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Drmike · 15th May 2008, 03:32

Quote: (Originally Posted by onetime)

That would be my guess. Each time the valve opens then closes the spring pressure pulls a bit of water in as it closes. If it's firing continually over that hour I'm sure it will add up. I doubt it would completely flood the unit in an hour but perhaps the unit was flooded when the diver came back to discover a non-functional Rebreather and was in the middle of a silt out.

Hmm, why would a staged rebreather thats over inflating with gas and venting from the opv be any more prone to flooding than the breather on your back during ascents? We dont see flooding on ascents, Ive never flooded any of my bobs either (that Im not breathing from) on ascents. You will always have +ve pressure in the loop so long as there is a spring closing force acting on the opv. That force will limit the min loop pressure to above ambient. So I dont buy it. I suspect the opv was leaking and combined with the orientation of the opv, this is what led to the flood.

How many of us do a +ve pressure test....I have to admit I rarely do a +ve

I can imagine a scenario where wet cells led to solenoid firing and loop venting. Over an hour the O2 supply could become exhausted. If the OPV isnt seating properly that only becomes a problem if its facing upwards. Once the O2 runs out CL, pressure starts to drop as gas is leaking out of opv. Once enough gas has leaked out and CL pressure has dropped to ambient pressure then water could begin to drip into the lung through the opv and exchange with gas in the CL (gas bubbling out as water drips in)

If the unit is staged with the OPV facing down and lowest part of loop this risk should be negated, as once cl pressure has dropped to ambient water wont go 'uphill' into the CL through a leaking opv.

So bottom line is if your going to stage your unit it would be wise to make sure your opv is not leaking (+ve or -ve test before hand) and whenever possible stage your unit with opv facing down. As long as the OPV is facing down no matter how crappy it is water shouldnt be able to enter the loop via it.

15th May 2008, 03:32	#24 (permalink)
Drmike Custom Title Allowed! Current Rebreather/s: MK 15.X Ouroboros Other CCR Home Build Other Rebreather/s: Inspiration Classic Other CCR Home Build Join Date: Feb 2005 Posts: 3,277	Re: Report from Fatality at Devil’s Ear Quote: (Originally Posted by onetime) That would be my guess. Each time the valve opens then closes the spring pressure pulls a bit of water in as it closes. If it's firing continually over that hour I'm sure it will add up. I doubt it would completely flood the unit in an hour but perhaps the unit was flooded when the diver came back to discover a non-functional Rebreather and was in the middle of a silt out. Hmm, why would a staged rebreather thats over inflating with gas and venting from the opv be any more prone to flooding than the breather on your back during ascents? We dont see flooding on ascents, Ive never flooded any of my bobs either (that Im not breathing from) on ascents. You will always have +ve pressure in the loop so long as there is a spring closing force acting on the opv. That force will limit the min loop pressure to above ambient. So I dont buy it. I suspect the opv was leaking and combined with the orientation of the opv, this is what led to the flood. How many of us do a +ve pressure test....I have to admit I rarely do a +ve I can imagine a scenario where wet cells led to solenoid firing and loop venting. Over an hour the O2 supply could become exhausted. If the OPV isnt seating properly that only becomes a problem if its facing upwards. Once the O2 runs out CL, pressure starts to drop as gas is leaking out of opv. Once enough gas has leaked out and CL pressure has dropped to ambient pressure then water could begin to drip into the lung through the opv and exchange with gas in the CL (gas bubbling out as water drips in) If the unit is staged with the OPV facing down and lowest part of loop this risk should be negated, as once cl pressure has dropped to ambient water wont go 'uphill' into the CL through a leaking opv. So bottom line is if your going to stage your unit it would be wise to make sure your opv is not leaking (+ve or -ve test before hand) and whenever possible stage your unit with opv facing down. As long as the OPV is facing down no matter how crappy it is water shouldnt be able to enter the loop via it. __________________ Cave diving is a sport Wreck diving is a sport Diving in general is a sport 'Rebreather diving' is not a sport its the delusional obsession with a highly dangerous and often inappropriate piece of equipment Last edited by Drmike : 15th May 2008 at 03:35.
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