trimix diving

[nerdkid]

hi i was just wondering how long can one bottle of 12 litre trimix last you?

[Kern]

Much the same as if it were air.

[RJP]

hi i was just wondering how long can one bottle of 12 litre trimix last you?

I have a set of doubles in the garage that have lasted 4 weeks so far, and as I'm still recuperating from surgery I expect they'll last another 4 weeks. After that, they'll last about 70min.

:d

But seriously, as Kern mentions, the fact that the tank has TMx in it has little to nothing to do with how long it lasts. Some folks find their SAC rate on deeper dives improves a bit with TMx due to clearer head, less anxiety, etc.

Especially given that you've only got ONE of them, and it's only 12l, I'm guessing you don't plan on going terribly deep, so why are you worried about TMx?

[nerdkid]

just wondering...

[Wookie]

It depends a lot on the mixture. If you have a 12 litre bottle of 10/70, and breath it at 20 feet or shallower, it'll last you the rest of your life....

By the same token, a bottle of 16/50 dived to 300 feet will last you the rest of your life, too.

Get some training, then come back and ask the question. Of course, you won't need to then.....

[ScubaFeenD]

It depends a lot on the mixture. If you have a 12 litre bottle of 10/70, and breath it at 20 feet or shallower, it'll last you the rest of your life....

By the same token, a bottle of 16/50 dived to 300 feet will last you the rest of your life, too.
.

Nice response :D

[DCBC]

hi i was just wondering how long can one bottle of 12 litre trimix last you?

Like all mixtures with open circuit it's dependent on depth and workload.

[ae3753]

Here's a good article on gas management and dive planning (http://www.nwgratefuldiver.com/articles/gas.html).

[peterbj7]

Actually jokes apart, helium will slowly escape through the sides of the tank, so an unused bottle doesn't last for ever.

But on the OP's question, if you feel the need to ask this sort of question you know nothing about gas management and you should be thinking of doing an advanced nitrox course. Trimix will come much later.

[Wookie]

Actually jokes apart, helium will slowly escape through the sides of the tank, so an unused bottle doesn't last for ever.



You're funny too. Although helium atoms will migrate through the lattice of carbon steel cylinder walls, it happens on a molecular level, not on any practical level. In other words, it theoretically happens, but is not measurable. All things being equal, if the gas didn't escape through the valve, the cylinder would have the same pressure in it a thousand years from now as it does today. It will have a few less molecules, however.

[ianr33]

if the gas didn't escape through the valve, the cylinder would have the same pressure in it a thousand years from now as it does today. It will have a few less molecules, however.

This is why its important to store trimix tanks upside down. The helium goes to the top of the tank rather than escaping out of the valve.

[Wookie]

This is why its important to store trimix tanks upside down. The helium goes to the top of the tank rather than escaping out of the valve.

D'oh! If you roll them, I hear they mix better.

[peterbj7]

You're funny too. Although helium atoms will migrate through the lattice of carbon steel cylinder walls, it happens on a molecular level, not on any practical level. In other words, it theoretically happens, but is not measurable. All things being equal, if the gas didn't escape through the valve, the cylinder would have the same pressure in it a thousand years from now as it does today. It will have a few less molecules, however.

Actually that seems not to be true. I discovered a part-used bottle of trimix that had been left over from a dive, and the tank not re-used for many months/a year. When I analysed the mix I found it down about 3 %age points from what it had been recorded and used at. Not a vast amount, granted, but certainly measurable.

[ianr33]

What's the accuracy on a helium analyzer?

[Superlyte27]

Only about a dozen things that could have come into play here...
lol...
I wonder why I keep logging in. Helium escaping through the sides of the tank. Geesh.
Rolling tanks to mix the nitrox. Wow.

[deepwater]

D'oh! If you roll them, I hear they mix better.

Roll them...crap I've doing it wrong all this time. I thought shaking them like a paint can was best.:dontknow:

[Wookie]

Roll them...crap I've doing it wrong all this time. I thought shaking them like a paint can was best.:dontknow:

Shaking like a paint can IS best. Next best is to get underway in 6-8's and keep the throttles firewalled. I hear crewboat driving is the best training...

I hear if yoiu roll the cylinders, the nitrox is better for deep diving, too.

[nerdkid]

do you guys actaullly shake or roll the bottle to mix the gases? omy..be serious! aahaha!

[Wookie]

do you guys actaullly shake or roll the bottle to mix the gases? omy..be serious! aahaha!

No. Those who understand gas laws do not shake or roll the bottle. It is just a joke. It is a trimix myth, like helium escaping from the cylinder (and oxygen and nitrogen not escaping) that seems to get a hold in some settings and never lets go. Wet filling cylinders to keep them cool is another such myth. (oooh, I opened a can of worms with that one) :popcorn:

[nerdkid]

hahahah! i see i see..yep i think you did..

[peterbj7]

Those who understand gas laws do not shake or roll the bottle. It is just a joke

I understand gas laws and I don't agree with you.

I do agree though that external cooling of a tank whilst it's being filled too fast is highly undesirable. It actually stresses the tank material more than letting it heat and cool naturally, though filling too fast is the main factor in shortening the life of a tank (especially an aluminum one).

[Wookie]

I understand gas laws and I don't agree with you.

That's OK, You shake and roll, and you'll be happier for it. I'll let the gas mix by itself, and I'll be happy. Neither one of us will likely change the others mind, and that's OK, at the end of the day, we will dive our mixes, be happy, and life will be good. We don't have to agree, especially about something so trivial.:D


I do agree though that external cooling of a tank whilst it's being filled too fast is highly undesirable. It actually stresses the tank material more than letting it heat and cool naturally, though filling too fast is the main factor in shortening the life of a tank (especially an aluminum one).

Exactly, or at least I agree with you wholeheartedly, although I don't know if fast filling shortens the tank life more than over filling. I try to do neither.