Propane fill question
OK I am officially confused. I took one of my 40lb. propane cylinders out of my new RV to have it filled. A note on the door of the propane compartment said do not fill over 80%, could cause fire,e...
Forum Discussion
dougrainer wrote:RinconVTR wrote:wnjj wrote:
The reason for not filling the garden sprayer to 100% is a functionality one. The reason for not filling the LP to 100% is a safety one. They operate on completely different principles.
No sir. They are the actually pretty similar in principle.
Go ahead and fill an LP tank 100%, it will not be functional for long due to lack of pressure. Liquid...it doesn't compress, remember? And LP will not remain a liquid, unless its under pressure. It requires a volume of "air"...under high pressure...for the tank to function.
SO that 20% is not just there for thermal expansion (safety), its there for pressurization as well. Just like the garden sprayer.
And that 20% is not a magic number, it can be much lower for these tanks to operate, don't get me wrong. The expansion rate of LP is very high. The US has very strict, protective rules, as we all know.
THERE IS NO AIR IN A LP TANK/CYLINDER. There is only LP vapor that is produced from the LP liquid in the tank. Soooooo, for a 100% full liquid tank, there is NO ROOM for the Liquid to vaporize. As I stated, 100% liquid will cause Liquid to flow OUT when the tank valve is opened and that will destroy the LP regulator. Doug
If you have a full container of liquid under pressure, the second you open the valve there is an increase in volume (the hose) which will drop the pressure rapidly. The first liquid to enter the hose will immediately boil off to gas. Now if the cylinder was at such a high pressure that adding the hose volume doesn't drop it below vapor pressure then liquid could flow to the regulator.
