True reading of propane tanks

[rgolding]

In January, we were preparing for a trip to Florida. I had filled and closed the valves on the LP tanks in the Fall, but wanted to check them. Both showed empty. I run a marina that fills propane tanks. Took tanks off and drug out to the facility to weigh and top off. They felt full, but still second guessing what I already knew. Put them both on the scale and one weigh 58 lbs and the other 56 lbs. , gauges showed empty. (58 lbs is a full 30 lb. tank) Reinstalled knowing they were full. Headed south and as the outside temps rose so did the amount of fuel on the gauges. Used whatever fuel we needed during the 2 week trip and headed home with still having plenty of fuel in tanks. As we got north to freezing temps, the gauges once again started the false readings. Its true that the gauges don't read true in freezing temps. Grandpa always said, if we have enough propane to make it to summer, we've got enough in the tank to run until fall for the kitchen stove and the hot water heater.

[Denali2012]

I know that propane can ice up lines and gauges, I wonder if that is part of the effect here. Thanks for posting the information, it's good to know!

[rgolding]

I think it is just denser and and isn't as much a gas, but more liquid. I know back in the days before the safety stop valves that are now in the LP tanks, we had to fill by weight. If cold you could put a lot more in and then as it warmed up, it would start bleeding off as it expanded in the tank. Our big tanks (500 gallons) that we fill small tanks from will vent off through the safety presure valves as the weather warms if they were filled on a colder day.

[Fuzzybutt]

The reason being propane stays in liquid form at -42 or -44 degree's ( C or F its the same temp). the colder it gets outside the more energy it needs to turn from a liquid to a gas. It is possible to have no pressure in a propane bottle at that temperature as the propane stays in liquid form and does not gas off ( boil) to create the flammable Vapor. You could pour yourself a glass of propane. You would also need a larger bottle with more surface area in colder weather to be able to boil enough propane to run your furnace in a -30 to -40 temp weather or even wrap the propane bottle with heating tape to keep the flow of gas going. It is not unheard of freezing the regulators in cold temperatures and shutting down the system