O2 on general rigs

[karstdvr]

When I pick up oxygen at my local welding shop it amazes to look at the welders doing the same. Their valves,connections, and regulators are lying in the bottom of the truck in piles of organic material,rust,and grease laden rags. These guys put this equipment on the oygen cylinders and do their daily welding for decades without a single incident. I remember being told that when NASA tried to recreate the Apollo 1 accident in pure oxygen environment,it took them many trials to get an oxygen facilitated fire. My comments aren't directed at don't do safe oxygen handling and component cleaning,because I still do it faithfully. It just amazes me that others can be complacant and never have an incident,yet I know a guy who was very anal-retentive with everything and melted the inside of his valve.

 

[Rick Murchison]

These guys put this equipment on the oygen cylinders and do their daily welding for decades without a single incident.

And this is yet another reason why oxygen is so very dangerous. It's instability and capriciousness promotes complacency. But if you ever have the chance to see the victim of an oxygen fire you will be disabused forever. Like a sleeping mad dog, you can walk by it day after day, but if it wakes up it'll chew you up in little pieces.
Oxygen may not burn, but it'll sure burn you if you aren't careful with it.
Rick

 

[karstdvr]

. But if you ever have the chance to see the victim of an oxygen fire you will be disabused forever.

I've seen the after effects of a couple blown haskels that were pumping oxygen.

 

[South Pacific Diver]

Having been a welder and ships gas free engineer for over 20 years combined with using high oxygen content gases in diving for almost the same length of time, I will throw in my humble opinion. Oxygen itself at reasonable pressures (2,300 psi or less)is not unstable. You have to do things to it such as introduce hydrocarbons to really cause problems and even then the reaction is not spontanious. Heat from an outside source or high flow would have to be generated to close the fire triangle. Welders do not run much of a risk because they use 2 stage regulators connected directly to the oxygen bottle. The input side is never over around 2,250 psi and the output is never over around 30 psi, even when using large cutting torches. My boys always knew that to let any petrolium base products in the welding area or around the oxygen equiment would cause the gates of hell to open up and the devil himself would come get them. Other than that we never took any special precautions.

Now in the diving community it get a little more complex. Folks want to run higher pressures, along with the oxygen moving through longer runs of small diameter hoses or tubing and sometimes boosting equipment. If not done correctly, that is a recipie for disaster. The simplest thing, such as oxygen getting behind a worn o-ring combined with long flow runs which generate heat can be disastrous. The single greatest assurance against an oxygen fire is keeping the equipment clean and metering the oxygen flow. Oxygen cleaning does not have to be taken to the nth degree either. All of my piping, hoses and fittings are cleaned using a de-greaser then hot water flushed for about 30 minutes (continuious flow) and then dried using hyper clean air. Assembly is done in a reasonably clean area and it is put into service. Any exposed fitting is bagged in airtight bags when not in use. Metering the oxygen flow is just as important. Needle valves and the ability to correctly use them is probably the most important componant in the system. You have to keep the flow constant and small. Being in a hurry is probably the greatest culprit in any oxygen fire.

Do not boost to a pressure higher then than the oxygen is supplied to you. There is a reason you can not buy a commercial oxygen cylinder at pressures greater than 23 - 2400 psi. If you cant get the mix you want staying below that, rethink how you are doing business. If you want to see the results of a semi controlled oxygen fire, watch someone use an exo-thermal cutting unit. Rick you have seen these. Give me a car battery, a hollow steel rod, jumper cables and high pressure oxygen and I will cut through 8 inches of armored steel like butter.

Lastly before I close this book. The tank valve and the cylinder along with the regulator first stage must be cleaned the same way described above. I personnaly will not partial pressure blend into tanks that I did not clean and know the history of. Everyone in my diving circles have identified their high mix regulators and they get special treatment. How important is cleaning regs that never see above an 75 to 80 mix? Dont know but I do know that if I am trusting my dive profile to that regs ability to function, then it is clean and has oxygen compatable software in it. That is my 6 cents worth....Ron

 

[Dive-aholic]

Hello clique,

I was wondering how much O2 you would be prepared/have put through your first stgae safely and regularly.

Of course, manufacturers stress a max 40% but I am sure, like the sell by dates on Christmas cards it means little...OR does it???

Thank you

boogey

40% is the liability amount manufacturers are willing to give us. Most regs will work fine with 100%. Just make sure when you get them serviced that they are O2 serviced. The main thing is to use cristolube. Some people recommend viton or edpm o rings, but the old rubber ones work as well, even with 100% O2. Yeah, I know, it's not recommended, but I have used them and know of other divers that use rubber o rings with high % O2 without problems. The only regs you have to be concerned about are titanium ones. Again, probably not a problem, but there have been studies done that recommend not using them with any enriched air. They seem to be safe with recreational limits. I wouldn't use them with 100% just because I don't want to be the statistic if there is one.

 

[BigJetDriver]

40% is the liability amount manufacturers are willing to give us. Most regs will work fine with 100%. Just make sure when you get them serviced that they are O2 serviced. The main thing is to use cristolube. Some people recommend viton or edpm o rings, but the old rubber ones work as well, even with 100% O2. Yeah, I know, it's not recommended, but I have used them and know of other divers that use rubber o rings with high % O2 without problems. The only regs you have to be concerned about are titanium ones. Again, probably not a problem, but there have been studies done that recommend not using them with any enriched air. They seem to be safe with recreational limits. I wouldn't use them with 100% just because I don't want to be the statistic if there is one.

Actually, this is the first post I have seen in a long time that offers advice I would consider dangerous.

People have done many silly things, and gotten away with it for a while, but to generalize that into advice to others is, in my opinion, a darn fool thing to do.

As has been pointed out by folks who have a lot of experience in dealing with O2 under pressure, if you are dealing with mixes up to and including 40%, all normal scuba equipment will work just fine. That is a safe and conservative statement.

100% oxygen under pressure is an ENTIRELY DIFFERENT ANIMAL.

Pouring 100% O2 into a tank as we do in partial pressure blending requires that the tank, and the valve be cleaned and set up for "Oxygen Service". That means proper cleaning, proper lubes, and proper o-rings.

When you are talking about 100% O2 under pressure coming OUT of a tank, the critical part is now the regulator. It needs to be set up for O2 service because it WILL be exposed to O2 molecules moving fast under pressure. The movement of those molecules can develop enough heat, given the proper fuel, to create ignition. Lest you think that is not possible, you need to know that a well-known cave diver had her hand injured by an O2 fire in a first stage she was working with. Others have been burned and killed by O2 fires.

The second stage is downstream and under much less pressure, so it may not be such a concern.

The up-shot is this. You don't have to be an anal retentive about it, but you need to show some serious respect when dealing with oxygen under pressure. You cannot just blandly say: "Uhh, I know guys who get away with it. You'll be OK!" That is just irresponsible. :no

 

[karstdvr]

When you are talking about 100% O2 under pressure coming OUT of a tank, the critical part is now the regulator.

Every incident I've ever seen and heard has occured from the valve,only one incident from a regulator. The first source of heat will be the adibiatic pressure from the valve. I won't say the regulator isn't important,but I sure give my valve a lot of attention

You don't have to be an anal retentive about it, but you need to show some serious respect when dealing with oxygen under pressure. You cannot just blandly say: "Uhh, I know guys who get away with it. You'll be OK!" That is just irresponsible. :no

Agreed,respect is important,but it isn't carrying a case of nitroglycerin either.

 

[Dive-aholic]

Actually, this is the first post I have seen in a long time that offers advice I would consider dangerous.

People have done many silly things, and gotten away with it for a while, but to generalize that into advice to others is, in my opinion, a darn fool thing to do.

As has been pointed out by folks who have a lot of experience in dealing with O2 under pressure, if you are dealing with mixes up to and including 40%, all normal scuba equipment will work just fine. That is a safe and conservative statement.

100% oxygen under pressure is an ENTIRELY DIFFERENT ANIMAL.

Pouring 100% O2 into a tank as we do in partial pressure blending requires that the tank, and the valve be cleaned and set up for "Oxygen Service". That means proper cleaning, proper lubes, and proper o-rings.

When you are talking about 100% O2 under pressure coming OUT of a tank, the critical part is now the regulator. It needs to be set up for O2 service because it WILL be exposed to O2 molecules moving fast under pressure. The movement of those molecules can develop enough heat, given the proper fuel, to create ignition. Lest you think that is not possible, you need to know that a well-known cave diver had her hand injured by an O2 fire in a first stage she was working with. Others have been burned and killed by O2 fires.

The second stage is downstream and under much less pressure, so it may not be such a concern.

The up-shot is this. You don't have to be an anal retentive about it, but you need to show some serious respect when dealing with oxygen under pressure. You cannot just blandly say: "Uhh, I know guys who get away with it. You'll be OK!" That is just irresponsible. :no

I was tired and maybe it didn't come across the right way. I wasn't recommending anyone use rubber o rings with O2, just stating that it's done. Viton o rings aren't as strong or durable as rubber o rings. They degrade more quickly. Okay, so you may have to change them out more often, but how often is enough. If a viton ring goes bad on the surface, what will the fast rush of O2 do to the reg? Again, I'm not recommending anything here, just providing some other thoughts.

Some people will tell you not to use titanium regs with anything over 21% because some people conducted some very controlled tests trying to get it to ignite and succeeded once. I believe they even managed to do this with 21% as well. Does this mean titatium regs should be destroyed?

What started the fire that injured that cave diver's hand? Was it the o rings or something else?

Like karstdvr says, respect for O2 is important, but it isn't NTG, which I also happen to deal with!

Bottom line, research everything out there and do what you're comfortable with. Don't just blindly follow the majority just because they said. Be informed and maked informed decisions.

 

[South Pacific Diver]

The up-shot is this. You don't have to be an anal retentive about it, but you need to show some serious respect when dealing with oxygen under pressure. You cannot just blandly say: "Uhh, I know guys who get away with it. You'll be OK!" That is just irresponsible.

Well said BJD

 

[boogeywoogey]

Dive-aholic,

Thanks. Your answer was welcome. Just pushing it slightly further, if you have nitrox cylinders, that are O2 clean, of course, would you push the mix above 40% or would you want to take precautions (another tank clean, clean the valves (sonically or otherwise?)....

Just wondering as I have some o2 stage cylinders I use to 40% with scubapro mk25 s600 DIN, viton and cristalube etc....but just wondering if I can safely use the whole kit with 40-100%?

boogey