JJCCR Exhale lung OPV alternative?

[DiveLikeAMuppet]

I agree. I think operational load or task loading is underestimated as risk and I think mitigating this by doing robust automation is one way of freeing up "RAM" for problem solving during an emergency.

I think the challenge would be OPV location on a JJ. In trim (cave or CCR, so maybe 15 degrees up) the dump valve is at the very bottom of everything, the gas bubble will be at the top of the unit So even if you replaced it with a drysuit-style autodump, it might not have much gas to dump until the loop volume becomes quite large and you would likely manually burp the loop much sooner especially on shallow stops.

 

[RedSix]

Actually I cannot see any benefit in an 'adjustable' OPV on a JJ.
If I am in the loop, I use my nose to dump gas. Minimum gas in the loop. No use of the OPV at all, except for a dil flush.
If I am not in the loop and ascend I frequently use the manual dumb valve to get rid of the expanding gas. And I want to be in total control of the dumping and the ascend. Hence the manual dump valve is exactly what I want in this case. Any "automatic valve" might dumb gas at the worst time.
What to keep in mind: the standard counterlungs of the JJ have an volume of 8L! If the lungs get full and the OPV opens you already have 5 to 8 L unwanted buoyancy! If this happens with my setup (quite balanced, like a CCR ideally should be), I already slept for a while. And I am in big trouble.

 

[Markus MDDT]

Actually I cannot see any benefit in an 'adjustable' OPV on a JJ.
If I am in the loop, I use my nose to dump gas. Minimum gas in the loop. No use of the OPV at all, except for a dil flush.
If I am not in the loop and ascend I frequently use the manual dumb valve to get rid of the expanding gas. And I want to be in total control of the dumping and the ascend. Hence the manual dump valve is exactly what I want in this case. Any "automatic valve" might dumb gas at the worst time.
What to keep in mind: the standard counterlungs of the JJ have an volume of 8L! If the lungs get full and the OPV opens you already have 5 to 8 L unwanted buoyancy! If this happens with my setup (quite balanced, like a CCR ideally should be), I already slept for a while. And I am in big trouble.

So what im getting from this is that the current position of the dumpvalve on the JJ and the unpredictable releasing of gas due to the design of the valve would not make you want to use such a device?
I think you are preaching a bit to the choir but anyway
Of course an adjustable valve would release (idealy) before lungs are bursting with gas. But for what I understand there isnt a valve with the resolution and the position needed to get the predictable and precise result I would think necessary to consider this.

I think Im convinced. The benefits of an adjustable dumpvalve on a JJ is not significant enough to consider replacing the current one. Does anyone disagree?

 

[RedSix]

Of course an adjustable valve would release (idealy) before lungs are bursting with gas.

This is exactly what the current valve does.
Since the volume of the counterlungs is 8L, these need to be completely full before dumping gas due to over-pressure. If a manually adjustable OPV dumps gas before the counterlungs are full, the trigger pressure might be quite low and hence very depended on the position and trim. There is a quite high chance to loose loop gas unintentionally. If the trigger pressure is higher, the lungs are full before the the OPV is triggered. And this means 5 to 8 kg too much buoyancy. This is something you don't want to have.

 

[Asheron]

I have lungs on my XCCR with adjustable and without adjustable dump. In training we were told to run it fully closed. Since then i have tried open and closed. When open they sometimes erroneously dump in very head down positions.

I have gone to running the non adjustable exclusively.

 

[sea_ledford]

I use the adjustable dump on my Prism, granted that is with FMCL, so different positioning challenges. Run it 1/4 turn from fully closed for regular diving, fully open for bailout or rescue (open buddies OPV before ascent).

If it is fully open, the CL don't really hold much gas at all since it has a weak spring pressure. It's basically a one way valve at that point.

The one time I actually have had to bailout, I forgot to open the OPV initially and dealing with buoyancy was a nightmare. I finally remembered about 4 minutes into the ascent, and it was like diving on OC - no need to deal with the loop at all after that.

 

[justinthedeeps]

I think it could work as a pullcorded adjustable auto-OPV combo, that could still be pulled open via the cord when "closed."

Open at the beginning of ascent, you get the option of a hands-free hip-up auto-dump in a workable trim position (perhaps ADV closed if bailed out). Now you can keep holding the spool/reel, light, signaling, doing gas switches, setting computers etc.... You could still pull the cord too, or manually open/close the mouthpiece. Options.

Too complicated?

We ended up opening someone's auto-OPV on another kind of CCR once while assisting with their struggle to manage a deco stop with an auto-inflating loop. It was kind of nice that there was an easy way to vent their loop for them instantaneously.

 

[mr_v]

... with an auto-inflating loop.

What's that? Technically, each loop "auto inflates" as you off gas. But do tell...

 

[justinthedeeps]

What's that? Technically, each loop "auto inflates" as you off gas. But do tell...

Yeah this was a diver who ended up getting task loaded enough to miss some things and start having loop volume issues. Maybe there was more to it than that, I don't remember. It wasn't my regular buddy, but it could happen to anyone. Everyone has some threshold of stress/distraction/panic beyond which mistakes will happen.

Combined with a solenoid going nuts on ascent they got buoyant and forgot about venting the loop. They were convinced it was runaway inflating. It was helpful to vent down their loop using the OPV right away at the deco stop, rather than keep trying to explain/manage a frazzled bailed out diver. This was a simple as rotating their OPV to fully 'open' and helping the excess gas out.

As soon as we eliminated their panic of excess buoyancy everything was basically fine, they started to remember everything about CCR again and were able to finish deco on the loop etc.

 

[GF99/99]

I have had units with the adjustable drysuit style dump and always kept them cranked closed as them would leak at inopportune times resulting in a buoyancy shift I wasn't expecting.
I have installed pull cord dumps on all of my current units and prefer that style.

I have lungs on my XCCR with adjustable and without adjustable dump. In training we were told to run it fully closed. Since then i have tried open and closed. When open they sometimes erroneously dump in very head down positions.

I have gone to running the non adjustable exclusively.

I second this.

I own a JJ as well and I have dived/own units with drysuit stye dump valves and much prefer the basic pull style. I actually find the adjustable OPV to be more "task" loading because to start you have to crank the thing closed, crank it open when I want to dump gas then crank it closed again. And repeat this over and over.

I don't know about in cave country but in Mexico some of the sidewinder guys have actually blocked off the drysuit OPV for the same reason. It is just annoying to have your OPV dump when you don't want it to. Which is one of the reason why Fathom put a pull dump valve on the Gemini.

So what im getting from this is that the current position of the dumpvalve on the JJ and the unpredictable releasing of gas due to the design of the valve would not make you want to use such a device?
I think you are preaching a bit to the choir but anyway
Of course an adjustable valve would release (idealy) before lungs are bursting with gas. But for what I understand there isnt a valve with the resolution and the position needed to get the predictable and precise result I would think necessary to consider this.

I think Im convinced. The benefits of an adjustable dumpvalve on a JJ is not significant enough to consider replacing the current one. Does anyone disagree?

I would agree. Think of it like its the same as swapping out the pull dump on your BCD for an adjustable one, not going to really gain much.