Understanding proper gas usage in regulator

[Bigbella]

I have used both air and nitrox (to EAN 40), interchangeably, in my regulators for years, without issue. When it comes to the real risk of combustion, there is really no free lunch.

Viton o-rings, used with 02-cleaned equipment, along with synthetic lubricants, such as Cristolube, are somewhat less likely to ignite; but, should they burn, those fumes are as toxic as hell; while conventional nitrile, along with silicone grease is considered a bit more flammable, those fumes are far less of an issue; and further, nitrile creates a more reliable seal, with greater mechanical properties than viton, with a far less chance of failure . . .

 

[NAM001]

I recently bought a full regulator setup for the first time. Looking through all of the manuals/documentation, something stuck out to me that I need clarification on:

"Air used in SCUBA diving may contain minute amounts of flammable hydrocarbons that are considered safe to breathe. Over time these hydrocarbons may accumulate and represent a fire risk if used with Nitrox or oxygen. Specifically filtered air is available, called hyper-filtered air. Regulators to be used with Nitrox and oxygen must not be used with normal compressed air."

Does this mean I cannot switch between regular air and nitrox whenever I want? Does my regulator have to be one or the other forever? Please advise. I currently am not Nitrox certified but I imagine I will be in the near-future. Thanks for any help!

All that that means is their legal department put a disclaimer out. When you get air and you want to insure to be in compliance with the warning ask if they fill tanks with standared E or hyperfiltered air. If HYP E you meet the requirement. Also understand that they can only respond with the last gas testing report that was done. it may have qualified as hyp E air a month ago but that does into mean it still is today. Personally I dont concern my self with the differences of E vs hyp E.

There are warnings also saying that if you have a titanium reg do not use it with nitrox > 40% because a fire could start under the right conditions. I looked on the net to readup. The warning was valid for O2 pressures 16K psi and above. None of our tanks operate in that range let alone our regs. Not saying that is a reason to ignore or comply just that , that info is out there and perhaps makers prefer to be over cautions than not as a business practice. Halloween superman costumes have a warning to say that the costume does not allow the wearer to actually fly.

 

[NAM001]

Sad discovery for me at a previous dive shop: two completely different compressors and filter stacks for air and EAN. Air wasn't even close to OCA. They didn't want to over-use their precious new EAN compressor. Air compressor was an old POS. Or more important, since they weren't compressing oxygen, their filter stack was minimal.

Unfortunately O2 regulations force that to happen. I have seen the fill shops you describe I have also seen the shops that only pump HYP E because it is cheaper to maintain one system than 2. the ones the use 2 systems have different maint requirements like having to O2 clean all O2 piping and components anually if pummping EAN. regular E air does not have that requirement. I have also seen regular E stations with a separate filter system on designated EAN fill lines that only HYP e filter the specific fill likes for nitrox. Those stations do not have to O2 clean all their lines only the short length that comes out of the HYP E filter to the tank.That could be 5 ft instead of 100 ft of line. Pumping EAN and Not PP filling is another situation in it self. another configuration I have seen is off the grade E compressor to grade E banks out of the grade E banks to both grade E fill whips and to a additional filtering string to make hyp E air for follow up EAN32 banking with its own fill whips. I ask to see the filling station where ever I go. It is always educational and gives insight into the shops operation morals. If their fill stations are shotty how much more is like that also.

 

[NAM001]

I have used both air and nitrox, interchangeably, in my regulators for years, without issue. When it come to the real risk of combustion, there is really no free lunch.

Viton o-rings, used with 02-cleaned equipment, are somewhat less likely to ignite; but, should they burn, those fumes are as toxic as hell; while conventional nitrile is considered a bit more flammable, those fumes are less of an issue; and further, nitrile creates a more reliable seal, with greater mechanical properties, and a far less chance of failure . . .

Not everywhere, some places are rubbish. Mostly I find it is as you expect but...

That was the initial purpose of the NITROX sticker. The sticker if present meant only OCA air allowed and that the tank was not a trimix tank. The inspection sticker if Nitrox marked should also tell the fill station only OCA fills allowed. Many monkeys dont understand what they are doing.

 

[lowwall]

Just a reminder that the OP was only asking about his reg, not filling tanks.

The answer to that question is.... Yes, your reg is fine for anything from air to 40% O2. You don't have to do anything when switching between air and Nitrox up to 40. You do not need to have separate reg sets.

 

[Bigbella]

Just a reminder that the OP was only asking about his reg, not filling tanks.

Asked and answered.

Presumably, he'll attach that spanking new regulator to a full tank of EAN 40 and crack that valve, if only for kicks. Some appreciation of the risks associated with mixed gases is always in order . . .

 

[epolice]

The responses were very informative and insightful. Thanks everyone, love this community!

 

[lowwall]

Asked and answered.

Presumably, he'll attach that spanking new regulator to a full tank of EAN 40 and crack that valve, if only for kicks. Some appreciation of the risks associated with mixed gases is always in order . . .

Is there really a risk of spontaneous combustion in this scenario? It's not a rhetorical question, I'd like to know.

I was under the impression that the only real danger in switching from air to EAN40 was when doing a tank fill using the partial pressure blending method.

 

[Bigbella]

Is there really a risk of spontaneous combustion in this scenario? It's not a rhetorical question, I'd like to know.

I was under the impression that the only real danger in switching from air to EAN40 was when doing a tank fill using the partial pressure blending method.

There's nothing "spontaneous" about it; has a real physical cause; and that other notion is better left to stories in The Daily Mail, about a 400 pound guy, rendered crispy in a La-Z-Boy.

I have seen partial ignitions on two occasions, back in the 1990s, when nitrox was first becoming popular, with P02 mixes less than forty percent -- one with viton o-rings ; the other, I recall, with nitrile. It's just slightly less likely, in terms of risk; but the difference between, say, thirty six and forty percent 02 is minimal. Both are combustible. The valves, on those occasions, were quickly closed, after everyone experienced an acrid burning smell; and two regulators got impromptu, if expensive rebuilds and a new hose or two. No harm; no foul.

The friction involved in cracking open a 242 bar (3500 psi) tank valve is seldom appreciated. Take a quick look at a cross section of any given first stage regulator; a tank valve; and take count of all of the sharp corners; sudden changes of direction, coupled with wide then suddenly narrowed passages -- all subject to friction -- along with a dozen or more greased o-rings and bits of nylon.

It is primarily that reason why EAN valves are slowly opened or damn well should be; and, ignoring that very safeguard, was the reason, I should think, for that partial ignition . . .

 

[lowwall]

...The friction involved in cracking open a 242 bar (3500 psi) tank valve is seldom appreciated. Take a quick look at a cross section of any given first stage regulator; a tank valve; and make an idle count of all of the sharp corners; sudden changes of direction, coupled with wide then suddenly narrowed passages -- all prone to friction -- along with a dozen or more greased o-rings and bits of nylon.

It is primarily that reason why EAN valves are slowly opened or damn well should be; and, ignoring that very safeguard, was the reason, I should think, for that partial ignition . . .

Thanks for the info. I'll be opening my valves more slowly when diving nitrox from now on.