DIR- Generic ADV question - converting JJ-CCR to GUE JJ-CCR

[Valkyrie2505]

I'm converting my factory set-up JJ-CCR into the GUE configuration.

I'm stuck on one thing - the ADV.

My ADV currently has two banjos - one with the shut-off valve.

On the GUE instructions and on Graham Blackmore's YouTube video on setting up the GUE JJ-CCR, I can clearly see that the ADV has only one banjo with no shut-off valve (to connect to the LP hose running from the right post first stage).

So, I'm assuming I need to remove the shut-off valve from one banjo.

What do I do with the second banjo that won't be used? (and doesn't seem to be on the ADV in the GUE videos and guides).

 

[PietroT]

The shut off valve can be removed (it is screwed on the upper banjo). I have removed mine and it was relatively easy.
You can remove the banjo with the valve from the T piece and try it “off board”, maybe with two wrenches.

I think the banjo thread is 3/8 male, so a cap for 1st stage LP should work.

There is an helicoil inside the T piece hole, please tighten the Banjo and the cap very gently.

Out of curiosity: is there no dil MAV in Gue configuration?

 

[RedSix]

I think the banjo thread is 3/8 male, so a cap for 1st stage LP should work.

Actually O-Ring needs to be replaced by one from the banjo. Standard blind plug o-rings have slightly smaller thickness.
Your CCR1 instructor should assist you during converting stock JJ to GUE-JJ. Converting JJ based on random youtube videos is a quite bad idea.

 

[RedSix]

Out of curiosity: is there no dil MAV in Gue configuration?

No, only ADV (without any shut-off) is fine. ADV can be used as a MAV if you just push the diaphragm. External gas can be connected to (O2-) MAV as well.

 

[Valkyrie2505]

Thanks everyone! JJ converted and passed all tests.

 

[phgachoud]

No, only ADV (without any shut-off) is fine. ADV can be used as a MAV if you just push the diaphragm. External gas can be connected to (O2-) MAV as well.

what are GUE thoughts about MAVs? JJs used to come only with O2 MAV and then a second version with DIL & O2 MAVs on top of of course ADV... And what are the thoughts regarding shutoff as well? guess its another point of failure you want to avoid, am wondering what are the pro shutoff on DIL arguments as well. Personnally have it out of my equipment and you can close the DIL valve at whatever moment, so not sure of its usage either.

 

[justinthedeeps]

I think the dil side mav is a convenience, it is less annoying than having to reach up to the ADV, especially in cold water gear. (But people coming from twinset academy love reaching behind the head?)

It is also convenient that it's on the same side as a stage that might be plugged in as an offboard diluent.
There is a also that nice look of symmetry

But for divers keeping multiple stage cylinders on the left, the diluent mav can easily get lost or pinned in that mess, or add clutter.

No surprise highly opinionated organization(s) decided to get picky about adding a bunch of stuff to the config, and then removed a few things to call it streamlined.

I am guessing there are some (old school?) divers who like to close (or remove) ADVs and use a dil mav only, but this is not a great idea for emergencies, sinking, or any other unexpected task loading. I think it is only a matter of time before a closed/no ADV leads to a can't breathe situation, hopefully we find that mav quickly and it is properly plugged and working....

Other CCRs (rEvo, others?) only have the one (often multigas) MAV on the right. The indexing seems to make this not too much of a confusion. Not sure about the gas routing in every case.

There is a reason on JJ that the diluent goes into the inhale side of the counterlungs and the oxygen goes into the exhale side.

 

[RedSix]

what are GUE thoughts about MAVs? JJs used to come only with O2 MAV and then a second version with DIL & O2 MAVs on top of of course ADV... And what are the thoughts regarding shutoff as well? guess its another point of failure you want to avoid, am wondering what are the pro shutoff on DIL arguments as well. Personnally have it out of my equipment and you can close the DIL valve at whatever moment, so not sure of its usage either.

GUE conversion removes both, dil mav and shut off. It is not needed. Off board dill can be plugged using O2 mav.

 

[jale]

I am guessing there are some (old school?) divers who like to close (or remove) ADVs and use a dil mav only, but this is not a great idea for emergencies, sinking, or any other unexpected task loading. I think it is only a matter of time before a closed/no ADV leads to a can't breathe situation, hopefully we find that mav quickly and it is properly plugged and working....

Well, when you dive without ADV, only with a MAV, and you place it correctly, you are not more tasked as when you need to add gas in your DS or in the wing!!!
At least you don't get an "involuntary" addition of hypo gas on/near the surface.

 

[justinthedeeps]

So the original question is answered,
Is it useful or relevant to discuss pros, cons, caveats?

Pros:
1. declutter the left D ring area
2. can't mistakenly shut off the ADV supply, which could cause inconvenience or even result in a compounding loss of buoyancy/panic situation during any descent, even a small one, whether intentional or otherwise
3. theoretically removes a couple "failure points" (though the Big Rig config itself introduces several of its own other new theoretical failure points)

Cons(?):
1. No longer have the convenience of manually tuning loop volume from a neutral arm position

2. An offboard diluent plug-in now crosses across the chest area to the O2 mav. Possibly more cluttersome? (though surely procedured)

3. Unless adding another LPI fitting to the JJ exhale ("O2") side MAV somehow, can't leave an offboard diluent plugged in there and still be able to do manual O2 addition to control ppO2 or do a 6m O2 flush at the same time (common near the end of some Mod3 ascents for 'standard' config divers). Need to do another plugin procedure to get manual O2 back?

4. An exhale-side dil MAV addition can not safely flush bad gas like an inhale-side addition can. (But irrelevant when the emergency 'bad loop gas' flush scenario involves reaching up to the ADV)

5. no shutoff on the ADV: going head down or duck diving near the surface on a hypoxic diluent could deliver enough gas to cause a shallow water blackout. Rare to get that much gas off the ADV under normal circumstances, but there are scenarios where that could happen, including rough, abnormal or turbulent surface conditions, over-venting of the loop, trying to descend head-first, dropping down to repeat a missed deco stop, etc.

Many of us are never using the ADV shut-off even when it is fitted, but I were coming up in a surf zone or tide rip or something it might occur to me, as would pre-bailing out to a breatheable OC cylinder.

Is anyone closing valves on hypoxic cylinders before final ascent? OC bailout regs (incl. necklace and long hose) might also be deadly when shallow.