Redundant trip solenoid valve shut-off for gas turbine fuel system

A method for controlling the flow of fuel to a gas turbine having a fuel supply conduit with a fuel valve, a controller, and a trip oil system including an actuator coupled to the fuel valve, a fluid conduit connected to the actuator and three interconnected trip oil valves disposed in the fluid conduit, said method comprising the steps of:

• a. setting the trip oil valves in a closed position to cause pressure in the fluid conduit to attain at least a level sufficient to activate the fuel valve;
• b. passing fuel through the fuel supply when the fuel valve is activated by pressure in the fluid conduit;
• c. maintaining pressure in the fluid conduit when just one of the trip oil valves moves to an open position which would allow fluid to pass through the trip oil valve;
• d. reducing pressure in the fluid conduit when two or more of the trip oil valves move to an open position, and
• e. deactivating the fuel valve when pressure is reduced in step (d) so as to cause the flow of fuel to the gas turbine to diminish.

In a fuel supply coupled to a gas turbine, a trip oil system comprising:

• an actuator operatively coupled to a fuel shut-off valve in said fuel supply, said actuator having a first position that opens the fuel shut-off valve to the flow of fuel to the gas turbine and second position that shuts off the flow of fuel to the gas turbine;
• a trip oil conduit connected to said actuator to apply an activating force to the actuator to switch the actuator to the first position;
• a trip oil valve manifold having a plurality of trip oil valves, each of said trip oil valves having first and second passages, the first passage being connected to the conduit and the second passage of another trip oil valve and the second passage being connected to a fluid drain, wherein each of said trip oil valves having an open position in which fluid can flow through the first and second passages and a closed position that prevents fluid flow through the passages, and
• where said manifold relieves hydraulic pressure in the conduit when at least two of said trip oil valves are in the open position and said actuator is disposed to said second position when pressure is relieved in the conduit.