Electro-hydraulic control system with fail-safe pilot valves

A method for directing fluid to at least one hydraulic actuator in an electro-hydraulic control system, the method comprising:

• providing at least one electronic controller;
• providing first and second fail-safe pilot valves being electrically connected to the at least one electronic controller which is arranged to control the operation of the first and second pilot valves,
• providing third and fourth fail-safe pilot valves being electrically connected to the at least one electronic controller which is arranged to control operation of the third and fourth pilot valves,
• providing a pilot operated main valve configured to control fluid flow to the at least one hydraulic actuator,
• fluidly connecting each of the first and second pilot valves and each of the third and fourth pilot valves to the pilot operated main valve and configuring each of said pilot valves to provide control action to the pilot operated main valve to control fluid flow to the at least one hydraulic actuator,
• connecting the first pilot valve and the third pilot valve in parallel via a first shuttle valve to a first pilot inlet port of the main valve,
• connecting the second pilot valve and the fourth pilot valve in parallel via a second shuttle valve to a second pilot inlet port of the main valve, wherein each of the first and second pilot valves and the third and fourth pilot valves includes a spool, an inlet port fluidly connected to a high-pressure fluid source, a first regulated outlet port fluidly connected to a first pilot input port or a second pilot inlet port of the main valve, and a second outlet port fluidly connected to a low pressure reservoir,
• supplying fluid from the high-pressure fluid source to the inlet port of a corresponding one of the first and second pilot valves and the third and fourth pilot valves;
• moving the spool of the corresponding one of the first and second pilot valves and the third and fourth pilot valves to a first position to enable fluid communication between the first regulated outlet port and the second outlet port of the corresponding one of the first and second pilot valves and the third and fourth pilot valves when the corresponding one of the first and second pilot valves and the third and fourth pilot valves is in a deactivated state,
• moving the spool to a second position to enable fluid communication between the inlet port and the first regulated outlet port when the corresponding one of the first and second pilot valves and the third and fourth pilot valves is in an activated state in which the direction input is provided to the pilot operated main valve, and
• if the spool of any of the fail-safe pilot valves becomes stuck in an open state during which a solenoid actuator of the corresponding one of the of fail-safe pilot valves moves into a non-actuated position corresponding to the deactivated state of the corresponding one of the fail-safe pilot valves while the spool remains in the second position corresponding to the activated state of the corresponding one of the fail-safe pilot valves whereby the solenoid actuator is disconnected from the spool, draining the first regulated outlet port of the corresponding one of the fail-safe pilot valves to the low pressure reservoir,
• wherein when the spool is stuck in the open state, the spool being in the second position enables fluid communication between the inlet port and the second outlet port via a fluid connection between an internal fluid line of the spool and a surrounding cavity in which pressurized fluid is accumulated, the internal fluid line being fluidly connected between the surrounding cavity and the low pressure reservoir whereby fluid flows from the high-pressure fluid source to the low pressure reservoir.