Rebreather Safety Improvement: Progressively opening Oxygen Cylinder Valve Seat

[Brad_Horn]

In a world first OSEL are quite happy to disclose that they are now supplying their rebreather valves with a progressively opening cylinder valve seat.

This is available as a free of cost safety upgrade during annual service for all Apocalypse Type IV CCR owners and can be bought with the NAUTEC valves OSEL supply. The two types OSEL offer in G5/8 and M26 are the T valve and the K valve, with the plastic knob.

For further details see Open Safety Equipment Ltd

To buy contact OSEL at sales@opensafety.eu

 

[Vicko]

What does this do exactly?

 

[Daedalus]

What does this do exactly?

It progressively opens the cylinder valve.

 

[bletso]

By slowly opening an O2 control valve you can reduce adiabatic heating and significantly reduce the chance of an O2 fire.

 

[Wookie]

What does this do exactly?

By reading the background material on their facebook page and web page, it appears to be a needle valve with a non-teflon disc. That means that as the valve is opened, it slowly allows gas to enter the system instead of the typical scuba valve which has a flat disc compared to the seat, which opens quickly and slams pressure downstream, which in the presence in the least bit of schmutz, would cause adiabatic heating resulting in a fire or small gas explosion.

Since all scuba discs are made of teflon, which is not oxygen compatible, this would eliminate valve disc fires, of which I have had at least 3 that I know of.

I am not a fan of the folks who run OSEL, but this is a huge step in the direction of oxygen safety in scuba applications. If the rest of the valve manufacturers step in line and adopt this change, that would be huge.

 

[Brad_Horn]

What does this do exactly?

Amongst the listed benefits in the above link, most critically for rebreather divers, it removes the risk of adiabatic compression which occurs when a valve is opened too fast.

If you have this happen on a good day, and the rest of the rebreather has been designed to prevent anything worse, your oxygen hose just bursts and oxygen flows out.
Bad day, the rebreather catches fire.
Really bad day, and the boat you were on burns to the waterline.

In the overall scheme of things it is only a small improvement but every little bit helps. And this is something that every rebreather, and for that matter oxygen stage cylinder, can be fitted with for the cost of a replacement NAUTEC valve from OSEL. Be it M18, M25 or 3/4NPSM in G5/8DIN and M26 options.

 

[Brad_Horn]

By slowly opening an O2 control valve you can reduce adiabatic heating and significantly reduce the chance of an O2 fire.

Agreed. The caveat is "slowly". And in the real world this just doesn't always happen.

 

[rjack321]

Since all scuba discs are made of teflon, which is not oxygen compatible, this would eliminate valve disc fires, of which I have had at least 3 that I know of.

Little correction...
Teflon is in the grand scheme of things O2 compatible (although everything will burn eventually)
https://www.teadit.com/assets/refer...bilidade/us/Tealon_Chemical_Compatibility.pdf

Most scuba seats are nylon which is less O2 compatible than Teflon. Nylon is used because Teflon is too plastic/malleable for an HP seat in a typical scuba valve design. Nylon seats can and do combust occasionally - possibly from contaminants on the seat but the seat by itself can burn too.

 

[Wookie]

Little correction...
Teflon is in the grand scheme of things O2 compatible (although everything will burn eventually)
https://www.teadit.com/assets/refer...bilidade/us/Tealon_Chemical_Compatibility.pdf

Most scuba seats are nylon which is less O2 compatible than Teflon. Nylon is used because Teflon is too plastic/malleable for an HP seat in a typical scuba valve design. Nylon seats can and do combust occasionally - possibly from contaminants on the seat but the seat by itself can burn too.

Thanks for that, I had no idea. But I have burned a number of discs in O2 scuba valves.

 

[moose_grunt]

Isn’t this the same thing that AP started doing last fall with their oxygen valves?

Oxygen Rebreather Cylinder Valve | AP Diving

Either way, it’s great to see manufacturers implementing additional safety measures to prevent oxygen fires.