One-hand or two-hand valve drills (back mount doubles)

[lermontov]

Anyone can walk across a plank suspended seven inches off the ground. The risk is low. It's another thing to walk the same plank when it's suspended 800 feet off the ground. The risk is high. The fear factor would overwhelm your average pool bunny trying to shut down a free-flowing regulator below 330 feet. If you cannot do it in less the 10 seconds, you have have a few minutes (maybe) to make it to the next gas switch. If you don't freeze up. Real tech divers spit out the regulator when practising real simulations before switching to the backup and shutting down the offending valve

the risk is the same - the fear will be different- dont ever recall having a free flowing reg thats already in my mouth - can it happen? and if its delivering gas why would you spit it out ?

 

[boulderjohn]

Real tech divers spit out the regulator when practising real simulations before switching to the backup and shutting down the offending valve.

I have no idea what you're talking about.

 

[crofrog]

I have no idea what you're talking about.

Well it’s obviously because you’re not a real tech diver like ASD

 

[boulderjohn]

Well it’s obviously because you’re not a real tech diver like ASD

That has to be the explanation.

 

[boriss]

Just to reinforce your point the valve drill is 3 separate excerises that are done sequentially.

1. Right post shut off, then reset
2. Isolator shut off, then reset
3. left post shut off, then reset
4. Flow check to verify all valves are where they should be at the termination of the drill...

In the failure procedure if the left post fails you shut off the left post. It you incorrectly judged the failure and there are still bubbles you continue down the failure procedure.



As far as maintaining trim and buoyancy if you can't maintain those while shutting the valve down then you need to question if your skill is suitable to be in an environment where your loss of buoyancy control can endanger you with either descending below the MOD of you gasses, ascending beyond your deco ceiling, or creating a loss of visibility or damage to the environment.

I was taught isolator gets shut off first. Reasoning is that until we figure out what the problem is we want to at least preserve the gas in one of the tanks.

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In general it's interesting to see the responses people have - all are valid in my opinion and the OP should really understand them all and see which apply to his situation. Part of being a technical diver is being a thinking diver and knowing what applies to your situation.

For example, being in a potentially silty cave, buoyancy and trim can be paramount. Alternatively, diving deep open water or even a large high-flow cave like Ginnie's Devil system, buoyancy and trim may not matter.

Plan your dive and dive your plan. Plan for contingencies and they may be different based on environment. We recently did a dive, with one CCR diver, and he went over his bailout plan prior to the dives. It's a rare event that a CCR diver bails out to OC, but this time, due to a failure of his computer we actually had to execute that plan and we were almost in the deepest part of the wreck. Everyone stayed calm, we knew the plan and all was fine.

 

[crofrog]

I was taught isolator gets shut off first. Reasoning is that until we figure out what the problem is we want to at least preserve the gas in one of the tanks.

The chance of it being a burst disc, manifold, or tank neck o-ring is significantly lower than it being a first stage or hose, and the risk of that lowers throughout the dive as the tanks are breathed down, and the ambient pressure on the tanks increase

By closing the isolator you don't learn anything about the failure, and still have to manipulate another valve guaranteed.

For example, being in a potentially silty cave, buoyancy and trim can be paramount. Alternatively, diving deep open water or even a large high-flow cave like Ginnie's Devil system, buoyancy and trim may not matter.

Buoyancy seems pretty important in deep ocean diving, sinking below your mods or rising above your deco is bad, and with less reference it requires a higher degree of refinement to maintain.

 

[boriss]

Buoyancy seems pretty important in deep ocean diving, sinking below your mods or rising above your deco is bad, and with less reference it requires a higher degree of refinement to maintain.

Buoyancy is always important; I was hoping it was understood that we're talking about perfect buoyancy vs moving a few feet here and there.

In certain caves moving just a couple of feet or excessive erratic motion can cause a major silt-out. Context is important, that's all.

 

[Jim Lapenta]

Anyone can walk across a plank suspended seven inches off the ground. The risk is low. It's another thing to walk the same plank when it's suspended 800 feet off the ground. The risk is high. The fear factor would overwhelm your average pool bunny trying to shut down a free-flowing regulator below 330 feet. If you cannot do it in less the 10 seconds, you have have a few minutes (maybe) to make it to the next gas switch. If you don't freeze up. Real tech divers spit out the regulator when practising real simulations before switching to the backup and shutting down the offending valve.

What a load of crap. You never spit the reg out. You really want to see someone die from your advice, don't you?

 

[Alaskan Scuba Dude]

when you learn a skill, it should be as gamelike as possible.

No, it should be pure instinct. That is why my skill is the same for free-flow and donor.

regardless you have team gas available in the form of min gas or a teammate’s 1/3 in a cave.

Depends on how many in the team. Two-man team and it's goodbye.

It takes quite some time for a set of doubles to lose all of its air, no need to stress out.

It take less when it's Trimix and you're at 11 ata.

If you hear bubbles on the left, you don't start with the right post. Y

It is difficult to distinguish which side the sounds are coming from.

the risk is the same - the fear will be different- dont ever recall having a free flowing reg thats already in my mouth - can it happen? and if its delivering gas why would you spit it out ?

Acrophobia. Recreational skills are different to tech skills. Trimix comes out quicker in a free-flow and the bubbles hitting the mask as you try to breathe normally is a major distraction. The primary reason: restore the breathing rhythm. No need to hold the free-flowing regulator in place. Try spitting out your regulator to simulate a free-flow, and then shut it down.

I have no idea what you're talking about.

I will call the nurse.

What a load of crap

Super heroes never reveal their true identity.

 

[Baydoun]

the risk is the same - the fear will be different- dont ever recall having a free flowing reg thats already in my mouth - can it happen? and if its delivering gas why would you spit it out ?

I have had a reg free flow at about 75ft while it was in my mouth, apparently due to having the first stage having the wrong IP, and handling too many things at once in cold water (inhale +drysuit inflate etc), but i don't understand why anyone would spit it out, I just bit down on the mouth piece and dealt with the problem. I'm not too experienced but seems dangerous to get rid of a reg that is still delivering breathable gas, even if it is at a higher rate.