Can you transfer gas from one bottle to another?

I'm a new guy on here but have learnt tons allready, thank you.Heres my first post, not sure if this is safe or even legal but I spoke to a guy who had a filler pipe to connect a large argon bottle to a smaller one, to transfer said gas from one to the other, very usefull methinks, he alleged they were readily available but I can't find any trace on the net. Do they exist? but more impotantly are they safe?
Thanks for your help.
Andy

Hi Andy, welcome to the forum.
This sort of question has come up time after time and the best answer is NO it is not safe! The pressures involved don't bear thinking about so unless you are fully experienced and equipped to decant gas it's just not worth the risk. Anyone doing so legally will be fully trained and have all the necessary equipment, it's not the sort of thing a diyer should attempt.

I was a commercial diver for 9 years and a sport divier for about 8 years before that nd regularly decanted from large bottles to smaller ones using compressed air at 230-300 bar, so as Wozza implied yes it can be done. Divers do it all the time, and most of them cack themselves every time they do it. Even a burst O ring, puts the the fear of god into you.

My advice is dont.

You need to use only the proper hoses and fittngs rated for this pressure involved. You cant let the cylinder overheat (and they heat up very quickly if you get it wrong), or letting the gas pass too quickly from one bottle to another, or using a cylinder that hasnt been checked for safety or numerous other things.

The last thing you need is a hose to burst or come loose at high pressure turning a large cylinder into a f****** huge catherine wheel with you stood close by with a 1m hose or more thrashing about until the cylinder is empty with it destroying everything in its path, and it will and nothing will stop all that stored up energy until both cylinders are empty (cos the one you are decanting into will want to empty its contents as well).

And you have to be near it to assess how fast the gases are transferring and to constantly adjust the transfer rate - bit of poisioned challice.

Very very dangerous.

Ive had numerous hoses burst on me underwater, it hurts, even with the damping effect of the water. Fortunately they were only ever the low pressure hoses that burst or broke free from their fittings, and they were only at 20 bar or so, it still hurts when you get hit round the back of the head with them even with a huge diving helmet on and you cant grab the hose cos its moving too fast with too much energy in it - all you can do is wait for the cylinder to empty.

Even though Ive been trained and done it for many many years I still wouldnt do it to save a few pounds - Ive seen the safety videos of what happens when it goes wrong and sooner or later it will.

If I was to do it now, I would have so many safety precautions in place to allow for the event of it going wrong, that it really wouldnt make it worth while to save the money.

Im sure a google search will find lots of examples of it going wrong.

Steve

Nice one Steve, very informative. Something makes me think this won't be the last time this gets asked though, people seem willing to try pretty much anything in their quest for cheap shielding gas.

Look at the pressures involved here folks, 200 BAR is 2940 psi which is 100 times the pressure of the average car tyre!

We all hate paying rental on cylinders which sit idle most of the time but there are now people offering non-rental deals on industrial gases, Adams Gas being one inparticular, pay a deposit, no monthly rental, once you've used the gas pay for a refill and you're away. What could be easier and safer than that for a low-volume user?

I think it might be a good idea to have a 'sticky' in the shielding gas section covering cylinder types and sizes, capacities, mixes plus safety advice. What does anyone else think?

Thanks guys, the joys of the internet and these forums, I always seek out expert advice before dabbling.

I dare say people do it Andy but is it really worth messing with something that could effectively be a bomb? I think not

The hoses and fittings are readily available, but not for that purpose.
Like Woz has said, it shouldn't be done.

I think it might be a good idea to have a 'sticky' in the shielding gas section covering cylinder types and sizes, capacities, mixes plus safety advice. What does anyone else think?

Good idea wozzz this is an endless question...... maybe something along the lines off "dont f**K with cylinders" could do the job........Or a less direct message sticky could be a link to BOCs cylinder safety web pages.

Good idea. We can stick this one for now - Steve's input especially is very informative.

If anyone fancies writing a post like Wozzaaah suggested we could stick that instead and link it to a load of other posts in the shielding gas section. I don't have the experience to write it myself.

Oxygen under pressure can be explosive in contact with any oil bases.... Acetylene becomes unstable above 2bar pressure & can combust in contact with copper... not got the time (or full in-depth knowledge) myself I'm afraid... just put it down as a NO!
weldequip

Oxygen under pressure can be explosive in contact with any oil bases.... weldequip

Ohhh so a rub round with an oily rag to make them thread's nice is not the best idea then...

I've seen worse

I've been a sportsdiver for over 20 years now and compressed air bottles still scare the hell out of me and so do Argon/CO2 bottles. Treat them with respect and allways tie them down. You do not want a potential bomb to fall over and damage/break off the valve...... There have been a number of well documented accidents here with both compressed air and welding gas cylinders that fell over. One cylinder litterally took off, went through a brick wall and ended up in the living room of an elderly couple across the street. 200+ bar of pressure deserves a lot of respect.....I would not encourage crossfilling cylinders unless you really know what you are doing. Do not mess with cylinders fom the scrapyard (some idiots use rejected scuba cylinders for CO2 storage..yes sir it's cheap

Regards, Robert

(some idiots use rejected scuba cylinders for CO2 storage..yes sir it's cheap
Regards, Robert

WHAT????!!!! crazy guy's

i had one of my friends think he could use a propane tank for co2 for his welder good thing i stopped him...... i don't even want think of what would of happen.

Yep, seen the photos of a 3l 230 bar pony cylinder that had had internal rust. It was only a year or so old, and in test, but literally ripped apart and destroyed the roof of the filling station. As I understand it, a 12l 230 bar dive cylinder contains about the same energy as you get in 2 hand grenade explosions. Bit scary when you have 2 strapped to your back, with only a thin steel plate between you and them.

Phil (Sports diver)

As Steve and Roop have said but will add to that.

What you cannot see is the fundamental flaw with anything containing pressure. Treat it with respect.

I do have 12ltr 300bar and 232bar 3ltr and 10.4ltr divers bottles here and it scares the sh.t out of me every time i open up that 300 bar to decant in to the 3ltr to about 205/210bar. All aluminium one needed the crack test 8 years ago due to wrong grade of aluminium found out 5 years after manufacture!

As part of what i do i design and build pressure orientated things, each one hydraulicly pressure tested to at least 3 times the operating pressure. The most dangerous are the cnc derived production/ kick it out manufacturers and those from China not governed by any law. Operating pressure on one for instance is up to 200 bar, the cylinder will permanently deform at 240bar due to the thin wall thickness. The way they get round it is to use blow off discs, but its not right.
The tube/cylinder may be ok, what about everything else, fittings, hoses, threads, etc.

Come very very close to getting it on what other people have done but looked visually ok externally! One legit trader put a 1/4"bsp male thread with a 1/8"bsp female up the inside in brass with 2lb of steel hanging off it. There was a problem to diagnose somewhere and two of us were looking down this cylinder seconds before it went. Luckily only 120bar in supposed to operate up to 232bar and took a couple of bricks out, not nice.

Back on track, even if you know what you are doing i would advise against it, novices and general users dont think about it which for at least 85% on here would be a big no, i have seen what happens even at 30bar with about 2cc. Thread fittings come in various pressure ratings, even a someone that deals with such can very easilly pick the wrong one up. Plan on the unexpected, it probably wont be your life but others 100's of yards down the road!

If you dont believe me theres some nice pictures knocking about on some US sites, lost the links it was around 6 years ago i had a look but none the less entertaining.

Anyone thinking of doing some moonlight filling of their gas bottles should have a look at the mythbusters episode where they blow holes in walls with gas cylinders, I think it's season 4, episode 21

Excellent episode! If that doesn't put you off having a go, nothing will!

Not getting put off by that episode is natures way of telling you that natural selection has picked you for the B-team ^^

filling bottles

Just looking to find a refill for my toy mig
Originally supplied with a disposable cylinder then converted to pub gas. The local brewery distribution center would exchange the Co2 cylinder for under a tenner, until it closed down. Another source was to get the cylinder refilled by a firm supplying car panels and hand tools Co2 was decanted from a large cylinder into a small cylinder via a hose while you waited!
Now need to find a reliable, safe and legal source for the occasional diy job.
I actually resorted to using a fire extinguisher when the pub gas ran out the outlet connection had the same thread but required a mole grip on the operating handle! Would this provide a effective, legal and cost effective source of the required sheilding gas?