Cross-filling welding bottles ?

[bcarwell]

I am <not> interested in filling a little oxy-acet welding bottle from a big bottle directly at full pressure due to safety issues (I understand you need high pressure steel braided hoses, a pressure gauge between the two, etc., etc., though I understand people do it, called "cross-filling" ?).

But I did wonder if its possible to fill a little bottle from a big bottle through the big bottle's regulator set to max pressure (80 ? whatever) ? I realize you wouldn't get much of a fill, but is this ever done and how much welding time would you get out of it ? A minute ?

I have a friend who has gone to the poor house refilling the little bottles at the welding supply store, since there is a base fee for filling anything. But the portability of those little OA rigs seems so nice if you just have to fix a small bracket or fence post etc. remotely- IF you could just figure out how to keep the little bottles filled cheaply.

Maybe propane welding is the way to go for this, but I understood from an instructional tape I saw that propane can be used for cutting torches but isn't so "hot" for welding literally- propane doesn't get hot enough for most applications.

Any thoughts ?

Bob

 

[MadReferee]

This is the type of question that should be asked of the welding professionals on one of the welding specific forums. I personally would never take seriously any advice on this topic that I got from any tractor forum, especially when appropriate manufacturer welding forums are available. The safety issues alone are more than enough to want a professional, experienced opinion.

Try asking your question on either the Hobart or Miller forums. If I am not mistaken, a question similar to yours was asked and answered not long ago.

Miller welding forum

Hobart welding forums

 

[Ford960]

Owners of high performance aircraft do this on a regular basis if they rely on the portable O2 systems to fly at higher altitudes. They will get a large bottle of O2 from the welding suppy house and then refill the small bottles used in the plane. In the pilot community it's well known.
To that end, several years ago I was selling items on Ebay and my best sellers were the O2 regulators that I could buy for a song at the local thrift shops...they were always bid on by pilots.

So to answer your question, yes you can refill the little bottles from a large one and you will get a decent fill that will last almost as long as from a welding supply house. The standard pressure will be 2200 psi and you can get the braided lines to transfer the O2. BTW, I'm a weldor.

I've also done this while working for a large fire dept. We had a cascade system to transfer air to the small bottles for breathing systems at 4000 psi.

Try not to "flash fill" the bottles but fill them slowly like a couple of minutes for each bottle.

 

[sandman2234]

I am <not> interested in filling a little oxy-acet welding bottle from a big bottle directly at full pressure due to safety issues.

Any thoughts ?

Bob

Yes, and no.
Yes, with the correct equipment you can fill an Oxygen cylinder from another one, or another two, which is the way I have done it. I got a set of steel pipes with fittings from a company that fills bottles commercially. They were fixing to throw it out, and I ponced on them.
As far as trans filling acetlene, don't make that mistake. Yes it can be done, but not safely by your average welder or tractor owner. There are several things to be aware of, and making a mistake with that gas can be extremely hazardous to your health and home/shop.
Why not just buy or lease a larger set of bottles and be done with it?
David from jax

 

[earthface]

NEVER I SAY NEVER Refill an acetylene bottle by pressure transfer. This gas will EXPLODE at a compression of over 30 psi if not desolved. This gas is DESOLVED in acetone and when filled into a tank it is PUMPED as a liquid. The reason the Acet tanks are so heavy for their size, there is a pourous core inside that the gas resides in. In the old days of carbide converters there were many spontainous ignition explosions of these units for over pressure.
Oxgen is a different story. It can be pressure pumped (bled) from bottle to bottle. Your hose/tube needs to be extremly CLEAN FREE of ANY oil or grease. They in the Aircraft industry are usualy clead after EVERY use, in a OIL free solution in an ultrasonic cleaner.
Your hose/tube should have a gauge and back flash protectors on each end. Use bleeder nuts to protect against high pressure blast when removing filler tubes. Always SLOWLY open valve of the feeder tank, with the empty tank open. Shut the filled tank first then the feeder tank. WEAR SAFTEY GOOGLES and CLEAN leather gloves always look off /away from the line when opening the feeder tank. A full tank 2200 psi, of Ox will SLICE an eye or flesh of the bone. This is not a job for the untrained or newbies. You need instruction to do it safly. People who do it on Aircraft are certified with much instruction. I have seen Aircraft (737) burned to the ground from improper handling of Ox during transfer fills.
Also if the tank being filled is very small it should be put in cold water as this tank will get HOT.

 

[sandman2234]

Thanks for backing me up on that earthface.
By the way, even larger bottles (120 cubic feet) will get hot if you try to transfer the gas too fast.
David from jax

Never cross fill acetylene, ever.


Never take a torch to an acetylene bottle either, although I have made some really good money doing it as a contract job for Uncle Sam. Bet that will make a lot of people wonder...
David from jax

 

[bx23barry]

What sandman and earthface said, Xs infinity

 

[mboulais]

I've never seen a local shop that filled those little bottles onsite. I drop my empties off and pick up full ones. the fee is per pound I think, but since the wieght in a full bottle doesn't change, it amounts to a flat fee. I think it's like $30 a bottle (I've only replaced them once in the last two years, about 6 mos ago)

 

[AnotherBueller]

Owners of high performance aircraft do this on a regular basis if they rely on the portable O2 systems to fly at higher altitudes. They will get a large bottle of O2 from the welding suppy house and then refill the small bottles used in the plane. In the pilot community it's well known.
To that end, several years ago I was selling items on Ebay and my best sellers were the O2 regulators that I could buy for a song at the local thrift shops...they were always bid on by pilots.

So to answer your question, yes you can refill the little bottles from a large one and you will get a decent fill that will last almost as long as from a welding supply house. The standard pressure will be 2200 psi and you can get the braided lines to transfer the O2. BTW, I'm a weldor.

I've also done this while working for a large fire dept. We had a cascade system to transfer air to the small bottles for breathing systems at 4000 psi.

Try not to "flash fill" the bottles but fill them slowly like a couple of minutes for each bottle.

SCUBA shops do the same thing

 

[yomax4]

Usually you are better off with a manifold system of various pressures in the tanks. and fill in steps with the small tank in a bucket of water. They get hot when you pump 2200# of pressure in them. Go slow so they don't blow was always the saying when I did helium transfills at a local welding supply I worked at.