tank? Often the internal portion of the valve is the most overlooked and often just the orings located at the neck and regulator connection (din being more popular for higher pressures) are only considered. Just another reason to replace to burst disk at least every time it's hydro tested. While I'm on a soap box there are no real requirements for visual inspection. I mean the dive industry generally accepts responsibility however there are no hardened rules requiring this be done. Nor is there any required formal training. With something so dangerous why is this?
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