| 摘要 |
In the delivery of bulk gasoline to an underground storage tank assurance that the vapor recovery hose is properly connected is provided by sensing of an excess vacuum in the delivery truck tank. Such vacuum occurs when air and/or gasoline vapor is not permitted to replace the gasoline drained from the truck tank. To prevent air from entering the truck tank when the vapor hose is not properly connected to both the truck tank and the storage tank (1) a complete dry break coupling is employed at the vapor hose connection to the underground tank so that vapor cannot be displaced from the storage tank nor can air enter the vapor hose if that connection is not made and (2) a dry break coupling is used only on the truck side of the vapor hose connection to the truck so that air cannot enter the truck tank unless that connection is made. To prevent discharge of gasoline from the truck tank when the vapor hose is not properly connected to both the truck tank and the storage tank a vacuum sensor, similar to that used for automatic service station automobile refueling nozzles, is mounted on the truck vapor line near the connection of the truck vapor line to the vapor hose. The vacuum sensor is attached to a standard air control valve on the air supply line in series with bottom dump (emergency) valves in compartments of the truck tank. If the hose is not properly connected, the vacuum created causes the air valve to close and in turn the compartment dump valves to close preventing further flow of gasoline.
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