It finally happened - my CCR tried to kill me

[rsingler]

Yes, the CE numbers are at specified depth. For example the EN14143 test for the JJ-CCR was at 40 and 100m. But the volume of CO2 injected into the loop was constant at 1.6lpm at 1ata.

The O2 and N2 molecules increase proportionately with depth. But if CO2 is completely scrubbed (not strictly true), then the only source for new molecules is metabolism, which only changes with workload, not depth. Your constant and stable production of CO2 molecules (at constant workload) at depth is now diluted by many more molecules of O2 and N2 from your gas supply, compressed by ambient pressure but supplied at constant volume.

 

[cathal]

Thanks for taking the time to explain that.

 

[tbone1004]

Stupid question, are these performance parameters to be corrected for depth e.g. at 10 meters, do we double these performace parameters?

no, but I can see where the confusion lies since when you are on open circuit you would have to correct for atmospheric pressure. Even in open circuit, the volume of gas moved stays the same, i.e. 2 liters per breath, 30 breaths per minute=60lpm or whatever the values are, but when we talk about gas consumption on scuba it is all normalized to atmospheric pressure, so that 60lpm when done at 4ata's/30m/100ft, the normalized consumption would be 240lpm of gas because of the gas density. It is still 60 liters per minute of gas moved in and out of your lungs, it is just 4x as dense.
On the rebreathers, since we aren't worrying about the gas consumption rate since you are only really "consuming" O2 at whatever metabolic rate your body is working at, there is no need to normalize back to atmospheric pressure.

I know it's a bit of a brain twister, but to switch from open circuit where we consume gas in volume to closed circuit where you consume mass of O2 and generate mass of CO2, it's a big dynamic shift.

 

[stuartv]

I'm not sure where this advice comes from, I dont see it in the latest rEvo user manual. I was advised that due to the doube O-rings hand tight is enough, same as for the scrubber cover.

I happened to talk to Richard Morton (Shearwater and rEvo tech) today. I asked him about the battery box. He said that the printing to turn it back 1/8 turn is somewhat new. He said that the Delrin that the battery box is made of actually expands and contracts with heat and cold a fair bit. As a result, it is not uncommon for a battery box with a lid that is screwed on really tight to get stuck, where the diver cannot get the lid off to change the battery.

So, the reason for turning it back 1/8 is just to ensure that it doesn't get stuck where you can't get it open. He confirmed that me having my battery box lid screwed all the way to tight (but only hand tight) would not be the reason my battery box flooded. It might have caused the lid to stick, but not to leak.

 

[lermontov]

He confirmed that me having my battery box lid screwed all the way to tight (but only hand tight) would not be the reason my battery box flooded. It might have caused the lid to stick, but not to leak.

so still unknown cause ?

 

[stuartv]

so still unknown cause ?

Yes. But, talking to Richard, he seemed to feel like it was most likely from having some kind of dirt/hair/whatever on the old battery box O-rings.

 

[Dusty123]

Where i work buries pumps every day in a high temp, high salinity, high pressure environment and orings unless pinched are rarely an issue. Stuart I think you are just cursed to flood things in the same way I kill Shearwater computers.

 

[stuartv]

Where i work buries pumps every day in a high temp, high salinity, high pressure environment and orings unless pinched are rarely an issue. Stuart I think you are just cursed to flood things in the same way I kill Shearwater computers.

Funny you should say that. The very first time I got in the pool with my first rEvo... I flooded the controller....

 

[cathal]

He confirmed that me having my battery box lid screwed all the way to tight (but only hand tight) would not be the reason my battery box flooded. It might have caused the lid to stick, but not to leak.

Just a shot in the dark regarding why your battery canister flooded. I flooded a Delrin epirb canister because I was unknowingly lubricating the threads with grease. I was later advised that the Delrin canister would only seal when the threads are completely dry. Just my 2c.

 

[Heat Miser]

Just a shot in the dark regarding why your battery canister flooded. I flooded a Delrin epirb canister because I was unknowingly lubricating the threads with grease. I was later advised that the Delrin canister would only seal when the threads are completely dry. Just my 2c.

ohh!