High O2 left for long periods...

[kinetic]

Hello,

Been a bit inactive on the deco diving front for a while after her indoors had a go...

I have 4 cylinders with varying nx mixes in them from 50 to 80 percent. not used for about 8 months.

What's the view? Would it be silly to use them? Regs attached also have not been used for same period..same question?

Thanks for any comments...keep 'em sensible....I know I'm a muppet.

Kinetic

[Sleepy]

Originally Posted by kinetic

Hello,

Been a bit inactive on the deco diving front for a while after her indoors had a go...

I have 4 cylinders with varying nx mixes in them from 50 to 80 percent. not used for about 8 months.

What's the view? Would it be silly to use them? Regs attached also have not been used for same period..same question?

Thanks for any comments...keep 'em sensible....I know I'm a muppet.

Kinetic

Should be OK to use but roll them around the floor for a while to remix the O2 with the air , then re-analise them. I left about 120 bar in a 7L of 82% last year, tested O2 and it had dropped by 4%. Shook it up for a while then retested in the morning, it was back to 82%. Best to check those regs out though.

[kinetic]

Cheers....appreciate it.....not thought about giving them a shake up but sounds sensible.

Regards.

kinetic

[DIVE BUDDHA]

8 months ?

mm i think for the cost of a few new fills i would simply get rid of the old gas!

[Richard Mason]

Originally Posted by DIVE BUDDHA

8 months ?

mm i think for the cost of a few new fills i would simply get rid of the old gas!

Why?

Would you dispose of the O2 in your club O2 kit after 8 months?

[Richard Mason]

Originally Posted by kinetic

Cheers....appreciate it.....not thought about giving them a shake up but sounds sensible.

Regards.

kinetic

I don't get this.

Does 21% settle out if left for a while? I don't think so; so why would any other mix of O2-N2 settle out or stratify? They're miscible gases, not salad dressing.

I'd have thought your regs should be ok too, provided they are still within their normal service interval.

After a protracted lay-off from diving, I once used a cylinder that was filled 4 years previously and it was fine but that was because at the time, the nearest serviceable compressor was 130 kms away and it was out of test by then. (annual hydro tests here).

I freely admit that I've had no training in the use of enriched gases for deco, so I'm no expert.

[DevonDiver]

As far as I was aware, the only really need to roll tanks and mix gases comes when using Helium. If you are only dealing with nitrox mixtures, then there should be no stratification of the gasses (and if there was, they'd probably mix themselves during the course of transporting the cylinders to your next dive site).

As for long term storage of the tanks, then there are several potential issues to consider:

1. Tank pressure. Have the tanks leaked at all...is the pressure suitable for the dives you are planning to conduct?

2. Gas mixture. There will be no issues of the gas 'going off' and neither N2 or O2 will leak from a tank at a greater rate than the other (with Trimix, the Helium can leak from a tank over time, changing the mix). You still need to re-confirm the O2% before diving the tanks though.

3. Tank deterioration. Storing high O2 mixtures for long periods will increase the opportunity for oxidisation (rusting) of the tanks to occur IF there was any moisture inside the tank. There could be internal corrosion. However, if your tanks are still in O2 Service AND you are happy that your tanks were initially filled with clean, dry, air and that no moisture could have entered the tanks since the last testing (you never completely drained them)...then you shouldn't have a problem.

The only reason for draining the gas would be in order to conduct a service on the tanks, if that was required or if you had any doubts about moisture/corrosion occurring. As for the stage regulators...just consider their condition, last O2 service and how they've been stored. If anything needs sorting out... it'll be the regs.

[MattS]

Originally Posted by kinetic

Thanks for any comments...keep 'em sensible....I know I'm a muppet.

Devon Diver has pretty much covered the bases on the gas. Re-analyse, check the pressures and you should be fine.

Take the time to do a shallow dive. Get the regs wet and breath off them for a few minutes. Leaving regs for to dry out for months worries me a great deal more than breathing 8 month old gas. You could put the regs in for a service, but it is equally a good idea to do a shallow dive afterwards to check they have been put back together in working order.

[BJ]

I left a tank of air for three years and all the nitrogen had settled to the bottom leaving the oxygen at the top (or was it the other way around?). Actually I'm lying. The air around the planet Earth has stayed mixed for millions of years!

[Richard Mason]

Originally Posted by MattS

Leaving regs for to dry out for months worries me a great deal more than breathing 8 month old gas.

Regs need to be kept wet?

How do we go with brand new regs from the shops? I'll bet that many of them would be several months old before sold. This diving lark is more dangerous than I thought.

Is this really an issue?