Pure O2 Handling?

[KentCe]

Now that I carry an O2 bottle on my back I would like to understand everything about handling/filling pure O2. I ordered the Oxygen Hacker and Booster books from AirSpeed Press. Any other good books to read? Classes to take? Useful websites?

Thanks, Kent

[canuckdiver]

I'm far from an expert, but I would think that a blending course from a tech agency would be a good start on getting practical experience with dealing with O2.

[caveseeker7]

Certainly the handling part should have been ... :upset:

One good thing to do with O2 other than using it in your rebreather is providing it. :D Take the DAN O2 Provider course http://www.diversalertnetwork.org/ The safe handling of O2 is part of it, as well as the medical aspects etc. . Training is usually done on an DAN O2 rig, but the RB will do in an emergency, or an O2 clean 2nd stage. Or better yet, OMS' O2 kit. just grab your tank and switch regs.
For a while they actually taught REMO (rebreather emergency medical oxygen) classes. Mini RB to extend the supply, but those are currently out of production. :( Takes the better part of a day, and should cost less than $100. Worth it.

[caveseeker7]

[padiscubapro]

KentCe once bubbled...
Now that I carry an O2 bottle on my back I would like to understand everything about handling/filling pure O2. I ordered the Oxygen Hacker and Booster books from AirSpeed Press. Any other good books to read? Classes to take? Useful websites?

Thanks, Kent

kent
Who are you taking your class with?? O2 handling should have been part of it.. (or at least a prerequisite)

I don't want to make this sound like an ANDI plug, but if you do have an ANDI facility near you I would look into their oxygen provider class, its considerable more involved than the Dan program, although the Dan program is much easier to find an instructor...

The typical ANDI oxygen provider clas takes 6-8 hrs of lecture and a few hours of hands on (as long as it takes to run the scenarios)... When I run the oxp class I charge $125 for 6 students, more if a smaller class... The typical dan class is 4 hours total (1 hour lecture 3, hours skills).. although I hear people do it shorter...

[KentCe]

To reply to the last two messages.

Filling O2 bottles was not part of my Inspiration class, nor my Nitrox class, nor Adv Nitrox class or even my DAN O2 class. I believe the only comment was "turn the valve sloooowwwwly" and not the low details why this is important.

Of course after posting my question my copy of "OXYGEN HACKER'S COMPANION" arrive which was exactly what I was looking for (including the reason for slow valve movement).

[padiscubapro]

KentCe once bubbled...
To reply to the last two messages.

Filling O2 bottles was not part of my Inspiration class, nor my Nitrox class, nor Adv Nitrox class or even my DAN O2 class. I believe the only comment was "turn the valve sloooowwwwly" and not the low details why this is important.

Of course after posting my question my copy of "OXYGEN HACKER'S COMPANION" arrive which was exactly what I was looking for (including the reason for slow valve movement).

WOW!

depending on the persons prior training determines how much time I spend on oxygen handling, but even the most knowledgeable person gets at least 30 minutes of review of basic handling principals...

The most important rule to remember is don't forget about adiabatic compression.. Oxygen being pressurised generates an incredible amount of heat as opposed to air. The heat generated along with any particulate matter can easily cause any fuel available to combust...

If you are going to do any cross filling make sure you use an oxygen compatible needle valve... and fill slooooooooooooooowly.

60psi per minute is a pretty acceptable rate.. If you are going to fill faster you must keep the gas cold....

[DrySuitDave]

Ok, allow this newbie to play the village idiot for a moment, and allow me to ask the question, where are all the injured and dead oxygen handlers?

I have an oygen clean whip to decant from a huge aviation grade low pressure cylinder and it takes about a minute to fill from 500 psi to 2000 psi. That is with the valve cracked open slightly. I let it set for 5 minutes or so to allow the cylinder to cool in case I can squeeze out a little bit more 02 before I disconnect it. I never touch the end pieces, and I always put the cpas on both ends right back on after use, and I never touch the insides of those.

At my LDS, they fill my 02 cylinder to about 2000 psi in about the same time, but when they boost it, they give me another 1000 psi in about 15 seconds. Why is their rig not blown to smithereens?

Lastly, I have heard all this technical sounding stuff about how oxygen in cylinders above 2500 psi is very dangerous, so where are the reports of all the injured Inspiration users who had problems with filling the AP 02 cylinder rated to 3000 psi to 3000psi?

I just got in a new DOT approved spare Inspiration 02 cylinder, made by the same company which is Faber I believe, and all of a sudden thanks to the infinite wisdom of the US Government, I lost 600 psi....

Now let me preface all this by stating I have not taken a gas blending class (my rebreather blends my gas for me) nor an 02 class as mentioned, so if myself and my LDS and all the rest of us who fill our 02 cylinders much quicker and to 3000 psi are all just living on borrowed time till we join the rest of the dead rebreather cylinders users, well hey, I can just blame it on ignorance! lol

Thoughts?

[Se7en]

It's the combustion triangle thingy. You need fuel plus heat plus O2 to get combustion.
Now O2 you got lots of, so you need to reduce the other two.

If you are absoulutely, 100% sure that you have nothing that can combust coming in contact with the O2, then you could bounce it around all over the show, no problems. Ditto, if you do everything slowly and carefully so there is no heat, you can have your gear as mucky and horrible as you like.

However, most of us tend to assume that there is at least some fuel, so we try to keep gas speeds and heat down, just to be safe. If you are scrupiously clean, you may get away with a bit more heat... but remember what you are betting on it...
One time in 10 000 it may save someone when they pick up a cylinder which has some oil or grease in the valve.

Sure, I'm probably being way conservative, but it doesn't cost much to wait a little longer.

Se7en

[padiscubapro]

DrySuitDave once bubbled...
Ok, allow this newbie to play the village idiot for a moment, and allow me to ask the question, where are all the injured and dead oxygen handlers?

I have an oygen clean whip to decant from a huge aviation grade low pressure cylinder and it takes about a minute to fill from 500 psi to 2000 psi. That is with the valve cracked open slightly. I let it set for 5 minutes or so to allow the cylinder to cool in case I can squeeze out a little bit more 02 before I disconnect it. I never touch the end pieces, and I always put the cpas on both ends right back on after use, and I never touch the insides of those.

At my LDS, they fill my 02 cylinder to about 2000 psi in about the same time, but when they boost it, they give me another 1000 psi in about 15 seconds. Why is their rig not blown to smithereens?

Lastly, I have heard all this technical sounding stuff about how oxygen in cylinders above 2500 psi is very dangerous, so where are the reports of all the injured Inspiration users who had problems with filling the AP 02 cylinder rated to 3000 psi to 3000psi?

I just got in a new DOT approved spare Inspiration 02 cylinder, made by the same company which is Faber I believe, and all of a sudden thanks to the infinite wisdom of the US Government, I lost 600 psi....

Now let me preface all this by stating I have not taken a gas blending class (my rebreather blends my gas for me) nor an 02 class as mentioned, so if myself and my LDS and all the rest of us who fill our 02 cylinders much quicker and to 3000 psi are all just living on borrowed time till we join the rest of the dead rebreather cylinders users, well hey, I can just blame it on ignorance! lol

Thoughts?

The reason for slow filling is to keep risks down.. If EVERYTH(ING is CLEAN (no fuel) and no particles for impingement you could probably instantenously fill a cylinder. By keeping the fill rate low it allows a larger safety margin when filling..

The most dangerous time is when you are first starting the fill... if you use a needle valve and slowly start the pressurization process (adiabatic compression is reduced) and then you can increase the rate.. doing a fast fill just causes the gas to get very hot, and you have to let it cool anyway and retop off.. do a hot fast fill to 3000 psi and when it cools doen I bet you have less than 2500...

The fastest I fill an o2 tanks is about 250-300 psi a minute, and thats in a cold water bath on cylinders I know are clean... re:my personal cylinders...
and I start them off slow.....

An example of a potentially dangerous situation is when you HEAR squeeling when someone is starting the fill, if there is fuel available things can happen....

I can fill a dirty cylinder 10,000 times without incident, and the 10,001 fill blows up.. well I'm probably dead... I'll play it safe.. and fill slowly..

Another point of contention, the higher the pressure the more unstable oxygen becomes... the percentage of free oxygen atoms increases causing a jump back and forth between an o2 and o3 molecule which releases energy.. That why the highest you usually see oxygen cylinders rated is 2400 psi...

a free oxygen atom is HIGHLY reactive, it doesn't want to stay free in wants to bind to something..

[Jaap]

Why do so many people indicate the maximum safe filling rate in psi? That doesn't make any sense to me as it isn't a measure of the filling rate!

Lets say you fill with maximum 100psi per minute. That is only a small trickle of gas if your filling a 13cu ft bottle but the same 'recomendation' applied to a 120-twin set would result in a considerably greater flow!

Why not talk in terms of flow instead of that arbitrary 'psi per minute'-talk?

By the way in europe the industy standard oxygen bottles are usually 200bar (approx 3000psi) and that works just fine.

/Anders

[Stone]

I can't measure flow directly. I *can* set my valve so that the pressure gauge needle is moving at 100 psi per minute.

[blacknet]

Hello,

welding supply shops do carry flow meters. Also doesn't the o2 hackers manual state that filling smaller bottles becomes more artful due to it's small size? Think it also states you have to use a reduced flow rate depending on the bottle size.

Ed

[Jaap]

Well using the manometer to provide information on the filling rate is not what I'm questioning.

What I find strange is the fact that a lot of people seem to over simplify things when they think that 'x psi per minute' is a measure of the filling rate regardless of the cylinder size.

[runvus4]

Expanding on the heat "Fire Triangle", a fire requires three components: Fuel, Oxygen and Heat.

Oxygen itself does not burn, but the greater amount of Oxygen present, the lower the "flash point" of a subtance, or the temperature required for an item to ignite. For O2 cannisters or high O2 mixes, lets just assume that you can't remove O2 from the fire triangle for SCUBA tank purposes.

Fuel is just that, anything that may burn, which while highly unlikely, can include metal should the flash point be reached, which is why TI is usually not cleared for high O2 concentrations, the flash point is lower than steel/brass/aluminum. Also, CGA grade E gas has a hydrocarbon limit of 25ppm and hyperfiltered air has a limit of .1 ppm, which explains why Nitrox tanks should only be topped off or filled with Hyperfiltered or "Oxygen compatible" air.

Ignition or heat for fill purposes usually means the temperature by which any fuel sources can ignite. This is the only side of the fire triangle that you can really manipulate. Heat caused by compressing gas is also known as Adiabatic Heat. This effect should be readily observed from the "hot fill" that. what you can't see is that the gas inside is significantly higher than the tank itself, especially at the point of entry to the tank from the valve. In my gas blending manual, it notes that a rapid pressuraization of a tank to 2000psi from zero can generate gas temperatures as high as 1600 degrees. If you are doing this and have not had a problem, then your equipment is properly spec'ed out in that you are using O2 compatable components and you are lucky enough not to have had any contaminants. I would highly reccomend that you stop that practice and not be anywhere near your LDS fill station when they are filling if they continue to do fill pure Oxygen that fast. You may get away with it 10000 times, but you only need one time to get caught behind the eight ball to ruin what would have otherwise have been the rest of your life. Since it is the pressurization of gas that generates the heat (change in PSI, not the CuFt/min pumped), you control the heat by controling the PSI per minute. The recomended max fill rate for High O2 gasses is 70 to 100 psi per minute, though 60 psi per minute is often used as slower is better as far as heat generation is concerned, and 60psi/min is far easier to eyeball than 70 or 100psi/min. As always, there may be local regulations concerning gas handling that may apply to your specific situation so you may want to check with whomever supplies your gasses.

[Jaap]

Just trying to clearify a few things. The term 'Adiabatic' refers to a process that is thermally insulated from the surrounding so that no heat can escape. The filling of tanks is not strictly adiabatic since the outside of the bottles lose heat during the process.

I agree with the fact that the temperature inside a bottle being filled is highly dependent of the pressure rise and not directly dependant of the actual flow. The actual bottle temperature can become dangerously high during rapid high oxygen fills. I have heard that this is a specific problem for oxgen and nitroxtanks made out of composite materials without metallic liners since the actual bottel can ignite if the temperatur is allowed to high. A friend that used to work for a company making bottles told me a rapid fill giving a bottel an outside temperature of around 50-60 Celsius (around 120 F) could give an internal bottle temperatur as high as 259 C (480 F) wich is damaging to some composites.

But I don't think that that is always the most important issue dealing with oxygenfills.

Most high pressure oxygen related accidents seem to be caused by adiabatic compession related problems originating in the filling line and not in the tank.

Near adiabatic compession occurs is when a gas in a confined space such as a filling line is suddenly subjected to a high pressure that rapidly compress the gas to a fraction of its original volume in such a short time that the heat that is evolved cannot escape. For example when a decanting hose filled with oxygen at ambient pressure is rapidly subjected to high pressur oxygen.

As said in the last posting the temperaute can sertainly sometimes reach around 1600F (approx 850C) or even higher during these events. But this maximum temperatur occurs in the filling line and only for a very brief amount of time not in the tank. If the decanting hose is contaminated or if the polymer in the hose has a flamepoint that is to low ignition could occur if enought energy is transfered to the contaminant/polymer.

So high temperature is not enough in order to achive ignition, the heat transfer to the material that is to ignite must also be taken into consideration. Just like if you would try to ignite a pice of paper or some oil with a spark, just a spark is not always enough just because the energytransfer is to limited.

So in my way of thinking several things are important in order to stay safe. Slow opening of valves reduce the risk of sudden adiabatic comperssion in the fill line. The increase in pressure and the actual flow rate are also important. If the flow in the filling line is to high friction and vibrations could tranfer enough energy to casue an ignition of the polymer or possible contaminants in the valves and fillinghose.