To ADV or not to ADV

[broady]

Originally Posted by nigelH

<shrug>I use it all the time as part of my normal loop control. The flow stop is only there for a neg test and the dreadful day when it breaks.

I'm on all the time too but like the sound of Gareth's idea of switching off shallow or at least getting in the habit of doing so now before I start using Hypoxic dils.

Cheers

Graham

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[Okeanos]

My ADV has been shut off for ages now, I run manual only. Perhaps it's because of the way I dive the unit.

I tried it the other day and it free-flowed, I think it needs servicing or removing altogether.

[Ferg3333]

Originally Posted by Okeanos

I tried it the other day and it free-flowed, I think it needs servicing or removing altogether.

So what are the benefits against risks:

Risks:

increased probability of flooding unit - via inverting diaphram.
freeflow of diluent - need additional flow stop (chance of missing a dive)
additional ports used on the manifold - extra risk??? probably not even worth noting.

Benefits

faster decent
'open loop'

I was once told, "if when you reach this level of training if you can't push a button then you shouldn't be diving this equipment. The ADV is a nice addition, but is it a £200 nice addition."

Whereas I see a BOV as a life saver as hypercapnia scares the shit out of me, hence fresh fill every day as a rule, unless the time limit is met.

[NotDeadYet]

Like Gareth, I switch mine off when I reach the shallows and I'm on hypoxic dils. Bit more complicated on the KISS as a flowstop isn't reachable (have to switch the cylinder off) which meant a bit of hose/manifold re-rigging to run the wing from my bailout.

I'd rather have it than not. Risks you mention: I've replaced the diaphragm on mine with a tougher disc of inner tube, I don't know if that's an option on the AP unit or not. I'm yet to have a freeflow of dil but the CK valve is an upstream design so will tend to fail closed as long as there's gas in the line. My ADV is run straight from the cylinder so bypasses the manifold completely, again probably not an option on the YBOD.

As for benefits... being able to flush, open loop or semi-close hands free for me is of major benefit. On a mCCR I think an ADV is essential because the risk of the PO2 drifting into the danger zones is higher than eCCR. On eCCR, I've no idea... when the f***ing thing arrives I can find out...

[nigelH]

Originally Posted by broady

I'm on all the time too but like the sound of Gareth's idea of switching off shallow or at least getting in the habit of doing so now before I start using Hypoxic dils.

The idea doesn't appeal to me at all. If something causes you to sink from your deco stop you want something back in the loop so you can breathe while you fix the real problem.

Hypoxic mixes are only a problem on the surface but trying to grab a sinking buddy with both hands and sudenly discovering the lungs are flat and sucking may well be a contributory factor in certain incidents.

[Padowan]

You'll do well to unseat the diaphragm, it's clamped in place with a lock ring. Not saying it'll never happen but I think you'd have to try hard.

I've got one, and I can descend as fast as any OC diver I know, even when trying to drive a video camera and keep hold of a shotline.

Yes there are additional weak points put into the loop when you install it, but I think if you're careful with your kit prep and look after things, then you should be fine. The loop integrity is the only issue that you can't mitigate out with an alternative gas strategy. You could plumb offboard into the injection buttons if something blows on the LP Dil side or, as in my case, use my BOV to inject offboard dil if my onboard needs to be switched off cos of a leak/blown o-ring. You also have the ability to plumb in 2 diluents (or 3 if you have 2 manual buttons) sumiltaneously, which can give you lots of options for SCR. With my setup, I could have one dil into the ADV, one into the BOV and another into the manual inject if I so desired.

Hands free SCR or open loop if really nice, especially if you are the kind of person who like to be doing stuff with your hands underwater (videoing/spidging/getting dinner), rather than just looking around twiddling your thumbs.

I agree that it's a nice to have, certainly not an essential, but then if you cut back all the non-essential, nice to have parts of most breathers out there, you'd have something pretty simple!

[Odin]

Yes to ADV.
reduces task loading, makes dil flushing easier, If working hard on the surface will give you gas easily - just make sure it is not a hypoxic dil mix!
Hanging onto a camera, and a shotline, and suddenly wanting a bit more in the CL's makes the ADV worthwhile.

[Depth-junkie]

Originally Posted by nigelH

The idea doesn't appeal to me at all. If something causes you to sink from your deco stop you want something back in the loop so you can breathe while you fix the real problem.

Hypoxic mixes are only a problem on the surface but trying to grab a sinking buddy with both hands and sudenly discovering the lungs are flat and sucking may well be a contributory factor in certain incidents.

If your shallow enough to be switching the ADV off, you have 2 hands and 2 buttons available if needed to add gas for a scenario like you mentioned, ones the DIL button the other 02. Im sure with 2 hands and 2 buttons you can give some ut a squirt. Or if needed just switch it back on again

The reason for switching it off, is to stop any ADV leak causing a problem. Also allows you to maintain min loop better/easyer when off gassing like mad into the loop for the 1st 20-30min of monster deco @ 6m with no possible way for the ADV to fire adding Low po2 gas to the loop causing big swings in PO2. Also means from 6m up and surface swims back to the ladder, climbing back up the ladder etc the only thing i put in my loop is 02 or DIL by my own manual actions and not accidentaly by a big suck causing the ADV to fire. And from 9m up the only thing that goes into my loop is pure 02




ATB
Gareth

[nigelH]

Originally Posted by Depth-junkie

If your shallow enough to be switching the ADV off, you have 2 hands and 2 buttons available if needed to add gas for a scenario like you mentioned, ones the DIL button the other 02. Im sure with 2 hands and 2 buttons you can give some ut a squirt. Or if needed just switch it back on again

So explain why I need to shut it off then?

[Ferg3333]

Originally Posted by nigelH

So explain why I need to shut it off then?

You would have to press one or two buttons depending on your depth i.e at 3m a flush of 10/50 wouldn't support life so you would just have to add o2 or flush with o2 from 6m up since you can breath the dil at 6m. This is my take on why the adv is shut off any deeper and you would need to turn the flow stop on or add dil or you could switch to another dil with GCS.

But then I maybe wrong and other options are available