WO2009035231A2

WO2009035231A2 - Hydraulic control device for turbine valve

Info

Publication number: WO2009035231A2
Application number: PCT/KR2008/005205
Authority: WO
Inventors: Chang Sung Hwang; Dan Hyeon Kim; Sang Gwon O; Seok Gyu Jeong; Seung Yong Lee
Original assignee: Chang Sung Hwang; Dan Hyeon Kim; Sang Gwon O; Seok Gyu Jeong; Seung Yong Lee
Priority date: 2007-09-10
Filing date: 2008-09-04
Publication date: 2009-03-19
Also published as: KR100774568B1; WO2009035231A3

Abstract

A hydraulic control device for controlling a turbine valve is disclosed. The hydraulic control device includes a hydraulic pressure generating unit (1), a hydraulic pressure control unit (2), a hydraulic pressure actuating unit (3) and hydraulic attachments. The hydraulic pressure generating unit has an oil tank (12), an oil cooler (14) and a variable delivery type hydraulic pump (10). The hydraulic pressure control unit has a safety valve (20) and a servo valve (24). The hydraulic pressure actuating unit has a servo cylinder (30) and accumulators (32). The hydraulic attachments have a pressure reducing valve (40) and dump valves (42) and (43). Unlike the conventional control device, the present invention has a relatively simple structure. In addition, the pressure in a system can be maintained in a stable condition, and accuracy in controlling the turbine valve is increased, thus enhancing the quality of electricity supply created by a turbine.

Description

Description HYDRAULIC CONTROL DEVICE FOR TURBINE VALVE

Technical Field

[1] The present invention relates to a hydraulic control device for controlling the opening or closing of a turbine valve which supplies steam to a turbine, or for when a turbine trip occurs, interrupting the supply of steam so as to control the amount of electricity generation. Background Art

[2] As is well known to those skilled in the art, hydraulic actuators are devices, which convert hydraulic energy, generated from pumps, into mechanical energy. According to operating method, the hydraulic actuators are classified into hydraulic cylinders, hydraulic motors and hydraulic oscillating actuators.

[3] The hydraulic cylinders are actuators which convert hydraulic energy into linear reciprocating motion to conduct mechanical operation. The hydraulic motors are actuators which convert hydraulic energy into rotating motion to conduct mechanical operation. The hydraulic oscillating actuators are used as devices which for special purposes perform angular motion of less than 360°.

[4] In such hydraulic actuators, continuously variable speed control can be realized by changing the pressure and the flow rate of fluid using a control valve, and the direction, in which output force corresponding to a load is applied, can be freely controlled, thus being convenient for a user. Therefore, the hydraulic actuators have been widely used in various kinds of mechanical apparatuses, which control the operation thereof using hydraulic pressure.

[5] For example, a turbine for converting mechanical energy into electric energy using steam is typically provided with a hydraulic control device, which includes a hydraulic actuator and is used as a means for precisely controlling opening and closing of a turbine valve, which allows the supply of steam or, when a turbine trip occurs, interrupts the supply of steam.

[6] The general construction of such a conventional hydraulic control device for controlling opening and closing of a turbine valve will be schematically described herein below. As shown in FIG. 1, the conventional hydraulic control device includes a fixed delivery type hydraulic pump 100, such as a gear type hydraulic pump, a relief valve 200, an unloading valve 220, a servo valve 240, a servo cylinder 300 and an accumulator 320. The hydraulic control device having the above-mentioned construction forms an independent system. Furthermore, the hydraulic control device further includes a pressure reducing valve 400 and dump valves 420 and 430. [7] However, in the conventional hydraulic control device controlling opening and closing of the turbine valve, because the fixed delivery type hydraulic pump 100, which discharges a fixed amount of fluid regardless of the state of the device, is used, the pressure in the device is caused to be extremely variable. As a result, accuracy in controlling the turbine valve using the servo cylinder 30 is markedly deteriorated.

[8] Therefore, in the case where the fixed delivery type hydraulic pump 100 is used, a separate valve unit, including the relief valve 200 and the unloading valve 220 as a pair, is certainly required to maintain the pressure in the entire system within a predetermined range. In this case, the increased number of components of the device complicates the structure of the device. As well, to maintain the pressure in the system constant, frequent opening or closing of the relief valve 200 and the unloading valve 220 are required while the fixed delivery type hydraulic pump 100 is operated. This reduces the lifetime of the relief valve 200 and the unloading valve 220, thus increasing the maintenance and repair costs of the device.

[9] Moreover, the frequent opening or closing operation of the relief and unloading valves 200 and 220 induces malfunction of the valve, thus making the pressure in the system unstable. In this case, accuracy in controlling the turbine valve is reduced, with the result that the quality of electrical supply created by the turbine deteriorates. Disclosure of Invention

Technical Problem

[10] Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a hydraulic control device for turbine valves which has a simple structure and is constructed such that the pressure in a system can be maintained stably without frequently opening or closing valves and such that accuracy in controlling the turbine valve can be enhanced. Technical Solution

[11] In order to accomplish the above object, the present invention provides a hydraulic control device for a turbine valve, including: an oil tank to contain working fluid therein; an oil cooler provided in the oil tank to cool the working fluid; a variable delivery type hydraulic pump provided in the oil tank, the variable delivery type hydraulic pump applying a pressure to the working fluid to discharge the working fluid outside the oil tank; a safety valve for maintaining a constant system pressure, the safety valve being operated when an abnormal pressure occurs in the system; a servo valve to control a moving route, a flow rate, and a pressure of the working fluid; a servo cylinder operated by the working fluid, which is controlled in the moving route, the flow rate and the pressure thereof by the servo valve, thus controlling opening or closing of the turbine valve; an accumulator provided on a pipe branched off from a pipe, connecting the hydraulic pump to the servo valve, the accumulator accumulating high-pressure hydraulic energy; and a pressure reducing valve provided on a return pipe, connecting the servo valve to the oil tank, and a plurality of dump valves provided on respective branch pipes, connecting the accumulator to the return pipe.

[12] Preferably, the variable delivery type hydraulic pump may comprise a plunger pump, which is constructed such that a plunger is rotated by a rotating shaft and simultaneously reciprocates in a cylinder block, thus compressing and discharging the working fluid from the oil tank. As such, in the case where the hydraulic pump comprises the plunger pump, a separate relief valve and a separate unloading valve, which are required in the conventional fixed delivery type hydraulic pump, are unnecessary, thus simplifying the structure of the device, and reducing the volume thereof.

[13] Furthermore, the safety valve may be formed by integrating a relief valve, limiting a maximum pressure in the system, with an unloading valve, maintaining system pressure within a predetermined range. The safety valve is installed to achieve the purpose of maintaining the pressure in the system within a desired range in time of emergency. However, because the pressure in the system is generally maintained constant by the use of the variable delivery type hydraulic pump, when the hydraulic pump is normally operated, the safety valve is not operated, unlike the conventional relief valve and unloading valve. Therefore, the present invention can solve the problem of the conventional technique, in which the lifetime of the hydraulic valve is reduced attributable to the operation of frequently turning on/off the hydraulic valve. Thereby, the maintenance and repair costs of the device can be markedly reduced.

[14] Preferably, the servo valve may comprise a jet pipe type servo valve, which has a relatively simple structure and can be prevented from being undesirably turned off or malfunctioning due to adherence of a spool when it is operated. This jet pipe type servo valve may include: a torque generating unit to generate torque in an amature using a magnetic force generated in a coil; and a nozzle to move leftwards or rightwards in proportion to an intensity of the torque, generated in the amature by the torque generating unit. The nozzle may be coupled to a spool through a link. The spool may follow the nozzle, such that the spool may be moved leftwards or rightwards in conjunction with the left or rightward movement of the nozzle for a distance corresponding to the displacement of the nozzle. Working fluid, discharged from the nozzle, is supplied into a chamber, which is formed in a valve body and delimited by one end of the spool, via, of two passages formed in the valve body, one corresponding passage aligned with the outlet of the displaced nozzle, thus assisting the left or right movement of the spool, thereby increasing the control accuracy of the servo valve. [15] The servo cylinder may comprise a double acting cylinder or a single acting cylinder.

[16] The accumulator may comprise a piston type accumulator, having a piston provided in a cylinder so as to be reciprocatable, wherein the space in the cylinder is partitioned by the piston into a gas chamber and a fluid chamber, into which the working fluid is drawn. In the case where the accumulator is a piston type, there is an advantage in that, even if an emergency situation occurs, emergency rehabilitation work can be implemented without turning off the system, unlike the conventional use of a blade type accumulator.

[17] The piston type accumulator may have a sensor, which monitors a position of the piston relative to the amount of working gas, supplied into the gas chamber through a gas supply valve, so as to detect leakage of gas from the gas chamber. In this case, because malfunction of the accumulator can be easily detected, preliminary measures to cope with the malfunction can be conducted within an early time frame.

Advantageous Effects

[18] A hydraulic control device for a turbine valve according to the present invention uses a plunger type variable delivery hydraulic pump, which converts mechanical energy into pressure energy of fluid and varies a discharge rate depending on a load pressure. Therefore, a separate relief valve and a separate unloading valve, which have been required in the conventional system using the fixed delivery type hydraulic pump, are unnecessary. Thus, the structure of the device can be simplified and the volume thereof can be reduced.

[19] Moreover, although the present invention is provided with a safety valve to prevent occurrence of abnormal pressure in the system and thus ensure the safety of the system, because the variable delivery type hydraulic pump generally maintains the pressure in the system stable, when the hydraulic pump is normally operated, the safety valve is not operated, unlike the conventional technique using the relief valve and the unloading valve. Therefore, a problem of a reduction of the lifetime of the hydraulic valve attributable to operation of frequently turning on/off the hydraulic valve can be solved. Thereby, the maintenance and repair costs can be markedly reduced.

[20] Furthermore, the pressure in the system can be maintained stable by the use of the variable delivery hydraulic pump. Hence, the control accuracy of the turbine valve is increased, thus enhancing the quality of electrical supply created by a turbine. Brief Description of the Drawings

[21] FIG. 1 is a hydraulic circuit diagram showing the general construction of a conventional hydraulic control device for controlling a turbine valve;

[22] FIG. 2 is a partially broken perspective view showing the general construction of a hydraulic control device for controlling a turbine valve, according to the present invention; [23] FIG. 3 is a hydraulic circuit diagram showing the general construction of the hydraulic control device according to the present invention; [24] FIG. 4 is a sectional view showing the construction of a plunger type variable delivery hydraulic pump as one example of a hydraulic pump used in the present invention;

[25] FIG. 5 is a sectional view of a safety valve used in the present invention;

[26] FIG. 6 is a sectional view showing the general construction of a jet pipe type servo valve used in the present invention; [27] FIG. 7 is a sectional view showing the general construction of an accumulator used in the present invention; and [28] FIGS. 8 and 9 are views showing results of pressure tests done to obtain pressure states in systems of the conventional hydraulic control device of FIG. 1 and the hydraulic control device of FIG. 2 according to the present invention, respectively.

Best Mode for Carrying Out the Invention [29] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the attached drawings. [30] FIG. 2 is a partially broken perspective view showing the general construction of a hydraulic control device for controlling a turbine valve, according to the present invention. FIG. 3 is a hydraulic circuit diagram showing the general construction of the hydraulic control device of the present invention. [31] Referring to FIGS. 2 and 3, the hydraulic control device for controlling the turbine valve according to the present invention includes a hydraulic pressure generating unit

1, a hydraulic pressure control unit 2, a hydraulic pressure actuating unit 3 and hydraulic attachments. The hydraulic pressure generating unit 1 has an oil tank 12, an

011 cooler 14 and a variable delivery type hydraulic pump 10. The hydraulic pressure control unit 2 has a safety valve 20 and a servo valve 24. The hydraulic pressure actuating unit 3 has a servo cylinder 30 and accumulators 32. The hydraulic attachments have a pressure reducing valve 40 and dump valves 42 and 43.

[32] The oil tank 12 is filled with working fluid, which is the working medium for generating power using hydraulic pressure. The oil cooler 14 is installed in the oil tank

12 to cool working fluid, which is returned into the oil tank 12. Although the detailed construction of the oil cooler 14 is not illustrated in the drawings, the oil cooler 14 may have the same structure as that of a typical heat exchanger, in which a circulation pipe for circulation of cooling water, for example, cold water or refrigerant, is arranged between headers, which are disposed at upper and lower positions spaced apart from each other by a predetermined distance, so that cooling water supplied from the upper header circulates the circulation pipe and thus cools working fluid in the oil tank. Preferably, the oil cooler 14 is made of stainless steel to prevent it from being corroded by working fluid.

[33] The variable delivery type hydraulic pump 10, which is operated by a motor, compresses working fluid, which is charged in the oil tank 12, and thus discharges working fluid outside the oil tank 12. It is preferable that a plunger pump, in which a plunger 120 is rotated by a rotating shaft 110 and simultaneously reciprocates in a cylinder block 130 to discharge working fluid outside the oil tank 12, as shown in FIG. 4, be used as the variable delivery type hydraulic pump 10. As such, in the case where the plunger pump is used as the hydraulic pump 10, it is unnecessary to use a separate relief valve and a separate unloading valve, which are required to maintain constant pressure in the system when the conventional fixed delivery type hydraulic pump is used as the hydraulic pump. Therefore, the structure of the device can be simplified and the volume thereof can be reduced.

[34] The safety valve 20 may be constructed such that a relief valve 21, which limits the maximum pressure in the system, and an unloading valve 22, which maintains the pressure in the system within a predetermined range, are integrated with each other, as shown in FIG. 5. In the present invention, the safety valve 20 is installed to achieve the purpose of maintaining the pressure in the system within a desired range in time of emergency. However, because the pressure in the system is generally maintained constant by the use of the variable delivery type hydraulic pump 10, when the hydraulic pump is normally operated, the safety valve 20 is not operated, and only when the pressure in the system is abnormal will the safety valve 20 be operated intermittently, unlike the conventional relief and unloading valves. Therefore, the present invention can solve the problem of the conventional technique using the fixed delivery type hydraulic valve, this problem being that the frequent turning on/off of the fixed delivery type hydraulic valve causes a reduction in the lifetime of the hydraulic valve. Thereby, the maintenance and repair costs can be markedly reduced.

[35] A jet pipe type servo valve, which has a relatively simple structure and can be prevented from being undesirably turned off or malfunctioning due to adherence of a spool when it is operated, is preferably used as the servo valve 24. The jet pipe type servo valve is constructed such that torque is generated in an amature by magnetic force generated in a coil, and such that a nozzle and a spool which are operated in conjunction with each other are moved to the left or the right in proportion to the intensity of the generated torque, and such that a flow rate of fluid is increased or reduced depending on the degree with which the spool is moved. Such a jet pipe type servo valve has advantages of high performance and high responsibility.

[36] In detail, as shown in FIG. 6, the jet pipe type servo valve used in the present invention includes a torque generating unit 244, which generates torque in an amature 242 using magnetic force generated in a coil, and a nozzle 246, which moves to the left or the right in proportion to the intensity of the torque generated in the amature 242 by the torque generating unit 244. The nozzle 246 is coupled to a spool 248, which controls a flow rate and a direction of fluid, through a link 247 such that they are operated in conjunction with each other. Thus, the spool 248 is moved in proportion to a displacement of the nozzle 246 to the left or the right depending on the direction, in which the nozzle 246 is moved. Working fluid, which is discharged from the nozzle 246, is supplied into one of two chambers 249a and 249b, which are formed in the valve body 245 on opposite sides of the spool 248, via, of the two passages 245a and 245b formed in the valve body 245, one passage aligned with the outlet of the nozzle 246, thus assisting the left or right movement of the spool 248.

[37] Although the structure of the servo cylinder 30 is not shown in the drawings, the servo cylinder 30 may comprise a double acting cylinder, which has oil feeding ports in a cylinder tube on respective opposite sides of a piston ring that is installed in the cylinder tube, or a single acting cylinder, which has a single oil feeding port in one end of a cylinder tube around a piston ring so that working fluid for operating the piston is fed into or discharged from the cylinder tube through the oil feeding port.

[38] The accumulators 32 are coupled to respective pipes, which are branched off from a pipe used to connect the hydraulic pump 10 and the servo valve 24, so as to accumulate surplus energy of fluid, discharged at high pressure by the hydraulic pump in the system. Depending on the fluid moving route control of the dump valves 42 and 43, working fluid, which has accumulated in the accumulators 32, may be moved to the servo cylinder 30 to conduct mechanical operation or may be returned to the oil tank 12 along a return pipe R/P.

[39] As shown in FIG. 7, preferably, each accumulator 32 comprises a piston type accumulator, in which a piston 322 is provided in a cylinder tube 321 so as to be recip- rocatable in the longitudinal direction and the space in the cylinder tube 321 is partitioned by the piston 322 into a gas chamber 324 and a fluid chamber 326, which stores fed working fluid therein. As such, in the case where the accumulator 32 is a piston type, even if an emergency situation occurs, emergency rehabilitation work can be implemented without turning off the system, unlike the conventional technique using the blade type accumulator. Therefore, there is an advantage in that general maintenance and repair of the device are on the whole simplified.

[40] Here, the piston type accumulator 32 may be provided with a sensor (not shown), which monitors the position of the piston 322 relative to the amount of working gas, supplied into the gas chamber through a gas supply valve 328, so as to detect leakage of gas from the gas chamber. In this case, because malfunction of the accumulator 32 attributable to leakage of gas from the gas chamber 324 is easily detected, preliminary measures for preventing the malfunction can be conducted early on, thus fundamentally preventing the system being required to be turned off for a long time to repair a malfunction.

[41] Meanwhile, the pressure reducing valve 40 is provided both on the return pipe R/P, which connects the servo cylinder 30 to the oil tank 12, and on a pipe (not designated by a reference numeral), which connects the return pipe R/P to the accumulator 32. The pressure reducing valve 40 serves to reduce the pressure when high pressure working fluid, which has been accumulated in the accumulator 32, is returned to the oil tank 12. The dump valves 42 and 43 are respectively provided on the return pipe R/P and on several branch pipes (not designated by a reference numeral), which connect the return pipe R/P to the accumulators 32. The dump valves 42 and 43 serve to change the moving route of fluid such that high-pressure energy of fluid, which has been accumulated in the accumulator 32, can be transmitted to the servo cylinder 30.

[42] In the drawings, reference numeral 25 denotes a filter, provided on a pipe, which connects the hydraulic pressure generating unit to the hydraulic pressure control unit, to remove impurities from high pressure fluid supplied from the hydraulic pressure generating unit.

[43] As such, in the embodiment of the present invention having the above-mentioned construction, because the plunger type variable delivery hydraulic pump 10, which converts mechanical energy into pressure energy of fluid and varies a discharge rate depending on a load pressure, is used, a separate relief valve and a separate unloading valve, which have been required in the conventional system using the fixed delivery type hydraulic pump, are unnecessary. Therefore, the structure of the device can be simplified and the volume thereof can be reduced.

[44] In detail, in the case of the conventional fixed delivery type hydraulic pump, for example, a gear type hydraulic pump, because a fixed amount of fluid is output regardless of the amount of fluid required by the system, the pressure of output fluid is generally unstable, as shown in the graph of FIG. 8. Therefore, the power consumption of the system is increased. Furthermore, because the pressure of output fluid cannot be controlled, a separate hydraulic pressure control valve, including the relief valve and the unloading valve, is absolutely necessary. However, in the case of the variable delivery type hydraulic pump 10 of the present invention, the amount of fluid discharged from the pump is automatically controlled in response to the amount of fluid required by the system. Hence, as shown in FIG. 9, the pressure of fluid in the system is generally stable, thus reducing the power consumption of the system. Furthermore, because the pump itself has a pressure control function, a separate relief valve or a separate unloading valve is not required. Thereby, the possibility of mal- function of the valve can be reduced, thus enhancing the reliability of the system.

[45] Moreover, although the present invention is provided with the safety valve 20 to prevent occurrence of abnormal pressure in the system and thus ensure the safety of the system, because the variable delivery type hydraulic pump 10 generally maintains the pressure in the system stable, when the hydraulic pump is normally operated, the safety valve 20 is not operated, unlike the conventional technique using the relief valve and the unloading valve. Therefore, a problem of a reduction of the lifetime of the hydraulic valve attributable to the operation of frequently turning on/off the hydraulic valve can be solved. Thereby, the maintenance and repair costs can be markedly reduced.

[46] Although the preferred embodiment of the present invention has been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims

[1] A hydraulic control device for a turbine valve, comprising: an oil tank to contain working fluid therein; an oil cooler provided in the oil tank to cool the working fluid; a variable delivery type hydraulic pump provided in the oil tank, the variable delivery type hydraulic pump applying a pressure to the working fluid to discharge the working fluid outside the oil tank; a safety valve for maintaining a pressure in a system constant, the safety valve being operated when an abnormal pressure occurs in the system; a servo valve to control a moving route, a flow rate, and a pressure of the working fluid; a servo cylinder operated by the working fluid, which is controlled in the moving route, the flow rate and the pressure thereof by the servo valve, thus controlling opening or closing of the turbine valve; an accumulator provided on a pipe branched off from a pipe, connecting the hydraulic pump to the servo valve, the accumulator accumulating high-pressure hydraulic energy; and a pressure reducing valve provided on a return pipe, connecting the servo valve to the oil tank, and a plurality of dump valves provided on respective branch pipes, connecting the accumulator to the return pipe.

[2] The hydraulic control device according to claim 1, wherein the variable delivery type hydraulic pump comprises a plunger pump, including a plunger to be rotated by a rotating shaft and reciprocating in a cylinder block, thus compressing and discharging the working fluid from the oil tank.

[3] The hydraulic control device according to claim 1 or 2, wherein the safety valve is formed by integrating a relief valve, limiting a maximum pressure in the system, with an unloading valve, maintaining a pressure in the system within a predetermined range.

[4] The hydraulic control device according to claim 3, wherein the servo valve comprises a jet pipe type servo valve, the jet pipe type servo valve comprising: a torque generating unit to generate torque in an amature using a magnetic force generated in a coil; and a nozzle to move leftwards or rightwards in proportion to an intensity of the torque, generated in the amature by the torque generating unit, wherein the nozzle is coupled to a spool through a link, the spool being moved leftwards or rightwards in conjunction with left or right movement of the nozzle in proportion to a displacement rate of the nozzle, and working fluid, discharged from the nozzle, is supplied into a chamber, formed in a valve body and delimited by one end of the spool, via, of two passages formed in the valve body, one corresponding passage aligned with an outlet of the displaced nozzle, thus assisting the left or right movement of the spool.

[5] The hydraulic control device according to claim 4, wherein the accumulator comprises a piston type accumulator, having a piston provided in a cylinder so as to be reciprocatable, wherein a space in the cylinder is partitioned by the piston into a gas chamber and a fluid chamber, into which the working fluid is drawn.

[6] The hydraulic control device according to claim 5, wherein the piston type accumulator has a sensor, monitoring a position of the piston relative to an amount of working gas, supplied into the gas chamber through a gas supply valve, so as to detect leakage of gas from the gas chamber.