Some small propane loads can be supplied with vapor drawn directly off the top of a tank. Heat is conducted from outside the tank to the propane liquid at a rate sufficient to support the required vaporization. In the process, a gallon of liquid propane will become approximately 36 cubic feet of vapor.
For industrial and larger commercial loads, this simple approach to vaporization has limited application. Instead, "vaporizers" are used to heat the liquid LPG, creating the needed volume of vaporized gas. Vaporizers are available in sizes from ten gallons per hour to thousands of gallons per hour and use a variety of methods that impact several aspects of overall system design.
Vaporizers add sensible heat to bring the liquid to the boiling point, latent heat to change the phase of the LPG from liquid to gas, and superheat to allow some handling of the gas without re-condensation.