Fast opening valve apparatus

Claim 1

A fast opening valve means for rapid actuation of a steam valve actuator, said valve actuator responding to hydraulic fluid supplied thereto from a source of hydraulic fluid through a control servo valve, and said valve actuator for positioning a valve stem of a steam valve in accordance with a control error signal supplied to said control servo valve, wherein the control error signal is representative of the difference between a demand control signal and a position feedback signal, the position feedback signal corresponding to the position of said valve actuator, said valve actuator for moving said valve stem to open said steam valve upon increased hydraulic fluid flow being supplied to said valve actuator, the fast opening valve means comprising: means for generating a fast open command signal when said control error signal exceeds a predetermined reference signal value; fast valve means hydraulically coupled in parallel with said control servo valve, said fast valve means for opening a supplemental hydraulic fluid supply line between said valve actuator and the source of hydraulic fluid in response to said fast open command signal, wherein the hydraulic attenuation of said control servo valve for a predetermined control position of said control servo valve remains constant regardless of the amount of hydraulic fluid flow in said supplemental hydraulic fluid supply line; an auxiliary source of hydraulic fluid hydraulically coupled between the source of hydraulic fluid and said control servo valve and said fast valve means, said auxiliary source for substantially maintaining hydraulic fluid pressure upstream said control servo valve and said fast valve means during the opening of said supplemental hydraulic fluid supply line; means for generating a positional stop command signal when the position feedback signal exceeds a predetermined feedback reference; means for isolating said fast open command signal from said fast valve means in response to the positional stop command signal, thereby preventing opening the supplemental hydraulic fluid supply line; means for limiting the control error signal corresponding to a demand control signal for opening the steam valve to a first magnitude; and means for substituting a second magnitude for said first magnitude when said fast open command signal is generated and during the interval that said positional stop command is not generated, said second magnitude being larger than said first magnitude.

Claim 8

A method for regulating an actual steam flow in a steam turbine, said steam turbine including steam flow control means for controlling said actual steam flow and an actuator operatively coupled to said steam flow control means for effecting continuous control of said actual steam flow, said actuator responsive to hydraulic fluid provided thereto, comprising: supplying hydraulic fluid along a first hydraulic fluid path to said actuator in response to a demanded steam flow; and supplying hydraulic fluid along a second hydraulic fluid path to said actuator when the actual steam flow is less than the demanded steam flow, wherein said second hydraulic fluid path is in parallel with said first hydraulic fluid path; limiting the amount of hydraulic fluid supplied along the second hydraulic path in response to a first predetermined magnitude when the actual steam flow is within a first predetermined value of maximum steam flow; and limiting the amount of hydraulic fluid supplied along the second hydraulic path in response to a second predetermined magnitude when the actual steam flow is within a second predetermined value of maximum steam flow, wherein a predetermined flow of hydraulic fluid is supplied along the first hydraulic fluid path at a constant hydraulic attenuation regardless of hydraulic fluid supplied along the second hydraulic fluid path.

Claim 9

A method for regulating an actual steam flow in a steam turbine, said steam turbine including steam flow control means for controlling said actual steam flow and an actuator operatively coupled to said steam flow control means for effecting continuous control of said actual steam flow, said actuator responsive to hydraulic fluid provided thereto, comprising: supplying hydraulic fluid along a first hydraulic fluid path to said actuator in response to a demanded steam flow; and supplying hydraulic fluid along a second hydraulic fluid path to said actuator when the actual steam flow is less than the demanded steam flow, wherein said second hydraulic fluid path is in parallel with said first hydraulic fluid path; limiting the amount of hydraulic fluid supplied along the second hydraulic path in response to a first predetermined magnitude when the actual steam flow is within a first predetermined value of maximum steam flow; and limiting the amount of hydraulic fluid supplied along the second hydraulic path in response to a second predetermined magnitude when the actual steam flow is within a second predetermined value of maximum steam flow, wherein a predetermined flow of hydraulic fluid is supplied along the first hydraulic fluid path at a constant hydraulic attenuation regardless of hydraulic fluid supplied along the second hydraulic fluid path.