Types of O2

[Houman]

Hi,

Since I don't have an oxygen refilling provider at my local airport and it is expensive and a hassle to fly to a nearby airport where the have, to pay the exorbitant 75$ of refill and 20$ of landing fee each time I need to fill it up, I have decided to set something up in my hangar.

After contacting several O2 providers in the region, I have found couple of them that actually can do delivery to my local airport. Their business is usually supplies O2 to welder shops or medical clinics. According to both, their medical grade O2 should be better or as good as the O2 I'm getting from the other airport.

I have absolutely no knowledge of the different grade of O2 when refilling, can someone point me to the right direction. I obviously don't want to put my life or those of my passengers in any undue risk.

I'm fully equipped now with O2 pulse oximeters and spare emergency tank for 2...

Thanks !!!

[Marauder]

There is no difference between oxygen sources. They fill the welder grade from the same Dewar as the medical ones. There is a difference however if the oxygen is being considered for medical usage. Protocols by the FDA come into play at that point. If they are telling you they have a "medical" brand, it means they want to charge you more for it.

Just tell them you want a bottle(s) of O2 for aviation usage.

[Marauder]

BTW - if you need information on the hardware setup, let me know. smcray from this site helped me with the sources of parts. I can forward you that information.

[mooniac15u]

The difference in medical and welding grade oxygen is in the protocols for handling the cylinders.  Welding grade cylinders may have other residual contaminents in the cylinder.  If you don't mind breathing some residual acetylene then welding grade is fine.

[Houman]

BTW - if you need information on the hardware setup, let me know. smcray from this site helped me with the sources of parts. I can forward you that information.

I would appreciate getting that information..

Thanks !!!!

[mooniac15u]

There are no residual welding gasses in standard welding O2 tanks.

 

Also, there are no special protocols for "handling" the O2 cyl's either.

 

The only difference is that medical grade O2 has minimum contaminant specifications that the O2 must meet for human consumption. In other words, it is just like the FAA and certification of aircraft parts...Your FAA approved alternator belt is somehow 'special" just because it was pulled from the automotive belt production line at the Gates rubber and tire company and stamped with a PMI number and charged double for it. ... yes the belt has been shown to pass minimum aircraft safety standards to be deemed "certified", but the belt didn't require any more engineering than any other automotive belt had at the time of manufacture.  The belt is the same and the O2 is the same...

 

  Welding gas happens to be CLEANER than the medical standards for human consumption (yes that is TRUE), and that is why the medical O2 is filled directly from welding O2 filling valves.   Medical O2 requires that it PROVE compliance to pass the certification, whereas welding requires no certification at all.  Just because it is used for welding doesn't mean that it is bad or inferior.

 

P Mc

 

Medical grade oxygen cylinders are evacuated prior to filling with oxygen.  Welding cylinders can potentially be back-contaminated with acetylene and they are not required to be evacuated prior to refilling.

[Hank]

Medical grade oxygen cylinders are evacuated prior to filling with oxygen. Welding cylinders can potentially be back-contaminated with acetylene and they are not required to be evacuated prior to refilling.

It's easy to evacuate yourself, just remove the hoses and turn the valve. Once it's empty, close the valve and unchain the cylinder from the wall.

The back up O2 bottles I've seen for people on oxygen generators look just like the ones I have at work hooked to the torch. Big, green and scratched up.

[Piloto]

Come down here to South Florida and have it filled for $15 at a local SCUBA dive shop by the beach with Nitrox capability. Watch the bikinis while they fill your tank. Nitrox comes from separate Oxygen and Nitrogen tanks. But they will fill yours from the oxygen tank only.

 

José

[mooniac15u]

It's easy to evacuate yourself, just remove the hoses and turn the valve. Once it's empty, close the valve and unchain the cylinder from the wall.

The back up O2 bottles I've seen for people on oxygen generators look just like the ones I have at work hooked to the torch. Big, green and scratched up.

Evacuation of the cylinder requires pulling a vacuum on it. If you only open it to atmospheric pressure you will still have 1 tank volume of residual gas.

If you are refilling your own cylinder it really isn't a problem. I was referring to the potential risk associated with taking delivery of a replacement cylinder of unknown history.

[chrisk]

Come down here to South Florida and have it filled for $15 at a local SCUBA dive shop by the beach with Nitrox capability. Watch the bikinis while they fill your tank. Nitrox comes from separate Oxygen and Nitrogen tanks. But they will fill yours from the oxygen tank only.

 

José

 

I was not aware they had separate nitrogen tanks.  I always assumed normal compressed air was mixed with pure O2.  Another learning event for me.

[chrisk]

For O2, I am under the impression that it all comes from the same big tank, but the difference is in testing it.  Medical is tested for contaminants.  Aviation is tested for contaminants and moisture (so it doesn't freeze and block at altitude).   Where I live, a 300 CF bottle is around $15 for welders gas, and around $25 for aviation gas.  Given my rate of consumption, it cost me about $40 more per year to have certified aviation O2.  Well into the noise of airplane expenditures.  Landing and parking at the wrong airport easily cost that much for one night of FBO fees.

[Marauder]

Marauder...

Perhaps it is best NOT to tell them that your O2 bottle is for aviation use. In fact, it is best to remove the "AVIATION USE ONLY" label off of the tank and throw it away...

I went into my local Airgas retailer to get my O2 tank filled. They took one look at it and curtly handed it back to me, saying that "we don't fill airplane O2 tanks here."

Turns out that Airgas has a policy to limit their aircraft-related product liability. I spoke with the regional manager and he cofirmed the judgement of his store owner...no aviation tanks filled locally unless the tank is sent to the main filling station somewhere in the northern US states. I immediately called one of the big wig CEO's at Airgas' main office and had a long conversation with him, and he again confirmed the policy of no aviation tanks are to be filled to the end-user. He cited liability issues. (He was the one who told me of the purity of the welding O2 and how tanks are handled vs medical grade in the previous post.)

So, I took it next door to their competitor, and to my dismay, I found they too have adopted the same policy. No aircraft tanks are to be filled.

Some independent weling places still fill the aviation tanks, but there ar no locations within 100 miles of where I live. So, unless I take it to the local FBO, or ship the tank outside the state, I can't fill up my O2 tank for a reasonable price.... That is why I now buy my own large o2 welding - purpose tank and crossfeed it to my aviation bottle.

The bottom line to answer Marauder's post is that you probably don't want to tell them its for "aviation usage"

Phil Mc

I think as you pointed out it depends on who you are going to. When I was having them refill my aviation sized cylinder, they told me to make sure I told the clerk it was for aviation usage and not "medical". It was clear that the cylinder I brought in was not going to be used for a welding activity.

Once it is declared "medical" they told me they are required to follow the FDA protocol for medical devices. I have heard that some suppliers ask for the prescription for the oxygen. Not sure if that is true, but the rumors persist.

I think if you go down the transfill path, asking for an oxygen tank or having your own tank refilled is sufficient to ensure you don't get caught up in the FDA a protocol.

[mooniac15u]

For O2, I am under the impression that it all comes from the same big tank, but the difference is in testing it.  Medical is tested for contaminants.  Aviation is tested for contaminants and moisture (so it doesn't freeze and block at altitude).   Where I live, a 300 CF bottle is around $15 for welders gas, and around $25 for aviation gas.  Given my rate of consumption, it cost me about $40 more per year to have certified aviation O2.  Well into the noise of airplane expenditures.  Landing and parking at the wrong airport easily cost that much for one night of FBO fees.

 

You're right, it typically comes from the same tank.  That's really a cost/logistics issue.  Medical grade oxygen is considered a pharamceutical product so there are GMP specifications for production facilities, equipment, training, quality control, etc.  Once a producer gets that set up it doesn't make much sense to maintain a separate production setup for "lower" grade oxygen.

[cliffy]

Most FBOs order their refill tanks from the same gas plants that the welding shops do, no difference in the order. The trouble comes when you want the gas plant to fill a medical or aviation cylinder. So do, some don't for liability reasons. If you empty a gas cylinder to "0" pressure you have the chance of inducing water vapor into the cylinder. That is why you never should drain one completely. In the airline business if a cylinder comes out completely empty it gets pulled and sent to the shop to be baked making sure it is dry inside.

I can see no way that acetylene would ever get into an O2 cylinder. Acetylene cylinders have a filler inside with acetone impregnated into it to avoid explosion when filled to high pressure. Acetylene is never put in large O2 cylinders. That is why they look different and are made different than O2 cylinders. They are also filled to a much lower pressure than O2 cylinders.

Setting up to refill your a/c O2 tanks is not too difficult but requires the correct equipment and a little training.

Rule # 1- Never have any oil products (petroleum) in, around or near your oxygen set up. Oil and grease will spontaneously catch fire in the presence of O2. All of your tools for servicing need to be dedicated to only that job and no other. Never lubricate anything that near to or uses oxygen, even your dedicated tools.

Rule #2- NO SMOKING while refilling O2. Should be self explanatory but it does happen.

Rule #3- Fill slowly so as to not build up high temperatures in the filling tank. Fill fast the tank warms up giving a higher reading than when cold. As soon as it cools you have a lower pressure than you thought for use.

Rule #4- Keep your O2 cylinders chained to the wall and not standing loose or build a rack to lay them down on their sides. You don't want them to fall over an knock the valve off!

In reality you will need at least 2 big cylinders of O2. One to bring the a/c tank up to say 1500 psi and the second to top it off. They usually come filled to about 2000-2200 psi. Your a/c tank uses 1800 psi. So after about 2 fills the first tank will be below 1800 and not able to top off the a/c tank. This is where the second tank comes in. Use the lower pressure tank for the initial filling and the second high pressure one for the top off to 1800-1850 psi. You have to have a pressure gauge to measure the filling cylinder pressure. Never just fill from a big tank to an a/c cylinder without a pressure gauge.

Get a little training on how tight to secure the various fittings. A small fill "B" nut can be broker off or stripped very easily by tightening too tight. The bigger nuts can leak if not tightened correctly. When you are done- ALWAYS-ALWAYS-ALWAYS- turn off the big tank valve before you try to disconnect any lines.

I've seen it tried otherwise and it ain't pretty. Hope this helps.

[N601RX]

I would also place the cylinder being filled in a container of water.  It will allow you to fill it completely without having a pressure drop after filling it and it will help contain the mess if something goes wrong.

[mooniac15u]

I can see no way that acetylene would ever get into an O2 cylinder. Acetylene cylinders have a filler inside with acetone impregnated into it to avoid explosion when filled to high pressure. Acetylene is never put in large O2 cylinders. That is why they look different and are made different than O2 cylinders. They are also filled to a much lower pressure than O2 cylinders.

 

 

I'm not talking about miss-filling.  There are a lot of protocols in place to prevent that.  The danger of contamination comes from back pressure when the oxygen cylinder internal pressure drops while there is still pressure present from another compressed gas cylinder in a connected or closed system.  Regulators should prevent this but they can, and do, fail.  The point is that you don't know what found its way into a cylinder of unknown history.  With medical grade O2 the pre-fill evacuation should remove residual contamination.

 

If you are refilling your own cylinder, then it really isn't a problem because you know where it has been.

[Jim Peace]

Someone mentioned it earlier.....it has to do with moisture content.  Aviation O2 is very dry as to not cause a frozen blockage somewhere in the supply.  In many O2 systems the bottles are located very far from the flight deck and sometimes against a sidewall.  The bottles and plumbing gets cold.  Very COLD......no moisture also means less corrosion in the tank over time.

 

I am not sure where O2 bottles and plumbing are located in most of the Mooneys.  If you have a portable system with everything in the heated flight deck then it may not be a big deal.

[Amelia]

Medical oxygen, as I understand it, has the moisture bubbled in at the patient's bedside. In the green cylinder, it's the same as any other O2.

 

I'm sure tired of paying $75 or more for a top-off. Would be quite interested in figuring out how to rig a system of my own, but pressures and valves and fittings, oh, my! Maybe I could offer to buy the refill setup for the airport, and arrange to have a couple of big bottles delivered, in exchange for having somebody smarter than I do the filling. I bet a modified kid's little red wagon would be ideal to move them from one place to another.

[DonMuncy]

Mimi,

It really isn't difficult to do the filling yourself. And hooking up the equipment is not very difficult.

As in most things aviation, it is the cost that gets you. If you only need a fill up twice a year, you will never pay for the fill-up system. 

Unless, (like me), the convenience of having it in your own hangar, for your use when ever you want it, makes it worthwhile.

You will need a large tank. Check Craig's list, etc. for prices, or call the local welding shop and get their price. The size of the tank is not too important, as long as it is big (4 ft tall or so). You will likely get 3 or 4 fills out of the tank before the pressure drops too much. Having two tanks (to cascade) increases the number of fills available.

Check folks like Aerox for a flexible hose and a fitting to fit the filling port on your plane. The gauge, copper tubing and fittings are locally available and relatively inexpensive.

If the prices for the tank(s) doesn't deter you, let me know and I will make you up a list and photos to get you fixed up.

Feel free to PM me with specific questions.  

[chrisk]

I bought the O2 transfill connector (FBO-1) at http://www.aviationoxygen.com/aerox-aviation-oxygen/oxygen-refill-station-equipment.html  My plane only needs the Scott connector, so I got a discount for getting only that adapter.  Next on the list was a welding cart from Harbor Freight.  Then two very large bottles of O2 from a local gas supplier.   --Filling the plane is not hard at all.  The large O2 bottles are however very heavy, and might be more difficult for a smaller person to move around (put on the welding cart).

 

As with Don, I am not sure of the return on investment for having my own O2 system, but I think it will pay off in about a year.  It is absolutely very convenient and with refill costs being low,  I generally use O2 well below the FAR limits. I've noticed I feel sharper after a long flight if I have been using O2.

[Houman]

So I have been looking around and it seems that for me to have a refilling setup in my hangar, it would take about 1K$, including rent for 2 x 330 cubic feet tanks medical grade and O2, connections and all... So not a small investment, and I'm not sure how many times I can fill up my 22 cubic feet with those tanks, since when the pressure is low, I will need a refill, so can't really count on being able to really empty the tank according to the vendor I have been talking to, but having 2 tanks kinds of resolves that issue, but still...

 

On the other hand, I have found a medical clinic in town that is willing to fill up my tank with medical grade O2 for about 40$ to 50$ , without any hassle , so I think I will start that way and then eventually see how many times a year do I really need to fill up and if having all that setup is really worth it. I'm thinking that maybe paying a bit more each time and not have to make a big initial investment and all the hassle that goes with it might be worth it...

 

 

[chrisk]

The "investment" is closer to $600 if you rent the tanks.  And if you decide you don't like filling your own tanks, you could always sell the trans-fill station for not to much of a loss.  

 

Anyway, for my plane the O2 tank is built in, which makes it very inconvenient to get a re-fill, unless you do it yourself.  There is no taking the tank to the local welding shop or scuba shop.   It requires a visit to a shop with an airport presence.   And at my home drome, that means 9-5, M-F.  And they charge around $75 for a fill, even if I just want it topped off for a long trip.

 

 

 

Filling it myself is really pretty easy

[N201MKTurbo]

The tech at the gas plant that I use told me that it is not uncommon for welding cylinders to be contaminated with the fuel gas (acetylene). It happens when the user runs an oxygen tank completely dry while using a torch. The fuel gas will run back through the torch and the oxygen line to the cylinder. He always smells the cylinder before he fills it to see if it smells of acetylene.

 

That is why I don't trade out cylinders. I always have them fill mine from the manifold. He said that the cascade can sometimes get contaminated.

 

The ABO and medical bottles are always filled directly from the manifold. The manifold is the plumbing that goes directly back to the giant Dewar of LOX.

[DrBill]

I had the same problem.   I got a used Oxygen cylinder off  Craigslist for $25 (it's a big one about 5 ft high).  I bought the transfil adapter from here:

http://www.deltaoxygensystems.com/id125.html

I get my O2 bottle filled at a local Welding supply (ARC WELDING SUPPLIES). for c $20 (swap tank).

http://www.arcwelderssupply.com/Default.aspx?p=gas

Ask around at mechanic shops where they get their O2 from . Prices vary widely.

 

To refill my portable bottle, I hook up the adapter and tighten.  Open the portable bottle valve.  SLOWLY open the supply bottle a little at a time to about 1/2 way then watch the pressure equalize. When it's done (pressure increase stops) close all valves.  Open the purge valve on the transfil adapter to purge the line of pressure. Remove the adapter from the portable tank.

With one supply tank you'll get progressively less and less "FULL TANK" but the price of a refill is so cheap you get 3 or 4 then swap the big one out.

 

Let me know if you have any questions...

I just filled up my mechanics WELDING TANK (small one) from my tank for him. I don't use much O2 flying right now (long story).

BILL

[KSMooniac]

On the other hand, I have found a medical clinic in town that is willing to fill up my tank with medical grade O2 for about 40$ to 50$ , without any hassle , so I think I will start that way and then eventually see how many times a year do I really need to fill up and if having all that setup is really worth it. I'm thinking that maybe paying a bit more each time and not have to make a big initial investment and all the hassle that goes with it might be worth it...

 

This is what I've done with my portable bottle for now... I'm not a heavy user of O2 yet since I'm not  a turbo owner.  My AME wrote a standing Rx to be placed on file at a local Home Health supply... I drop off my bottle one day and pick it up the next for $15.