Oxygen shut off valve on KISS valve/O2 CMF orifice? (or just use the tank valve)

marekm

Hi everyone,

What are peoples thoughts on adding a ball valve to shutoff oxygen to the KISS valve or an O2 constant mass flow orifice (or maybe even a needle valve). Also, should the valve shut off oxygen just to the orifice, while keeping the manual O2 inject valve pressurised, or shut down both orifice and MAV. Alterntatively, is a shut off valve trying trying to fix a problem that does not exist since you can just close the O2 cylinder valve to do the same thing.

Thanks in advance.

-Marek

Duncan Price

I thought about this and have a ball valve on my O2 feed where there is a leak (needle valve) present. This is so that I can isolate the O2 feed without depressurising the low pressure hose and first stage that feeds it. Occasionally I have put a second stage on the O2 regulator so in the event of the rebreather failing, I still have access to O2 for decompression. If the same thing happened without the ball valve then I would have to disconnect the feed to achieve the same effect.

Closing the O2 tank valve might lead to the first stage working loose (even if it was DIN) as it depressurised.

marekm

Thanks Duncan. So decompression issues aside, the bigger concern is the DIN reg working lose once the O2 system depressurises, and then the O2 venting as you turn the O2 tank valve back on. I heard Mark Chase's account of this happening during a training course so it may be quite common.

Next question, should the ball valve shut down the O2 supply to the orifice only, or the manual O2 inject button as well. I can see the rational of shutting down the O2 orifice if the IP starts creeping on the O2 first stage, resulting in the PO2 rising. Shutting down the O2 orifice leaves you with the ability to keep running in pure mCCR mode.

However, I have read about some people using the shutoff valve to shut down the supply pressure to the manual O2 injection just incase the manual inject button jams on. Any point in doing that?

Cheers.

-Marek