Refilling small c-25 bottle from a larger one

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Anybody ever do it? If so, what does your rig look like?Ive worked places where we had central manifolds for gas, so I figure this would be about the same.Im thinking that I might be able to rig up a hydraulic hose between the tanks, open the lower pressure tank, then the higher, and the two should eventually end up at the same pressure (the average between the higher and lower pressures).Am I missing something? I know about the obvious risks from high pressure gas, but is there something else Im missing?The reason I want to do this is because I have a larger lease bottle of C25 and a small owned bottle of c25. It costs basically the same to fill either bottle although one holds 3x the gas!I figure I can save a bit of money by only filling the large one, then dumping some gas into the small one when needed. Am I crazy, lol?
Reply:if you do a search on here this has been covered a few times search keyword transfillMiller Xmt 350Lincoln Ln-25Ahp 200xSmith Gas Mixer AR/HTig is my Kung FuThrowing down dimes and weaving aboutInstagram http://instagram.com/[email protected]
Reply:May I ask why you want the smaller bottle instead of just using the bigger one? Is it a portable setup and the smaller tank is easier to move around or am I missing something? Sent from my Galaxy Nexus using Tapatalk 2
Reply:Originally Posted by WookieWeldingif you do a search on here this has been covered a few times search keyword transfill
Reply:Originally Posted by SpeedracerbubbaMay I ask why you want the smaller bottle instead of just using the bigger one? Is it a portable setup and the smaller tank is easier to move around or am I missing something? Sent from my Galaxy Nexus using Tapatalk 2
Reply:I have done it with nitrogen bottles at work  I just mated two hoses and opened the little bottle then the big and them turned the regulator on the big bottle till I was 100psi below the little bottles MAWP. It works great. The little bottle is for an echometer gun to Test fluid levels in our NG producing wells an since it's all about safety i have one big bottle mounted up in a wellhouse and I take the little bottle to the other well pads which are about 10 miles apartMiller Syncrowave 210 w/CK FlexLoc 150  3/6/14ESAB PCM 1125 Plasma CutterAtlas 12x36 LatheACER 9x42 3hp millHarig 612 Surface GrinderDRINK Machine              welding&fabrication
Reply:I built a hose to do it, but have never used it.  My plan was to bleed a little gas, then tighten fittings and top it off.  i don't see why it won't work as long as you don't run the small one 100% empty and you bleed gas through the line.  I fill O2 cylinders and SCBA cylinders all the time for the fire dept that way. Stilll pay attention to the hydrostat and inspection dates.   At that point go ahead and exchange it.
Reply:Originally Posted by blackbart As long as you don't run the small one 100% empty.
Reply:CO2 is a little different than other gasses like argon, nitrogen etc. It will be in liquid form at higher pressures. It will also have a big cooling effect when you depressurize it.I have transfilled argon, helium and other gasses more times than I care to remember and each gas have their things to look out for but I would be very careful with C25 due to the CO2 content. Perhaps check with someone who fills fire extinguishers and such who have experience with CO2 at high pressure.
Reply:I've done a lot of transfilling over the years, mostly for mixing dive gasses. It's seldom cost effective however. One important thing to keep in mind is that everything in the system has to be rated for high pressure. Standard Home depot parts and fittings won't cut it. They will literally explode like a grenade at high pressures used when transfilling. Also keep in mind cylinders equalize by pressure, not by volume. Rather than retype all of this, I'll just cut and paste what I've posted up before on this subject... Originally Posted by DSWYes it's possible with a few issues that need to be adressed. One: Unless you know 100% what you are doing NEVER TRY THIS WITH O2!! If you get even the least bit of oil, dirt or other contaminant in the valve or transfil whip it will blow up on you. Like as in killed dead. This is not an area to be cheap on. I doubt you want to do O2 but it's for others that might think this is a good idea. It's not.Note it will cost you a fair amount to build a transfer whip to do inert gas. All parts must be rated to at least 3000 psi. Your 2 inert gas nipples and nuts will set you back probably $30-50, You'll need a couple HP couplings, about another $15 last time I got some, and then the HP line. The last one I got set me back about $50. You will need some sort of bleeder to relieve the presure in the line so you can unhook it. These are not standard parts that are easy to locate. The only simple ones I'm aware of come from the supplier I get SCUBA stuff from. They run $100 each. A HP tee and HP valve would work also but will end up costing as much or more. So you end up with close to $150-200 in parts... Oh and if you try and go "cheap" with standard pipe fittings... Remember they will act like a grenade when they blow since at best they are rated at 150 psi and you are standing at ground zero. And they WILL blow, no ifs, ands or buts! There's a good reason HP fittings are not cheap.Oh now it gets good. Cylinders equalize in pressure, not volume. So if you want to "fill" a 20cf from a 200cf ( a 200 makes my math easier to work out) you can't just subtract 20 from 200, then 20 from 180 and so on. (thats assuming pressure on the 200 is at max to start and not 1/2 full) The 1st  "fill will get you about 18 cf if the fill is done very slow so the cyl stay at the same temp. Note the small cyl will heat up as the gas is compressed so in reality you get maybe 16cf. The next one will only get you maybe 13cf. by "fill" #4 you would be lucky to get 8 cf  in the 20 and thats assuming best conditions the 20 is dead empty and the 200 was only used to fill the 20cf cyl. The numbers are slightly better if the big cylinder is larger, say a 282cf, but you only get maybe 2 more fills at best. If the bigger cyl was a 100cf it's much worse and you won't get more than 2 so so fills at best.That means for your $150-200 expenditure,+ $30 fill on the large cylinder, you get one semi good fill, 2 so so fills and one that won't get you 1/2 and hour of weld time. For the same $200 lets say, you'd have gotten 10 perfect fills. A better option is to get a 2nd larger cylinder and use the 20 only when you have no other choice. In that case that same $200 in gas would have netted you 6 times the gas that getting the10 small cyl would have gotten you if you swapped, vs the 4 fills you got in partial amounts transfilling.I mix gas for diving and I have to do this regularly in remote locations. It's very inefficient and not usually cost effective, but it's the only option some times. The only way to make this work well is to have several large cylinders and cascade from each as the pressure drops. That adds a lot of cost and some more waste as you dump lines between swaps. For most this is a very poor way to "save" money..
Reply:DSWI fill O2 cylinders all the time (weekly for 30 years).  I have a hard plumbed (pressure rated) hard line and go from a low cyl to a higher one (like a manifold,but manually) am I missing something?  Obviously there is no sealant or oil, I do it for all the local fire depts. So I have 3 big bottles, I start filling with the low one, disconnect and reconnect on the next, saving the high pressure tank to top off the small cyl.  I do the same thing with SCBA and SCUBA rescue air tanks, but I use a manifold connected to several tanks. Those are twice the pressure and I do them in a safety tank. Those have a serviced compressor rated to put out 5000PSI, depending on the tank.  I did build a HP whip hose to fill C25 tanks, but have yet to use it.Last edited by blackbart; 06-12-2013 at 12:43 AM.
Reply:I've now refilled a C18 into smaller bottles with a transfill whip. Bottle comes at 3000 psi so the partial pressure of the CO2 is 540 psi. At that pressure and at room temperature all CO2 is in it's gas phase, not liquid.It worked out fine but I filled slowly because the gaslines and valves got very cold.
Reply:Originally Posted by Pete.S.I've now refilled a C18 into smaller bottles with a transfill whip. Bottle comes at 3000 psi so the partial pressure of the CO2 is 540 psi. At that pressure and at room temperature all CO2 is in it's gas phase, not liquid.It worked out fine but I filled slowly because the gaslines and valves got very cold.
Reply:Originally Posted by shovelonThat is the one thing that scares me Pete. I too  transfer very slow, but the hoses and fittings get very cold. I keep wondering what would happen if the braided hose gets brittle enough to crack. BAMM!