How to Size Propane Gas Tanks

Both boil-off rate and use rate need to be taken into account. In cold weather one would need a larger tank for butane than propane for the boil-off rate to keep up with the use rate.

Doesn't the rate of use govern how fast(rate) the gas boils off the liquid. If the rate is too fast the temperature of the liquid drops. With that you will also have a drop in line pressure. What you are looking at is the surface area of the tank in order to absorb heat at rate of use to keep a consistent temperature in the liquid so pressure doesn't fluctuate much.

It is easer to just use a vaporizer to replace the heat lost to vaporisation.

A vaporizer is kinda like a water heater. Some are electric, some are gas fired.

The surface area of liquid gas in contact with the tank and the ambient temperature will be the limiting factors for the boil off rate to sustain the minimum gas pressure acceptable for plant operation.

As such the tank should be sized to keep operations going until you are about down to 10% capacity , or in large installations switch over to second tank or use externally heated evaporators.

Garth.

It does not have anything to do with boil off. Propane tanks are build strong enough that as the pressure builds the propane is under more and more pressure until the pressure itself will prevent any vapor form forming.

All propane tanks are permitted to be filled only to 80% of capacity. Propane has a very large coefficient of growth. If you fill your tank when it is very cold and then you have a hundred degree day - the liquid propane will grow a great deal. Liquid is not compressible and then the tank might rupture. this is prevented by only filling to eighty% leaving the 20% to abbsorb the growth!

The vapor pressure of propane (C₃H₈) depends on temperature. Vapor pressure of 100% propane at temperatures ranging -30 - 110^oF (-42 - 43^oC) are indicated in the diagram and table below:

This is the maximum pressure at each of these temperature. and the pressure is depend of ambient temperature.

An important property of propane is the expansion of liquid as it is warmed. Propane's volume increases about 1-1/2% for every 10°F (5.5°C) it is warmed. Heat the propane 100°F (55°C), and the container liquid volume will increase 15%. And again the volume is dependent on ambient temperature.