Transfill adapters for oxygen tanks

[rslaback]

Years ago when I purchased a torch set I went with a portable unit instead of a full size tank cart deal because I wanted it to be portable. Having it be so has saved my bacon numerous times. However, swapping out MT and 20cu ft tanks is about the most expensive gas per volume that you can buy.

Recently I picked up a VarmitGetter to kill the gophers in my shop yard and with it I just procured a 80 cu ft oxygen tank. I am considering refilling my own torch oxygen bottles instead of swapping. The gopher blower upper uses LP so there is no plan to stop swapping out the acetylene tank (plus acetylene scares the **** out of me). The gas in the 80 cu ft oxygen tank is cheaper by volume than the 20. I know they make transfill adapters to do just this but was curious if anyone has experience doing this.

 

[rlitman]

Have you grown tired of living? If not, leave this one to the pros.

 

[cvairwerks]

It's not a hard process, but totally unforgiving of being sloppy or not adhering to some very specific safety rules. One of the tasks that I do at work is refilling some much smaller high pressure oxygen bottles. From near empty, a single bottle takes anywhere from 45 minutes to two hours per bottle, based on a number of factors at the time. Temperature and flow rate have to be controlled within a fairly narrow set of parameters, coupled with absolute cleanliness of the fittings and hose internals.

Unless you are going thru several bottles a month, you are better off changing to the bigger bottles and an appropriate cart to move them.

 

[laser3kw]

Unless you are going thru several bottles a month, you are better off changing to the bigger bottles and an appropriate cart to move them.

This^^^
I have a lot of experience filling industrial gases. Literally well over 100,000.
I would not recommend trans filling to anyone other than qualified, trained, fill professionals. Worse than PVC airlines in shop.

 

[Lwel9226]

Keep the 20 cuft full and ready to go portable when needed and use the 80 cuft for everyday use around your shop....
Best of both worlds....

LynnW

 

[rslaback]

This^^^
I have a lot of experience filling industrial gases. Literally well over 100,000.
I would not recommend trans filling to anyone other than qualified, trained, fill professionals. Worse than PVC airlines in shop.

Can you elaborate as to the dangers? It seems like such a straight-forward task with a few key safety parameters to follow: No oil based lubricants, slow fill rate, order of procedure etc.

 

[cvairwerks]

Cleanliness is the big one. Any type of hydrocarbon contamination can lead to violent results. You are dealing with pressures up to 20x what your average air compressor puts out. Temp changes due to rapid volume changes can start runaway problems. A small leak in a confined atmosphere can lead to an excessively high oxygen concentration. That will have catastrophic results should there be any ignition source. You have to be extremely careful in selecting hose materials due to material and pressure compatibility. You need to have a way to restrain both the supply and the target bottles that provides adequate security and cooling. There’s probably more if I sat down and ran thru all our safety stuff with a detailed reading.

 

[laser3kw]

^^^^

Cleanliness is the big one. Any type of hydrocarbon contamination can..............

X2

 

[cvairwerks]

Almost forgot the other huge one behind cleanliness.......STATIC CONTROL.....You can generate several thousand volts of static electricity if you have on the wrong clothing in certain atmospheric conditions. A 1kV spark when you touch something that provides a ground, will often not be felt by the person. As small as that 1kV is, it's enough to outright kill or induce latent failures in static sensitive circuits and is enough of a spark to ignite things in an oxygen rich atmosphere.

 

[rlitman]

Cleanliness is the big one. Any type of hydrocarbon contamination can lead to violent results. You are dealing with pressures up to 20x what your average air compressor puts out. Temp changes due to rapid volume changes can start runaway problems...

That contamination could be as little as a stray fingerprint. The rapid volume changes due to the differences in pressures involved can surpass what we see in diesel engines (and remember that we're talking about an oxygen enriched environment where autoignition temperatures are far lower than in air, so yes, it's 20x the pressure in your compressor, but 100x the partial O2 pressure), and can exceed the autoignition temperature of steel when gas is allowed to flow too quickly.

Plus there are other risks. Three people died in the incident described here (****) from a cylinder that had flash rust found on it interior walls due to probably air contamination because it was allowed to be completely emptied.

 

[dnschmidt]

Keep the 20 cuft full and ready to go portable when needed and use the 80 cuft for everyday use around your shop....
Best of both worlds....

LynnW

Clearly the best solution.

 

[BDT/NWMN]

If refilling small oxygen cylinders yourself was a safe and reasonable solution to saving money; Allot of people would be doing it. One more consideration in doing this would be to first review any DOT regulations that pertain to transporting ANY such cylinders on a public roadway... whether self refilled or not. Best to read up on this one.

 

[rslaback]

If refilling small oxygen cylinders yourself was a safe and reasonable solution to saving money; Allot of people would be doing it. One more consideration in doing this would be to first review any DOT regulations that pertain to transporting ANY such cylinders on a public roadway... whether self refilled or not. Best to read up on this one.

Is this you saying that there are regulations about this or that there might be/probably are?

 

[cvairwerks]

DOT has regs that come into place when transporting certain gasses and above certain quantities for anything but air. I don’t know the current limits, as I rarely transport anything more than a single cylinder these days.

 

[BDT/NWMN]

Regulations exist, but to what extent they are enforced in different jurisdictions is know to vary..

 

[cvairwerks]

Regulations exist, but to what extent they are enforced in different jurisdictions is know to vary..

Yep, varies quite a bit. Was going down the service road one day and noticed a guy sitting in a parking lot with a bunch of 100 pound propane cylinders. Didn’t stop, but wondered who he pissed off.

 

[Mallen]

Can you elaborate as to the dangers? It seems like such a straight-forward task with a few key safety parameters to follow: No oil based lubricants, slow fill rate, order of procedure etc.

I know this is a few years old, but I thought I would add this because it's directly relevant and hopefully anyone else coming across this and thinking the same thing will think twice. I used to work at a lab that did among other things, analysis of work place accidents. (More like disasters) One of the incidents that was investigated was an explosion of an oxygen bottle. It has happened at a hospital where they were refilling portable bottles. Two guys were doing it, and then one of them noticed that one of the bottles was very hot. It subsequently exploded, taking one man's arm off and I instantly killing the other. We received a box with the fragments of the cylinder. On the inside surface near what was once the bottles neck there was a area about 10cm across by 10cm in length and about 2mm deep that looked shiny and smooth. We didn't find any trace of contamination on the surfaces that could have caused it.

The final conclusion was that the bottle has overheated when filling and the surface of the aluminum, in contact with 100% oxygen had caught fire. The aluminum oxide layers porosity reduced the amount of oxygen that could get to the meta, eventually blocking it entirely but there was enough heat generated that the fire spread at edges. That caused the bottle to heat up until it burst.

Another interesting case of pure oxygen causing things to burn that font normally is the Apollo 13 incident. Due to a damaged relay, the wiring overheated and the Teflon insulation, in contact with liquid oxygen caught fire causing the tank to explode. Not something to screw around with.

 

[rsanter]

Interesting conversation and Information

I have a trans fill,hose (braided steel line) that looks commercial made.
I got it from an older guy I knew that filled his small bottle from his big bottle and did it many times.
I was never there when he did it so not sure his process

 

[cvairwerks]

You have to do the fill slowly and limit the bottle temp rise. When we do bottles at work, we limit our pressure changes to 200 psig per step. We also try and limit the temp rise to no more than 15 degrees during the fill. A 300 liter bottle needing a full charge can take us from 20 minutes to an hour depending on source bottle pressures and hangar ambient temp. We monior the bottle temp via IR temp gun, taking a reading every few minutes.