Patent ID: 7380565

Claim:
A system for preventing a fuel spill from a connecting line extending between a first and second reducer fitting on a first and second fuel tank, respectively, wherein the first fuel tank is in pressure communication with the second fuel tank such that fuel flows from one of the first and second fuel tanks to the other when there is a pressure difference between the pressure acting on fuel in the first fuel tank and in the second fuel tank, the system comprising: (a) a first safety valve immersed in the fuel in the first fuel tank, wherein the first safety valve has an outlet coupler connected to the first reducer fitting, and wherein the first safety valve has an inlet coupler through which fuel enters the first safety valve; (b) a second safety valve immersed in fuel in the second fuel tank, wherein the second safety valve has an outlet coupler connected to the second reducer fitting, and wherein the second safety valve has an inlet coupler through which fuel enters the second safety valve; and (c) wherein each of the first and second safety valves comprises: (c1) a cylindrical housing through which the fuel flows, the housing having a diameter; (c2) a piston assembly comprising: (c2A) a first disc-shaped piston having a diameter slightly smaller than the housing diameter such that the first piston freely slides within the housing, wherein the first piston has at least one orifice defined therein, and wherein the first piston has an upstream face and a downstream face; (c2B) a second disc-shaped piston positioned downstream from the first piston, the second piston having a diameter substantially equal to the first piston diameter, wherein the second piston has at least one orifice defined therein, wherein the second piston has an upstream face and a downstream face, and wherein fluid entering the safety valve housing exerts a flow force on the first piston and the second piston in the direction of fuel flow; (c2C) a shaft connecting the first piston to the second piston; (c2D) a valve stem extending from the downstream face of the second piston, wherein the second piston is attached to a first end of the valve stem; and (c2E) a stop attached to a second end of the valve stem; (c3) a valve seat with an opening substantially shaped and sized to matingly receive the stop; and (c4) a spring positioned in the housing against the downstream face of the second piston assembly such that the spring exerts a spring force on the second piston in a direction opposite the general direction of flow, wherein when the flow forces acting on the piston assembly sufficiently exceed the spring force acting on the downstream face of the second piston, the piston assembly moves in the direction of flow until the stop engages the valve seat and substantially shuts off the fuel flow to the connecting line.