Isolator Manifold Procedures for solo divers in particular

[Walter]

Bill now carries a pony on every dive. It enables him to surface safey in the event of a similar situation.

 

[Stoo]

Bill now carries a pony on every dive. It enables him to surface safey in the event of a similar situation.

LOL... I used to use a 13 cf pony on a single 72... until I had a reg freeze-up at a depth where I shouldn't have been on a single 72. The reg froze open thankfully, but the tank was empty by the time I got up to about 120. I switched to the pony and made it to the top OK... even managed the mandatory 12 second safety stop. It was shortly after this that I started wearing doubles most of the time.

I once read a line in a book... "Experience is what you gain immediately after you needed it..." I don't remember what it referred to, but it stuck with me and it always seems to fit in these types of situations!

 

[MaxBottomtime]

As someone who has had a tank neck O-ring fail I can assure you that I always dive with a way to isolate each reg, whether it's doubles or a single with an H valve.

 

[Scuba]

If you folks are referring to Dr Bill, unless I missed something the cause why his regulator stopped delivering air at depth was never determined. Everything else is speculation.

Diving with a closed isolator valve precludes one single gas leak from depleting all gas in the doubles. Barely open may increase the time it takes to deplete all gas and provide warning through increased breathing resistance, (how useful? any examples) this also increases the risk of accidental closure and resulting issues. Accidental closure is probably a bigger concern in an environment where valve may come in contact with solid objects. These are rare and preventable occurrences. There is also always the possibility of this valve failing itself. Another million to one?

As someone who has had a tank neck O-ring fail I can assure you that I always dive with a way to isolate each reg, whether it's doubles or a single with an H valve.

Out of curiosity, when was the last time that the neck O-ring was replaced or maintained before this dive. Where you able to determine the cause for failure? How bad was the gas leak?

As you probably know, an H valve will not keep gas from escaping if the tank neck O-ring fails..

 

[Finless]

I agree that, in theory, an isolator doesn't do anything that shutting down a reg wouldn't do, except in the rare cases mentioned... neck o-ring, burst disk failure etc., all of which I agree are unlikely.

But, an "isolator manifold" will give you access to the remaining gas in the "shut down cylinder"

 

[Stoo]

But, an "isolator manifold" will give you access to the remaining gas in the "shut down cylinder"

Of course. I was assuming this was a doubles set-up. I agree, shutting off the valve on a single wouldn't be all that helpful Although, both of my singles have H valves...

S

 

[matt_unique]

....shutting off the valve on a single wouldn't be all that helpful

S

Only helpful if you are feathering your air or providing a temporary break to allow the first stage to warm up. I had a reg freeze on me just once. I took an extra long breath and she stayed open. I knew exactly what had happened so I closed that post for a few seconds, then reopened slowly and the problem was resolved. I was on doubles and had another reg to grab/isolator as well. In this particular instance I did not reach for the isolator first because I knew why she froze and that it was indeed the right post.

--Matt

 

[Walter]

But, an "isolator manifold" will give you access to the remaining gas in the "shut down cylinder"

Actually, no. Any manifold will give you access to the air in both tanks. The isolator, if closed, will prevent you from having access to air in the shut down tank. That's its purpose, to isolate one tank from the other.

 

[diverbrian]

Brian,

Bill's problem was the inability to get air out of the valve, not the valve leaking. If I remember correctly, something blocked the particle tube. It was on a single tank, but had it been on doubles, turning off the isolator would have accomplished nothing but cutting his air supply in half.

Actually, it wouldn't have cut his air in half either. You aren't getting air out of a clogged tank valve in any event. It would have simply been an a non-event.

I used it because it was the quickest example of something no one thinks of happening that happens once in a while.

In other news, tank O-rings have been known to extrude out. Rarely does it happen, but do you wish to be the victim when it does? The pony is nothing more than a bail-out and that is fine.

Unfortunately, most of my diving lately requires more than "bail-out" capability. Manifolded doubles with an isolator allows the isolation of the faulty tank (in the rare event that it is required) without the extra pressure gauge hanging around that a set of independent doubles requires.

The shut-offs to the regs themselves are obviously required in cold water. I have been known to dive with my regs set a little too sensitive and they have been known to reward me with a free-flow. No worries! Reach back, shut down offending reg and switch to back-up until primary thaws. Then re-open valve and continue dive. Heck, continue dive while doing the above as it isn't that difficult!

Half of what is left of double 130's (if it is the O-Ring problem and assuming rule of third was used) is still enough gas to do whatever I need to do to get the surface without a deco obligation. This is most especially true with deco bottles involved (as I am not a cave diver, those stay with me).

The use of an isolator valve is starting to become questioned and I really do understand the reasoning. But, then I just don't like the thought of loosing all of my gas to tank o-ring failure. If I am diving with a manifold that I can't isolate one side of, I may as well be diving independent doubles. At least then a failure of this type doesn't run the risk of taking all of my gas.

 

[Walter]

The use of an isolator valve is starting to become questioned and I really do understand the reasoning. But, then I just don't like the thought of loosing all of my gas to tank o-ring failure. If I am diving with a manifold that I can't isolate one side of, I may as well be diving independent doubles. At least then a failure of this type doesn't run the risk of taking all of my gas.

The isolator is a failure point. It's more likely to fail than either a burst disk or a tank neck o-ring.

You are correct that a clogged particle tube isn't going to let air out of the tank, isolator or not, my mistake.