Patent Description:
A steam turbine system uses steam to drive one or more steam turbines. A main supply line having a main valve is configured to control a steam supply to each steam turbine, whereas a bypass line having a bypass valve is configured to bypass the steam supply to a cold reheat and/or a condenser. In operation, a main actuation system controls the main valves, whereas a separate bypass actuation system controls the bypass valves. The main and bypass actuation systems may differ from one another in a variety of ways, such as different components, different actuation fluids, different capacities, different specifications, or any combination thereof. Unfortunately, the two actuation systems (e.g., main and bypass actuation systems) add considerable costs for the initial purchase and installation, maintenance, and subsequent repairs or replacements. Additionally, the two actuation systems consume significant space at a site and may require equipment from different vendors, including different control systems or controls software. A need exists for an actuation system capable of operating both main valves and bypass valves to help reduce the foregoing disadvantages.

<CIT> discloses a device for regulating the intercept valves of a steam-turbine plant supplied with a boiler with low capacity of thermal modulation. The device has: a hydraulic circuit, designed to supply a linear hydraulic actuator for actuation of a system of levers for opening and closing the intercept valves simultaneously; a hydraulic power distributor, designed to supply the linear hydraulic actuator selectively; and a control device, designed to control the hydraulic power distributor as a function of a signal correlated to the mode of operation of the steam-turbine plant for partializing without solution of continuity opening of the intercept valves between a position of complete closing and a position of maximum opening.

A system may include a hydraulic power unit having a tank, a pump assembly, and a header. The tank is configured to store a common hydraulic fluid. The pump assembly is configured to pump the common hydraulic fluid from the tank to provide a pressurized hydraulic fluid. An accumulator assembly is configured to store the pressurized hydraulic fluid. The header is coupled to the pump assembly and the accumulator assembly, wherein the header is configured to supply the pressurized hydraulic fluid to one or more main valves and one or more bypass valves of a steam turbine system.

A system may include a steam turbine, a main control system, a bypass control system, and a hydraulic power unit coupled to the main control system and the bypass control system. The main control system has one or more main valves coupled to the steam turbine. The bypass control system has one or more bypass valves coupled to the steam turbine. The hydraulic power unit is configured to supply a common hydraulic fluid at a pressure sufficient to operate the one or more main valves and the one or more bypass valves.

A method may include storing a common hydraulic fluid in a tank of a hydraulic power unit, pumping the common hydraulic fluid from the tank via a pump assembly of the hydraulic power unit to provide a pressurized hydraulic fluid, and storing the pressurized hydraulic fluid via an accumulator assembly of the hydraulic power unit. The method also includes supplying the pressurized hydraulic fluid to one or more main valves and one or more bypass valves of a steam turbine system via a header of the hydraulic power unit, wherein the header is coupled to the pump assembly and the accumulator assembly.

Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this invention.

In certain embodiments as discussed below, a common hydraulic power unit (HPU) is configured to operate both main valves and bypass valves of a steam turbine system. The common HPU has equipment with specifications suitable for both the main valves and the bypass valves. For example, the components of the common HPU generally have specifications meeting the greater requirements of either the main valves or the bypass valves, such that specifications may substantially exceed the requirements of one of the main valves or the bypass valves. The common HPU helps to reduce the costs and space consumption of the components used to actuate the main valves and the bypass valves, particularly by sharing the components (e.g., hydraulic tanks, hydraulic pumps, hydraulic accumulators, hydraulic filters and conditioning equipment, hydraulic heating and cooling equipment, monitoring equipment (e.g., sensors), and the control system). The common HPU also helps to simplify maintenance, because only the one common HPU will undergo inspections, repairs, and replacements of the various components. The common HPU also provides substantial improvements by sharing the components, which may be substantial upgrades over components previously used for either of the main valves or the bypass valves in separate actuation systems. The following discussion presents the common HPU in context of a combined cycle power plant; however, the common HPU may be used in any hydraulically controlled system having both main valves and bypass valves. Each of the components and features described in the drawings is intended for use in various combinations with one another.

<FIG> is a schematic of an embodiment of a combined cycle power plant <NUM> having a gas turbine system <NUM>, a heat recovery steam generator (HRSG) <NUM>, a steam turbine system <NUM>, and a common hydraulic power unit (HPU) <NUM>. The gas turbine system <NUM> cycle is often referred to as the "topping cycle," whereas the steam turbine system <NUM> cycle is often referred to as the "bottoming cycle. " By combining these two cycles as illustrated in <FIG>, the combined cycle power plant <NUM> may lead to greater efficiencies in both cycles. In particular, exhaust heat from the topping cycle may be captured and used to generate steam in the HRSG <NUM> for use in the bottoming cycle. However, the HRSG <NUM> may be configured to generate and supply steam for other uses in the combined cycle power plant <NUM>. The common HPU <NUM> has a plurality of components, monitoring functions, and control functions shared between main and bypass fluid control systems of the steam turbine system <NUM>. In particular, the common HPU <NUM> generally eliminates the use of completely separate actuation systems (e.g., hydraulic power units) for the main and bypass fluid control systems. The specific features and operating characteristics of the common HPU <NUM> are discussed in further detail below.

As illustrated, the gas turbine system <NUM> includes an air intake section <NUM>, a compressor section <NUM>, a combustor section <NUM>, a turbine section <NUM>, and a load <NUM>, such as an electrical generator. The air intake section <NUM> may include one or more air filters, antiicing systems, fluid injection systems (e.g., temperature control fluids), silencer baffles, or any combination thereof. The compressor section <NUM> includes multiple compressor stages <NUM>, each having multiple rotating compressor blades <NUM> coupled to a compressor shaft <NUM> and multiple stationary compressor vanes <NUM> coupled to a compressor casing <NUM>. The combustor section <NUM> includes one or more combustors <NUM>. A shaft <NUM> extends between the compressor section <NUM> and the turbine section <NUM>. Each combustor <NUM> includes one or more fuel nozzles <NUM> coupled to one or more fuel supplies <NUM>, which may supply fuel through primary and secondary fuel circuits. The fuel supplies <NUM> may supply natural gas, syngas, biofuel, fuel oils, or any combination of liquid and gas fuels. The turbine section <NUM> includes multiple turbine stages <NUM>, each having multiple rotating turbine blades <NUM> coupled to a turbine shaft <NUM> and multiple stationary turbine vanes <NUM> coupled to a turbine casing <NUM>. The turbine shaft <NUM> also connects to the load <NUM> via a shaft <NUM>.

In operation, the gas turbine system <NUM> routes an air intake flow <NUM> from the air intake section <NUM> into the compressor section <NUM>. The compressor section <NUM> progressively compresses the air intake flow <NUM> in the stages <NUM> and delivers a compressed airflow <NUM> into the one or more combustors <NUM>. The one or more combustors <NUM> receive fuel from the fuel supply <NUM>, route the fuel through the fuel nozzles <NUM>, and combust the fuel with the compressed airflow <NUM> to generate hot combustion gases in a combustion chamber <NUM> within the combustor <NUM>. The one or more combustors <NUM> then route a hot combustion gas flow <NUM> into the turbine section <NUM>. The turbine section <NUM> progressively expands the hot combustion gas flow <NUM> and drives rotation of the turbine blades <NUM> in the stages <NUM> before discharging an exhaust gas flow <NUM>. As the hot combustion gas flow <NUM> drives rotation of the turbine blades <NUM>, the turbine blades <NUM> drive rotation of the turbine shaft <NUM>, the shafts <NUM> and <NUM>, and the compressor shaft <NUM>. Accordingly, the turbine section <NUM> drives rotation of the compressor section <NUM> and the load <NUM>. The exhaust gas flow <NUM> may be partially or entirely directed to flow through the HRSG <NUM> to enable heat recovery and steam generation.

The HRSG <NUM> may include a plurality of heat exchangers and/or heat exchange components <NUM> disposed in different sections, such as a high pressure (HP) section <NUM>, an intermediate pressure (IP) section <NUM>, and a low pressure (LP) section <NUM>. The components <NUM> may include economizers, evaporators, superheaters, or any combination thereof, in each of the HP, IP, and LP sections <NUM>, <NUM>, and <NUM>. The components <NUM> may be coupled together via various conduits and headers, and the HRSG <NUM> may route one or more flows of steam (e.g., low pressure steam, intermediate pressure steam, and high pressure steam) to the steam turbine system <NUM>. In the illustrated embodiment, the components <NUM> of the HRSG <NUM> include a finishing high pressure superheater <NUM>, a secondary re-heater <NUM>, a primary re-heater <NUM>, a primary high pressure superheater <NUM>, an inter-stage attemperator <NUM>, an inter-stage attemperator <NUM>, a high pressure evaporator <NUM> (HP EVAP), a high pressure economizer <NUM> (HP ECON), an intermediate pressure evaporator <NUM> (IP EVAP), an intermediate pressure economizer <NUM> (IP ECON), a low pressure evaporator <NUM> (LP EVAP), and a low pressure economizer <NUM> (LP ECON). The HRSG <NUM> also includes an enclosure or duct <NUM> housing the various components <NUM>. The functionality of the components <NUM> is discussed in further detail below.

The steam turbine system <NUM> includes a steam turbine <NUM> having a high pressure steam turbine (HP ST) <NUM>, an intermediate pressure steam turbine (IP ST) <NUM>, and a low pressure steam turbine (LP ST) <NUM>, which are coupled together via shafts <NUM> and <NUM>. Additionally, the steam turbine <NUM> may be coupled to a load <NUM> via a shaft <NUM>. Similar to the load <NUM>, the load <NUM> may include an electrical generator. The HRSG <NUM> may be configured to generate a high pressure steam for the high pressure steam turbine <NUM>, an intermediate pressure steam for the intermediate pressure steam turbine <NUM>, and a low pressure steam for the low pressure steam turbine <NUM>. In certain embodiments, an exhaust from the high pressure steam turbine <NUM> may be routed into the intermediate pressure steam turbine <NUM> through the primary re-heater <NUM>, the inter-stage attemperator <NUM>, and the secondary re-heater <NUM> within the HRSG <NUM>, and an exhaust from the intermediate pressure steam turbine <NUM> may be routed into the low pressure steam turbine <NUM>. The steam turbine <NUM> may discharge a condensate <NUM> (or the steam may be condensed in a condenser <NUM> downstream from the steam turbine <NUM>), such that the condensate <NUM> can be pumped back into the HRSG <NUM> via one or more pumps <NUM>.

In operation, the exhaust gas flow <NUM> passes through the HRSG <NUM> and transfers heat to the components <NUM> to generate steam for driving the steam turbine <NUM>. The exhaust steam from the low pressure steam turbine <NUM> may be directed into the condenser <NUM> to form the condensate <NUM>. The condensate <NUM> from the condenser <NUM> may, in turn, be directed into the low pressure section <NUM> of the HRSG <NUM> with the aid of the pump <NUM>. The condensate <NUM> may then flow through the low pressure economizer <NUM>, which is configured to heat a feedwater <NUM> (including the condensate <NUM>) with the exhaust gas flow <NUM>. From the low pressure economizer <NUM>, the feedwater <NUM> may flow into the low pressure evaporator <NUM>. The feedwater <NUM> from low pressure economizer <NUM> may be directed toward the intermediate pressure economizer <NUM> and the high pressure economizer <NUM> with the aid of a pump <NUM>. Steam from the low pressure evaporator <NUM> may be directed to the low pressure steam turbine <NUM>. Likewise, from the intermediate pressure economizer <NUM>, the feedwater <NUM> may be routed into the intermediate pressure evaporator <NUM> and/or toward the high pressure economizer <NUM>. In addition, steam from the intermediate pressure economizer <NUM> may be routed to a fuel gas heater <NUM>, where the steam may be used to heat fuel gas for use in the combustion chamber <NUM> of the gas turbine system <NUM>. Steam from the intermediate pressure evaporator <NUM> may be routed to the intermediate steam turbine <NUM>.

The feedwater <NUM> from the high pressure economizer <NUM> may be routed into the high pressure evaporator <NUM>. Steam from the high pressure evaporator <NUM> may be routed into the primary high pressure superheater <NUM> and the finishing high pressure superheater <NUM>, where the steam is superheated and eventually routed to the high pressure steam turbine <NUM>. The inter-stage attemperator <NUM> may be located in between the primary high pressure superheater <NUM> and the finishing high pressure superheater <NUM>. The inter-stage attemperator <NUM> may enable more robust control of the exhaust temperature of steam from the finishing high pressure superheater <NUM>. Specifically, the inter-stage attemperator <NUM> may be configured to control the temperature of steam exiting the finishing high pressure superheater <NUM> by injecting a cooler feedwater spray into the superheated steam upstream of the finishing high pressure superheater <NUM> whenever the exhaust temperature of the steam exiting the finishing high pressure superheater <NUM> exceeds a predetermined value.

In addition, an exhaust from the high pressure steam turbine <NUM> may be directed into the primary re-heater <NUM> and the secondary re-heater <NUM>, where it may be re-heated before being directed into the intermediate pressure steam turbine <NUM>. The primary re-heater <NUM> and the secondary re-heater <NUM> may also be associated with the inter-stage attemperator <NUM>, which is configured to control the exhaust steam temperature from the reheaters. Specifically, the inter-stage attemperator <NUM> may be configured to control the temperature of steam exiting the secondary re-heater <NUM> by injecting cooler feedwater spray into the superheated steam upstream of the secondary re-heater <NUM> whenever the exhaust temperature of the steam exiting the secondary re-heater <NUM> exceeds a predetermined value. The arrangement of the components <NUM> of the HRSG <NUM> is merely one possible example for use with the common HPU <NUM>, and the components <NUM> may be arranged differently within the scope of the present invention as defined by the appended claims.

The steam turbine system <NUM> further includes a fluid control system <NUM> having a main control system <NUM> and a bypass control system <NUM> coupled to the common HPU <NUM>. As illustrated, the fluid control system <NUM> includes a high pressure steam supply line or conduit <NUM> coupled to the finishing high pressure superheater <NUM> and an inlet into the high pressure steam turbine <NUM>, a high pressure bypass line or conduit <NUM> coupled to the high pressure steam supply line <NUM>, and a discharge or return line <NUM> coupled to an outlet of the high pressure steam turbine <NUM> and the primary re-heater <NUM>. The high pressure steam supply line <NUM> includes one or more high pressure main valves <NUM>, each driven or actuated by an independent hydraulic actuator <NUM> to move between open and closed positions.

For example, as shown in <FIG>, the high pressure main valves <NUM> may include a high pressure main steam control valve <NUM> (e.g., HP main control valve) and a high pressure main steam stop valve <NUM> (e.g., HP main stop valve). The HP main control valve <NUM> is actuated by one of the hydraulic actuators <NUM> (e.g., actuator 144A) to adjust (e.g., increase or decrease) a flow of the high pressure steam into the high pressure steam turbine <NUM>, and the HP main stop valve <NUM> is actuated by one of the hydraulic actuators <NUM> (e.g., actuator 144B) to enable or disable (e.g., stop) the flow of the high pressure steam into the high pressure steam turbine <NUM>.

The high pressure bypass line <NUM> includes one or more high pressure bypass valves <NUM>, each driven or actuated by an independent hydraulic actuator <NUM> to move between open and closed positions. For example, the high pressure bypass valves <NUM> may include a high pressure bypass pressure control valve <NUM> (e.g., HP bypass control valve), a high pressure bypass spray water isolation valve <NUM> (e.g., HP bypass spray isolation valve), and a high pressure bypass spray water control valve <NUM> (e.g., HP bypass spray control valve). The HP bypass control valve <NUM> is actuated by one of the hydraulic actuators <NUM> (e.g., actuator 152A) to adjust (e.g., increase or decrease) a pressure of the high pressure bypass flow being diverted away from the HP steam supply line <NUM>. The HP bypass spray isolation valve <NUM> is actuated by one of the hydraulic actuators <NUM> (e.g., actuator 152B) to enable or disable (e.g., stop) the flow of a water spray configured to attemperate the high pressure bypass flow prior to return to the HRSG <NUM>. The HP bypass spray control valve <NUM> is actuated by one of the hydraulic actuators <NUM> (e.g., actuator 152C) to adjust (e.g., increase or decrease) the flow of the water spray configured to attemperate the high pressure bypass flow prior to return to the HRSG <NUM>. In certain embodiments, the water used for the water spray is delivered from the feedwater <NUM> or another source of water in the HRSG <NUM>.

As further illustrated in <FIG>, the fluid control system <NUM> includes an intermediate pressure steam supply line or conduit <NUM>, an intermediate pressure bypass line or conduit <NUM>, and a discharge or return line <NUM>. The intermediate pressure steam supply line or conduit <NUM> is fluidly coupled to outlets of the intermediate pressure evaporator <NUM> and the secondary re-heater <NUM> and an inlet into the intermediate pressure steam turbine <NUM>. The intermediate pressure bypass line or conduit <NUM> is fluidly coupled to the intermediate pressure steam supply line <NUM>. The discharge or return line <NUM> is fluidly coupled to an outlet of the intermediate pressure steam turbine <NUM> and an inlet into the low pressure steam turbine <NUM>. The intermediate pressure steam supply line <NUM> includes one or more intermediate pressure main valves <NUM>, each driven or actuated by an independent hydraulic actuator <NUM> to move between open and closed positions.

For example, as shown in <FIG>, the intermediate pressure main valves <NUM> may include an intermediate pressure main steam control valve <NUM> (e.g., IP main control valve) and an intermediate pressure main steam stop valve <NUM> (e.g., IP main stop valve). The IP main control valve <NUM> is actuated by one of the hydraulic actuators <NUM> (e.g., actuator 168A) to adjust (e.g., increase or decrease) a flow of the intermediate pressure steam into the intermediate pressure steam turbine <NUM>, and the IP main stop valve <NUM> is actuated by one of the hydraulic actuators <NUM> (e.g., actuator 168B) to enable or disable (e.g., stop) the flow of the intermediate pressure steam into the intermediate pressure steam turbine <NUM>.

The intermediate pressure bypass line <NUM> includes one or more intermediate pressure bypass valves <NUM>, each driven or actuated by an independent hydraulic actuator <NUM> to move between open and closed positions. For example, the intermediate pressure bypass valves <NUM> may include an intermediate pressure bypass pressure control valve <NUM> (e.g., IP bypass control valve), an intermediate pressure bypass steam shutoff valve <NUM> (e.g., IP bypass shutoff valve), an intermediate pressure bypass spray water control valve <NUM> (e.g., IP bypass spray control valve), and an intermediate pressure bypass spray water isolation valve <NUM> (e.g., IP bypass spray isolation valve). The IP bypass control valve <NUM> is actuated by one of the hydraulic actuators <NUM> (e.g., actuator 176A) to adjust (e.g., increase or decrease) a pressure of the intermediate pressure bypass flow being diverted away from the IP steam supply line <NUM> to condenser <NUM>. The IP bypass shutoff valve <NUM> is actuated by one of the hydraulic actuators <NUM> (e.g., actuator 176B) to enable or disable (e.g., stop) the bypass flow being diverted away from the IP steam supply line <NUM>. The IP bypass spray control valve <NUM> is actuated by one of the hydraulic actuators <NUM> (e.g., actuator 176C) to adjust (e.g., increase or decrease) the flow of the water spray configured to attemperate the intermediate pressure bypass flow prior to return to the condenser <NUM>. The IP bypass spray isolation valve <NUM> is actuated by one of the hydraulic actuators <NUM> (e.g., actuator 176D) to enable or disable (e.g., stop) the flow of a water spray configured to attemperate the intermediate pressure bypass flow prior to return to the condenser <NUM>. In certain embodiments, the water used for the water spray is delivered from the condenser <NUM>, a water tank, or another source of water in the HRSG <NUM>.

As further illustrated in <FIG>, the fluid control system <NUM> includes a low pressure steam supply line or conduit <NUM>, a low pressure bypass line or conduit <NUM>, and a discharge or return line <NUM>. The low pressure steam supply line or conduit <NUM> is fluidly coupled to outlets of the low pressure evaporator <NUM> and the discharge or return line <NUM> from intermediate pressure steam turbine <NUM> and to an inlet into the low pressure steam turbine <NUM>. The low pressure bypass line or conduit <NUM> is fluidly coupled to the low pressure steam supply line <NUM>. The discharge or return line <NUM> is fluidly coupled to an outlet of the low pressure steam turbine <NUM> and an inlet into the low pressure economizer <NUM>. As discussed above, the return line <NUM> includes the condenser <NUM> and the pump <NUM>. The low pressure steam supply line <NUM> includes one or more low pressure main valves <NUM>, each driven or actuated by an independent hydraulic actuator <NUM> to move between open and closed positions.

For example, as shown in <FIG>, the low pressure main valves <NUM> may include a low pressure main steam control valve <NUM> (e.g., LP main control valve or admission valve) and a low pressure main steam stop valve <NUM> (e.g., LP main stop valve). The LP main control valve <NUM> is actuated by one of the hydraulic actuators <NUM> (e.g., actuator 198A) to adjust (e.g., increase or decrease) a flow of the low pressure steam into the low pressure steam turbine <NUM>, and the LP main stop valve <NUM> is actuated by one of the hydraulic actuators <NUM> (e.g., actuator 198B) to enable or disable (e.g., stop) the flow of the low pressure steam into the low pressure steam turbine <NUM>.

The low pressure bypass line <NUM> includes one or more low pressure bypass valves <NUM>, each driven or actuated by an independent hydraulic actuator <NUM> to move between open and closed positions. For example, the low pressure bypass valves <NUM> may include a low pressure bypass pressure control valve <NUM> (e.g., LP bypass control valve), a low pressure bypass steam shutoff valve <NUM> (e.g., LP bypass shutoff valve), a low pressure bypass spray water control valve <NUM> (e.g., LP bypass spray control valve), and a low pressure bypass spray water isolation valve <NUM> (e.g., LP bypass spray isolation valve). The LP bypass control valve <NUM> is actuated by one of the hydraulic actuators <NUM> (e.g., actuator 206A) to adjust (e.g., increase or decrease) a pressure of the low pressure bypass flow being diverted away from the LP steam supply line <NUM>. The LP bypass shutoff valve <NUM> is actuated by one of the hydraulic actuators <NUM> (e.g., actuator 206B) to enable or disable (e.g., stop) the bypass flow being diverted away from the LP steam supply line <NUM>. The LP bypass spray control valve <NUM> is actuated by one of the hydraulic actuators <NUM> (e.g., actuator 206C) to adjust (e.g., increase or decrease) the flow of a water spray configured to attemperate the low pressure bypass flow prior to return to the condenser <NUM>. The LP bypass spray isolation valve <NUM> is actuated by one of the hydraulic actuators <NUM> (e.g., actuator 206D) to enable or disable (e.g., stop) the flow of the water spray configured to attemperate the low pressure bypass flow prior to return to the condenser <NUM>. In certain embodiments, the water used for the water spray is delivered from the condenser <NUM>, a water tank, or another source of water in the HRSG <NUM>.

The common HPU <NUM> is configured to provide hydraulic power to actuate or control operation of the main control system <NUM> and the bypass control system <NUM>. For example, the common HPU <NUM> is configured to provide hydraulic power to actuate or control the main valves <NUM>, <NUM>, and <NUM> of the main control system <NUM> via the hydraulic actuators <NUM>, <NUM>, and <NUM>, respectively. By further example, the common HPU <NUM> is configured to provide hydraulic power to actuate or control the bypass valves <NUM>, <NUM>, and <NUM> of the bypass control system <NUM> via the hydraulic actuators <NUM>, <NUM>, and <NUM>, respectively. Advantageously, the components and functionality of the common HPU <NUM> are shared between both the main control system <NUM> and the bypass control system <NUM>, thereby eliminating the need for separate hydraulic power units for main valves and bypass valves. The common HPU <NUM> has a plurality of shared components <NUM> as discussed in further detail below.

As shown in <FIG>, the shared components <NUM> may include one or more hydraulic reservoirs or tanks <NUM>, one or more hydraulic pumps <NUM>, one or more hydraulic accumulators <NUM>, a hydraulic conditioning, heating, and cooling system <NUM>, and a monitoring and control system <NUM>. The system <NUM> includes a thermal system <NUM> and a conditioning system <NUM> configured to control the temperature and quality of the hydraulic fluid (e.g., common hydraulic fluid used for main and bypass valves). The system <NUM> includes a monitoring system <NUM> and a control system <NUM> configured to monitor and control operation of the common HPU <NUM>. The tanks <NUM> are configured to store the hydraulic fluid, including fresh/new hydraulic fluid, returned hydraulic fluid, and treated hydraulic fluid. The pumps <NUM> are configured to pressurize the hydraulic fluid to a sufficient pressure for both the main control system <NUM> and the bypass control system <NUM>. The hydraulic accumulators <NUM> are configured to store the pressurized hydraulic fluid, so that sufficient hydraulic fluid is readily available for actuation of the main valves <NUM>, <NUM>, and <NUM> and the bypass valves <NUM>, <NUM>, and <NUM>. The hydraulic accumulators <NUM> may include bladder type accumulators, piston-cylinder accumulators, spring-biased accumulators, metal bellows type accumulators, or another type of accumulator applying mechanical energy to store the pressurized hydraulic fluid. The hydraulic conditioning, heating, and cooling system <NUM> is configured to maintain a proper condition or quality of the hydraulic fluid and to maintain a proper temperature of the hydraulic fluid. For example, the thermal system <NUM> may include one or more heat exchangers, heaters, or coolers configured to transfer heat to or from the hydraulic fluid. The conditioning system <NUM> may include one or more particulate filters, water removal units, separators, or any combination thereof. The conditioning system <NUM> is configured to remove particulate matter, water, or other undesirable materials from the hydraulic fluid.

The system <NUM>, including the monitoring and control systems <NUM> and <NUM>, is configured to monitor and control operation of the common HPU <NUM>, the fluid control system <NUM>, and various aspects of the steam turbine system <NUM>. The monitoring system <NUM> is configured to monitor a plurality of sensors <NUM>, designated as "S", distributed throughout the combined cycle power plant <NUM>. The control system <NUM> may include one or more controllers, each having one or more processors <NUM>, memory <NUM>, and instructions <NUM> stored on the memory <NUM> and executable by the processor(s) <NUM> to perform various control functions for delivering the hydraulic power to the main control system <NUM> and the bypass control system <NUM>. The control system <NUM> of the common HPU <NUM> also may interact with a controller <NUM> of the combined cycle power plant <NUM>, wherein the controller <NUM> includes one or more processors <NUM>, memory <NUM>, and instructions <NUM> stored on the memory <NUM> and executable by the processor(s) <NUM> to perform various control functions for operating the gas turbine system <NUM>, the HRSG <NUM>, the steam turbine system <NUM>, and the fluid control system <NUM>. In certain embodiments, the control system <NUM> may communicate information (e.g., sensor feedback, alerts, alarms, etc.) and/or provide control signals to the controller <NUM>, or vice versa.

The sensors <NUM> may be communicatively coupled to the controller <NUM> and/or the control system <NUM> via communication wires or wireless communication circuity. The sensors <NUM> may be disposed at one or more locations in the air intake section <NUM>, the compressor section <NUM>, the combustor section <NUM>, the turbine section <NUM>, the HRSG <NUM>, and the steam turbine system <NUM>. For example, the sensors <NUM> may be disposed at one or more locations in each of the high pressure steam turbine <NUM>, the intermediate pressure steam turbine <NUM>, and the low pressure steam turbine <NUM>. The sensors <NUM> also may be disposed along each of the lines <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, thereby helping to monitor various fluid parameters between the HRSG <NUM>, the steam turbines <NUM>, <NUM>, and <NUM>, the main valves <NUM>, <NUM>, and <NUM>, and the bypass valves <NUM>, <NUM>, and <NUM>.

Additionally, the sensors <NUM> may be coupled to and/or distributed throughout the common HPU <NUM> communicating through controller <NUM>, such as at each of the shared components <NUM> (e.g., tanks <NUM>, pumps <NUM>, accumulators <NUM>, etc.). For example, the sensors <NUM> may include flow sensors, pressure sensors, temperature sensors, fluid level sensors, fluid composition sensors, flame sensors, vibration sensors, clearance sensors, trip sensors, or any combination thereof. The feedback from the sensors <NUM> may be used by the controller <NUM> and/or the control system <NUM> in a variety of ways.

In certain embodiments, if the controller <NUM> and/or the control system <NUM> observes undesirable sensor feedback within the HRSG <NUM>, the steam turbine system <NUM>, the fluid control system <NUM>, or the common HPU <NUM>, then the controller <NUM> and/or the control system <NUM> may provide an alarm or an alert to a user via an electronic display or may change operation of the common HPU <NUM> or the fluid control system <NUM>. For example, depending on sensor feedback from the sensors <NUM>, the controller <NUM> and/or the control system <NUM> may trigger a trip of the fluid control system <NUM>, actuate the bypass valves <NUM>, <NUM>, and <NUM> to open or close using the common HPU <NUM>, and/or actuate the main valves <NUM>, <NUM>, and <NUM> to open or close using the common HPU <NUM>. In certain embodiments, the HPU <NUM> may provide the hydraulic power to partially or completely open the bypass valves <NUM>, <NUM>, and <NUM> and/or partially or completely close the main valves <NUM>, <NUM>, and <NUM>. Additionally, the HPU <NUM> may provide the hydraulic power to partially or completely close the bypass valves <NUM>, <NUM>, and <NUM> and/or partially or completely open the main valves <NUM>, <NUM>, and <NUM>.

The common HPU <NUM> is configured to provide hydraulic power using a hydraulic fluid, such as a self-extinguishing, fire-resistant fluid with a high auto-ignition temperature suitable for both the main valves <NUM>, <NUM>, and <NUM> and the bypass valves <NUM>, <NUM>, and <NUM>. For example, the auto-ignition temperature may be greater than or equal to about <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> degrees Celsius. The hydraulic fluid stored in the tanks <NUM> may include, for example, a self-extinguishing (fire-resistant) phosphate ester fluid. One such fluid is a self-extinguishing (fire-resistant) synthetic non-aqueous triaryl phosphate ester fluid. For example, the hydraulic fluid may include trixylenyl phosphate, trixylenyl and t-butylphenyl phosphate, t-butylphenyl phosphate having <NUM>-<NUM>% triphenyl phosphate, t-butylphenyl phosphate having low levels (e.g., less than <NUM>, <NUM>, <NUM>, <NUM>, <NUM> %) of triphenyl phosphate, or any combination thereof. In certain embodiments, the hydraulic fluid may include one or more of the self-extinguishing fluids described above, which are sold under the tradename FYRQUEL® by ICL Industrial Products of Gallipolis Ferry, WV, and which are distributed globally.

The common HPU <NUM> may be configured to pressurize the hydraulic fluid to a pressure suitable for both the main valves <NUM>, <NUM>, and <NUM> and the bypass valves <NUM>, <NUM>, and <NUM>. For example, the HPU <NUM> may be configured to pressurize the hydraulic fluid up to a pressure of at least <NUM>, <NUM>, or <NUM> kPa (<NUM>, <NUM>, or <NUM> psig) in certain embodiments. Again, the same hydraulic fluid and its associated properties may be used for both the main valves <NUM>, <NUM>, and <NUM> and the bypass valves <NUM>, <NUM>, and <NUM>.

As illustrated in <FIG>, the common HPU <NUM> supplies the pressurized hydraulic fluid to each of the hydraulic actuators <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> of the respective valves <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> via one or more hydraulic supply lines or conduits <NUM>, and the common HPU <NUM> receives a return hydraulic fluid from each of the hydraulic actuators <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> of the respective valves <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> via one or more hydraulic return lines or conduits <NUM>. In certain embodiments, each of the hydraulic actuators <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> may have a dedicated or independent hydraulic supply line <NUM> and a dedicated or independent hydraulic return line <NUM>. Additionally, in certain embodiments, the common HPU <NUM> may deliver the pressurized hydraulic fluid to the hydraulic actuators <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> in one or more groups, such as groups of bypass valves, groups of main valves, and/or groups of valves associated with the high pressure steam turbine <NUM>, the intermediate pressure steam turbine <NUM>, and/or the low pressure steam turbine <NUM>.

<FIG> is a schematic of an embodiment of the steam turbine system <NUM> and the fluid control system <NUM> coupled to the HRSG <NUM> and the common HPU <NUM> of <FIG>, further illustrating details of the main control system <NUM> and the bypass control system <NUM>. Unless stated otherwise, each of the components illustrated in <FIG> are the same as described in detail above with reference to <FIG>. Although <FIG> does not illustrate certain details and components shown in <FIG>, these components are part of the illustrated system of <FIG>. For example, the HRSG <NUM> and the common HPU <NUM> include the components and functions described above with reference to <FIG>. Additional details, which are not shown in <FIG> for simplicity, are further illustrated in <FIG>.

As illustrated in <FIG>, the high pressure steam supply line <NUM> extends in a steam flow direction from the HRSG <NUM> to the inlet of the high pressure steam turbine <NUM>, while the high pressure bypass line <NUM> extends in a bypass flow direction from the high pressure steam supply line <NUM> back to the HRSG <NUM>. As described above, the HP main control valve <NUM> and the HP main stop valve <NUM> are configured to control the high pressure steam flow along high pressure steam supply line <NUM> to the high pressure steam turbine <NUM>, and the HP bypass control valve <NUM> is configured to control the high pressure steam bypass flow along the high pressure bypass line <NUM> from the high pressure steam supply line <NUM> back to the HRSG <NUM>. As further illustrated in <FIG>, the HP bypass spray isolation valve <NUM> and the HP bypass spray control valve <NUM> are disposed along a water supply line or conduit <NUM> leading to one or more spray nozzles <NUM>, which are configured to inject a water spray into the high pressure bypass line <NUM> to attemperate the high pressure steam bypass flow prior to return to the HRSG <NUM>. The water supply line or conduit <NUM> may be coupled to the feedwater line <NUM>, a water supply tank, or another source of water.

The valves for the intermediate pressure steam turbine <NUM> have a similar arrangement as the valves for the high pressure steam turbine <NUM>. For example, the intermediate pressure steam supply line <NUM> extends in a steam flow direction from the HRSG <NUM> to the inlet of the intermediate pressure steam turbine <NUM>, while the intermediate pressure bypass line <NUM> extends in a bypass flow direction from the intermediate pressure steam supply line <NUM> back to the condenser <NUM>. The IP main control valve <NUM> and the IP main stop valve <NUM> are configured to control the intermediate pressure steam flow along intermediate pressure steam supply line <NUM> to the intermediate pressure steam turbine <NUM>. The IP bypass control valve <NUM> and the IP bypass shutoff valve <NUM> are configured to control the intermediate pressure steam bypass flow along the intermediate pressure bypass line <NUM> from the intermediate pressure steam supply line <NUM> back to the condenser <NUM>. As further illustrated in <FIG>, the IP bypass spray isolation valve <NUM> and the IP bypass spray control valve <NUM> are disposed along a water supply line or conduit <NUM> leading to one or more spray nozzles <NUM>, which are configured to inject a water spray into the intermediate pressure bypass line <NUM> to attemperate the intermediate pressure steam bypass flow prior to return to the condenser <NUM>. The water supply line or conduit <NUM> may be coupled to the condenser <NUM>, a water supply tank, or another source of water.

The valves for the low pressure steam turbine <NUM> have a similar arrangement as the valves for the high and intermediate pressure steam turbines <NUM> and <NUM>. For example, the low pressure steam supply line <NUM> extends in a steam flow direction from the HRSG <NUM> to the inlet of the low pressure steam turbine <NUM>, while the low pressure bypass line <NUM> extends in a bypass flow direction from the low pressure steam supply line <NUM> back to the condenser <NUM>. The LP main control valve <NUM> and the LP main stop valve <NUM> are configured to control the low pressure steam flow along low pressure steam supply line <NUM> to the low pressure steam turbine <NUM>. The LP bypass control valve <NUM> and the LP bypass shutoff valve <NUM> are configured to control the low pressure steam bypass flow along the low pressure bypass line <NUM> from the low pressure steam supply line <NUM> back to the condenser <NUM>. As further illustrated in <FIG>, the LP bypass spray isolation valve <NUM> and the LP bypass spray control valve <NUM> are disposed along a water supply line or conduit <NUM> leading to one or more spray nozzles <NUM>, which are configured to inject a water spray into the low pressure bypass line <NUM> to attemperate the low pressure steam bypass flow prior to return to the condenser <NUM>. The water supply line or conduit <NUM> may be coupled to the condenser <NUM>, a water supply tank, or another source of water.

In operation, the common HPU <NUM> is configured to supply the pressurized hydraulic fluid through one or more hydraulic supply lines <NUM> to each of the hydraulic actuators <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> of the respective valves <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, thereby providing shared hydraulic power for both the main control system <NUM> (e.g., main valves <NUM>, <NUM>, and <NUM>) and the bypass control system <NUM> (e.g., bypass valves <NUM>, <NUM>, and <NUM>). The common HPU <NUM> also includes one or more hydraulic return lines <NUM> coupled to the hydraulic actuators <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> of the respective valves <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, thereby returning hydraulic fluid back to the common HPU <NUM>. All other aspects of the HPU <NUM>, the fluid control system <NUM>, the HRSG <NUM>, and the steam turbine system <NUM> are the same as described in detail above.

<FIG> is a schematic of an embodiment of the common HPU <NUM> of <FIG> and <FIG>, further illustrating details of the shared components <NUM> used for both the main control system <NUM> and the bypass control system <NUM>. Unless stated otherwise, each of the components illustrated in <FIG> are the same as described in detail above with reference to <FIG> and <FIG>. Although <FIG> does not illustrate certain details and components shown in <FIG> and <FIG>, these components are part of the illustrated system of <FIG>. Additional details, which are not shown in <FIG> and <FIG> for simplicity, are further illustrated in <FIG>.

As illustrated in <FIG>, the common HPU <NUM> includes the tank <NUM>, a pump assembly <NUM> having a plurality of the pumps <NUM> coupled to the tank <NUM>, a manifold <NUM> (e.g., a common or one-piece manifold) coupled to the pump assembly <NUM>, a header <NUM> (e.g., a common or one-piece header) coupled to the manifold <NUM>, an accumulator assembly <NUM> having a plurality of the accumulators <NUM> coupled to the header <NUM>, a trip system <NUM> coupled to the tank <NUM> and the main control system <NUM>, the hydraulic conditioning, heating, and cooling system <NUM> coupled to the tank <NUM>, and the monitoring and control system <NUM> coupled to various components of the common HPU <NUM>.

In certain embodiments, the tank <NUM> may include a single tank split into multiple sections, multiple separate tanks, or a combination thereof. The design, capacity, and surface area of the tank <NUM> may be configured to increase air detrainment, increase flow distribution within the tank, and reduce the footprint size of the tank <NUM>. The tank <NUM> may include suction lines, discharge lines, and internal baffles <NUM> inside the tank <NUM> arranged to improve air detrainment of the hydraulic fluid, e.g., triaryl phosphate ester hydraulic fluid, which may be prone to air entrainment and varnishing at high fluid temperatures. In certain embodiments, the tank <NUM> may be split into three sections: a fluid return section <NUM>, a detraining section <NUM>, and a main pump section <NUM>. The fluid return section <NUM> includes one or more dip tubes <NUM> coupled to one or more strainers <NUM> configured to draw the hydraulic fluid for cooling and conditioning by the system <NUM>. The detraining section <NUM> is configured to receive a return flow of the cooled hydraulic fluid from the system <NUM>. The main pump section <NUM> has one or more dip tubes <NUM> coupled to one or more strainers <NUM> configured to feed the hydraulic fluid into the pumps <NUM> of the pump assembly <NUM>. The HPU <NUM> may include one or more drain return lines <NUM> configured to discharge the hydraulic fluid into the tank <NUM> below an operating fluid level <NUM> to reduce aeration. In certain embodiments, the tank <NUM> may include customer connections for the hydraulic fluid drain return flow back from the steam valves (e.g., the main valves <NUM>, <NUM>, and <NUM> and the bypass valves <NUM>, <NUM>, and <NUM>), wherein the drain return flow back to the tank <NUM> terminates below the operating fluid level <NUM>.

The tank <NUM> also may include a variety of sensors <NUM>, such as a fluid level transmitter or sensor <NUM>, a fluid temperature transmitter or sensor <NUM>, and a fluid pressure transmitter or sensor <NUM>, which are configured to monitor a fluid level, a fluid temperature, and a fluid pressure of the hydraulic fluid in the tank <NUM>. The fluid level sensor <NUM> is configured to monitor the level of hydraulic fluid in the tank <NUM>, thereby enabling the monitoring and control system <NUM> to trigger alarms for excessive high or low levels of the hydraulic fluid in the tank <NUM>. The fluid temperature sensor <NUM> is configured to monitor the temperature of the hydraulic fluid in the tank <NUM>, thereby enabling the monitoring and control system <NUM> to trigger alarms in response to high hydraulic fluid temperatures, such as greater than <NUM>, <NUM>, or <NUM> degrees Celsius. The fluid pressure sensor <NUM> is configured to monitor the pressure of the hydraulic fluid in the tank <NUM>, thereby enabling the monitoring and control system <NUM> to trigger alarms in response to high or low pressures in the tank <NUM> (e.g., based on upper and lower pressure thresholds) as well as to start and stop the pumps <NUM>.

The tank <NUM> also may include a variety of visual gauges or indicators <NUM>, such as a fluid level indicator <NUM>, a fluid temperature indicator <NUM>, and a fluid pressure indicator <NUM>, which are configured to provide a local visual indication of a fluid level, a fluid temperature, and a fluid pressure of the hydraulic fluid in the tank <NUM>. The visual gauges or indicators <NUM> may include mechanical gauges, electronic gauges or displays, or any combination thereof. In certain embodiments, the indicators <NUM> may be independent from one another, or the indicators <NUM> may be integrated into a single common indicator (e.g., an electronic display coupled to a processor-based unit, a computer, or a controller). The tank <NUM> also may include one or more tank magnets <NUM> configured to collect any ferrous particles in the hydraulic fluid within the tank <NUM>.

The tank <NUM> may be a stainless steel tank having the internal baffles <NUM>. The internal baffles <NUM> create a fluid flow path from the fluid return section <NUM> to the main pump section <NUM>, which allows for sufficient de-aeration time for the hydraulic fluid. The tank <NUM> volume is sized to hold all of the hydraulic fluid in the system, including the amount of hydraulic fluid in the feed and drain lines, wherein substantially all of the hydraulic fluid will flow back to the tank <NUM> during a shutdown condition. The pumps <NUM>, accumulators <NUM>, heat exchangers (e.g., thermal system <NUM>), filters (e.g., conditioning system <NUM>), manifolds (e.g., <NUM>), and valves may be mounted on the top and/or side walls of the tank <NUM>. The tank <NUM> also may include access hatches <NUM> and <NUM> (e.g., removable access panels) to enable user access inside the tank <NUM>.

The common HPU <NUM> includes the pump assembly <NUM> having the plurality of pumps <NUM>, which may be the same or different from one another. For example, the pumps <NUM> may include two or more redundant pumps, such as rotary pumps, axial reciprocating pumps, or a combination thereof. For example, the pumps <NUM> may include two or more redundant pressure-compensated, variable-displacement, axial-piston pumps. In certain embodiments, one or more pumps <NUM> (e.g., primary pumps) are configured for normal operation, while one or more pumps <NUM> (e.g., secondary pumps) are configured as backup pumps. The pumps <NUM> may be driven by AC motors, DC motors, or a combination thereof.

The pumps <NUM> may be configured to pressurize the hydraulic fluid to a suitable pressure (e.g., at least <NUM>, <NUM>, or <NUM> kPa [<NUM>, <NUM>, or <NUM> psig]) for both the main valves <NUM>, <NUM>, and <NUM> and the bypass valves <NUM>, <NUM>, and <NUM>. The maximum flow of the pumps <NUM> may be set by a maximum volume stop at operating pressure and the rated motor load current. The discharge pressure of the pumps <NUM> may be maintained constant by a pressure compensator, which modulates a discharge flow to maintain a given pressure at the outlet of each pump <NUM>, provided that the downstream system creates a sufficient back pressure. The suction side of each pump <NUM> may include a pump suction isolation valve <NUM> and position switches <NUM> (included as part of the sensors <NUM> coupled to the pump assembly <NUM>). The pump suction isolation valve <NUM> is in fluid communication with at least one of the dip tubes <NUM> in the tank <NUM>. The strainer <NUM>, which is coupled to the dip tube <NUM>, is configured to protect the pump <NUM> against larger particulates/foreign objects being sucked into the pump <NUM>. The pump suction isolation valve <NUM> is configured to isolate the suction side of the pump <NUM> from the tank <NUM> during maintenance of the pump <NUM>. The position switches <NUM> are configured to detect the position of the pump suction isolation valve <NUM> (e.g., open or closed valve position) and provide a permissive (e.g., valve fully open) for starting a motor <NUM> of the pump <NUM>. The discharge side of each pump <NUM> also may include one or more filters <NUM> configured to remove contaminants upstream of the manifold <NUM>.

The manifold <NUM> may include and/or couple with a plurality of valves and filters along each of a plurality of fluid flow paths, circuits, or lines <NUM>, which are coupled with the plurality of pumps <NUM> of the pump assembly <NUM>. In other words, each pump <NUM> has its own redundant line <NUM> through the manifold <NUM> to the header <NUM>. For each line <NUM> coupled to a respective pump <NUM>, the manifold <NUM> may include one or more of a safety valve <NUM> (e.g., safety pressure relief valve), a bleed valve <NUM> (e.g., air bleed valve), a filter <NUM> (e.g., high pressure particulate filter), an isolation valve <NUM>, and a check valve <NUM>. The safety valve <NUM> may be configured to protect the line <NUM> from overpressurization in the event of a pump compensator failure, a component mis-adjustment, or another problem. The bleed valve <NUM> may be configured to automatically bleed air to the drain return line <NUM> on startup and then close for normal operation. The filters <NUM> may be configured to filter out particulate or other contaminants in the hydraulic fluid. The isolation valves <NUM> and the check valves <NUM> are configured to enable changes of the filters <NUM> during operation.

The manifold <NUM> also includes and/or couples with one or more sensors <NUM> (e.g., sensors <NUM>) and visual gauges or indicators <NUM>. For example, the sensors <NUM> and indicators <NUM> may be coupled to the safety valves <NUM>, the bleed valves <NUM>, the filters <NUM>, the isolation valves <NUM>, and/or the check valves <NUM>. The sensors <NUM> may include, for example, temperature sensors, flow rate sensors, fluid composition sensors, and/or pressure sensors (e.g., differential pressure sensors). In certain embodiments, the sensors <NUM> (e.g., differential pressure sensors) are configured to monitor a differential pressure across the filters <NUM> and trigger alarms in response to high differential pressures (e.g., based on one or more pressure thresholds). Accordingly, the sensors <NUM> may include pressure sensors disposed upstream and downstream of the filters <NUM>, e.g., discharge pressure sensors at the discharge of the pumps <NUM> and header pressure sensors at the header <NUM>. Similarly, the indicators <NUM> may include, for example, temperature indicators, flow rate indicators, fluid composition indicators, and/or pressure indicators (e.g., differential pressure indicators). In certain embodiments, the indicators <NUM> (e.g., differential pressure indicators) are configured to indicate a differential pressure (e.g., pressure drop) across the filters <NUM>.

The manifold <NUM> then routes the hydraulic fluid into the header <NUM>, which in turn couples with the accumulator assembly <NUM> via an accumulator manifold <NUM>, the trip system <NUM> via a trip manifold <NUM>, and a bypass valve <NUM> extending to the tank <NUM>. The bypass valve <NUM> is configured to enable draining of the header <NUM> to the tank <NUM> for maintenance and/or commissioning of the pumps <NUM>.

The accumulator assembly <NUM> is configured to receive the hydraulic fluid from the common header <NUM> and provide instantaneous flow during transient conditions, such as valve actuator transients (e.g., resetting valves after a trip event). The accumulator assembly <NUM> may include the hydraulic accumulators <NUM>, such as <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or more hydraulic accumulators <NUM>. The size and quantity of the hydraulic accumulators <NUM> may depend on system demand during transient conditions (such as a turbine reset). The hydraulic accumulators <NUM> may include, for example, bladder type hydraulic accumulators, such as accumulators with one side of a bladder pre-charged with a gas (e.g., inert gas such as nitrogen gas) and the other side of the bladder storing pressurized hydraulic fluid. The hydraulic accumulators <NUM> also may include a piston-cylinder accumulator, a bellows accumulator, or any other pressure storage reservoir. During high flow transient demands, the pressurized hydraulic fluid stored in the hydraulic accumulators <NUM> (e.g., bladder type hydraulic accumulators) is configured to provide additional capacity to maintain header pressure in the header <NUM>. For example, the hydraulic accumulators <NUM> are designed to provide sufficient capacity to handle the demands of the main control system <NUM>, the bypass control system <NUM>, and the trip system <NUM>.

Each hydraulic accumulator <NUM> is disposed along a fluid path, circuit, or line <NUM> having an isolation valve <NUM>, a drain valve <NUM>, and a safety valve <NUM> (e.g., safety pressure relief valve). The isolation valves <NUM> are configured to open or close to enable or disable pressure transfer from the hydraulic accumulators <NUM> to the header <NUM>. The drain valves <NUM> are configured to drain hydraulic fluid through drain return lines <NUM>, <NUM> back to the tank <NUM>. The safety valves <NUM> are configured to relieve pressure to protect the accumulator assembly <NUM> from an over pressure condition. The safety valves <NUM> may be configured to return hydraulic fluid back to the tank <NUM> via the drain return lines <NUM>, <NUM>. The isolation valves <NUM> and the drain valves <NUM> may be configured to enable maintenance of the accumulator assembly <NUM> by isolating the accumulator assembly <NUM> from the header <NUM> and draining hydraulic fluid to the tank <NUM>.

The common HPU <NUM> may include a variety of the sensors <NUM> and controls <NUM> configured to monitor and control components of the common HPU <NUM>, including the tank <NUM>, the pump assembly <NUM>, the manifold <NUM>, the header <NUM>, the accumulator assembly <NUM>, and the trip system <NUM>. In certain embodiments, the sensors <NUM> include pressure sensors, temperature sensors, fluid level sensors, fluid composition sensors, flow rate sensors, or any combination thereof, at each of the illustrated components. For example, the sensors <NUM> may include the sensors <NUM> (e.g., <NUM>, <NUM>, and <NUM>) coupled to the tank <NUM> as discussed above, sensors <NUM> (e.g., <NUM>) coupled to the pump assembly <NUM>, the sensors <NUM> (e.g., <NUM>) coupled to the manifold <NUM> as discussed above, sensors <NUM> (e.g., <NUM>) coupled to the header <NUM>, and sensors <NUM> (e.g., <NUM>) coupled to the accumulator assembly <NUM>. Similarly, the controls <NUM> may include controls <NUM>, <NUM>, and <NUM> coupled to the pump assembly <NUM>, the manifold <NUM>, and the accumulator assembly <NUM>, respectively. These sensors <NUM> and controls <NUM> are configured to enable the monitoring and control system <NUM> to monitor operating parameters of the common HPU <NUM> and to control various components to ensure proper supply of hydraulic fluid for the steam turbine system <NUM> (e.g., main control system <NUM> and bypass control system <NUM>).

The sensors <NUM>, such as the sensors <NUM>, <NUM>, and <NUM> coupled to the tank <NUM> and the sensors <NUM> coupled to the manifold <NUM>, are already described in detail above. The sensors <NUM> coupled to the pump assembly <NUM> (e.g., one or more sensors <NUM>) may include pump discharge pressure sensors configured to monitor a discharge pressure from the pumps <NUM>. The sensors <NUM> coupled to the header <NUM> (e.g., one or more sensors <NUM>) may include one or more header pressure sensors (e.g., three header pressure sensors) configured to monitor a header pressure of the header <NUM>. The monitoring and control system <NUM> may be configured to start and/or increase the speed of the pumps <NUM> if the header pressure drops below a first threshold header pressure, such as below <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> kPa (<NUM>, <NUM>, <NUM>, <NUM>, or <NUM> PSIG). In certain embodiments, the monitoring and control system <NUM> may be configured to trigger an alarm and trip the common HPU <NUM> if two out of three header pressure sensors indicate a low pressure of the header <NUM> (e.g., below a second threshold header pressure). The second threshold header pressure may be less than the first threshold header pressure, such as below <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> kPa (<NUM>, <NUM>, <NUM>, <NUM>, or <NUM> PSIG). Similarly, the sensors <NUM> coupled to the accumulator assembly <NUM> (e.g., one or more sensors <NUM>) may be configured to measure fluid pressure, such that the monitoring and control system <NUM> may be configured to trigger alarms and/or trips if the fluid pressure drops below one or more pressure thresholds.

The controls <NUM>, such as the controls <NUM>, <NUM>, and <NUM>, may be configured to actuate valves, control operation and speed of the motors <NUM> driving the pumps <NUM>, and generally control the fluid flow through the common HPU <NUM>. For example, the controls <NUM> may be configured to control the opening and closing of the isolation valves <NUM> and to start and/or control the speed of the motors <NUM> of the pumps <NUM> in the pump assembly <NUM>. Similarly, the controls <NUM> may be configured to control the opening and closing of the bleed valves <NUM>, and the isolation valves <NUM> of the manifold <NUM>. By further example, the controls <NUM> may be configured to control the opening and closing of the isolation valves <NUM>, the drain valves <NUM>, and the safety valves <NUM> of the accumulator assembly <NUM>. Additionally, in certain embodiments, the controls <NUM> may be configured to control pressurization in each of the accumulators <NUM>, such as by controlling a gas pressure (e.g., inert gas such as nitrogen gas) used to maintain a pressure of the stored hydraulic fluid.

As discussed above, the common HPU <NUM> includes the trip system <NUM> configured to protect the steam turbine system <NUM> in the event of a turbine protection trip event. The trip system <NUM> is configured to provide pressurized hydraulic fluid to the steam turbine valves (e.g., main valves <NUM>, <NUM>, <NUM>), which acts as a permissive for the valves (e.g., main valves <NUM>, <NUM>, <NUM>) to operate in a normal operating control mode. Upon a trip, the trip system <NUM> depressurizes the hydraulic fluid trip supply (FSS) to the steam valves (e.g., main valves <NUM>, <NUM>, <NUM>), causing them to rapidly move to their safe (e.g., trip mode) position. The trip system <NUM> may be configured with a two-out-of-three system, which works on the two-out-of-three voting logic.

The trip system <NUM> includes the following components: electronic trip devices (ETDs) having trip valves <NUM>, proximity switches <NUM>, and block valves <NUM>. The trip valves <NUM> may include trip valves <NUM>, <NUM>, and <NUM>, such as solenoid valves, configured to operate as pilots to drive the main directional control valves. The proximity switches <NUM> may include proximity switches <NUM>, <NUM>, and <NUM> configured to monitor the position of the ETDs (e.g., trip valves <NUM>, <NUM>, and <NUM>) and provide feedback to the controller <NUM> and/or the control system <NUM>. The block valves <NUM> may include block valves <NUM>, <NUM>, and <NUM> configured to block the hydraulic fluid trip supply (FSS) from entering a main trip oil header and the ETDs (e.g., trip valves <NUM>) during a trip mode and to enable flow through the ETDs (e.g., trip valves <NUM>) during a reset mode. The trip system <NUM> is designed to maintain main header pressure (e.g., common header <NUM>) during a trip mode, by blocking flow to the trip manifold using the block valves <NUM>. The trip system <NUM> configuration (with two-out-of-three voting logic) allows for the ETDs (e.g., trip valves <NUM>) to be individually tested on-line (without tripping the system), to assure proper functioning during a trip event. When a trip is initiated, the three ETDs (e.g., trip valves <NUM>) de-energize to rapidly depressurize the hydraulic fluid trip supply (FSS) and drain the trip hydraulic fluid back to the tank <NUM>. The path of the trip hydraulic fluid is controlled by the directional control valves.

As illustrated, the hydraulic conditioning, heating, and cooling system <NUM> includes the thermal system <NUM> and the conditioning system <NUM> configured to control the temperature and quality of the hydraulic fluid. For example, the thermal system <NUM> is configured to heat and/or cool the hydraulic fluid to maintain a temperature of the hydraulic fluid within upper and lower temperature thresholds. The conditioning system <NUM> is configured to condition the hydraulic fluid by, for example, removing water, particulates, or other undesirable materials from the hydraulic fluid. Additional details of the hydraulic conditioning, heating, and cooling system <NUM> are discussed in detail below with reference to <FIG>.

<FIG> is a schematic of an embodiment of the hydraulic conditioning, heating, and cooling system <NUM> of the common HPU <NUM> of <FIG>. In the illustrated embodiment, the monitoring and control system <NUM> of the common HPU <NUM> is communicatively coupled to various sensors <NUM>, valves <NUM>, and components <NUM> of the hydraulic conditioning, heating, and cooling system <NUM> as indicated by dashed lines <NUM>, such that the monitoring system <NUM> can monitor sensor feedback from the sensors <NUM> and the control system <NUM> can control operation of the valves <NUM> and the components <NUM> to control the temperature and quality of the hydraulic fluid. The thermal system <NUM> includes a thermal control flow path or loop <NUM> coupled to the tank <NUM>, wherein the loop <NUM> includes a suction strainer <NUM> disposed in the tank <NUM>, a pump motor assembly <NUM> having a pump <NUM> driven by a motor <NUM>, one or more heaters <NUM>, one or more filters <NUM>, and one or more coolers <NUM>. In certain embodiments, the heaters <NUM>, the filters <NUM>, and the coolers <NUM> may be arranged in a different sequence or in parallel with one another.

Similarly, the conditioning system <NUM> includes a conditioning flow path or loop <NUM>, wherein the loop <NUM> includes a suction strainer <NUM> disposed in the tank <NUM>, a pump motor assembly <NUM> having a pump <NUM> driven by a motor <NUM>, one or more conditioning media <NUM>, and one or more filters <NUM>. In certain embodiments, the conditioning media <NUM> and the filters <NUM> may be arranged in a different sequence or in parallel with one another. Each of the loops <NUM> and <NUM> includes various sensors <NUM> and valves <NUM> to facilitate monitoring and control by the monitoring and control system <NUM>. During operation of the common HPU <NUM>, the pump motor assemblies <NUM> and <NUM> may be run continuously to circulate the hydraulic fluid through the thermal system <NUM> and the conditioning system <NUM>.

The loop <NUM> of the thermal system <NUM> includes a plurality of fluid conduits interconnecting the components. For example, the loop <NUM> includes a fluid conduit <NUM> (e.g., supply conduit) between the suction strainer <NUM> and the pump <NUM>, a fluid conduit <NUM> between the pump <NUM> and the heaters <NUM>, a fluid conduit <NUM> between the heaters <NUM> and the filters <NUM>, a fluid conduit <NUM> between the filters <NUM> and the coolers <NUM>, and a fluid conduit <NUM> (e.g., return conduit) between the coolers <NUM> and the tank <NUM>. In the illustrated embodiments, the valves <NUM> in the loop <NUM> may include valves <NUM>, <NUM>, and <NUM> along the respective fluid conduits <NUM>, <NUM>, and <NUM> to facilitate control of the fluid flow through the heaters <NUM>, the filters <NUM>, and the coolers <NUM>. For example, the valves <NUM>, <NUM>, and <NUM> may include one-way valves (e.g., check valves), safety valves, pressure control valves, thermostatic control valves, distribution or transfer valves, or any combination thereof. For example, the valves <NUM> may distribute the flow of hydraulic fluid to each of the heaters <NUM> in equal or different flow rates and pressures, the valves <NUM> may distribute the flow of hydraulic fluid to each of the filters <NUM> in equal or different flow rates and pressures, and the valves <NUM> may distribute the flow of hydraulic fluid to each of the coolers <NUM> in equal or different flow rates and pressures.

Additionally, the fluid conduits <NUM>, <NUM>, and <NUM> may be coupled to the fluid conduit <NUM> via conduits <NUM>, <NUM>, and <NUM> having respective valves <NUM>, <NUM>, and <NUM>. The valves <NUM>, <NUM>, and <NUM> are configured to open and close fluid flow through the conduits <NUM>, <NUM>, and <NUM> to the fluid conduit <NUM> (e.g., return conduit), thereby enabling a bypass flow of the hydraulic fluid between pump <NUM>, the heaters <NUM>, the filters <NUM>, and the coolers <NUM>. In certain embodiments, the valves <NUM>, <NUM>, and <NUM> may include pressure relief valves or thermostatic control valves. The pressure relief valves may open upon reaching one or more pressure thresholds in the fluid flow of hydraulic fluid. The thermostatic control valves may regulate the fluid flow of hydraulic fluid based on temperature of the hydraulic fluid, and thus may open upon reaching one or more temperature thresholds in the fluid flow of hydraulic fluid.

As further illustrated, the sensors <NUM> in the loop <NUM> may include sensors <NUM>, <NUM>, and <NUM> coupled to the heaters <NUM>, the filters <NUM>, and the coolers <NUM>. The sensors <NUM> may be configured to monitor temperature, pressure, flow rate, content of contaminants (e.g., water), or any combination thereof. For example, the sensors <NUM> may monitor the foregoing parameters (e.g., temperature) at upstream, internal, and/or downstream locations relative to each of the heaters <NUM>. Similarly, the sensors <NUM> may monitor the foregoing parameters (e.g., temperature) at upstream, internal, and/or downstream locations relative to each of the coolers <NUM>. The sensors <NUM> may monitor the foregoing parameters (e.g., pressure) at upstream, internal, and/or downstream locations relative to each of the filters <NUM>. For example, the sensors <NUM> (e.g., pressure sensors) may monitor a pressure drop across each of the filters <NUM>, such that the monitoring system <NUM> may trigger an alarm if the pressure drop exceeds one or more pressure thresholds. The foregoing sensor measurements are used by the monitoring and control system <NUM> to increase or decrease flow of the hydraulic fluid through the thermal system <NUM> to maintain a temperature between upper and lower temperature thresholds.

The heaters <NUM>, the filters <NUM>, and the coolers <NUM> of the thermal system <NUM> may include a variety of configurations and equipment. For example, the heaters <NUM> may include electric heaters, heat exchangers configured to transfer heat between the hydraulic fluid from the tank <NUM> and a thermal fluid (e.g., heated water), heating solenoids configured to block flow of the thermal fluid to the coolers <NUM>, or a combination thereof. The filters <NUM> may include particulate filters, such as cartridge filters, configured to capture any particulate over a threshold size. In certain embodiments, the filters <NUM> may have a rating of Beta3><NUM>. The coolers <NUM> may include heat exchangers configured to exchange heat between the hydraulic fluid from the tank <NUM> and a thermal fluid (e.g., water) via one or more coolant supplies <NUM>, which are coupled to the coolers <NUM> via fluid conduits <NUM> and <NUM>. The heat exchangers of the coolers <NUM> may include, for example, <NUM>% capacity heat exchangers. The sensors <NUM> may further include one or more sensors <NUM> coupled to the coolant supplies <NUM>, such that the monitoring system <NUM> can monitor parameters of the coolant supplies <NUM> (e.g., temperature of the thermal fluid).

The loop <NUM> of the conditioning system <NUM> includes a plurality of fluid conduits interconnecting the components. For example, the loop <NUM> includes a fluid conduit <NUM> (e.g., supply conduit) between the suction strainer <NUM> and the pump <NUM>, a fluid conduit <NUM> between the pump <NUM> and the conditioning media <NUM>, a fluid conduit <NUM> between the conditioning media <NUM> and the filters <NUM>, and a fluid conduit <NUM> (e.g., return conduit) between the filters <NUM> and the tank <NUM>. In the illustrated embodiments, the valves <NUM> in the loop <NUM> may include valves <NUM> and <NUM> along the respective fluid conduits <NUM> and <NUM> to facilitate control of the fluid flow through the conditioning media <NUM> and the filters <NUM>. For example, the valves <NUM> and <NUM> may include one-way valves (e.g., check valves), safety valves, pressure control valves, distribution or transfer valves, or any combination thereof. For example, the <NUM> may distribute the flow of hydraulic fluid to each of the conditioning media <NUM> in equal or different flow rates and pressures, and the valves <NUM> may distribute the flow of hydraulic fluid to each of the filters <NUM> in equal or different flow rates and pressures.

Additionally, the fluid conduits <NUM> and <NUM> may be coupled to the fluid conduit <NUM> via conduits <NUM> and <NUM> having respective valves <NUM> and <NUM>. The valves <NUM> and <NUM> are configured to open and close fluid flow through the conduits <NUM> and <NUM> to the fluid conduit <NUM> (e.g., return conduit), thereby enabling a bypass flow of the hydraulic fluid between the pump <NUM>, the conditioning media <NUM>, and the filters <NUM>. In certain embodiments, the valves <NUM> and <NUM> may include pressure relief valves. The pressure relief valves may open upon reaching one or more pressure thresholds in the fluid flow of hydraulic fluid.

As further illustrated, the sensors <NUM> in the loop <NUM> may include sensors <NUM> and <NUM> coupled to the conditioning media <NUM> and the filters <NUM>. The sensors <NUM> and <NUM> may be configured to monitor temperature, pressure, flow rate, content of contaminants (e.g., water), or any combination thereof. For example, the sensors <NUM> and <NUM> may monitor the foregoing parameters at upstream, internal, and/or downstream locations relative to each of the conditioning media <NUM> and filters <NUM>. In certain embodiments, the sensors <NUM> and <NUM> (e.g., pressure sensors) may monitor a pressure drop across each of the conditioning media <NUM> and filters <NUM>, such that the monitoring system <NUM> may trigger an alarm if the pressure drop exceeds one or more pressure thresholds. The foregoing sensor measurements are used by the monitoring and control system <NUM> to increase or decrease flow of the hydraulic fluid through the conditioning system <NUM> to maintain a suitable quality of the hydraulic fluid (e.g., particulate and/or water content less than a threshold).

The conditioning media <NUM> and the filters <NUM> of the conditioning system <NUM> may include a variety of configurations and equipment. In certain embodiments, the conditioning media <NUM> may include an ion exchange type acid control media to keep the hydraulic fluid total acid number (TAN) under a threshold to help reduce the possibility of fluid varnishing. The filters <NUM> may include particulate filters, water removal elements, or a combination thereof. For example, the filters <NUM> may include cartridge filters, centrifugal separators, gravity separators, or any combination thereof. The filters <NUM> (e.g., particulate filters) may have a rating of Beta3><NUM>.

The tank <NUM> may further couple to an air drying system <NUM> having an air intake system <NUM> and an air discharge system <NUM>. The air intake system <NUM> may include an air supply <NUM> and an air dryer <NUM> configured to supply and dry an airflow into the tank <NUM>. The air supply <NUM> may include one or more fans, air filters, conduits, or a combination thereof. The air dryer <NUM> may include a dehumidifier, a desiccant material, or a combination thereof. The air discharge system <NUM> may include a tank breather <NUM>, which allows release of the air flow provided by the air intake system <NUM>. Accordingly, the dry airflow from the air intake system <NUM> may absorb moisture inside the tank <NUM> to generate a moist airflow, which is then discharged through the tank breather <NUM>.

The common HPU <NUM> described in detail above with reference to <FIG> may be used to improve the operation of the steam turbine system <NUM>. For example, the common HPU <NUM> may use a common hydraulic fluid (e.g., self-extinguishing, fire-resistant fluid) for both the main control system <NUM> and the bypass control system <NUM>, wherein the properties are selected to meet the greater demands of each of the systems <NUM> and <NUM>. The common HPU <NUM> also may improve one or more aspects of the startup, shutdown, and turbine trip processes of the steam turbine system <NUM>.

<FIG> is a flow chart of an embodiment of a startup process <NUM> for the steam turbine system <NUM> of the system <NUM>. As illustrated in <FIG>, the startup process <NUM> may include starting up the gas turbine system <NUM> (block <NUM>) followed by various steps using the common HPU <NUM>. For example, block <NUM> of the startup process <NUM> may include at least partially opening the high pressure bypass pressure control valve <NUM> (e.g., a minimum opening) to control upstream pressure and, based on a downstream temperature set point, opening the high pressure bypass spray water isolation valve <NUM> and the high pressure bypass spray water control valve <NUM> to start spraying water to control a downstream temperature, wherein hydraulic fluid from the common HPU <NUM> is used to facilitate opening of the high pressure valves <NUM>, <NUM>, <NUM>. In block <NUM>, the startup process <NUM> may further include opening the intermediate pressure bypass steam shutoff valve <NUM> (e.g., open to <NUM>% open) and at least partially opening the intermediate pressure bypass pressure control valve <NUM> to control upstream pressure (e.g., a minimum opening) and, based on the downstream temperature set point, opening the intermediate pressure bypass spray water isolation valve <NUM> and the intermediate pressure bypass spray water control valve <NUM> to start spraying water to control the downstream temperature, wherein hydraulic fluid from the common HPU <NUM> is used to facilitate opening of the intermediate pressure valves <NUM>, <NUM>, <NUM>, <NUM>.

In block <NUM>, the startup process <NUM> may include modulating the high pressure bypass pressure control valve <NUM> and the intermediate pressure bypass pressure control valve <NUM> to control upstream pressure set points, and modulating the high pressure bypass spray water control valve <NUM> and the intermediate pressure bypass spray water control valve <NUM> to control the downstream temperature, wherein hydraulic fluid from the common HPU <NUM> is used to facilitate opening of the valves. In block <NUM>, the startup process <NUM> may further include opening the low pressure bypass steam shutoff valve <NUM> (e.g., open to <NUM>% open) and at least partially opening the low pressure bypass pressure control valve <NUM> and, based on the downstream temperature set point, opening the low pressure bypass spray water isolation valve <NUM> and the low pressure bypass spray water control valve <NUM> to start spraying water to control the downstream temperature, wherein hydraulic fluid from the common HPU <NUM> is used to facilitate opening of the low pressure valves <NUM>, <NUM>, <NUM>, <NUM>.

In block <NUM>, the startup process <NUM> may include opening and modulating the intermediate pressure main steam control valve <NUM> and the intermediate pressure main steam stop valve <NUM> when a steam turbine floor pressure reaches an intermediate pressure, wherein hydraulic fluid from the common HPU <NUM> is used to facilitate opening of the intermediate pressure valves <NUM>, <NUM>. In block <NUM>, the startup process <NUM> may include opening and modulating the high pressure main steam control valve <NUM> and the high pressure main steam stop valve <NUM>, wherein hydraulic fluid from the common HPU <NUM> is used to facilitate movements of the high pressure valves <NUM>, <NUM>. In block <NUM>, the startup process <NUM> may include opening and modulating the low pressure main control and stop valves <NUM>, <NUM>, wherein hydraulic fluid from the common HPU <NUM> is used to facilitate opening of the low pressure valves <NUM>, <NUM>.

In block <NUM>, the startup process <NUM> may include fully opening the intermediate pressure main steam control valve <NUM> upon reaching a maximum open set point and closing the intermediate pressure bypass pressure control valve <NUM>, the intermediate pressure bypass spray water isolation valve <NUM>, and the intermediate pressure bypass spray water control valve <NUM>, wherein valve closing may be achieved with actuator springs configured to depressurize valve actuators of the valves. In block <NUM>, the startup process <NUM> may include changing a high pressure turbine control to an inlet pressure control (IPC) mode when the high pressure bypass pressure control valve <NUM> reaches a minimum opening set point, and closing the high pressure bypass pressure control valve <NUM>, the high pressure bypass spray water isolation valve <NUM>, and the high pressure bypass spray water control valve <NUM>, wherein valve closing may be achieved with actuator springs configured to depressurize valve actuators of the valves.

In block <NUM>, the startup process <NUM> may include closing the low pressure bypass pressure control valve <NUM> upon reaching a minimum position, and closing the low pressure bypass spray water isolation valve <NUM> and the low pressure bypass spray water control valve <NUM>, wherein valve closing may be achieved with actuator springs configured to depressurize valve actuators of the valves. In certain embodiments, in the foregoing startup process <NUM>, the valve opening may be achieved by pressurizing valve actuators (e.g., actuator cylinders) for the valves using the common HPU <NUM>, whereas valve closing may be achieved with actuator springs configured to depressurize the valve actuators (e.g., actuator cylinders) of the valves, or vice versa. The foregoing startup process <NUM> is one possible example for the system <NUM>. However, the common HPU <NUM> may be used in a variety of ways to facilitate startup process <NUM>.

<FIG> is a flow chart of an embodiment of a shutdown process <NUM> for the steam turbine system <NUM> of the system <NUM>. As illustrated in <FIG>, the shutdown process <NUM> may include initiating a shutdown command and beginning to unload the steam turbine system <NUM> in proportion to steam flow decrease (block <NUM>). In block <NUM>, the shutdown process <NUM> may include triggering a stop command when the gas turbine system <NUM> reaches a threshold load (e.g., <NUM>% load), changing control (e.g., stopping Inlet Pressure Control (IPC) mode) and closing the intermediate pressure main steam control valve <NUM>, starting to modulate the high pressure bypass pressure control valve <NUM>, opening the high pressure bypass spray water isolation valve <NUM>, and starting to modulate the high pressure bypass spray water control valve <NUM>. In block <NUM>, the shutdown process <NUM> includes, when the high pressure main steam control valve <NUM> opening reaches a minimum steam turbine load, starting to close the intermediate pressure main steam control valve <NUM>, starting to modulate the high pressure bypass pressure control valve <NUM>, opening intermediate pressure bypass spray water isolation valve <NUM>, and starting to modulate the intermediate pressure bypass spray water control valve <NUM>. In block <NUM>, the shutdown process <NUM> includes closing (e.g., simultaneously) all main valves (e.g., <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>) when the intermediate pressure main steam control valve <NUM> and the high pressure main steam control valve <NUM> are at the same open positions. In block <NUM>, the shutdown process <NUM> includes closing all bypass valves (e.g., <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>) upon reaching a minimum opening set point. In certain embodiments, in the foregoing shutdown process <NUM>, the valve opening may be achieved by pressurizing valve actuators (e.g., actuator cylinders) for the valves using the common HPU <NUM>, whereas valve closing may be achieved with actuator springs configured to depressurize the valve actuators (e.g., actuator cylinders) of the valves, or vice versa.

<FIG> is a flow chart of an embodiment of a steam turbine trip process <NUM> for the steam turbine system <NUM> of the system <NUM>. As illustrated in <FIG>, the steam turbine trip process <NUM> may include closing (e.g., simultaneously) all main valves (e.g., <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>) in response to a stream turbine trip (block <NUM>). In block <NUM>, the steam turbine trip process <NUM> includes opening (e.g., simultaneously) all bypass valves (e.g., <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>) at intermediate calculated positions to release pressure and control outlet temperatures. In block <NUM>, the steam turbine trip process <NUM> includes closing all bypass valves (e.g., <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>) upon reaching minimum opening set points. In certain embodiments, in the foregoing steam turbine trip process <NUM>, the valve opening may be achieved by pressurizing valve actuators (e.g., actuator cylinders) for the valves using the common HPU <NUM>, whereas valve closing may be achieved with actuator springs configured to depressurize the valve actuators (e.g., actuator cylinders) of the valves, or vice versa.

Claim 1:
A system (<NUM>), comprising:
a steam turbine system (<NUM>);
a main control system (<NUM>) having one or more main valves (<NUM>, <NUM>, <NUM>) coupled to the steam turbine system (<NUM>);
a bypass control system (<NUM>) having one or more bypass valves (<NUM>, <NUM>, <NUM>) coupled to the steam turbine system (<NUM>); and
a hydraulic power unit (<NUM>) coupled to the main control system (<NUM>) and the bypass control system (<NUM>), wherein the hydraulic power unit (<NUM>) is configured to supply a hydraulic fluid at a pressure sufficient to operate the one or more main valves (<NUM>, <NUM>, <NUM>) and the one or more bypass valves (<NUM>, <NUM>, <NUM>), the hydraulic fluid being common among the one or more main valves (<NUM>, <NUM>, <NUM>) and the one or more bypass valves (<NUM>, <NUM>, <NUM>).