not sense that the pressure inside the tank has exceeded the pre set pressure limit the heater will continue to heat the process gas as it is withdrawn from the tank through conduit 54 according to the process of the present invention in order to maintain a certain minimum delivery pressure the equilibrium of vapor and liquid product inside the tank storage container 12 must remain above a corresponding minimum bulk temperature during gaseous flow of product to the customer 39 s house line through conduit 54 the loss of energy in the tank 12 is balanced by the amount of energy added using the external heater 48 and the amount of heat transfer into or out of the system which is dependent upon the ambient temperature when the ambient temperature is equal to the specified minimum bulk temperature of the fluid in the tank no heat transfer will take place therefore the heater 48 is the only source of energy to replace the energy loss due to product flow out of the tank as the ambient temperature drops below the minimum specified bulk temperature of the product in the tank 12 the heater duty will increase depending on the heat capacity of liquefied gas it will be necessary to use a multiple pass heat exchanger containing a number of passes designated 34 n 34 in order to compensate for the vapor.