Transfering Liquid Propane from one tank to another.

topic posted Thu, August 2, 2007 - 6:56 PM by  Knagi
So far my understanding of this is limited to, "Hey that's a really bad idea, don't ever try that"

I have the Adaptor to connect a 20lb tank to a disposabe tank, and after roaching ten+ 1lb tanks last weekend I have the drive (Vast amounts of waste and cost that is a priority to deal with). What I'm missing is the know how and understanding of what moving "Liquid" Propane from one tank to another consists of, what dangers and other such important bits.

What I hope for is to simply refill them disposiable tanks, or buy a nice tank I can refill off the gas station supplied ones.

posted by:
  • Unsu...
    Those little adapters are death traps. Those ittle cylinders are designed for sigle use.

    So the first big reason why refillingthose little disposable cylinders, has to do with the properties of propane. Propane like to expand and contract with heat just like any other material. Only propane expands significantly faster than the tank. If the disposable cylinder is accidentaly or unknowingly filled pat its safe full level, it can run out of room to expand. This used to be a common problem with 20 lb cylinders and trained profesionals, and now OPD (Overfill Protection Device) valves are required on all bulk cylinders smaller than 100 lbs. If the propane in the cylinder runs out of room, the pressure in the cylinder increases quickly and drastically. Something to the effect of 40psi per degree farenheit. Yes. 40 psi.

    If one were to accidently overfill a dispoable cylinder, with the temperature being say, 60 F one evening the tank would have a pressure of around 90 psi or so. but say the next day at eleven in the morning its now 70 F out. the pressure in the tank just went up and additional 280 psi. that's only a ten degree rise in temperature, but its pushing the limits of the cylinder design. Imagine what happens if three hours later its 102F outside. Its not pretty. the tank will rupture.

    Additionally, the little disposable cylinder is basically just soldered together. the solder joint was not designed to be repeatedly exposed to fill pressure then emptied and repeated over and over again.

    Those little disposable cylinders are cheap enough. Not worth the risk to yourself or others in my opinion.
  • also, once you refill those, you aren't allowed to transport them in a motor vehicle.

    If you watch the markets well, Primus and a few other European camp stove makers used to make 2-4lb cylinders that look like short bar-b-q cans. These are made much more solidly and are designed to be refilled. They don't have the OPD or whatever it is, but they are much safer and do fit in a backpack.
    • Drifting propane is illegal. Most if not all states require a license to handle any type of liquid propane transfer yes you can buy those adapters and you can own them but at least here in fl it is illgeal to use them ( plus they dont work worth a shit).

      When my propane guy was selling me all the parts not to make drifting hoses (that we would never dream of using ) to refill 100lb bottles from my 300lb bottle. he also explained about a type of frezze up on the valve I forgot the name but remember that type of explosion from fire fighter school its not a pretty thing the tank blows then the propane explodes.

      If your going to drift be careful.and remember propane is heavier than air its hasnt floated away its at your feet..
      • Ok So I have it's Illegal, Doubley so to drive it around.
        It's dangerous due to a rise in pressure with rise in temp.
        Released gases collect on the ground.

        I really like the primus tank, The first one I ran into carried a slogan of save money and the enviroment.

        So if it were filled in open area with no open flame then directly apply'ed to effects device for immedate use, this of course is never going to happen anyways since we are only talkin about the theory here, would all be well? I have the feeling that there are more dangers or possible ways to violently explode a tank unintentionally, I just want to be aware of them.
        • ok, look guys, heres the deal, those little 1lb tanks are rated for propane pressures, aka 300 psi working pressure and a burst of around 1000. you can refill them all day long. let them sit in the sun, boil them if it gets your rocks off. the only thing is unless you modifie them to relieve gas you will never actually fill them with liquid propane. bottom line i have done every kind of fucked up stupid ass experiment with those and i can tell you they are strong as fuck. in fact, i found one once that had been i a fire and had expanded to about 20% bigger and still had all its propane in it! yes, it is illegal to transport them if you fill them your self, but since the dont have accessible reliefs , and you cant really fill them totally full, who cares! dont tell the damn cop you filled them youre selfs. and, they are welded together, not soldered.
  • ok, you've heard all the warnings, and it still sounds like you're intent on doing this... lets say this again... do it by yourself, away from anyone else, and don't let that refilled tank near anyone else, so when it fucks up, you only kill yourself.... I work in Special effects, and we go through 10 to 20 of those tanks a day in normal use, and when were doing explosions, we intentionally rupture the tanks. Almost everything that was said in this thread is true, the exception being the fellow who indicated that you can put a tank in the sun and its fine... that is correct AS LONG AS IT IS THE ORIGINAL FILL AND CONDITION. IF you overfill the tank, it will explode if it gets heated. I teach workshops on high pressure liquid propane, and we NEVER overfill, and NEVER pressurize a retail tank. Technically it is illegal to refill any vessel not rated for propane, but I am licensed to refill propane under very specific conditions, which allows me to transfer liquid propane into CUSTOM BUILT PRESSURE VESSELS only. Please don't do this, its really not worth the savings... the tanks are maybe $4 ea? what are you using the small tanks for anyway? You can buy adapters that will allow you to plug a 20 lb tank into any appliance that uses the small 1 lb tanks...

    • yeah, thats true, if you over fill a 1lb tank an leave it int sun the pressure relief will blow.i came to the same conclusion that its not worth filling them unless you use them in a very specific application. i wont go into details but in one instance i needed to be able to fill a 1lb tank inboard to specific robot. ,
      really , yeah its kind of pointless. and personally i don't care who does or does not do it.
      have fun.
      • Unsu...
        True story:

        A long time burner (who shall remain nameless) and flame effect innovator with lots of experience was filling an empty tank of a flame effect with a LPG tank. He turned the tank upside down to get liquid into the empty tank. Well he apparently did not shut the LPG tank off well enough, so when he disconnected it, liquid propane started to squirt out. LPG is something like 40 degrees below zero, so the valve quickly got too cold to touch, then it froze over. Nothing to do but step back & watch the whole tank empty into the yard. Fortunately there were not any ignition sources nearby & it happened in the countryside.

        Also, while I'm at it, remember that propane is heavier than air so don't try refilling your bottles near a basement window or any boat hull type of structure.

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