Why CCR?

[WD8CDH]

Makes me wonder how many of those ever said " if something goes wrong I will just bail " and neglected maitenance or cut the pre dive inspection short.

One difference between OC and RB is with some of the possible failures, you have no sign of the failure. With OC, if the reg fails, you know it instantly. With an RB if you are breathing a mix with not enough O2, unless you look at your PO2 readout or have a HUD or notice that no O2 was being injected, the first sign can be unconsciousness. A little late to even know that you need to bail.

Less chance of that happening with a mCCR than with an eCCR because the mCCR diver will usually develop a rhythm of looking at the PO2 readout often enough that if there was a total loss of injection, the PO2 would still be high enough on your next reading.

I know, at least for me, I subconsciously predict if I need to inject O2 and how much before I even look at the display based on ongoing exertion.

 

[gr8fuldiverNC]

I can't remember the thread I saw earlier but someone was explaining how your bailout gas goes further with a CCR than when OC which didn't really make since to me at the time but maybe someone will chime in that has the right training and can fully explain what I read.

Bailout gas goes further if you can connect offboard bailout to your ccr, then its just like diving it regularly, assuming nothing else is wrong. otherwise (like with computer/O2 cell failure) you can use it scr, by blowing ever 3rd or 4th breath out your nose, extending gas by 3 or 4 times. If you cant hook up offboard bailout, or you have total nonrecoverable loop flood, or scrubber failure, you are on pure oc, and gas supplies wont be extended.

 

[wedivebc]

Bailout gas goes further if you can connect offboard bailout to your ccr, then its just like diving it regularly, assuming nothing else is wrong. otherwise (like with computer/O2 cell failure) you can use it scr, by blowing ever 3rd or 4th breath out your nose, extending gas by 3 or 4 times. If you cant hook up offboard bailout, or you have total nonrecoverable loop flood, or scrubber failure, you are on pure oc, and gas supplies wont be extended.

So why bother with SCR mode if you are having to carry the same amount of bailout. At least with OC bailout you can plan a decompressiopn schedule.

 

[marchand]

So why bother with SCR mode if you are having to carry the same amount of bailout. At least with OC bailout you can plan a decompressiopn schedule.

Why not? I would rather use scr mode (if I have that option) and fudge the deco a little just in case a staged bailout bottle goes MIA or is otherwise unusable.



I find it interesting that no one has mentioned minimum loop volume yet...

 

[wedivebc]

Why not? I would rather use scr mode (if I have that option) and fudge the deco a little just in case a staged bailout bottle goes MIA or is otherwise unusable.



I find it interesting that no one has mentioned minimum loop volume yet...

Well I guess if you have a failed rb and you have lost your bailout you're not having a good day but I would not default to the worst of all options first.

 

[marchand]

Just curious, why do you consider switching to scr the worst of all options?

 

[wedivebc]

Just curious, why do you consider switching to scr the worst of all options?

If I bail out to OC I can plan deco gases that will give me an exit profile similar to my CCR schedule. If I had have to bail out to SCR what is my deco profile? The main circumstance that would cause one to use SCR is loss of electronics. You have no idea of your actual PO2 when using SCR so deco has to be planned for worst case scenario which will require you to spend much more time in the water. In the waters I dive in an extra hour in the water is a big deal.
You still have to carry all the required bailout gas in the event of a full loop or scrubber failure so why bother with SCR?

 

[Rick Inman]

So why bother with SCR mode if you are having to carry the same amount of bailout.

Time (if you need it)?

I'm been away for a bit and have really enjoyed reading this thread. Thanks all.

 

[marchand]

You have no idea of your actual PO2 when using SCR so deco has to be planned for worst case scenario which will require you to spend much more time in the water.

Really? I was under the impression that when diving an scr you can approximate with reasonable accuracy what your average fo2 will be.

 

[wedivebc]

I don't expect you to believe me. Try it using air dil descent to 100 ft and exhale thu your nose every 4 breaths
You should get about 0.8 po2
Now swim a while and see what happens
So what will happen when you don't have a po2 display?