Manifold shutdown procedure

[Albion]

In my experience that is the worst of both worlds. If the valve is that easy to close it may roll off and you could accidently close the valve, exhaust your 1/2 your gas supply and then not know the you had 1/2 remaining. I have actually heard of this happening.
I think a valve should be all off or all on.

good point thanks

 

[kramynot2000]

The procedure has changed over time. So some of the posts here have the older version of the information.

The newest procedure calls for shutting down the right post first. If there is still a leak, then shut down the isolator. Of course, one is to signal the buddy as early into the process as possible.

It used to be advocated to isolate and breathe down the leaking side until no gas remained, thus conserving the most gas for exit/surfacing. However, the newer determination is that doing so will only postpone what will later turn into an out of gas situation. With the added pressure of the leaking situation and the need to exit and surface, calculating for Murphy's Law, the out of gas situation will occur at the worst time during the exit, where there is higher likelihood of this turning into an even more serious situation.

So the new procedure is to switch to the backup regulator and shut down the right post. If the leak continues, shut down the isolator. Signal the buddy as early as possible.

Sorry if I'm thick headed on this, but how would shutting down the right post first save any more air than going for the isolator first? Is the thinking that the most likely failure is a right 1st stage failure and so you shut down that first? I'm just trying to understand the rationale behind this, thanks.

 

[novadiver]

still limted esxperience in this field , but is there any merit to having the isolation valve one turn from closed. during normal breathing this would allow both tanks to remain balanced, but in the event of a mjor failure would act as an orifice to prevent to much flow from one side to the other, until you could shut it down.

only problem i see is that you would need to do some playing around, opening closing to make sure where it WAS positoned if it was knocked

Albion. by only haveing the iso. cracked open the pressure at depth could close it. I saw this happen to a buddy at 60 feet in a single tank rig. He open his valve while gearing up to check the pressure but didn't open it up fully before the dive started. At 60 feet this diver started flipping out with an ooa. We just started the dive so I figured he was just practicing an OOA , untill I saw his arms and legs wildly flailing, You can tell when an OOA is for real.

 

[Uncle Pug]

I've never had a *real* behind the head in the water gas loss... but I've experienced simulations where the instructor used an air nozzle placed at various locations and the correct response was to shut down which ever side the sound was coming from.

It wasn't at all hard to tell either (with the exception of a simulation of cross-over o-ring failure... not knowing exactly which side of the isolator was leaking... but closing the isolator in either case was called for.)

With bubbles coming from the right post area the proceedure was to shut down that valve and if the bubbles continued then it was the more unlikely tank to valve o-ring failure or bust disk and the isolator was shut down. Same proceedure if the bubbles are coming from the left post.

The idea behind shutting down the offending post first, as I understand it, is to deal with the most likely problem (a leak involving the first stage) and save all the gas.

 

[salty]

Sorry if I'm thick headed on this, but how would shutting down the right post first save any more air than going for the isolator first? Is the thinking that the most likely failure is a right 1st stage failure and so you shut down that first? I'm just trying to understand the rationale behind this, thanks.

The majority of the time this is where the problem will be. You breath from the right post so this gets the most use. Unless you know what specificaly caused the problem, like striking the overhead and knocking the left post loose, you have to start somewhere.

Look at a manafold and think of the failures, First stage problems are the most comman. This is easily fixed by just shutting down the post.

Less comman is a tank o-ring or burst disk. If you hear something and shut down the right post you switch to the back up and check the pressure gauge on the left post. If the gauge is going down fast than shut the isolator. After the iso is shut you can see where the leak is truly coming from.

I think that to be efficent you need a consistant reaction to the problebm. Most of the time it will be a simple first stage leak and the correct fix is a post shutdown since this is the most comman problem this should be the first response.

 

[wedivebc]

The majority of the time this is where the problem will be. You breath from the right post so this gets the most use. Unless you know what specificaly caused the problem, like striking the overhead and knocking the left post loose, you have to start somewhere.

Look at a manafold and think of the failures, First stage problems are the most comman. This is easily fixed by just shutting down the post.

Less comman is a tank o-ring or burst disk. If you hear something and shut down the right post you switch to the back up and check the pressure gauge on the left post. If the gauge is going down fast than shut the isolator. After the iso is shut you can see where the leak is truly coming from.

I think that to be efficent you need a consistant reaction to the problebm. Most of the time it will be a simple first stage leak and the correct fix is a post shutdown since this is the most comman problem this should be the first response.

Hick's Law(1952), which states:

RT = K log2 (N+1)

where RT = reaction time, K = a constant, and N = the number of possible choices.

Simply put, the more choices you have in a given situation, the longer it takes for you to react, and that the reaction time increases substantially for each additional choice.

 

[detroit diver]

So do you speak for every training agency when you say that is THE way it's done or are you saying that the agency where you recieved your training teaches this way now?........

I think he answered the original question, which was:

"how many of you have had massive gas loss and what procedure did you follow."

 

[ScubaDadMiami]

Sorry if I'm thick headed on this, but how would shutting down the right post first save any more air than going for the isolator first? Is the thinking that the most likely failure is a right 1st stage failure and so you shut down that first? I'm just trying to understand the rationale behind this, thanks.

Sorry I wasn't clearer. The original post said "in the event of gas loss behind your head were [sic] you can't see exactly which post has the failure." I based my answer accordingly. When you can detect from where the leak is coming, you should shut down per that requirement and not just shut down the right post by wrote memorization.

 

[scubafool]

Good question. I have considered putting plugs in the isolation bar and making them independant. I bought them as double so I guess that is why. When I am travelling I only need to bring bands and I would be just as happy with 2 al80s run independant.

Well, after a rather lengthy discussion with someone who dives manifolded doubles, I thought I had a good handle on the benefit of a manifolded doubles set, but by this, I might not after all.

The way I understand it, the biggest reason to dive manifolded doubles vs. independent doubles is that in the event of a regulator failure, shutting down the post that the defective regulator is attached to shuts down the supply to that regulator, while still allowing you to breathe the gas in that tank through the other regulator. With independant doubles, you don't have this option. Am I misunderstanding something here?

 

[wedivebc]

Well, after a rather lengthy discussion with someone who dives manifolded doubles, I thought I had a good handle on the benefit of a manifolded doubles set, but by this, I might not after all.

The way I understand it, the biggest reason to dive manifolded doubles vs. independent doubles is that in the event of a regulator failure, shutting down the post that the defective regulator is attached to shuts down the supply to that regulator, while still allowing you to breathe the gas in that tank through the other regulator. With independant doubles, you don't have this option. Am I misunderstanding something here?

That is correct, but with proper gas manement that is not an issue since with the method I use you will have enough gas to complete the dive in the event of a reg failure and you will actually end up with more gas should the failure involve a burst disk, a manifold O-ring or a tank O-ring. Even though those failures are not as common as reg freeflow the chances are still greater than zero. The main benefit is that a valve shutdown does not become a matter of life and death with independants and during a wreck dive (and cave) the possibility of being in a location where you may not have freedom of movement to complete the shutdown in a timely manner.