Needed for Cavern??

[aquaregia]

Most (not all) doubles have an isolation valve between the two tanks. They are far more redundant.

I'm afraid I still don't understand. Don't H-valves allow you use two regulators that can be shut down independently, either of which can access the entire air supply? Isn't that the same as what an isolation manifold gives you?

 

[PfcAJ]

Almost.

There is still a tank neck o ring, and there is still a burst disk (which can rotate if the ceiling is struck just right, true story), as well as the barrel o-rings that the H adapter uses. Valve knobs can also be broken off while dislodging a reg at the same time. Rare, but possible.

 

[ianr33]

How is this less redundancy than manifolded doubles? All I can come up with is the tank neck oring, which doesn't seem like a common failure point. Am I wrong, or is there something else I didn't consider.

Burst Disc.

Again, not common but it can happen. (especially if you wack it on the ceiling)

 

[The Chairman]

I'm afraid I still don't understand. Don't H-valves allow you use two regulators that can be shut down independently, either of which can access the entire air supply? Isn't that the same as what an isolation manifold gives you?

They do. But an isolation manifold is better yet. Two tanks are more redundant than one tank.

I have evolved now to diving to single tanks when I enter an overhead environment.

 

[The Chairman]

I'm afraid I still don't understand. Don't H-valves allow you use two regulators that can be shut down independently, either of which can access the entire air supply? Isn't that the same as what an isolation manifold gives you?

They do. But an isolation manifold is better yet. Two tanks are more redundant than one tank.

I have evolved now to diving two single tanks when I enter an overhead environment.

 

[Superlyte27]

The added redundancy is basically that there are two tanks for supply. Should a burst disk fail or oring at the valve into the tank, there would still be another tank in double's format.

I'm convinced that completely independant doubles are probably the best way to go. It negates the use of at least 4 orings necessary by installing an isolator. I gotta switch to sidemount.

 

[Superlyte27]

What happens when that Cavern becomes a cave though, because of a silt out, or a storm above etc?

I hope they had a great instructor that taught them how to deal with a bad situation and they have the wherewithall to actually make it through it. Sadly, most people teach agency minimums. Scary huh? Pass the qualifications and you get a card.

 

[Superlyte27]

These are the people who have no business being in a cavern. There are too many variables and things that can go wrong to be in there without the training and proper equipment and proper mindset.

Well, if they had a good instructor, then they've gotten proper training. If they follow that training then they have the proper equipment. In the event of an emergency, hopefully they have the mindset that will save them.

Quite honestly, no one knows how they will react in a real emergency until they've been in one. Hopefully, when an emergency arises your mind will flash back to that training and get you out alive.

 

[Superlyte27]

Almost.

There is still a tank neck o ring, and there is still a burst disk (which can rotate if the ceiling is struck just right, true story), as well as the barrel o-rings that the H adapter uses. Valve knobs can also be broken off while dislodging a reg at the same time. Rare, but possible.

I doubt you could rotate a burst disk with a ceiling under pressure. Ask the guy I shot a burst disk at when I tried to "rotate" the burst disk out of tank with a wrench that still had air in the tank. I thought to myself seconds before I did something really really stupid. Man this think is friggin tight in here. I gotta get a bigger ratchet. Never occured to me that I forgot to drain the tank.

But, one could burst, one could shear off.

 

[PfcAJ]

The added redundancy is basically that there are two tanks for supply. Should a burst disk fail or oring at the valve into the tank, there would still be another tank in double's format.

I'm convinced that completely independant doubles are probably the best way to go. It negates the use of at least 4 orings necessary by installing an isolator. I gotta switch to sidemount.

Except for the part that if you really lose a tank, half of your gas is gone right when your heart rate is going to be at its highest. Plus, you're back to the same old "which reg do I donate" thing.