Should the controller continue to maintain setpoint if you bail out to OC?

bgpartri

I'm wondering what people think the controller should do if you bail out to OC. And I would love to hear the reasons for your choice.

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ScubaDadMiami

Not sure I get what you are shooting for here, or perhaps it is my lack of understanding of how other units operate. Pretty much, the only times I will bail out will be in cases of:

• Hypoxia, in which case I will get right back on the loop once I have taken my sanity breaths and flushed to get PO2 back to the range where I can fly manually. So, maybe the solenoid got stuck closed in this case (since I would never let my PO2 drop critically low from lack of monitoring ), and electing what the computer should do is likely not to have much of an effect unless the solenoid suddenly starts to work on its own or then sticks open after finally opening. In the latter case, see hyperoxia.
• Hyperoxia, in which case I am guessing that the solenoid is stuck open, and the computer won't be able to do anything here. I'll be using the O2 valve once I have bailed out if I am going to return to the loop.
• Hypercapnia, in which case whatever the PO2 reads really doesn't matter since the high levels of CO2 will cause me to bail out, and I can switch my computer to OC from that point. I guess the computer could cause the solenoid to fire during ascent if the PO2 drops too low. However, that doesn't seem like a very big deal. It will fire every once in a while if I am making a very long ascent, and I might have to drain a little gas from the counterlungs.
• Flooded loop, in which case it really doesn't matter much what happens.

Am I missing something here?

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6Gill

I would like to see it go to a lower setpoint (something still breathable). Reason is our beloved KISS OPV is very difficult to reach and the CL would be tending to inflate and increase bouyancy control issues at a time when things are busy enough.

Jerry

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6Gill

To clarify the my previous post.... The KISS is a manual but for eCCR it would be somewhat of a factor if the solonaid were continuing to fire i.e. current limited sensors etc.

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onetime

I'm torn between two choices but opted for completely stop O2 injection. Reason for that is to limit changes in buoyancy.

The second option would have been to switch to the lower set point. That way, assuming I know what my lower set point was, I could check displays to see if it's settling where it should while I've been on OC for a chance at potentially going back on the loop.

koputai

Good question Bruce.
I'm in two minds, either stop all together, or continue as is.
I'd be thinking 'stay at setpoint' so that the unit is always in a fairly stable PPO2 state if for some reason you go back to it.
However, I'll choose 'stop everything' as the increasing buoyancy when ascending is too much hassle when you already busy and/or stressed.
If you do feel like going back to the loop, it's no hassle to drive it up manually.

Regards,
Jason.

Genesis

First question: How does the controller know you bailed?

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divetheworld

Because you told it you have as it has integrated deco.
The Shearwater has 5 CC and 5OC gas lists. Four button presses and you are OC with OC gas lists on the look ahead deco. Mucho useful. If it had a setpoint controller built it like the Titan's has............

In the mean time the loop......

Well, I have a suggestion.
There are three scenarios I can think of in bailing to OC;

1. Sanity breaths, generally three or four breaths from the bail or DIL gases. I wouldnt even bother to switch the computer over for these. Leave running setpoint.

2. Bail at depth to sort some broken shit out. chances are you will try to flush for possible CO2 or buffer your loop PO2 because of an error. If all goes well you will be back on the loop and back with the program. Leave running setpoint.

3. Cluster f@ck. All went completely south and your on OC for the long journey home. Possibly following No.2. Its doubtfull you will attempt a loop restart until maybe you are at 6m for running O2 rebreather for deco. No point running setpoint because the bouyancy will be a pain in the arse.

Logically, I would say that the computer should maintain setpoint for a limited period of time when switched to OC, then cease maintaning setpoint until it is switched back to CC. Then the controller should automatically select low setpoint as at this time it is simply a parachute. The manual would discribe this process, but for all intents and purposes the user would assume no setpoint control.
How long should it remain on setpoint before timing out? Maybe 1 minute to hazard a guess.
The guess is based upon how far you can ascend safely in 1min and how long 1min is at depth when sorting your crap out. Good compromise IMHO.

Brent

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PCDiver

I voted for something else.

Why don't you make it a user configureable option?

UKSteve

Hi,

One problem with the controller remaining on the high set point is continuous injection when you get to a depth where the set point is more than is achievable with 100% O2 in the loop. This would potentially cause bouyancy problems until you either switched the controller to the low set point or closed the O2 valve.

Thus, either low set point, or ppO2 of 0.4 or 0.21 would seem ok.

Danger of shutting injection off completely is a very hypoxic loop once you start to ascend - one that could black you out very quickly indeed if you tried to breath it.

Steve