System and method for regulating the speed of a steam turbine by controlling the turbine valve rack actuator

A system for regulating the speed of a turbine by operating the steam valve rack assembly to adjust the flow of steam to the turbine by controlling the position of the turbine valve rack actuator in response to oil within a first pressure range fed, reacting to signals from a closed loop speed control system, through a proportional valve to the valve rack actuator, comprising:

• (A) a source of oil within a second pressure range lower than the first pressure range;
• (B) an oil accumulator;
• and
• (C) pressure intensifying means arranged to receive oil within the second pressure range from the source, increase the pressure thereof to within the first pressure range, and circulate the oil within the first pressure range to the oil accumulator and the proportional valve;
• (D) emergency stop valve system comprising
• (1) a first emergency stop valve;
• (2) a second emergency stop valve;
• and
• (3) an emergency solenoid valve;
• whereby in response to an external signal the emergency solenoid valve operates to dump oil within the first pressure range from the first and second emergency stop valves to an oil drain permitting the first and second emergency stop valves to open and allow oil within the first pressure range from the oil accumulator to flow through the first emergency stop valve to the first side of the turbine valve rack actuator and oil within the first pressure range to drain from the second side of the turbine valve rack actuator through the second emergency stop valve closing the turbine valve rack actuator and the steam valve rack assembly cutting off the supply of steam to the turbine.

A method for regulating the speed of a turbine by operating a steam valve rack assembly to adjust the flow of steam to the turbine by controlling the position of the turbine valve rack actuator in response to oil within a first pressure range fed, reacting to signals from a closed loop speed control system, through a proportional valve to the the turbine valve rack actuator, comprising the steps of:

• (A) utilizing oil within a second pressure range from a source thereof to operate pressure intensifying means to increase the pressure thereof within the first pressure range;
• (B) circulating oil within the first pressure range to the proportional valve and to an oil accumulator containing inert gas within a third pressure range;
• (C) continuing the circulation of oil within the first pressure range to the oil accumulator for storage therein whereby the pressure of the inert gas therein is equalized to within the first pressure range;
• (D) releasing and transferring on demand at least a portion of the oil stored in the oil accumulator within the first pressure range to the proportional valve and to the turbine valve rack actuator to adjust the position thereof to control the flow of steam to the turbine when a signal from the closed loop speed control system calls for a reduction in the speed of the turbine and to open the turbine valve rack assembly and increase the flow of steam to the turbine when a signal from the closed loop speed control system calls for an increase in the speed of the turbine.