Manifold shutdown procedure

[novadiver]

I've just read a post in another forum on SB and I'm in shock at the advice given in the event of massive gas loss.

in the event of gas loss behind your head were you can't see exactly which post has the failure , I was taught that the first thing that was done was to turn off both the isolation manifold and the left post. if you can still hear the gas loss then you know it is the right post and you breath that tank down first as it losses gas, or turn the left post back on and shut the right post down to see if this stops the gas loss. if this does not stop the gas loss you turn the post back on and breath it down first. if it does stop the gas loss then you can open the manifold and use the gas in the right tank.

All this should take no more than 5 to 10 seconds.That's a long time.

that said, how many of you have had massive gas loss and what procedure did you follow. am I off base here when I hear someone tell another diver to shut down the posts first, one at a time in order to find the offending post, or does every one go right to the manifold and left post

I'm alway willing to hear new ideas!

 

[matt_unique]

I've just read a post in another forum on SB and I'm in shock at the advice given in the event of massive gas loss.

in the event of gas loss behind your head were you can't see exactly which post has the failure , I was taught that the first thing that was done was to turn off both the isolation manifold and the left post. if you can still hear the gas loss then you know it is the right post and you breath that tank down first as it losses gas, or turn the left post back on and shut the right post down to see if this stops the gas loss. if this does not stop the gas loss you turn the post back on and breath it down first. if it does stop the gas loss then you can open the manifold and use the gas in the right tank.

All this should take no more than 5 to 10 seconds.That's a long time.

that said, how many of you have had massive gas loss and what procedure did you follow. am I off base here when I hear someone tell another diver to shut down the posts first, one at a time in order to find the offending post, or does every one go right to the manifold and left post

I'm alway willing to hear new ideas!

I was trained to go for the isolator first to save half my gas if I don't know where the gas loss is coming from. I always do this for my drills as well.

I have only once had a free flow but I knew exactly what the cause was and I knew closing my right post would solve the problem. I had a brand new reg and took an unusually deep breath in 46 degree water during a deco dive on the U853. The water temp was 46 degrees and at the time of my free flow I was at 120'. I knew it was my right post regulator so I shut down my right post for a few seconds, then opened it slowly, and I was fine for the rest of the dive.

If I heard a boom and had no idea where the gas was coming from I would definitely have gone for my isolator then posts.

--Matt

 

[flw]

About 5 years ago, still on oc then, trusty twin 12's with tx50/40's. Nearing the end of a 20+ish minute/ 68m bottom time, I spyed something sparkly underneath a plate. Wriggling to try and get it, I clattered my back-up reg, which then jammed full-on with my hand stuck down the back of the engines, so I had to free my hand first before being able to turn off the offending regulator - my buddy just happened to have his head down a hole about 10m away at the time.
Was close the the shotline anyway to headed up - little bit unnerving not to have any idea how much I had left, as the contents gauge was on the shut down reg, but my buddy came up close by and all stops were completed without any incident.
What did we learn - well, the reg was just back from service that week, and had been a bit 'light' on the surface, but ok, - it simply turned out the ip was set a bit high - something I could have easily sorted out myself. My buddy was also using an 'Alpinist' approach to rb diving that day - oddly enough we no longer do this, we all carry enough independant bail-out
Oh - from memory I ended up with around 40b left in my cylinders

 

[wedivebc]

I've just read a post in another forum on SB and I'm in shock at the advice given in the event of massive gas loss.

in the event of gas loss behind your head were you can't see exactly which post has the failure , I was taught that the first thing that was done was to turn off both the isolation manifold and the left post. if you can still hear the gas loss then you know it is the right post and you breath that tank down first as it losses gas, or turn the left post back on and shut the right post down to see if this stops the gas loss. if this does not stop the gas loss you turn the post back on and breath it down first. if it does stop the gas loss then you can open the manifold and use the gas in the right tank.

All this should take no more than 5 to 10 seconds.That's a long time.

that said, how many of you have had massive gas loss and what procedure did you follow. am I off base here when I hear someone tell another diver to shut down the posts first, one at a time in order to find the offending post, or does every one go right to the manifold and left post

I'm alway willing to hear new ideas!

My approach is based on the fact that I often dive solo so I have to be truly redundant. Although I have never had an experience like flw's I was taught to dive in such a way to survive such an episode.
I dive with my manifold closed. Before the flames start and people start telling me I don't have access to as much gas let me explain how it works.

long hose on right post (not always solo) and 2 spgs of course. I start my dive breathing 1/3 of right tank changing to left tank, and continue till 1/3 is breathed from that. At this point I turn the dive and continue to breath left side. After 2/3 of left tank breathed I switch back to right post to complete dive. I still keep 1/3 back for contingencies and no matter where in the dive I have a failure and no matter which side fails I will always have enough gas to make it back safely. My only gas drill required is to change to my good reg. I can then choose to shut down the offending post or use my time for things like finding my guideline before things get too silty. I can do my shut down when it is safe to proceed. I have been doing it this way for several years and the action of checking spgs and changing regs is about as task loading as shifting gears on a standard tranmission car. It becomes automatic and I don't even think about it.
Although I am not a cave diver, sidemount divers use a similar technique and I am sure that is where this method was adapted from.

 

[simbrooks]

A question, not a flame:
Why go to the expense of getting an isolating manifold when it sounds like you are configuring/diving as independant doubles?

 

[wedivebc]

A question, not a flame:
Why go to the expense of getting an isolating manifold when it sounds like you are configuring/diving as independant doubles?

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.

 

[kramynot2000]

In my tech class we were told go for isolater first to save 1/2 the gas and then try to determine which tank is losing pressure. One suggestion was to look at pressure guage and if it was going down, if it was, leak was on the left tank so you breathe off that first until empty and then switch to right tank and visa versa.

Anyway, we were getting ready for a dive and my buddy was ready to roll off the boat when a high pressure seat (I think) of his right post first stage blew. Because of the way it was facing, the air was rushing out of the first stage from the right post to the left. I was right next to him so I shut down his right post and we replaced the first stage, but afterward he said he couldn't tell where the leak was coming from based on the sound. Made me really think about training to hit that isolater first.

 

[ScubaDadMiami]

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.

 

[Albion]

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

 

[wedivebc]

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.

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?

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..

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.