Steam valve apparatus

In one embodiment, a steam valve apparatus includes: a hydraulic cylinder including an internal space sectioned into first and second chambers by a piston operated by a hydraulic liquid; a first passage to supply the hydraulic liquid to the first chamber; a second passage connecting the first and second chambers; a third passage to drain the hydraulic liquid from the second chamber; an electromagnetic valve switched between first and second states; a first cartridge valve opening the first passage when the electromagnetic valve is in the first state and closing the first passage when the electromagnetic valve is in the second state; and a second cartridge valve closing the first passage when the electromagnetic valve is in the first state and opening the first passage when the electromagnetic valve is in the second state.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2010-231582, filed on Oct. 14, 2010; the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a steam valve apparatus installed in a steam system of a turbo machine such as a steam turbine in a power plant.

BACKGROUND

In a power generation facility and the like that uses a turbo machine such as a steam turbine, various protection apparatuses for detecting phenomena such as an abnormal rise of an rpm (rotation speed), an extension difference, an oscillation enlargement, a high temperature in a low-pressure evacuation (exhaust) chamber, lowering of a bearing hydraulic pressure, lowering of a discharge pressure of a main oil pump, and a failure of a boiler/power generator and preventing accidents from occurring or minimalizing damages due to the accidents are provided.

For example, a hydraulic system of a steam valve apparatus as follows is disclosed. Specifically, in addition to a case where an rpm of a normally-driven steam turbine is increased to a set rpm or more, an anomaly (abnormality) of the steam turbine is detected at an anomaly (abnormality) detection portion of a protection apparatus. The anomaly detection portion generates an electric signal, and a main steam stop valve set at a steam inlet of the steam turbine is closed based on the signal so that a steam influx to the steam turbine is blocked.

Hereinafter, the structure of the power generation facility of the related art will be described with reference toFIG. 3.

It should be noted that the steam valve apparatus described below is a collective term for, for example, a main steam stop valve, a governor valve, a reheat steam stop valve, and an intercept valve that are set in the steam turbine.

InFIG. 3, a steam discharged from a boiler100passes through a main steam stop valve101and a governor valve102and enters a high-pressure turbine (HT)103. After an expansion work in the high-pressure turbine (HT)103, the steam returns to the boiler100via a check valve104.

After that, the steam heated by a reheater (RH) enters a medium-pressure turbine (MT)107via a reheat steam stop valve105and an intercept valve106. The steam undergoes an expansion work in the medium-pressure turbine (MT)107and enters a low-pressure turbine (LT)108to additionally undergo an expansion work. The steam that has undergone the expansion work in the low-pressure turbine (LT)108is changed into water in a condenser109and supplied to the boiler100again after being pressure-raised in a feed pump (FP)110(steam circulation). The high-pressure turbine (HT)103, the medium-pressure turbine (MT)107, and the low-pressure turbine (LT)108are coupled to the same axis as a power generator (not shown) to drive it.

The plant shown inFIG. 3is structured as follows to raise an operation efficiency of the plant. Specifically, a high-pressure turbine bypass valve111is set between an upstream side of the main steam stop valve101and an inlet side of the reheater (RH) of the boiler100, and a low-pressure turbine bypass valve112is set between an outlet side of the reheater (RH) and the condenser109. As a result, irrespective of whether the turbine is driven or not, circulation drive of a boiler system alone can be performed.

It should be noted thatFIG. 3shows an example of a typical steam turbine power generation facility. It is also possible to use a uniaxial or multi-axial combined cycle power plant by combining a gas turbine (not shown) with the steam turbine power generation facility and replacing the boiler100with an exhaust heat recovery boiler.

The power generation facility shown inFIG. 3includes various protection apparatuses for preventing accidents from occurring in the power generation facility or minimalizing, in case of accidents, damages due to the accidents. The protection apparatuses detect phenomena such as an abnormal rise of a turbine rpm (rotation speed), an increase in an expansion of a turbine shaft length, an oscillation enlargement, a temperature rise in a low-pressure evacuation chamber, lowering of a bearing hydraulic pressure, lowering of a discharge pressure of a main oil pump, and a failure of a boiler/power generator.

For example, in a case where an rpm of a normally-driven turbine is increased to a set rpm or more and a case where other turbine anomalies occur, an anomaly (abnormality) detection portion detects the anomaly and outputs an electric anomaly (abnormality) signal. The anomaly signal is transmitted to high-speed operation electromagnetic valves21and22set in a hydraulic drive apparatus20of a main steam stop valve200shown inFIG. 4, for example.

Hereinafter, the structure of the hydraulic drive apparatus20of the main steam stop valve200will be described with reference toFIG. 4.FIG. 4shows a structure of a hydraulic drive system of the main steam stop valve that blocks energy from entering the steam turbine as an example of the main steam stop valve200.

InFIG. 4, the steam valve (steam valve apparatus)200includes a main valve201, a piston202, a hydraulic cylinder203, a lower cylinder204, an upper cylinder205, and a hydraulic system206. The hydraulic cylinder203is a double-action type and the inside thereof is sectioned into the lower cylinder (valve-open-side chamber (first chamber))204and the upper cylinder (valve-close-side chamber (second chamber))205by the piston202. The hydraulic cylinder203includes, on both the valve-open side and the valve-close side, inlet and outlet ports for a hydraulic oil (hydraulic liquid). The hydraulic system206is equipped with a hydraulic pipe (also called oil passage (or passage)) and various valves and connects the lower cylinder204and the upper cylinder205to a hydraulic pressure generator and an oil tank (not shown). It should be noted that the piston202, the hydraulic cylinder203, and the hydraulic system206constitute the hydraulic drive apparatus20of the steam valve200.

In the main steam stop valve200, a valve position can be controlled using a servo valve25to be described later. As the main steam stop valve200, a valve in which a sub valve is incorporated for controlling a steam flow amount at the time of activation and the like can be used.

A steam pressure acts on an upstream side of the main valve201of the main steam stop valve200. Due to the hydraulic oil accumulated in the lower cylinder204located at a lower portion of the hydraulic cylinder203that accommodates the piston202coupled to the main valve201, a hydraulic pressure acts on the lower portion of the piston202. As a result, the main valve201is opened over the steam pressure.

On the other hand, when an anomaly (abnormality) occurs in the steam turbine, the main valve201is closed by discharging the oil accumulated in the lower cylinder204of the piston202.

InFIG. 4, the hydraulic oil26is supplied from the hydraulic pressure generator (not shown). The hydraulic oil26is first split into two hydraulic pipes pl1and pl2at an inlet-side branch point J1of the hydraulic system206surrounded by dashed lines. The hydraulic pipe pl1is connected to a first oil filter27, and the hydraulic pipe pl2is connected to a second oil filter (oil filter dedicated to servo valve)28. The hydraulic oil that has entered the first oil filter27from the hydraulic pipe pl1is additionally split into two hydraulic pipes pl3and pl4at an outlet-side branch point J2of the first oil filter27.

The hydraulic pipe pl3as one of the pipes is connected to a P port of the servo valve25responsible for a steam flow amount control function of the steam valve200. The servo valve25accommodates a movable spool (reel-type shaft) inside a sleeve (tube) having inlet and outlet ports. By receiving a valve position control signal transmitted from a turbine control apparatus (not shown) by a coil25C, the spool position is controlled. A pilot oil of the servo valve25is supplied via the second oil filter28.

The valve position control signal from the turbine control apparatus (not shown) is input to the coil25C. Based on the valve position control signal, the hydraulic oil26supplied to the P port from the hydraulic pipe pl3reaches a branch point J3via a B port.

The hydraulic oil26is supplied from the branch point J3to the lower cylinder204of the piston202via a hydraulic pipe pl9. At the same time, the hydraulic oil26is also supplied to A ports of cartridge valves29and30via a hydraulic pipe pl10. The piston202of the main steam stop valve200operates to be opened and closed by the hydraulic oil26that has passed the servo valve25.

On the other hand, the hydraulic pipe pl4as the other one of the pipes split at the branch point J2described above is additionally split into two hydraulic pipes pl5and pl6at a branch point J4. The hydraulic pipe pl5is connected to a P port of the high-speed operation electromagnetic valve21, and the hydraulic pipe pl6is connected to a P port of the high-speed operation electromagnetic valve22. The high-speed operation electromagnetic valves21and22are structured as a “3-port 2-position single-action electromagnetic valve” that includes a sleeve, 3 inlet and outlet ports provided in the sleeve, and a spool that is movably accommodated in the sleeve.

The high-speed operation electromagnetic valves21and22are important apparatuses for blocking the steam (steam energy) that enters the steam turbine when any anomaly (abnormality) occurs in the steam turbine. Therefore, the high-speed operation electromagnetic valves21and22constantly maintain an excitation state when the steam turbine is driven normally and are put to a non-excitation state at the time an anomaly (abnormality) occurs. Further, an anomaly (abnormality) signal to the high-speed operation electromagnetic valve21is applied to duplexed excitation coils23aand23bfrom a sequence circuit (not shown). Similarly, an anomaly signal to the high-speed operation electromagnetic valve22is applied to duplexed excitation coils24aand24bfrom a sequence circuit (not shown).

As described above, during normal drive of the steam turbine, the excitation coils23a,23b,24a, and24bof the high-speed operation electromagnetic valves21and22are constantly in an excitation state. Therefore, the hydraulic oil26passes the high-speed operation electromagnetic valves21and22from the P port to the A port. After that, the hydraulic oil26is supplied to the secondary side of the cartridge valves29and30attached to the high-speed operation electromagnetic valves21and22, respectively, via hydraulic pipes pl13and pl14. It should be noted that the B ports of the cartridge valves29and30are connected to the port of the upper cylinder205of the hydraulic drive apparatus20and also connected to the T port of the servo valve25via the hydraulic pipe pl7.

The hydraulic oil26that has passed through the servo valve25and been supplied to the A ports on the primary side of the cartridge valves29and30and the hydraulic oil26that has passed the P and A ports of the high-speed operation electromagnetic valves21and22from the hydraulic pipes pl5and pl6and been supplied to the secondary side of the cartridge valves29and30simultaneously act on the valving elements31and32of the cartridge valves29and30. Therefore, forces that act on both sides of the valving elements31and32are balanced. As a result, the valving elements31and32of the cartridge valves29and30do not move.

Here, assuming that the anomaly detection portion of the protection apparatus of the steam turbine (not shown) has detected an anomaly, an anomaly signal is output from the anomaly detection portion and electrically transmitted to the coils23a,23b,24a, and24bof the high-speed operation electromagnetic valves21and22provided in the hydraulic drive apparatus20of the steam valve200shown inFIG. 4via a sequence circuit (not shown).

When input with the anomaly signal, the coils23a,23b,24a, and24bof the high-speed operation electromagnetic valves21and22invert to a non-excitation state from the previous constant excitation state. By the inversion of the high-speed operation electromagnetic valves21and22, the passage of the hydraulic oil26is switched. Before the switch, the hydraulic oil26passes the high-speed operation electromagnetic valves21and22from the P port to the A port and is supplied to the secondary side of the cartridge valves29and30via the hydraulic pipes pl13and pl14. After the switch, the hydraulic oil26is discharged to an oil tank (not shown) via the hydraulic pipe pl8and an oil-drain port33.

Therefore, the valving elements31and32are pushed back by a hydraulic force of the hydraulic oil26supplied to the primary side from the hydraulic pipe pl10via the servo valve25in the cartridge valves29and30, and the A ports are opened. As a result, the hydraulic oil26accumulated in the lower cylinder204of the piston202reaches the A ports of the cartridge valves29and30via the hydraulic pipes pl9and pl10and discharged from the B ports of the cartridge valves29and30. Consequently, the steam valve200closes.

At this time, the B ports of the cartridge valves29and30are connected to the port of the upper cylinder205located at an upper portion of the piston202of the hydraulic drive apparatus20by the hydraulic pipe pl7. Therefore, the hydraulic oil from the B ports of the cartridge valves29and30enters the upper cylinder205. The hydraulic oil26that has entered the upper cylinder205is discharged to the oil tank (not shown) from the upper cylinder205of the piston202via the hydraulic pipe pl8and the oil-drain port33.

As described above, the hydraulic oil26accumulated in the lower cylinder204of the piston202in the hydraulic cylinder203temporarily enters the upper cylinder205of the piston202. As a result, an action to press down the piston202occurs. In addition, since the upper cylinder205acts as an oil tank, the steam valve200can be more-rapidly and positively closed.

It should be noted that since reset springs34and35of the valving elements31and32are incorporated on the secondary side of the cartridge valves29and30, if the hydraulic pressure of the A ports of the cartridge valves29and30is eliminated, the valving elements31and32of the cartridge valves29and30automatically return to a fully-closed state so as to block the A ports by the forces of the reset springs34and35.

The hydraulic drive apparatus20of the steam valve200shown inFIG. 4includes the servo valve25and controls the valve position of the main valve201. It should be noted that the main valve may be simply turned ON and OFF depending on the purpose of the steam valve.

FIG. 5is a structural diagram of a drive apparatus40of a steam valve300of the related art having the ON/OFF function. It should be noted that inFIG. 5, components having the same functions as those ofFIG. 4are denoted by the same symbols, and overlapping descriptions will be omitted as appropriate.

InFIG. 5, the steam valve300includes a main valve301, a piston302, a hydraulic cylinder303, a lower cylinder304, an upper cylinder305, and a hydraulic system306. The hydraulic cylinder303is a double-action type and the inside thereof is sectioned into the lower cylinder (valve-open-side chamber)304and the upper cylinder (valve-close-side chamber)305by the piston302. The hydraulic cylinder303includes, on both the valve-open side and the valve-close side, inlet and outlet ports for a hydraulic oil. The hydraulic system306is equipped with a hydraulic pipe (also called oil passage (or passage)) and various valves and connects the lower cylinder304and the upper cylinder305to a hydraulic pressure generator and an oil tank (not shown). It should be noted that the piston302, the hydraulic cylinder303, and the hydraulic system306constitute the hydraulic drive apparatus40of the steam valve300.

Points of the hydraulic system306shown inFIG. 5different from those of the hydraulic system206shown inFIG. 4are as follows. Specifically, the second oil filter28adopted inFIG. 4is removed, and the servo valve25is replaced with a test electromagnetic valve36(also called third electromagnetic valve). The test electromagnetic valve36is operated in a non-excitation state (i.e., constant non-excitation state) during normal drive.

As in the servo valve25, in the test electromagnetic valve36, a position of a spool movably accommodated in a sleeve having inlet/outlet ports is controlled by a coil. At a time a valve test is carried out for preventing an adhesion of a valve shaft of the steam valve300from occurring during normal drive, a simulation signal is transmitted from a test apparatus (not shown) to a coil36C of the test electromagnetic valve36. Based on the simulation signal, the coil36C is excited, and the port is switched. By being connected to the hydraulic pipe pl7via the A port of the test electromagnetic valve36, the hydraulic pipe pl9is connected to the port of the upper cylinder305.

Accordingly, the oil in the lower cylinder304of the piston302is gradually discharged from the oil-drain port33via the hydraulic pipes pl9and pl7, the upper cylinder305, and the hydraulic pipe pl8. As a result, the main valve301of the steam valve300is closed. After the main valve301of the steam valve300is fully closed, the test electromagnetic valve36is inverted to a non-excitation state from an excitation state. Consequently, the main valve301gradually opens, and the valve test ends.

If inadequate components in the hydraulic drive apparatus can be replaced with adequate components without stopping the steam turbine in normal drive, damages that occur can be minimalized.

As described above, the hydraulic pipes of the steam valve apparatus used in the steam turbine is a highly-reliable hydraulic system. However, the steam valve apparatus of the related art may not operate normally when a feature failure or operation failure occurs in the servo valve or the test electromagnetic valve during normal drive, for example.

A high-pressure hydraulic oil is constantly supplied to the hydraulic pipes of the steam valve apparatus of the related art. Therefore, the hydraulic oil scatters when a part of the hydraulic pipes is opened to replace inadequate components with adequate components. For the reason described above, it has been difficult to remove inadequate components and replace them with adequate components during normal drive of the steam turbine in the hydraulic pipes of the steam valve apparatus of the related art.

In this embodiment, inadequate components can be removed and replaced with adequate components during normal drive of a turbo machine such as the steam turbine. As a result, a maintenance property of the steam valve apparatus is improved.

DETAILED DESCRIPTION

In one embodiment, a steam valve apparatus includes: a steam valve apparatus includes: a steam valve passing or blocking a steam to a turbo machine; a piston operated by a hydraulic liquid to open or close the steam valve; a hydraulic cylinder including an internal space sectioned into a first chamber and a second chamber by the piston, the first chamber being on a close side of the steam valve, and the second chamber being on an open side of the steam valve; a first passage to supply the hydraulic liquid to the first chamber; a second passage connecting the first chamber and the second chamber; a third passage to drain the hydraulic liquid from the second chamber; an electromagnetic valve switched between a first state and a second state based on an input of a signal; a first cartridge valve opening the first passage when the electromagnetic valve is in the first state and closing the first passage when the electromagnetic valve is in the second state; and a second cartridge valve closing the first passage when the electromagnetic valve is in the first state and opening the first passage when the electromagnetic valve is in the second state.

Hereinafter, embodiments will be described with reference to the drawings. It should be noted that structural components that are the same as those ofFIGS. 4 and 5described above are denoted by the same symbols, and descriptions thereof will be omitted. Different points will be mainly described.

First Embodiment

FIG. 1is a structural diagram of a drive apparatus of a steam valve according to a first embodiment. The first embodiment is an embodiment for solving the problem of the related art shown inFIG. 4. The following points ofFIG. 1are different from those ofFIG. 4.

The first point is as follows. In the case of the related art shown inFIG. 4, the high-speed operation electromagnetic valves21and22have been structured as a “3-port 2-position single-action electromagnetic valve”. In contrast, high-speed operation electromagnetic valves (also called first and second electromagnetic valves)521and522of the first embodiment are structured as a “4-port 2-position single-action electromagnetic valve”. Accompanying this, ends of hydraulic pipes pl11and pl12are connected to an output B port side of the high-speed operation electromagnetic valves521and522.

The second point is as follows. Cartridge valves (also called first and third cartridge valves)525and526are newly provided on an input port side of the servo valve25. Output port sides of the cartridge valves525and526are connected to the other ends of the hydraulic pipes pl11and pl12so as to come into communication with the B port side of the high-speed operation electromagnetic valves521and522.

Hereinafter, with reference toFIG. 1, the structure of the hydraulic system206will first be described in detail regarding the first embodiment.

InFIG. 1, the hydraulic pipe pl1connected to a hydraulic pressure generator (not shown) is connected to the first oil filter27provided on the inlet side of the hydraulic system206surrounded by dashed lines. The hydraulic pipe pl1is split into two hydraulic pipes pl3and pl4at the branch point J2on the outlet side of the first oil filter27. Of the two hydraulic pipes, the hydraulic pipe pl3functions as an oil fill tube that connects the branch point J2and the P port of the servo valve25. At an intermediate portion of the hydraulic pipe pl3, the two cartridge valves525and526are cascaded (connected in series).

Specifically, of the two cartridge valves, the A port of the cartridge valve526is connected to the branch point J2by the hydraulic pipe pl3. The B port of the cartridge valve526is connected to the A port of the cartridge valve525. Further, the B port of the cartridge valve525is connected to the P port of the servo valve25by the hydraulic pipe pl3.

The cartridge valves526and525are each sectioned into a primary side (input/output port side) and a secondary side (control port side) by valving elements528and527. Reset springs (elastic bodies)530and529of the valving elements528and527are incorporated on the primary side of the cartridge valves526and525, respectively. When a hydraulic pressure on the secondary side (control port side) of the cartridge valves525and526disappears, the reset springs529and530automatically restore the valving elements527and528by their restoring forces. As a result, the A ports of the cartridge valves525and526are fully opened. Here, desirably, valve sheets of the valving elements527and528are a poppet-shaped metal touch that totally prevents leakage and of a tight-shut type having a function to totally stop the flow of fluid.

The pilot oil of the servo valve25is split at a branch point on a downstream side of the B port of the cartridge valve525and supplied via the second oil filter28. Since the second oil filter28is serially arranged with the first oil filter27, it may be omitted. Pressure detection taps531and532are provided on the downstream side of the B ports of the cartridge valves525and526, respectively. By connecting a pressure sensor to the pressure detection taps531and532, a pressure of the hydraulic oil26can be measured.

Incidentally, the hydraulic pipe connected to the B port of the servo valve25is split into the hydraulic pipes pl9and pl10at the branch point J3. The hydraulic pipe pl9as one of the pipes is connected to the lower cylinder204of the hydraulic cylinder203. The hydraulic pipe pl10as the other pipe is connected to the A ports of the cartridge valves (also called second and fourth cartridge valves)29and30.

Insides of the cartridge valves29and30are sectioned into the primary side and the secondary side by the valving elements31and32, respectively. The reset springs (elastic bodies)34and35of the valving elements are incorporated on the secondary side. The B ports of the cartridge valves29and30are connected to the T port of the servo valve25by the hydraulic pipe pl7.

On the other hand, the hydraulic pipe pl4as the other one of the pipes split at the branch point J2is further split into the hydraulic pipes pl5and pl6at the branch point J4. Of those, the hydraulic pipe pl5is connected to the P port of the high-speed operation electromagnetic valve521via an orifice. The hydraulic pipe pl6as the other pipe is connected to the P port of the high-speed operation electromagnetic valve522via an orifice.

It should be noted that the high-speed operation electromagnetic valves521and522are structured as a “4-port 2-position single-action electromagnetic valve” and include duplexed excitation coils523a,523b,524a, and524b.

The excitation coils523a,523b,524a, and524bare constantly excited during normal drive of the steam turbine and maintain the spools inside the sleeves at positions shown in the figure (referred to as first position). As a result, the P port (first port) and A port (fourth port) out of the 4 inlet and outlet ports provided in the sleeve are in communication with each other, and the B port (third port) and T port (second port) are also in communication with each other. When the excitation coils523a,523b,524a, and524bare put to a non-excitation state from the excitation state, the high-speed operation electromagnetic valves521and522move the spools from the first position to a different position (second position) in the sleeves by the restoring forces of the springs. As a result, the P and B ports are in communication with each other, and the A and T ports are also in communication with each other. The term “communication” used herein refers to a state where the inlet and outlet ports (refers to P, A, B, and T ports) provided in the sleeves are in communication with one another by a passage formed in the spool to thus form an oil passage, that is, a state where the hydraulic oil26flows.

In the constant excitation state shown inFIG. 1, the A, B, and T ports of the high-speed operation electromagnetic valves521and522are connected as follows. The A ports are connected to the secondary side of the cartridge valves29and30via the hydraulic pipes pl13and pl14. The B ports are connected to the secondary side of the cartridge valves525and526via the hydraulic pipes pl11and pl12. The T ports are connected to the upper cylinder205by the hydraulic pipe pl8and thus connected to the oil-drain port33.

Next, an operation of the steam valve apparatus according to the first embodiment will be described.

During normal drive of the steam turbine, the valves of the hydraulic system206shown inFIG. 1are opened and closed as follows. Specifically, a hydraulic pressure caused by the hydraulic oil26acts on the lower cylinder204of the hydraulic cylinder203. On the other hand, since an oil tank (not shown) is connected to the upper cylinder205from the oil-drain port33, a hydraulic pressure does not act on the upper cylinder205. Therefore, the main valve201opens so that the main steams flow. The high-speed operation electromagnetic valves521and522are maintained in the constant excitation state. Therefore, the hydraulic oil26filtered by the first oil filter27is supplied to the P ports of the high-speed operation electromagnetic valves521and522via the hydraulic pipes pl5and pl6. After that, the hydraulic oil26flows from the P ports to the A ports and is supplied to the secondary side of the cartridge valves29and30via the hydraulic pipes pl13and pl14, respectively.

At this time, the T ports of the high-speed operation electromagnetic valves521and522are connected to an oil tank (not shown) from the oil-drain port33. Therefore, since a hydraulic pressure is not applied to the T ports, the A ports of the cartridge valves525and526are opened by the restoring forces of the reset springs529and530.

Therefore, the hydraulic oil26filtered by the first oil filter27sequentially passes the cartridge valves526and525to be supplied to the P port of the servo valve25. The hydraulic oil26is also supplied to the primary side (A ports) of the cartridge valves29and30via the hydraulic pipe pl10from the B port of the servo valve25.

The hydraulic oil26supplied to the primary side (A ports) of the cartridge valves29and30and the hydraulic oil26supplied to the secondary side thereof simultaneously act on both sides of the valving elements31and32and are balanced. Therefore, the valving elements31and32themselves do not move. As a result, the A ports of the cartridge valves29and30maintain the constantly-closed state.

A case where the anomaly (abnormality) detection portion of the protection apparatus detects an anomaly (abnormality) during normal drive of the steam turbine described above will be discussed.

When an anomaly occurs in the steam turbine, the anomaly detection portion in the protection apparatus (not shown) detects the anomaly and outputs an electric anomaly signal. The electric anomaly signal is transmitted to the coils523a,523b,524a, and524bof the high-speed operation electromagnetic valves521and522in the hydraulic system206shown inFIG. 1via a sequence circuit apparatus (not shown).

Upon receiving the electric anomaly signal, the high-speed operation electromagnetic valves521and522in the constant excitation state are put to a non-excitation state. Therefore, the spools are moved from the first position to the second position by the restoring forces of the springs. As a result, the hydraulic oil26that has passed the P and A ports to be supplied to the secondary side of the cartridge valves29and30in the constant excitation state is blocked. This is the operation of the high-speed operation electromagnetic valves521and522.

When the high-speed operation electromagnetic valves521and522are operated, forces acting on the valving elements31and32of the cartridge valves29and30are unbalanced. Therefore, the valving elements31and32move upwardly from the state shown in the figure to open the A ports. As a result, the hydraulic pipes pl10and pl7come into communication with each other via the A and B ports of the cartridge valves29and30.

After that, the hydraulic oil26accumulated in the lower cylinder204maintained at the same oil pressure as the A ports of the cartridge valves29and30passes the hydraulic pipes pl9and pl10and the A and B ports of the cartridge valves29and30to be discharged to the hydraulic pipe pl7side. Further, the hydraulic oil26enters the upper cylinder205from the hydraulic pipe pl7and is discharged to an oil tank (not shown) from the oil-drain port33via the hydraulic pipe pl8. Therefore, the piston202is lowered from the state shown in the figure to close the main valve201of the steam valve200.

At the same time, by the operation of the high-speed operation electromagnetic valves521and522described above, the hydraulic oil26from the hydraulic pressure generator passes the P and B ports and supplied to the secondary side of the cartridge valves525and526via the hydraulic pipes pl11and pl12. As a result, in the cartridge valves525and526, the valving elements527and528move downwardly from the state shown in the figure against the restoring forces of the reset springs529and530to thus fully close the A ports.

In the case of the related art (FIG. 4), when the main valve201is closed, the hydraulic oil26from the hydraulic pressure generator has passed the servo valve25to be discharged from the oil-drain port33to the oil tank via the A and B ports of the cartridge valves29and30. According to the first embodiment, since the valving elements527and528of the cartridge valves525and526fully close the A ports, it is possible to prevent the hydraulic oil26from the hydraulic pressure generator from flowing out.

It should be noted that in the descriptions above, the case where the anomaly (abnormality) detection portion of the protection apparatus detects an anomaly during normal drive of the steam turbine has been taken as an example. However, the hydraulic drive apparatus20similarly operates even in a case where the high-speed operation electromagnetic valves521and522are switched from the constant excitation state to a non-excitation state based on a simulation signal at the time of a valve test using a test apparatus (not shown) instead of the case where the anomaly of the steam turbine occurs.

As described above, in the first embodiment, the cartridge valves525and526are cascaded on the upstream side of the servo valve25, that is, in the middle of the oil fill tube. Further, at the time an anomaly occurs or during a valve test of the turbo apparatus, the high-speed operation electromagnetic valves521and522are operated to close the cartridge valves525and526. Therefore, the hydraulic oil26supplied to the servo valve25can be positively blocked.

As a result, even when an inconvenience occurs in the servo valve, defective components can be easily replaced with non-defective components without stopping the drive. Therefore, the maintenance property of the steam valve apparatus is improved, and reliability of the entire steam turbine including the steam valve apparatus can be additionally improved.

Further, by closing the cartridge valves525and526and blocking the hydraulic oil26to be supplied to the servo valve25, the servo valve connected on the downstream side of the cartridge valves525and526can be easily removed and replaced without concerning leakage of the hydraulic oil. Therefore, the maintenance property of the steam valve apparatus is improved. In the replacement, it is desirable for pressure detection taps531and532provided on the downstream side of the B ports of the cartridge valves525and526to measure the oil pressure and check that there is no oil pressure. Since the leakage from the cartridge valves525and526can be checked, an additional safety can be secured.

Furthermore, the high-speed operation electromagnetic valves521and522and the cartridge valves525and526are duplexed, and the cartridge valves525and526are cascaded. Therefore, by merely operating one of the cartridge valves, the hydraulic oil26to be supplied to the servo valve25can be positively blocked.

It should be noted that it is also possible to provide two electromagnetic valves that are turned ON/OFF in place of the two cartridge valves525and526. However, with the ON/OFF-type electromagnetic valves, a time delay or a miss in cooperation (malfunction) are expected to happen with respect to an anomaly signal from the sequence circuit apparatus. Moreover, since the ON/OFF-type electromagnetic valves structurally have a spool shape that does not include a valve sheet, it is difficult to fully block leakage of the hydraulic oil. Therefore, the ON/OFF-type electromagnetic valves are presumed to be inferior to the cartridge valves525and526adopted in the first embodiment in reliability.

In addition, in the first embodiment, the high-speed operation electromagnetic valves521and522are restored (from non-excitation state to excitation state) for the first time when the steam turbine is reset. Therefore, since being operated, the cartridge valves525and526are in the fully-closed state until being restored. Consequently, from the time the valves are operated to a time the valves are restored, the hydraulic oil26from the hydraulic pressure generator is not supplied to the servo valve25provided on the downstream side of the cartridge valves525and526.

As a result, during a period before the steam turbine is reset, even when an instruction signal to open a valve is erroneously input to the servo valve25, the steam valve200is not opened. In other words, it can be said that the steam valve apparatus is an extremely safety-conscious steam valve apparatus that also assumes a role as one type of protection apparatus.

Second Embodiment

Hereinafter, a second embodiment of the present invention will be described with reference toFIG. 2.FIG. 2is a structural diagram of a drive apparatus of a steam valve according to the second embodiment.

A hydraulic system306of the second embodiment is an embodiment for solving the problems of the related art shown inFIG. 5, and many structural components are the same as the hydraulic system206of the first embodiment shown inFIG. 1. The hydraulic system306is structurally different from the hydraulic system206shown inFIG. 1in that the servo valve25is replaced with the test electromagnetic valve36(also called third electromagnetic valve). Since other points can be analogically explained fromFIGS. 1 to 5, detailed descriptions will be omitted herein, and only a general outline will be described.

In the case of the second embodiment, when the high-speed operation electromagnetic valves521and522are operated based on an anomaly signal from the anomaly detection portion or a simulation signal at the time a valve test is carried out, the A ports of the cartridge valves525and526are fully closed. Therefore, the hydraulic oil26to be supplied to the test electromagnetic valve36from the hydraulic pressure generator (not shown) is blocked.

According to the second embodiment described above, the cartridge valves525and526are cascaded on the upstream side of the test electromagnetic valve36, that is, in the middle of the oil fill tube. Further, the high-speed operation electromagnetic valves521and522are operated by transmitting an anomaly signal or a simulation signal to the steam valve from the sequence circuit (not shown) to thus close the cartridge valves525and526. Therefore, the hydraulic oil26to be supplied to the test electromagnetic valve36can be positively blocked, and even when an inconvenience occurs in the electromagnetic valve, defective components can be easily replaced with non-defective components without stopping the drive. Therefore, the maintenance property of the steam valve apparatus is improved, and reliability of the entire steam turbine including the steam valve apparatus can be additionally improved.

Further, by blocking the hydraulic oil26to be supplied to the test electromagnetic valve36by closing the cartridge valves525and526as described above, the test electromagnetic valve36connected on the downstream side of the cartridge valves525and526can be easily removed and replaced without concerning leakage of the hydraulic oil. Therefore, the maintenance property of the steam valve apparatus is improved. In the replacement, it is desirable for the pressure detection taps531and532provided on the downstream side of the B ports of the cartridge valves525and526to measure the oil pressure and check that there is no oil pressure. Since the leakage from the cartridge valves525and526can be checked, an additional safety can be secured.

Furthermore, the high-speed operation electromagnetic valves521and522and the cartridge valves525and526are duplexed, and the cartridge valves525and526are cascaded. Therefore, by merely operating one of the cartridge valves, the hydraulic oil26to be supplied to the test electromagnetic valve36can be positively blocked.

In addition, in the second embodiment, the high-speed operation electromagnetic valves521and522are restored (from non-excitation state to excitation state) for the first time when the steam turbine is reset. Therefore, since being operated, the cartridge valves525and526are in the fully-closed state until being restored. Consequently, from the time the valves are operated to a time the valves are restored, the hydraulic oil26from the hydraulic pressure generator is not supplied to the test electromagnetic valve36provided on the downstream side of the cartridge valves525and526.

As a result, during a period before the steam turbine is reset, even when an instruction signal to open a valve is erroneously input to the test electromagnetic valve36, the steam valve200is not opened. In other words, it can be said that the steam valve apparatus is an extremely safety-conscious steam valve apparatus that also assumes a role as one type of protection apparatus.

Moreover, in the drive mechanism of the steam valve apparatus of the related art, after an anomaly occurs in the steam turbine and the high-speed operation electromagnetic valves21and22are operated and put to a non-excitation state, the oil to the piston302that has been supplied via the test electromagnetic valve36until then is discharged from the oil-drain port33via the A ports of the cartridge valves29and30without remaining in the lower cylinder304. According to the second embodiment, by closing the cartridge valves525and526in an interlocking manner with the operation of the high-speed operation electromagnetic valves521and522, the hydraulic oil26is blocked. Therefore, the hydraulic oil26can be prevented from being discharged from the oil-drain port33irrespective of whether the test electromagnetic valve36is opened or closed.

As described above, according to the embodiments above, the maintenance property of the steam valve apparatus can be improved.