Modified MAV from my Sentinel for my JJ-CCR

[Mattp]

Regarding O2 we teach diver to manually fly the unit in the event of solenoid failure or gas loss requiring plugged O2. The problem here is thats only a good option on linear swims as in deep water or initial ascent from depth you get big spikes from the aggressive addition supplied by the MAV so we decided best action wold be to Bailout and not risk o2 toxicity as this could have been the cause of at least one fatality.

You can possible return to the loop when you get in shallower water for deco advantages.

Another option i dive standard on my JJ is this a MAV with needle fine control adjustment same hoses and connections as standard rig.

ISC manage this situation with a duel solenoid for the military.

 

[Tiptopperoo]

I want to be able to isolate the JJ ADV without having to reach so far back if you fit one directly. The Sentinel gas block would let you do this.

Can you isolate individually with that block or would you just unplug the ADV feed?

I want to be able to plug in offboard diluent and use it through the ADV as well as MAV. The Sentinel gas block would let you do this.

Ar cienu,
TB.

I'm looking at adding a Y-block into the 3to1 manifold on the JJ dil side. This would then have a QC6 female off one hose and the other hose goes to the dil 1st stage. This way I could feed everything from an off board tank if I needed, just turn the off board on and the on board off.



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[Tiptopperoo]

The problem here is thats only a good option on linear swims as in deep water or initial ascent from depth you get big spikes from the aggressive addition supplied by the MAV so we decided best action wold be to Bailout and not risk o2 toxicity as this could have been the cause of at least one fatality.

Why not plug in a 50% instead? It may make it more manageable at depth if you're having problems with 100%.

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[Diving Dave]

I'm looking at adding a Y-block into the 3to1 manifold on the JJ dil side. This would then have a QC6 female off one hose and the other hose goes to the dil 1st stage. This way I could feed everything from an off board tank if I needed, just turn the off board on and the on board off.

We're looking at doing the same, just using the dil 1st stage instead of the y-block.

 

[Baron015]

Can you isolate individually with that block or would you just unplug the ADV feed?

On the standard Sentinel block the flow stop is on the hose feeding the ADV, so manual add still works.

I'm looking at adding a Y-block into the 3to1 manifold on the JJ dil side. This would then have a QC6 female off one hose and the other hose goes to the dil 1st stage. This way I could feed everything from an off board tank if I needed, just turn the off board on and the on board off.

Yep that would do it.

 

[Tiptopperoo]

We're looking at doing the same, just using the dil 1st stage instead of the y-block.

The problem with that, is that if the dil 1st stage leaks, you will also lose your off board. I have a one way check valve that will go on the hose from the onboard 1st stage. This way I can still use my off board in the case of a dil 1st stage failure.

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[Diving Dave]

There's an isolator between the dil 1st stage and the y-block separating critical (breathing) and non-critical(wing/adv) sides. If the dil 1st stage goes you isolate to protect the critical path (bailout-BOV) and feather tank valve to operate the other systems as necessary. Assuming the isolator is functional, the breathing system is unaffected by failures in any other component - it becomes a direct feed between bailout and BOV.

 

[Tiptopperoo]

I'm struggling to get my head around that one Dave. Any chance of a diagram? I'm keen to look at all available options before deciding on one.
I should do one too.

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[divingtactics]

Another Concept for offboard bailout - in addition to onboard twin 7's, not instead of

Here was something I played with a couple of months back.

Twin 7's are running valves up on my JJ.

Extender to get the 1:2 manifold away from the hose swages.
1:2 manifold to give me another port.
Check valve so gas only comes in from offboard, doesn't go out from onboard to offboard.
Swivel adapter to adapt check valve to standard scuba 3/8UNF.
Standard Miflex Hose
QC6 Female, which sits down the left hand D-ring ready to plug in on the boat. (I've had this machined to connect to a standard scuba hose)

Other end is a DESO sealed QC6 male sitting on the offboard tank reg, which also has a standard LP inflator to drive MAV and standard second stage for bailout.

It may not be the perfect solution, it is early days, open to critique and suggestions. I have purposely avoided having differing IP's in each first stage as I just wouldn't like to trust it. Dive is started with QC6 connected and offboard tank valve switched off.

I have proven the concept and it works at depth by turning off the onboard and then turning on the offboard tank valve. This was using different gasses in deep bailout (Hypoxic) and DIL (Normoxic).
If you have a first stage onboard reg or hose failure, you must disconnect the QC6 or you will lose all gasses.

I've removed this system now and put the JJ back to standard, but am keen to develop it further - especially for dives below 80m.

 

[Diving Dave]

If you have a first stage onboard reg or hose failure, you must disconnect the QC6 or you will lose all gasses.

Hi Jason, have you demonstrated this in practice? I would have thought in a balanced (Apeks) 1st stage you would have to have two independent failures within the 1st stage before you would lose gas backwards out of the system, for example, the valve seat orifice would need to be stuck open, AND the 1st stage-tank valve o-ring would have to go. There are a couple of different gas paths but all seem to require two points of failure before they become open. Each of these independent failures are obvious on occurring as well so it is unlikely you would proceed unknowingly with one failure in existence such that the second one opens the path.

Unless you are talking about the MP side, in which case I agree. But I have an isolator to separate the onboard from offboard in this eventuality allowing the offboard to remain plugged and the BOV to remain functional.

All the best,

Dave

 

[divingtactics]

I am talking about using the onboard reg LP ports as a manifold, so anything connected to any LP port will allow all gas to escape if you don't disconnect the feed to those ports.

If I was to cut the hose feeding my wing, then the gas would travel from the offboard reg to the onboard reg via the QC6, then from that port on the onboard reg to every other port connected to it, so total gas loss.

I agree that if this was to happen, you should have sufficient time to be able to disconnect but you do lose the BOV.

I'd be interested in seeing a picture of your setup with your isolator.