Tank vapor pressure control system

A vapor pressure control system for controlling the pressure in a fuel storage tank containing fuel which is in at least partially a vapor state, said system comprising:

• a cooling chamber for cooling the fuel vapor;
• a vapor intake line located between the tank and said cooling chamber;
• and
• a fan interposed in said vapor intake line between the tank and said cooling chamber.

A vapor pressure control system for controlling the pressure of fuel vapor in a fuel storage tank, comprising:

• a cooling chamber for cooling the fuel vapor, said cooling chamber having means to regulate its temperature;
• a vapor intake line located between the tank and said cooling chamber and allowing communication of fuel vapor between the tank and said cooling chamber;
• a fan interposed in said vapor intake line between the tank and said cooling chamber and, when caused to operate, which causes the circulation of the fuel vapor between the tank and said cooling chamber;
• a pressure sensitive switch which causes the fan to operate if the difference between the ambient air pressure and tank vapor pressure falls below a certain, minimum level, and which causes the fan to cease operating if the difference between the ambient air pressure and tank vapor pressure rises above a certain, maximum level;
• and
• a temperature sensitive switch which is capable of measuring the ambient temperature and which causes the fan to cease operating when the ambient temperature falls below a certain, minimum level, regardless of the difference between the ambient air pressure and tank vapor pressure.

A method for maintaining a vacuum in a fuel storage tank in order to facilitate the dispensing of fuel from the tank, comprising the steps of:

• providing a chilled chamber;
• providing a first passageway between the tank and the chilled chamber for allowing fuel vapor in the tank to enter the chilled chamber;
• providing a second passageway between the chilled chamber and the tank for allowing fuel vapor in the chilled chamber to return to the tank;
• providing a fan within the first passageway which, when operating, will cause the fuel vapor to circulate from the tank, through the first passageway into the chilled chamber, and then through the second passageway back into the tank;
• and
• providing a pressure sensitive switch which is capable of measuring the difference between the ambient air pressure and the vapor pressure inside the tank and which causes the fan to operate when the difference in pressure falls below a level required to maintain a sufficient vacuum in the tank.