A valve, installed in the product line of a pressurized system and positioned level with the top surface of a pump island, just below the dispenser. The valve is capable of automatically shutting off the flow of motor fuel in event of a fire at the dispenser, or in event the dispenser, fed by a submersible pump, is knocked over or pulled off its base.
If a car strikes the dispenser, or a motorist pulls away with the nozzle still in his car’s fill pipe, the dislodging of the dispenser could damage the piping and cause gasoline to spew onto the driveway, under pressure. An emergency shutoff valve is designed to operate when an accident of this sort dislodges the dispenser. The top portion of the valve shears off, releasing a spring-loaded poppet inside the valve that immediately closes, shutting off the flow of gasoline.
The valves are also equipped with fusible links, devices that will melt in intense heat. If a fire occurs at a pump island, the fusible link holding the valve open will melt and allow a spring-loaded internal poppet to close, shutting off the flow of gasoline.
Emergency shutoff valves are also referred to as impact valves, fire valves, shear valves, or crash valves.