inverted manifolded twins

[DaleC]

8 hours in a cave within the past 2 weeks....0 hours spent configuring gear. There's my sense of adventure

It's great that you enjoy cave diving. I hope you spend your time wisely there and find fulfillment. I know I spent much of my 20's and 30's engaged in similar adventures and don't regret it. You may think you are leading the charge "adventure wise" but I'm about 20 years ahead of you. Take a good hard look because one day you may be me (if your lucky and survive).
Here I am at your age. At this time I am running up mountains (literally) training for altitude climbing. A couple of months later I will be on sight free soloing frozen waterfalls:

I've kept various forms of fish for about twenty years and even make a living from it and I study their habitats so diving allows me to see these things "in situ" as it were. I'm no Dr Bill but in my small way I try. I'm also interested in the historical aspects of diving and the evolution of the mechanical systems we use. I've always been a student of history that way. That's why I'm participating in this thread. Part of that "interest" means that I spend some time on dry land trying to understand how those systems work; reading books, asking questions, looking at gear. I then dive those systems (when I can) to "feel" how they work. Is it ok if I pursue my adventures without the snide comments or will I only find validation if I put down my interests and take up yours?

 

[hobodiver]

Also, shutting down the isolator first is nonsense. Tank O-rings rarely extrude, and even more rarely underwater. However, regulators fail and become dislodged way more frequently. You can save MORE gas by shutting down the proper post (you can hear it when its by your head) and working with your team mate to see it it can be fixed or not. I prefer to have more resources at the end of any issue than less.

This is a primo example of convolution after convolution based on topside logic being applied underwater.

Do you always bet on black or red when you're playing roulette? Because that's more likely to win than betting on individual numbers.

Suppose a tank o-ring failure is 10 times less likely than a regulator failure, but loses gas 20 times faster....which is better?

I was taught to isolate first BTW.

 

[LiteHedded]

i would go for the one that's more likely.
of course my buddy would be there to help sort this out and odds are i could hear which post it was.

 

[ucfdiver]

Has an isolator EVER failed underwater....EVER?

 

[djcheburashka]

As a matter of accident analysis, are there any injuries that would have been prevented if the diver had shutdown their valves and isolator in a different order?

 

[LiteHedded]

As a matter of accident analysis, are there any injuries that would have been prevented if the diver had shutdown their valves and isolator in a different order?

i can think of one incident where shutting an isolator for no reason contributed to a fatality on the following dive because they forgot to reopen it.

it's all hearsay though. so i dunno

 

[ucfdiver]

i can think of one incident where shutting an isolator for no reason contributed to a fatality on the following dive because they forgot to reopen it.

it's all hearsay though. so i dunno

I was thinking the exact same thing. Sucked an o2 bottle down at depth because he thought he was OOA. Other than servicing gear, the isolator should really never be closed, and it's arguable if there's any reason at all for it.

 

[djcheburashka]

Other than servicing gear, the isolator should really never be closed, and it's arguable if there's any reason at all for it.

Wait a sec... I don't think any of us are aware of any isolator failure accidents. Or any "wrong-order" accidents. But burst disc blowouts are not that rare, and in that case the isolator is necessary.

 

[ucfdiver]

Wait a sec... I don't think any of us are aware of any isolator failure accidents. Or any "wrong-order" accidents. But burst disc blowouts are not that rare, and in that case the isolator is necessary.

Oh right, I forgot about people who have burst disk that aren't doubled, location ruins perspective at times I suppose.

 

[Druid]

Anyone dive with inverted manifolded twins. My dive buddy has difficulty reaching valves when used upright and is considering going inverted. It would seem to be the answer to his problems but the only valve protectors we can find are flimsy custom diver style that look as though they will bend as soon as you stand the tank on them. Any experience on protectors or diving inverted in general

Well, it's been a long journey from the OP, with some predictable responses I don't dive inverted twins, but I've seen a few people who do and I have no issues with them. Someone posted a list of potential problems and the only one I would agree with is that you can't hear a leaking first stage. You can reach the isolator, even with a stage. Custom length hoses are fairly easy to source but will cost a bit more, and you only really need one - the long hose.

There's a useful thread on a UK based board here, and a link to the manufacturer of probably the best valve protector/stand that I've seen here.