fill a tank at home?

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Can I fill a smaller 75/25 tank from a larger one?What is needed, a simple high pressure hose?The reason why I ask is because I use 300cf cylinders in my shop but my father has a small 110v mig. I gave him a small tank for it and I have it filled for him. The cost to have it filled is silly high compared to my larger ones. I don't care if it does not fill to max. I can simply fill it more often.Thank you for any replies, even the safety Nazis.Tim Beeker.
Reply:To a certain degree the answer is yes. It is possible to build a transfill whip to do what you propose however... (Read the rest below real carefully) I used to build this sort of equipment on a regular basis for diving so I know exactly whats involved.I'll simply copy my responce from the exact same question that was posted up in the past.http://weldingweb.com/vbb/showthread.php...light=transfil 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:Thank you DSW.I think I will pursue this farther.I actually fill hydraulic bladder type accumulators at work with dry nitrogen.To bleed the line after the valves are off we just crack the line.I will NOT be ever trying to fill oxygen. I do understand the danger.Tim Beeker.
Reply:Pm sent..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:Originally Posted by tnjindI actually fill hydraulic bladder type accumulators at work with dry nitrogen.To bleed the line after the valves are off we just crack the line.
Reply:Originally Posted by RaptorDunerComplete accumulator charge kits made in the USA are less than $500 and the correct bleed off fitting is less than that. I would have your employer look into them.
Reply:Think about a way to chill the small tank.I've got the kit that allows you to fill small propane bottles from the bigger BBQ ones. That is part of the procedure. We put the small bottle in the fridge freezer for a while before. Tad difference because it is in liquid gravity type fill. But If the bottle being filled is chilled, you should wind up with a wee bit more as the end result.
Reply:Originally Posted by CosmicRamblerThink about a way to chill the small tank.I've got the kit that allows you to fill small propane bottles from the bigger BBQ ones. That is part of the procedure. We put the small bottle in the fridge freezer for a while before. Tad difference because it is in liquid gravity type fill. But If the bottle being filled is chilled, you should wind up with a wee bit more as the end result.
Reply:I have an aluminum 20# co2 bottle with the valve swapped out for argon that I use for mobile TIG. I really like the size and convenient handle on the 20# co2 bottle. I fill it from my big bottle at the shop. I used to swap them, but I moved and the new LWS (rhymes with bear's ***) doesn't have this configuration, and I would have to wait (or plan ahead, god forbid) for them to fill it, usually about a week. I have a pretty basic set up with two male ends and a 3000 psi braided stainless hose to connect the bottles.Last edited by fortyonethirty; 10-02-2011 at 03:25 PM.Ian TannerKawasaki KX450 and many other fine tools
Reply:do you use co2 or argon in the bottle? I expect the bottle would explode under high pressure, so I suspect you are just using an argon regulator for co2?Dynasty 200DXPassport plus w/ spoolmate 100victor 315c oxy/(act and prop)Miller digital elitemilwaukee power tools
Reply:Co2 and argon bottles fill at same working presure.  Usualy around 22 to 24 hundred lbs.  modern air bottles for diving are basicaly aluminum also Mac
Reply:I monitor cylinder pressure when transfilling by using a Western tee with a standard oxygen regulator. The CGA-540 whip connects the cylinders and the tee allows use of the regulator to monitor pressure and for line bleeding. To bleed, crack the reg and the system will dump at low regulated pressure.  I never "suddenly" open high-pressure valves. I open the valve on the empty cylinder, crack the valve on the full one, and walk away. The pressures will equalize at leisure after which I close the cylinder valves, bleed the lines, and put everything away. We used the same tee/whip setup to gang oxygen cylinders for our cutting stations and argon cylinders for our TIG booths. Tees, fittings, and whips are reasonable.BTW, I transfill outdoors and wear safety gear including welding gloves, jacket and face shield. I have decades of gaseous and liquid aircraft oxygen servicing experience in the Air Force and know how not to go boom. My transfill whip etc. live in dedicated plastic bags and are stowed in a clean, dry location as is done in military tool rooms. No one else uses my gear. I don't get "up close" with it and I reach out full length to open and close valves.  I wear nothing with any oil residue.Everyone should see the Navy LOX safety film. It's no joke.Inert gas would be no problem, just know and observe the correct pressures for your equipment. Use properly rated fittings ALL of which you can buy from Western Enterprises who have many vendors online. Compare prices since they vary quite a bit.I prefer buy the nut/nipples separate and buy 1/4" NPT female-ended whips. It's not like individual owners will wear out lots of parts, but I prefer setups I can repair.I have been at ground zero with an O2 fire with a system similar to this where everything was done right and things still went wrong.
Reply:Originally Posted by farmallThat compressor piping wasn't behind armor or even basic metal shielding. That you posted it was excellent, but the shop should have provided you a safer workspace and PPE.
Reply:The aluminum bottle I use, I bought from the LWS, with argon in it, and the argon valve installed. I am not brave enough to mess with the valve on a gas cylinder. The pigtail I use looks just like the one farmall posted, it's rated for 3000 psi also and says that it was tested at 6000 psi. I always check the pressure in a new parent bottle with a regulator, before hooking up the hose to transfer. I am slightly casual with the argon, but I will not fool with any other gases, especially oxygen, I'd let the pro's handle it. On a side note, do CO2 mix gases liquify like straight CO2?Ian TannerKawasaki KX450 and many other fine tools
Reply:Farmall, great video - The Man from LOX!Rick V 1 Airco Heliwelder 3A/DDR3 CTC 70/90 amp Stick/Tig Inverters in Parallel1 Lincoln MIG PAK 151 Oxy-Acet
Reply:DSW, you forgot to sell him some continuing education.."..if you'd like to learn more about gas blending, then you should check out the PADI TEC/REC gas blending course..."
Reply:Actually I've had several friends who teach gas blending ask me to come and speak at their classes about what happened to me and how even being careful and doing things right is not a garantee to safety. That's part of the reason I've looked farther into what happened. Most teach NAUI for that, but almost all of them are NAUI / PADI / TDI instructors at a minimum.The good thing is that more and more shops now have the equipment and facilities to blend even basic nitrox, so the need for "home brewing" is decreasing. The bad thing is with the rise in rebreathers, more and more people are dealing with higher O2 pressures at 100%. A instructor friend of mine commented, that while on a trip he had a shop fill his alum 80 that he uses to trans fill O2 into his steel 2640 psi 26 cf clyders for his rebreather classes. The shop took a 3000 psi alum 80 to 3400psi with 100% O2.  Thats just insane!  He promptly dumped the excess down to a safe level.I've seen some scarry cyl's come in that are supposed to be "cleaned" for O2 service. I wouldn't even feel comfortable putting plain air into them. Our policy used to be if we didn't service them ( there were a few shops we accepted their O2 service also) we wouldn't fill them for high O2 contents..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:Assuming that the transfer pigtail fills with air between uses, wouldn't it introduce air into the cylinder being filled, eventually leading to contaminated gas in the filled cylinder?
Reply:Originally Posted by welds4dAssuming that the transfer pigtail fills with air between uses, wouldn't it introduce air into the cylinder being filled, eventually leading to contaminated gas in the filled cylinder?
Reply:Thanks to all for the info.DSW, I found a couple of Western fill whips on Ebay.Tim Beeker.
Reply:If you think all co2 cylinders run at the same pressure as argon cyls, you have another think coming check the shoulder stamps
Reply:Here's the skinny on shoulder stamps: http://www.airgas.com/content/detail...=7000000000243According to the shoulder stamp on my aluminum 20# co2 bottle it's rated for 1800 psi.Ian TannerKawasaki KX450 and many other fine tools
Reply:To get a full cylinder while trasfilling you need to cascade from at least 2 larger cylinders, DSW has done an excellent job explaining how cylinders will equalize and why you can't get a complete fill.  Here's a good and simple explanation and example from Poseidon Air systems: http://www.poseidonair.com/cascade/index.htm  In the fire service we transfill both 2216 and 4500 psi SCBA breathing air cylinders from both compressors and mobile cascade systems, never ever never is a cylinder filled that isn't in a scatter guard or fill station, these are large heavy duty enclosures that will contain a cylinder rupture or other failure of any component of the cylinder.  I'll add my 2 cents of safety warning here, I would not attempt to transfill any cylinder without the proper components (as in a purpose professionally designed system), there is just too much that can go wrong.