Bit of info about doubles for a technical noob :)

[LiteHedded]

You forgot the silt out when your knees settled on the bottom.

Or the embolism when you breached the surface like a ballistic missile.

of course then you're going to fumble that safety spool and shear off a valve on the ceiling.

and your team is not there to help you and you die. all because you didn't want to signal the team.

 

[lowviz]

Right.. So I'm looking to broaden my diving ability/knowledge and start diving doubles ...........I'm just getting myself abit confused and having people say different things..

would be great if someone could explain it to me..

Cheers
James

This thread is getting interesting....

If I really can't tell, I'll shut down the right post. Either one of two things will happen: The leak will stop, or it won't. If it doesn't, I know one thing that it isn't and I shut down the isolator. ............

Above is one school of thought.

Ok... well, lets dive into this a bit more (pun intended).
.........You can't tell if it's a hose break, an o-ring at a hose on your first stage, a tank o-ring, burst disk, whatever. Your buddy hasn't even noticed you are signalling like crazy. Which valve do you twist first? Me personally, if I can't quickly determine where the leak is, I'm shutting down the isolator.

Another school of thought.

This is how I do my valve drill/fault finding !!

-Purge backup - make sure it works!!
-Shutdown both isolation and right post using both hands (one move)- This is important to save as much gas as you can (if there is a problem with isolation) and shorten time lapsed.
....................

Another school of thought.

I'm shutting down whichever post seems to be the side which is leaking. If it stops great, if it doesn't I'm shutting down the isolator.
............

Another school of thought.


To summarize:

1) Shutting the isolator first is intended to save half of your gas as fast as possible.

2) Shutting the right post first goes straight to the most likely problem with the intention of saving more than half of your gas.

3) Shutting your right post and isolation simultaneously is intended to save as much gas as possible but you are tying up both hands.

4) Figuring out which post to shut first is the analytical approach to saving as much gas as possible.


This is why there is so much disagreement about what is the "right" order. Which is best? -It depends on the situation that you are in.

In addition:
You should also know what is attached to each post without thinking about it. That way when you close down a post, you will know what you are about to lose.

 

[TSandM]

I think it's pretty reasonable to expect things that move and things that get connected and disconnected to fail more often than things that don't move and don't get changed. I've done 1000 dives or so, and have yet to have a tank neck o-ring failure during a dive (I've seen them leak, but you catch that by a tank that should be full that isn't, or during a bubble check.) I've seen burst discs leak -- again, caught during bubble check. I've seen LOTS of issues with DIN o-rings or with various things going wrong inside regulators, which makes a lot of sense in my mind.

I'm willing to say that, if I think it's on the right, closing the post is more likely to solve the leak that doing anything with the isolator (which won't solve ANY leak, but only isolate it). I'll trade the risk I'm wrong for the possibility I'm right

 

[Superlyte27]

I've seen a few burst disks go, it terrifies me. It zero's vis in a cave and it empties a tank quickly. The only failure I've had on a regulator ever was a freeflow due to ice buildup, and it emptied a tank just as quickly. Thankfully, I don't dive in 30 degree water much.

 

[LiteHedded]

burst disk? what's that?

 

[lowviz]

I think it's pretty reasonable to expect things that move and things that get connected and disconnected to fail more often than things that don't move and don't get changed. ...............

Yep.

I've seen a few burst disks go, it terrifies me. ...............

Yep.


I've dumped a few tanks just for grins and to see how long it takes. Don't have too much time but I'm betting that either of you could handle the worst situation. Training and practice.

Watching the fireworks in a state of brain-lock is the real issue. I think rjack321 alluded to that. Superlyte27 and I have more degrees of freedom than TSandM, -her training doesn't allow confusing the team. However, her theoretical survival rate is likely to be higher than ours.

Keep true to your training, comprehend the situation and you will most likely be fine.

burst disk? what's that?

Exactly one half of what goes in each holder..

 

[ajduplessis]

leaking gas and team separation. now you have two big issues to deal with.

foot on the banana peel...

If you can't shutdown valves and stay in contact with your team (on the move) in all conditions, you should reconsider what you are doing urgently!!

 

[ajduplessis]

I think it has to do with whether or not you're breathing normoxic.

Let me correct you. Normoxic TRIMIX

 

[PfcAJ]

the problem with shutting them down both at the same time is that you are unable to signal your team.

Primary objective is to save as much gas as possible. The rest is all secondary.

If you can't shutdown valves and stay in contact with your team (on the move) in all conditions, you should reconsider what you are doing urgently!!

Perplexing...

 

[ajduplessis]

Perplexing...

Why??? Can't you multi task? Or did (The rest is all secondary) confuse you??