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I Forge Iron

Gas on the brain


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I keep having a confusing problem with my forge. The LP tank keeps frosting over when I'm forging, so I have to shake the tank back and forth to get proper heat back in the fire. I could understand this if it were cold all the time, but I live in South Carolina. It was 57* today! Is this common? Or should I raise the tank up off the concrete floor? Help me!! I'm wasting time and fuel waiting on a good heat.

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A bigger tank is the solution,100# at least to run a forge.The frosting is caused by a compressed gas[any compressed gas] flowing thru a restriction i.e. orifice ,valve etc.When you cut the pressure the temp of the gas drops.The ambient temp does affect the flow but really only in pretty cold conditions or if the volume in the tank is low.The trouble with a warm water bath is that it won't be warm for long.A small oil pan heater might help.The cost would probably make a bigger tank a more viable option.You could get another small tank and just change them out,kind of a pain tho.

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You can also solve the problem by setting the propane tank in a garbage can of water. It don't have to be hot water right out of the garden hose will do fine.

As the pressure is relieved from the tank, it cools the remaining propane in the tank this continues till the temperature of the propane drops to near it's boiling point of about -44 degrees for pure propane. Once it has reached that temperature it will not vaporize. By shaking the tank you bring the liquid into contact with the warmer surface of the vapor space in the tank and cause it to boil to gas.

Keep in mind that what you are using is LPG not pure propane. It is a mixture of butane and propane, the further South you go the more butane is added to the mixture. Butane has a much higher boiling point that propane so it don't take nearly as much chilling to drop it to or near it's boiling point.

Placing the tank in water will keep the contents above the boiling point and allow the formation of gas. You will get ice freezing on the tank from the liquid level down.


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Just look into the bigger tank. Go down to your local gas store (praxair, airco, etc) and rent the Hundred pounder. It costs about $25/yr with a five year lease, and then the price of the gas is the same as it is to fill the 20#er, maybe even a bit less per pound. When you gotta lay out that first $125 or so, it seems high, but trust me, it's well worth it.

I went to a hundred #er, not because my tank was freezing, but because the xxxx safety flow check wouldn't flow high enough to run my big four burner. Iceing was not uncommon on the 20# on my smaller two burner, tho

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