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

iani

I voted something else, on Boris you basically turn the CCR controller off and the primary then functions as a standard VR3 so it continues to give you deco information, seems like the best solution to me.

Ian

silent running

Um yeah, what Jason said. Unless you're using a hypoxic dil below 9%, you're always a manual inject/button away from a breatheable loop. The bouancy issue/unit injecting to maintain PO2 above .16 is one more PITA than anyone needs in an OC BO situatiation... -Andy

rdmmdr

Controllers should on bailout shut down the loop injection. The loss of o2 and boyancy control, in a bailout situation will just add more problems to an already bad situation. This is not a situation of a few sanity breaths after overbreathing the scrubber. This is a full blown bail out, you will not be going back on the loop.

The question of having a controller try to reach an unattainable set point, this should be picked up as a missed injection and cause the unit to auto switch to a lower set point. This would help with current limited cells issues and allow for hands free operation. I use this type of system in my controller and have yet to find it a problem. I have no accessible power down switch underwater/bailout option due to having no deco in the controller, and a manual valve before the solenoid. so the problem of a failed open solenoid/ nuts controller can be dealt with.

rick

Gilles

After having bailed out, calmed down and assessed the situation, and decided on an off-loop ascent, first thing is get to the line, change the SP to .21 (Megs lowest setting), set the VR3 to OC, open the OPV, (if flooded loop, try to drain), and ascend. On ascent, assess feasibility of SC mode. If when this works, re-assess going back to CC mode.

I like lots of bail-out and practise. My panic avoidance exercise.

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webhead

Thinking out load here.....

So if the controller is always injecting to maintain PO2, why can't you shut your O2 off? Sure, you're batteries will drain a lot faster. For non-deco computers, unless you plan to go back on the loop before ending the dive, you don't need PO2 readings so if the batteries go, not an issue. For the deco versions, you do need the electronics for deco, depth, etc. So better have put new batteries in.

I would like to have a controller/deco computer that asks me to confirm that the setpoint will be set to manual when making the switch to OC.

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Genesis

Ok, if you TOLD the unit that you bailed, then I'd say leave the loop alone - perhaps with the "parachute" mode left enabled (e.g. if the loop goes under 0.21, inject to raise it to that point and alarm)

Trying to maintain setpoint with a closed loop is going to create some interesting buoyancy problems on ascent - that's not something I'd like to have happening in what is already likely a CF scenario.

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CCR900

If you have bailed from your rebreather for long enough to require OC software swtich surely its because you have a non recoverable fault with your rebreather so why would I want to go back onto it? If I were to go OC for a long period (i.e. not a quick sanity check) I really would not care what the cells say the loop contains....

There could be a rare occasions where you get long duration dives that go: CCR then OC deco (habitat for example) the CCR (say habitat to an exit of a cave) but these are rare and the user has time to drive the PO2 to safe levels before going back onto the loop. Decompression would be CCR/OC/CCR so no need to maintain set point.

Just an opinion, nothing more.

Rgds

F

Mark Chase

The solenoid would have to add 02 if you were ascending from depth and want to maintain a breathable loop

I would like it to auto switch to a low set point (0.4 is fine so thats what i voted for) to avoid problems of current limited cells high rates of 02 injection etc but still keeping a breathable loop.

I would have the option to switch off the solenoid completely (almost like the Hammer Head) but as a manual choice only so you physical have to go through the menu to get the thing to drop below life support levels.

I would want this system so it can offer me a chance to go back on loop if needs be and be assured of a breathable gas.

Why would you go back on loop?

Possibly the C02 hit has pushed breathing rate very high and that has drained your OC bailout, now things are better but you haven't made the surface yet. In shallow water the scrubber can become effective again so dill flush and go back on loop.

Hand set displays coming back on line? Cell problems sorted, Flood recovered?

Possibly there are more reasons possibly some of these are invalid but If there is a slim chance that there is a extra available breathing time on the rig ill embrace that idea.


The Hammer Head has the option to switch the solenoid off. However its never completely off in that it will always maintain a minimum set point of 0.16. This is a very useful function but sadly it needs to be higher up the menu list to be usable on some occasions and its actualy just quicker to select low set point.

ATB

Mark Chase

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cys

I voted for parachute (e.g. below 0.21) mode and agree with Genesis' summary.

On a unit like the classic KISS the O2 is added adjacent to the OPV, and on the other side of the scrubber in relation to the sensors. Consequently, in a OC bailout situation, without a diver breathing on the loop to mix the gas, if the solenoid tries to maintain setpoint the added O2 will escape out the OPV without affecting the pO2. Without intervention this will continue until the O2 bottle is drained.

seafox

This response is specific to the Optima.
I am interpreting B/O as either inboard or outboard B/0 but off the loop!
If you must B/O and remain off the loop and on B/O, you must switch the HH controller to OC mode and confirm what gas you are breathing.
The HH will then continue to compute your deco under B/O conditions.
Once you have switched the HH to OC mode it will no longer prompt the solenoid to fire.
There is safety feature on the HH relating to low P02, but as long as you are off the loop it doesn't much matter.

Cornel

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