Cascade system for filling small gas bottles

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Anyone have advice on how to setup a cascade system to fill small 20CF argon and 75/25 bottles?  the cost to exchange them locally is crazy for the cost of the gas.  I would like to be able to just run a hose from my 300CF to the 20 to fill it..   I can get the correct fittings from the LWS,  just not sure what type of hose to use? and where to get it.  I had my 40 filled in CA a few times this summer and they just filled it via a cascade system...Tiger Sales:  AHP Distributor    www.tigersalesco.comAHP200x; AHP 160ST; MM350P,  Spoolmatic 30A; Everlast PowerTig 185; Thermal Dynamics 60i plasma.  For Sale:  Cobra Mig 250 w/ Push-pull gun.  Lincoln Wirematic 250
Reply:http://www.tradera.com/pafyllningsdo...2448_166071025These old kits have been sold here in sweden for some time now, it is military surplus meant for filling small tanks with oxygen for medical use from a large tank - but the welding tanks have the same connections. A gauge to show how high pressure you get, a steel braided high pressure hose (important!) and two connections that fit the tanks. The instructions have some diagrams showing things as how many small tanks can be filled to diffrent pressures from one large tank, how the pressure varies with temperature, probably not very important for you but critical for medical use and small "medical" tanks rated at half the pressure of a full large tank. Just remember that as the pressure goes down in the large tank, so will the maximum amount of gas you can get into the small one. At half pressure, it can't give you more than half full - but still, probably alot cheaper than filling them locally now.The seller has suggested using adapters to make it fit tanks for other gases, but in your case, perhaps it is mostly useful as inspiration.
Reply:You're going to need 3 or more large tanks of gas to set up an effective cascade system, plus the necessary high pressure flexible lines and T fittings to connect them together. You will also need a charging line with a gauge and a tank adapter fitting to allow connection of your smaller tank. Your LWS should be able to set you up with everything you will need plus the basic training in it's proper use and safety.A cascade system consists of 3 or more large tanks connected together with high pressure lines, with an additional line to the right with a gauge to connect to the tank to be filled. You start the filling process by gradually opening the large tank on the right, nearest to the small tank. When the two tank pressures have equalized, you close the valve on the large tank. Then you go to the next large tank to the left and gradually open it. Again when the this tank and the small tank pressures equalize, you close the valve on this tank and then go to the next tank to the left and repeat the process, each time raising the pressure on the small tank until it reaches the pressure of the large tank. You do this until you have raised the pressure in the small tank up to the pressure contained in the last large tank. Remember to fill the small tank slowly as it is experiencing significant strain and heat build-up in this process. For safety, many gas filling stations have a large heavy metal can that you place the tank being filled into. This is done to contain the shrapnel and direct the blast upward in case the small tank being filled explodes. You absolutely don't want this to happen.As you draw off gas from the right tank you are removing the largest amount of gas, so it's pressure will drop rapidly as more and more small tanks are filled. Then when each additional tank is opened, the volume required to raise the small tank's pressure is less, so the large tank's pressure will not fall as much. You are  removing lesser amounts of gas from each tank as you move to each higher pressure large tank.  You must remember to never open more than one large tank valve at a time and work from right to left as you open them.or the large tank pressures will equalize and ruin your ability to use the cascade effectively.It's time to add a new large tank of gas to the cascade system whenever you can no longer fill the small tank to it's proper pressure. To do this you remove the tank with the lowest pressure from the right, move all of the remaining tanks one position  to the right, and then connect the new full tank on the left end. CharleyMiller MM252Miller Bobcat 225NTMiller DialArc HF / DIY Cooler2 Victor O/A TorchsetsMilwaukee 8" Metal SawMilwaukee Dry Cut "Chop" Saw 5 Ton Wallace Gantry Various Grinders, Benders, etc.
Reply:You may be looking for an inert gas transfer hose system. A transfill system can be purchased complete at BR welding supply. Building your own without having any experience is very dangerous. This is the one I bought and works perfectly.Western Inert Gas Transfer Kit TR-1http://www.brweldingsupplies.com/wes...sfer-kit-tr-1/Weld like a "WELDOR", not a wel-"DERR" MillerDynasty700DX,Dynasty350DX4ea,Dynasty200DX,Li  ncolnSW200-2ea.,MillerMatic350P,MillerMatic200w/spoolgun,MKCobraMig260,Lincoln SP-170T,PlasmaCam/Hypertherm1250,HFProTig2ea,MigMax1ea.
Reply:To fill from a 300 cf tank into a 20 requires a high pressures SS braided line or something similar in copper, HP fttings you can purchase at any LWS.  In that line you will need a HP guage able to read up to 1800 psi. The problem once the large tank drops below 1800 psi you no longer be able to completely fill the 20 and you will all ways have some lost residual in the large tank. The LWS uses Cascade for small tanks because they do not pay alot for the gas and there fore not much loss waste.  Shop around see if you can get a lower price.
Reply:Price for that transfill whip looks about right. I couldn't build them for much less even getting the parts wholesale when I worked at the dive shop.Charley pretty much covered the description of a cascade well.I've covered this in the past. Rather than retype what I've posted before, I'll simply cut and paste... 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:Having a bleed off capability (and rehearsed method to do such) to clear the whip hose and connected fittingsof residual air-prior to starting the fill helps to maintain gas purity.Blackbird