Coffee Break Training - Fire Protection Series: Inspection Techniques: Fuel Dispenser Emergency Shut-Off Valves [open pdf - 543KB]
" We drive past service stations every day where motorists are dispensing fuel into their cars or trucks from underground storage tanks. Modern motor vehicle fuel dispensing facilities use a turbine system where pumps immersed in the tanks push the fuel to the dispensers for consumer use. In a simple description, when the dispenser nozzle is open, the turbine pump is pushing the fuel into the vehicle that is being filled. As long as the nozzle, or any part of the supply pipe, remains open, the pump will continue to operate. Likewise, if the dispensing assembly (dispenser unit, hose and nozzle) is dislodged from its mount by impact or other means, the turbine continues to pump. In order to stop the flow when a dispenser is damaged, a listed, rigidly anchored emergency shut-off valve incorporating a fusible link or other thermally actuated device must be installed at the dispenser base. The shut-off valve is designed to close automatically in the event of severe impact or fire."
Coffee Break Training - Fire Protection Series No. FP-2014-21
United States Fire Administration: http://www.usfa.fema.gov/