Originally Posted by idroba
Propane in the tank is a liquid and changes to a gas (evaporates) to supply the system. It takes heat to evaporate the liquid to a gas. When it is very cold outside and you are using a lot of gas, the surface area of the tank is not large enough to heat the liquid so it evaporates. The liquid actually freezes solid in the tank and the evaporation to gas stops. The lower the level of propane in the tank, the easier it is to freeze the remaining propane.
You can gently heat the tank (say with a small heater or a light bulb) to heat the propane and un freeze it until it is all gone.
Just a little correction... Propane freezes at -356 degrees Fahrenheit, so you're not getting a solid chunk of propane in your tank. What happens is that as the liquid propane evaporates, it draws the tiny bit of heat left in the cold air out (same principle as an air conditioner uses, or the reverse of a heat pump) which does cool the remaining liquid propane even lower, which makes it evaporate slower, this supplying less gas to your appliances. The faster you draw it, the colder it gets, so the slower it evaporates...The advice on heating the tank does work. We use a water hose to safely warm freon tanks while working on A/C systems in cooler weather down here in Florida... You can use your torch set, but the pressure rises pretty quickly that way.
-Red, been to school on this stuff...