Motorhome Propane Tank Question

Guest Post

Propane Tank Question

...a still relevant question answered at a rally years ago by Miles Hartmann, a former Service Rep with the defunct Country Coach, Inc

We had to “burn off” a third of a tank of propane in order to have the fuel gauge replaced. The shop said the tank had to be empty before the gauge could be removed. However, after the gauge was replaced and before the tank was refilled, the stove would light? We cooked dinner in fact? How could this happen?

 

A 40-gallon tank with four gallons of liquid propane has potential to create 89 pounds of pressure when fully gassed. Propane boils at 44 degrees F. When liquid propane is sealed in a tank and the temperature rises above 44 degrees F. pressure is being built up. Just as a pressure cooker builds pressure when the water boils, the only difference is the temperature required to start the liquid to boil. Any time the temperature is 44 degrees F. or higher a tank with liquid propane will continue to gas and build pressure.

When a propane tank is evacuated or burned off quickly, the tank’s temperature drops to below 44 degrees F.  This causes the liquid propane to cool below its gassing point. At this time, even though 10 percent of the tank’s capacity is still in the tank in the form of liquid propane, the internal pressure will be near zero

 

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