Vapor recovery pump regulation of pressure to maintain air to liquid ratio

A method of operating a vapor recovery system that recovers vapors expelled from a vehicle during refueling at a fuel dispensing point and returns the vapors to an underground storage tank through a vapor flow path that is in fluid communication with an air to liquid regulator valve and a vapor pump, comprising:

• dispensing fuel into the vehicle through the fuel dispensing point;
• regulating an amount of vapor that is recovered through the fuel dispensing point with the air to liquid regulator valve in proportion to the fuel dispensed into the vehicle;
• detecting a parameter of the vapor recovery system;
• and
• maintaining a substantially constant pressure level in a first portion of the vapor return path that is disposed between the vapor pump and the air to liquid regulator valve.

A system for controlling a vapor recovery system that recovers vapors expelled from a vehicle during refueling at a fuel dispensing point and returns the vapors to an underground storage tank in a service station environment, comprising:

• an air to liquid regulator valve associated with the fuel dispensing point, the air to liquid regulator valve being configured to regulate an amount of vapor that is recovered through the fuel dispensing point for a given amount of fuel that is dispensed through the fuel dispensing point;
• a vapor pump that is in fluid communication with the air to liquid regulator valve, the vapor pump having an inlet side and an outlet side;
• a vapor flow path that is in fluid communication with the air to liquid regulator valve and the vapor pump;
• and
• a mechanical regulator valve that is in fluid communication with both the inlet side and the outlet side of the vapor pump, wherein the mechanical regulator valve is adapted to maintain a substantially constant pressure level in a first portion of the vapor flow path that is disposed between the inlet side of the vapor pump and the air to liquid regulator valve.

A method of operating a vapor recovery system that recovers vapors expelled from a vehicle during refueling at a fuel dispensing point and returns the vapors to an underground storage tank through a vapor flow path that is in fluid communication with an air to liquid regulator valve and a vapor pump driven by a variable speed motor, comprising:

• dispensing fuel into the vehicle through the fuel dispensing point;
• regulating an amount of vapor that is recovered through the fuel dispensing point with the air to liquid regulator valve in proportion to the fuel dispensed into the vehicle;
• detecting a parameter of the vapor recovery system, the parameter being related to rotational torque of the vapor pump;
• determining a rate of rotation of the vapor pump;
• comparing the detected parameter of the vapor recovery system to a look-up table of stored constants derived from measuring rotational torque of the vapor pump at various rates of rotation;
• and
• adjusting the detected parameter of the vapor pump such that the rotational torque of the vapor pump is substantially constant so that a substantially constant pressure is maintained at an inlet to the vapor pump.