[A/S] Another propane cylinder answer

["tdickieson" <lleather@xxxxxxxx>]

Arnie asks

  "If you start with a new empty tank or one that has been revalved, 
and the valve is open and you attach the fill hose to it and pump in 
liquid propane to the 80 percent of the water capacity of the tank, 
where does the air go? And if the 20 percent void doesn't have air in 
it, what is there? A tank that is over filled will sometimes freeze 
because liquid propane gets into the valve."

Okay - If done correctly, a new tank or a revalved tank is partially 
filled with propane.  Air being lighter than propane vapor, will rise 
to the top inside the tank, where the refiller will then purge it 
from the tank by allowing it to escape past the valve.  Once propane 
vapor begins to vent, the valve is closed, the tank is reattached to 
the fill nozzle, and the fill is completed.  This gets rid of the 
air. Now the cold.  When propane liquid converts to a vapor, it 
reduces its temperature to about 80 degrees or more below zero (I 
don't remember the exact temperature, but awfully cold) If this 
conversion is being done inside the valve because the tank is too 
full, then moisture from the ambient air around the valve, which 
cannot any longer contain this moisture, condenses and freezes on and 
in the valve, because the valve is metal, and thereby attracts 
condensation. (cold air can not contain as much moisture or humidity 
as warm air by content, even tho the humidity percentage may remain 
the same)