The shut-off valve was invented in Olean, New York in 1939 by Richard C. Corson. At a loading dock at the Socony-Vacuum Oil Company, Corson observed a worker filling a barrel with gasoline and thought it inefficient. The sound of a toilet flushing later gave him the idea for a “butterfly float.” After developing a prototype with his assistant, Paul Wenke, Corson gave the suggestion to the company who later filed for a patent in his name. The initial intent of the device was to “allow a person to fill more than one barrel at the same time.” This mechanism eventually developed into the modern gasoline pump cut-off valve.
Most modern pumps have an auto cut-off feature that stops the flow when the tank is full. This is done with a second tube, the sensing tube, that runs from just inside the mouth of the nozzle up to a Venturi pump in the pump handle. A mechanical valve in the pump handle detects this change of pressure and closes, preventing the flow of fuel.
The reference temperature for gasoline volume measurement is 60 °F or 15 °C.[10] Ten gallons of gasoline at that temperature expands to about 10.15 US gal (38.4 L) at 85 °F (29 °C) and contracts to about 9.83 US gal (37.2 L) at 30 °F (−1 °C). Each of the three volumes represents the same theoretical amount of energy. In one sense, ten gallons of gasoline purchased at 30 °F is about 3.2% more potential energy than ten gallons purchased at 85 °F. Most gasoline is stored in tanks underneath the filling station. Modern tanks are non-metallic and sealed to stop leaks. Some have double walls or other structures that provide inadvertent thermal insulation while pursuing the main goal of keeping gasoline out of the soil around the tank. The net result is that while the air temperature can easily vary between 30 and 85 °F (−1 and 29 °C), the gasoline in the insulated tank changes temperature much more slowly, especially in underground tanks, as deep soil temperature tends to remain in a narrow range throughout the year, regardless of air temperature.
Typically, individual pumps must be certified for operation after installation by a government weights and measures inspector, who tests that the pump displays the same amount that it dispenses. Measurement Canada is the federal agency responsible for pump regulations in Canada and stickers are displayed on the pumps.
