Manifold open or closed?

[Soggy]

Going way back to teh beginning of this point, you never did ask the guy if he knew what was in the other tank.....

I contend that if you made it all the way to the end of a dive without noticing your isolator is closed, you can't possibly *know* what is in the other tank. Perhaps if all one ever gets is air fills and never dives mixed gas, it's possible, but I'd like to believe that in this day and age we are all smart enough not to do that.

If you opened the isolator after the fill, how long do you think it would take for it to mix up?

That depends on the difference in mix and difference in pressure between the two tanks....18/45 is going to mix with 32% more rapidly than 36% and 32% or 21/35 and 18/45. Just like on and offgassing, this would be driven by pressure differentials and pressure gradients.

 

[Diver0001]

I contend that if you made it all the way to the end of a dive without noticing your isolator is closed, you can't possibly *know* what is in the other tank. Perhaps if all one ever gets is air fills and never dives mixed gas, it's possible, but I'd like to believe that in this day and age we are all smart enough not to do that.

I know people who only dive 32%. It's entirely possible that he knew what he had on the previous fill.....

On the other hand, if I discoverd my isolator closed during a dive (unlikely since, like you, I check things 50 times before I jump in) I would still have serious doubts. I would wonder if the guy who did the fill closed the isolator before filling or not and if he did, I would assume that he didn't ahve the grey matter to fill both tanks with the same thing....

In either event there is only one way to deal with it once the dive starts and that's to assume that the isolated gas is lost and act appropriately.

R..

 

[Diver0001]

That depends on the difference in mix and difference in pressure between the two tanks....18/45 is going to mix with 32% more rapidly than 36% and 32% or 21/35 and 18/45. Just like on and offgassing, this would be driven by pressure differentials and pressure gradients.

Exactly.... in other words a long time. Maybe an hour, maybe longer.... The question wasn't because we need a pricise answer. I just asked the question to get people thinking about it.

R..

 

[Soggy]

On the other hand, if I discoverd my isolator closed during a dive (unlikely since, like you, I check things 50 times before I jump in) I would still have serious doubts. I would wonder if the guy who did the fill closed the isolator before filling or not and if he did, I would assume that he didn't ahve the grey matter to fill both tanks with the same thing....

Exactly! This is the point....How many stories have we all heard or experienced of inept dive store employees who close the isolator, fill one side with air and the other with O2? There are sooo many things that could've gone wrong, and if you don't know *exactly* when that isolator became closed, that gas should be treated as unbreathable until an accurate analysis can be obtained.

 

[Diver0001]

Exactly! This is the point....How many stories have we all heard or experienced of inept dive store employees who close the isolator, fill one side with air and the other with O2? There are sooo many things that could've gone wrong, and if you don't know *exactly* when that isolator became closed, that gas should be treated as unbreathable until an accurate analysis can be obtained.

Actually, this makes for an interesting argument for always analyzing both of your tanks. It would trigger people to think about the isolator, if the contents were different you'd notice it and if they weren't but you still somehow managed to forget the isolator you would atleast know what was in the isolated tank....

R..

 

[Tom R]

Soggy,

Why are you even discussing this, everyone I dive with checks their manifolds to ensure they are open right at the gas shed. Any diver with the proper training would do so. He also dives with people with the buddy insperation Nuff said. If he don't want the right answer why argue with him. His mind is made up and therefore apply the appropriate rule.

Always check your valves and gas before you even leave the gas shed.
Always leave your manifold open
CFD there dude.

 

[Soggy]

Tom, as usual, you are right

 

[Diver0001]

Soggy,

Why are you even discussing this, everyone I dive with checks their manifolds to ensure they are open right at the gas shed. Any diver with the proper training would do so. He also dives with people with the buddy insperation Nuff said. If he don't want the right answer why argue with him. His mind is made up and therefore apply the appropriate rule.

Always check your valves and gas before you even leave the gas shed.
Always leave your manifold open
CFD there dude.

It's a good thing he did. Go back to the responses. There were a number of people who looked like they didn't get it (including the diver it happend to). Maybe they do now. Putting the point on the table and showing the patience to explain it 3 or 4 times if necessary, as Soggy did, does the uninitiated a lot more good than calling them dumb, don't you think? Do you think anyone ever learned anything by being called dumb?

And take another look at the responses. I think you have the story of they guy who chooses to dive with his isolator closed confused with the story of the guy who discovered it was closed during a dive and opened it. It's two different stories.

R..

 

[novadiver]

I thought the thread was about diving with the isolater off. When I got a short fill because the isolater was off, it didn't put me in any danger , it just pissed me off. It did throw my Fo2 off , 1-2% But it's not like I was going to tox with with a short fill , I'd be ooa first

 

[Diver0001]

I thought the thread was about diving with the isolater off. When I got a short fill because the isolater was off, it didn't put me in any danger , it just pissed me off. It did throw my Fo2 off , 1-2% But it's not like I was going to tox with with a short fill , I'd be ooa first

No worries, they weren't on about you. They were on about the guy in post #12.

R..