JP2006077831A - Electric driven control valve and plant equipped therewith - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent damage to a valve seat portion due to erosion by surely preventing the leakage of processed fluid from the valve seat portion of a valve body. <P>SOLUTION: In this electric driven control valve whose opening is controlled by giving a operation signal 10o from a control device 10 to an electric actuator 9 to drive a valve stem 8 and move a valve plug 7 via the valve stem 8, a timer 13 is provided for generating an output signal in the control device for every preset time. In accordance with the output signal 13o of the timer, a valve closing signal is given to the electric actuator for every preset time to periodically operate closing torque between the valve plug 7 and the vale seat portion 6. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electric drive type control valve, and more particularly to an electric drive type control valve in which measures against leakage of fluid from a valve seat portion are taken and a plant including the electric drive type control valve.

  An electrically driven control valve (hereinafter abbreviated as “electrically controlled valve”) is a combination of an electric actuator and a valve body that decelerates the rotation of the motor with a gear and opens and closes the valve with a feed screw. A cage is disposed in the valve chamber formed between the primary flow path (inlet flow path) and the secondary flow path (outlet flow path) of the valve casing, and the valve seat and valve plug are placed in the cage. And a valve body in which the valve plug is operated up and down by the valve stem, and an electric actuator that drives the valve stem (for example, see Non-Patent Document 1).

  The electric actuator is configured to receive an operation signal from the control device and operate the feed amount of the valve plug so as to obtain a valve opening corresponding to the value, and the valve plug corresponds to the operation signal. It can be stopped in a fully open state, a fully closed state, or an arbitrary valve opening.

  The control device gives an operation signal to the electric actuator only when the valve is operated, and after the valve moves (rotates) to a predetermined position, the operation signal disappears and the state is maintained by the electric actuator itself. Yes.

  As an example of using an electric control valve, it is common to control the valve opening continuously according to the deviation between the flow rate setting value and the feedback value, but electric control installed in the piping system of a thermal power plant In the valve, there is an example of use in which the valve is fully closed during normal plant operation.

  For example, in a thermal power plant, the feed water sent from the deaerator is boosted and supplied to the feed water heater to feed water to the boiler, and in order to prevent temperature rise by the boiler feed water pump, Control is performed to ensure the minimum required flow rate (minimum flow) of the pump. For this reason, in the unlikely event that the suction flow rate of the feed water pump becomes equal to or less than the minimum flow amount, the valve that is fully closed during normal plant operation is opened to recirculate the minimum flow amount to the deaerator.

Although it is not a technique applied to the boiler water supply system as described above, the primary side pipe pressure is detected in advance for a certain period of time prior to the valve monitoring operation mode and input to the actuator, and determination is made based on this data. By creating a reference and comparing the pressure fluctuation data detected in the monitoring operation mode with this criterion, whether or not the abnormal value of the pressure fluctuation value detected on the primary side is caused by the water hammer or If it is determined that it is caused by leakage to the secondary side of the valve, and if it is determined that it is caused by leakage to the secondary side, the valve actuator is operated to automatically adjust the valve fully closed position The invention as described above is disclosed (for example, see Patent Document 1).
Japan Society of Mechanical Engineers, Mechanical Engineering Handbook, January 15, 1968, 5th edition, 21st volume, pages 28 (21-28) JP 2002-181229 A (page 3, FIG. 2 to FIG. 4)

  The valve stem that opens when the minimum flow amount is recirculated to the above-described deaerator may rarely undergo thermal expansion and contraction due to temperature changes in the feed water. When the valve stem length expands and contracts, a slight gap is created in the contact surface between the valve seat part, that is, the valve plug and the valve seat part, from which high-temperature and high-pressure water is leaked. The seat can be damaged.

  Further, in the case of the invention described in the above-mentioned Patent Document 1, the leakage of the fluid is not directly detected on the secondary side of the valve, and the judgment criterion prepared in advance prior to the monitoring operation mode and the monitoring operation mode Since this is compared with the actual pressure fluctuation data detected, when this invention is applied to the water supply system of the above-mentioned thermal power plant, does it appear as pressure fluctuation on the primary side when a slight leak occurs in the fluid? Even if it appears as a pressure fluctuation on the primary side, it is very difficult to make a judgment standard in order to correctly discriminate from noise, and it becomes very difficult to design an actuator after all.

  Accordingly, the present invention has been made in view of such circumstances, and a first object of the present invention is to reliably prevent the leakage of fluid from the valve seat portion of the valve body and to prevent the valve seat by erosion. An object is to provide an electrically driven control valve and a plant provided with the electrically driven control valve so as to prevent the parts from being damaged.

  Further, the second object of the present invention is that when fluid from the valve seat portion of the valve body leaks, it can be detected easily and reliably to minimize the influence of the leakage, and the valve seat portion is caused by erosion. An object of the present invention is to provide an electric drive type control valve and a plant provided with the electric drive type control valve so as to prevent damage.

  Furthermore, a third object of the present invention is that a constant pressing force is always applied by a spring between the valve plug and the valve seat portion, so that the valve body is influenced by a change in tightening torque over time. An object of the present invention is to provide an electric drive type control valve and a plant provided with an electric drive type control valve so as to prevent damage to a valve seat portion caused by erosion.

  In order to achieve the above object, an electrically driven control valve according to a first aspect of the present invention provides an operation signal from a control device to an electrically operated actuator to drive a valve stem, and a valve plug is connected via the valve stem. In the electrically driven control valve that controls the valve opening by moving, a timer that generates an output signal every predetermined time is provided in the control device, and the electric actuator is predetermined based on the output signal of the timer. A valve closing signal is given every hour, and a closing torque is applied between the valve plug and the valve seat portion via the valve stem by the electric actuator.

  Further, the invention of the electrically driven control valve according to claim 2 drives the valve stem by giving an operation signal from the control device to the electrically operated actuator, and moves the valve plug through the valve stem to open the valve. In the electrically driven control valve configured to control the degree, a sensor for monitoring a physical quantity of fluid is provided in the secondary flow path of the valve casing, and a detection signal from the sensor and a predetermined set value are provided in the control device. And determining whether or not there is fluid leakage. When the determination unit determines that there is fluid leakage, a valve closing signal is given to the electric actuator, and the valve stem is A shut-off torque is applied between the valve plug and the valve seat through the valve.

  Further, the invention of the electrically driven control valve according to claim 4 provides the operation signal from the control device to the electrically operated actuator to drive the valve stem, and moves the valve plug through this valve stem to open the valve. In the electrically driven control valve in which the degree is controlled, the valve stem is provided with a spring having a direction in which a cutoff torque is always applied.

  According to the first invention, since a constant shut-off torque is applied between the valve plug and the valve seat portion periodically by a timer provided in the control device, the valve plug, There is no gap between the valve seat portions, and therefore it is possible to prevent the erosion from progressing to a situation where the valve seat portion is damaged.

  In addition, according to the second aspect of the invention, a sensor is provided in the secondary flow path of the valve body so as to monitor the fluid leakage, so that if there is a leakage from the valve seat, the valve plug 7 Since the closing torque is applied so that the valve plug 7 and the valve seat portion 6 are brought into close contact with each other, the leakage of the fluid can be stopped and the influence of the fluid leakage can be suppressed to the minimum.

  Furthermore, according to the third invention, since the valve plug is made to always apply a constant pressing force with the spring between the valve seat portions, there is no need to install various sensors, and a logic circuit is added to the control device. Without adding, it is possible to suppress the influence of the change in tightening torque over time on the valve body.

  Embodiments of an electrically driven control valve according to the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the part which is common throughout each figure, and the overlapping description is abbreviate | omitted.

Example 1
FIG. 1 is a sectional view showing in detail a valve body of a general electric control valve applied to the present invention.
In FIG. 1, reference numeral 1 denotes a valve body of an electric control valve provided in a recirculation system for ensuring a minimum flow amount of a boiler feed pump of a thermal power plant, and a primary flow path (inlet side flow) of a valve casing 2. 3) A cylindrical cage 5 is arranged in a vertical valve chamber formed between the secondary side flow path (outlet side flow path) 4 and the valve seat portion (seat ring) 6 and The valve plug 7 is disposed oppositely, and the valve plug 7 is driven up and down by the valve stem 8 to control the valve opening. The feed amount of the valve stem 8 is controlled by an electric actuator 9.

  Moreover, the electric actuator 9 receives the operation signal 10o from the control device 10 and accurately operates the feed amount of the valve plug 7 via the valve stem 8 so that the valve opening corresponding to the value is obtained. The position of the valve plug 7 can be maintained in a fully open state, a fully closed state (closed state), or an arbitrary valve opening degree by an operation signal.

FIG. 2 is a schematic diagram of the electric control valve according to the first embodiment of the present invention.
In the electric control valve according to the first embodiment, the control device 10 periodically gives an operation signal 10o to the electric actuator 9 in a state where the valve body 1 is fully closed, that is, a shut-off state. A shut-off torque is applied between the valve seat portions 6 periodically.

  That is, the control device 10 receives a control command 11i output from an arbitrary control unit (not shown), outputs a fully closed command signal output unit 11 that outputs a fully closed command signal 11o, and a valve closing signal 120. The valve opening ≦ 0% signal generating unit 12 to perform, the timer 13 for generating an output signal at predetermined time intervals, the valve closing signal 12o from the valve opening ≦ 0% signal generating unit 12, and the output signal 13o of the timer 13 And an AND circuit 14 that detects whether the AND condition is satisfied, and an OR circuit 15 that detects an OR condition between the output signal 14o of the AND circuit 14 and the fully closed command signal 11o of the fully closed command signal output unit 11. The operation signal 10o is output from the OR circuit 15 to the electric actuator 9 when the full-close command condition is met.

  When the valve body 1 itself is normal, once the full-close command signal 11o is output from the full-close command signal output unit 11, the electric actuator 9 brings the valve plug 7 and the valve seat 6 into close contact with each other with a predetermined shut-off torque. The state is set to the fully closed state. For this reason, the process fluid is blocked by the valve body 1.

  By the way, when the valve stem 1 is changed by the temperature change of the process fluid in the fully closed state of the valve main body 1 as described above, the shut-off torque changes, and in some cases, the valve plug 7 and the valve seat portion 6 are slightly changed. If a gap is formed and the process fluid leaks from the gap, and this state is left as it is, the valve seat portion 6 may be damaged by erosion.

  However, in the first embodiment, when the valve body 1 is fully closed, the operation signal 10o is given to the electric actuator 9 every predetermined time by the timer 13 provided in the control device 10, that is, periodically. Since a constant shut-off torque is applied between the valve plug 7 and the valve seat portion 6, even if the valve stem length expands or contracts due to a temperature change of the process fluid, the valve plug 7 and the valve seat portion 6 Therefore, it is possible to prevent a situation in which the valve seat portion 6 is damaged due to erosion due to leakage of the process fluid.

(Example 2)
FIG. 3 is a schematic view of an electric control valve according to Embodiment 2 of the present invention.
In the electric control valve according to the second embodiment, the secondary side channel temperature of the valve body 1 is constantly monitored and the secondary side channel temperature is set when the valve body 1 is fully closed (closed state). When the value exceeds the value, it is determined that there is a leakage of the process fluid, and the control device 10 intermittently moves to the valve seat portion with respect to the electric actuator 9 according to the secondary side flow path temperature change of the valve body 1. A deadline torque is applied.

  That is, a temperature sensor (TE) 16 is installed in the secondary side flow path 4 of the valve casing 2 to constantly monitor the secondary side flow path temperature, while an output signal 16o of the temperature sensor 16 is input to the control device 10. When the signal 16o is equal to or higher than a set value, the secondary side flow path temperature determination unit 17 that determines that there is a leakage of the process fluid and generates an operation output 17o is provided.

  When a slight gap is generated between the valve plug 7 and the valve seat 6 due to expansion and contraction of the valve stem 8 during plant operation, and the process fluid leaks from the gap, the temperature of the process fluid is detected by the temperature sensor 16 because the temperature is high. The detected temperature signal is input to the secondary flow path temperature determination unit 17 in the control device 10 and compared with the set value. If the temperature detected from the temperature sensor 16 is equal to or higher than a predetermined set value, the secondary side channel temperature determination unit 17 generates an operation output 17o. Then, the control device 10 gives a command for applying a constant shut-off torque between the valve plug 7 and the valve seat portion 6 to the electric actuator 9 via the AND circuit 14 and the OR circuit 15. As a result, the valve plug 7 is pushed down further toward the valve seat portion 6 than the current position to bring the valve plug 7 and the valve seat portion 6 into close contact with each other, thereby stopping the leakage of the process fluid.

  As described above, in the electric control valve according to the second embodiment, the secondary side flow path temperature of the valve body 1 is directly monitored by the temperature sensor 16 installed on the secondary side of the valve casing 2, and the detected temperature is If the secondary side flow temperature determination unit exceeds a preset value, it is determined that there is a leakage of the process fluid, and a closing torque is applied to the valve plug 7 to bring the valve plug 7 and the valve seat 6 into close contact with each other. Thus, the leakage of the process fluid can be stopped thereafter.

  Therefore, according to the second embodiment, even if the process fluid leaks due to a decrease in the tightening force torque due to the expansion and contraction of the valve stem length, it is not necessary to provide a difficult determination criterion as in the invention described in Patent Document 1. The apparatus can minimize the effects of process fluid leakage.

(Example 3)
FIG. 4 is a schematic diagram of an electric control valve according to Embodiment 3 of the present invention.
In the electric control valve according to the third embodiment, in the state where the valve body 1 is fully closed (closed state), the secondary side passage pressure of the valve body 1 is constantly monitored and the secondary side passage pressure is set. When the value exceeds the value, it is determined that there is a leakage of the process fluid, and the control device 10 intermittently moves to the valve seat portion with respect to the electric actuator 9 according to the change in the secondary side flow path pressure of the valve body 1. A deadline torque is applied.

  That is, a pressure sensor (PT) 18 is installed in the secondary side flow path 4 of the valve casing 2 to constantly monitor the secondary side flow path pressure, while an output signal 18 o of the pressure sensor 18 is input to the control device 10. Then, when the signal 18o becomes equal to or higher than a set value, a secondary side flow pressure determination unit 19 that determines that there is leakage of the process fluid and generates an operation output 19o is provided.

  When a slight gap is generated between the valve plug 7 and the valve seat 6 due to expansion and contraction of the valve stem 8 during plant operation, and the process fluid leaks from the gap, the pressure of the process fluid is detected by the pressure sensor 18 because the pressure is high, The detected pressure signal is input to the secondary flow path pressure determination unit 19 in the control device 10 and compared with the set value. If the detected pressure from the pressure sensor 18 is equal to or higher than a predetermined set value, the secondary side flow path pressure determination unit 19 determines that there is a leakage of the process fluid and generates an operation output 19o. Then, the control device 10 gives a command for applying a constant shut-off torque between the valve plug 7 and the valve seat portion 6 to the electric actuator 9 via the AND circuit 14 and the OR circuit 15. As a result, the valve plug 7 is pushed down further toward the valve seat portion 6 than the current position to bring the valve plug 7 and the valve seat portion 6 into close contact with each other, thereby stopping the leakage of the process fluid.

  As described above, the electric control valve according to the third embodiment directly monitors the secondary flow path pressure of the valve body 1 by the pressure sensor 18 installed on the secondary side of the valve casing 2, and the detected pressure is If the secondary side flow pressure determination unit exceeds a predetermined value, it is determined that there is a leakage of the process fluid, and a closing torque is applied to the valve plug 7 to bring the valve plug 7 and the valve seat 6 into close contact with each other. Thus, the leakage of the process fluid can be stopped thereafter.

  Therefore, according to the third embodiment, even if the process fluid leaks due to a decrease in the tightening force torque due to the expansion and contraction of the valve stem length, as in the second embodiment, a difficult determination standard like the invention described in Patent Document 1 is provided. The effects of process fluid leakage can be minimized with simple equipment that is not necessary.

Example 4
FIG. 5 is a schematic diagram of an electric control valve according to Embodiment 4 of the present invention.
In the electric control valve according to the fourth embodiment, the secondary side flow rate of the valve body 1 is constantly monitored in a state where the valve body 1 is fully closed (closed state), and the secondary side flow rate is scheduled. When the value exceeds the value, it is determined that there is a leakage of the process fluid, and the control device 10 intermittently moves to the valve seat portion with respect to the electric actuator 9 according to the change in the flow rate on the secondary side of the valve body 1. A deadline torque is applied.

  That is, a flow rate sensor (FT) 20 is installed in the secondary flow path 4 of the valve casing 2 to constantly monitor the secondary flow path flow rate, while the control device 10 receives the output signal 20 o of the flow rate sensor 20. When the signal 20o becomes equal to or higher than the set value, the secondary flow rate determining unit 21 that determines that there is a process fluid leak and generates an operation output 21o is provided.

  When a slight gap is generated between the valve plug 7 and the valve seat 6 due to expansion and contraction of the valve stem 8 during plant operation, and the process fluid leaks from the gap, the flow sensor 20 detects it. The detected flow rate signal is input to the flow rate determination unit 21 in the control device 10 and compared with a set value. If the detected flow rate from the flow rate sensor 20 is equal to or greater than a preset value, the secondary side flow rate determination unit 21 determines that there is a leakage of the process fluid and generates an operation output 21o. Then, the control device 10 gives a command for applying a constant shut-off torque between the valve plug 7 and the valve seat portion 6 to the electric actuator 9 via the AND circuit 14 and the OR circuit 15. As a result, the valve plug 7 is pushed down further toward the valve seat portion 6 than the current position to bring the valve plug 7 and the valve seat portion 6 into close contact with each other, thereby stopping the leakage of the process fluid.

  As described above, in the electric control valve according to the fourth embodiment, the flow rate sensor 20 monitors the presence or absence of the secondary side flow rate of the valve body 1, and the monitored value is set in advance by the flow rate determination unit 21. If the value is greater than the value, it is determined that there is a process fluid leak, and a closing torque is applied to the valve plug 7 so that the valve plug 7 and the valve seat 6 are in close contact with each other. be able to.

  Therefore, according to the fourth embodiment, even if the process fluid leaks due to the decrease in the tightening force torque due to the expansion and contraction of the valve stem length, as in the second embodiment, a difficult determination standard like the invention described in Patent Document 1 is provided. The effects of process fluid leakage can be minimized with simple equipment that is not necessary.

(Example 5)
FIG. 6 is a schematic diagram of an electric control valve according to Embodiment 5 of the present invention.
In the electric control valve according to the fifth embodiment, the spring 22 for pressing the valve plug 7 against the valve seat portion 6 at a constant pressure at all times is provided to the valve stem 8 in order to suppress the influence of the change in tightening torque over time. It is provided in the part.

  According to the fifth embodiment, it is not necessary to install the various sensors described above in the secondary flow path of the valve body 1, and it can be configured extremely simply without adding a logic circuit to the control device.

(Example 6)
FIG. 7 is a schematic view of an electric control valve according to Embodiment 6 of the present invention, and FIG. 8 is an enlarged cross-sectional view of a valve seat portion.
The electric control valve according to the sixth embodiment is provided with a spring 23 for constantly pushing up the valve seat portion 6 at a constant pressure in order to suppress the influence of a change in tightening torque over time. It is what.
According to the sixth embodiment, it is not necessary to provide a sensor as in the fifth embodiment, and the control device 10 can also be configured extremely simply without adding a logic circuit.

  In addition, although the embodiment described above was described with the valve installed in the recirculation system of the deaerator in mind, the present invention is not limited to this, for example, between the main steam pipe and the condenser in a nuclear power plant. The present invention can also be applied to a bypass valve provided in a bypass pipe to be connected (a valve that is fully closed during normal plant operation and fully opened during an emergency stop).

The detailed sectional view of the valve main part of an electric drive way control valve. The schematic diagram of the electric control valve which concerns on Example 1 of this invention. The schematic diagram of the electric control valve which concerns on Example 2 of this invention. The schematic diagram of the electric control valve which concerns on Example 3 of this invention. The schematic diagram of the electric control valve which concerns on Example 4 of this invention. The schematic diagram of the electric control valve which concerns on Example 5 of this invention. The schematic diagram of the electric control valve which concerns on Example 6 of this invention. The expanded sectional view of the valve seat part of the electric control valve which concerns on Example 6 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Valve body, 2 ... Valve casing, 3 ... Primary side flow path (inlet side), 4 ... Secondary side flow path (outlet side), 5 ... Cage, 6 ... Valve seat part, 7 ... Valve plug, 8 DESCRIPTION OF SYMBOLS ... Valve stem, 9 ... Electric actuator, 10 ... Control device, 11 ... Full-close command signal output part, 12 ... Valve opening <= 0% signal generation part, 13 ... Timer, 14 ... OR circuit, 15 ... AND circuit, DESCRIPTION OF SYMBOLS 16 ... Temperature sensor, 17 ... Secondary temperature determination part, 18 ... Pressure sensor, 19 ... Secondary pressure determination part, 20 ... Flow rate sensor, 21 ... Secondary flow rate determination part, 22 ... Spring, 23 ... Spring

Claims (6)

In the electrically driven control valve that controls the valve opening by applying an operation signal from the control device to the electric actuator to drive the valve stem and moving the valve plug through the valve stem.
The control device is provided with a timer for generating an output signal every predetermined time, and a valve closing signal for every predetermined time is given to the electric actuator based on the output signal of the timer, and the electric actuator passes the valve stem through the valve stem. An electrically driven control valve characterized by applying a shut-off torque between a valve plug and a valve seat. In the electrically driven control valve that controls the valve opening by applying an operation signal from the control device to the electric actuator to drive the valve stem and moving the valve plug through the valve stem.
A sensor for monitoring a physical quantity of fluid is provided in the secondary flow path of the valve casing, and the controller determines whether there is a fluid leak by comparing a detection signal from the sensor with a predetermined set value. When the determination unit determines that there is fluid leakage, a valve cutoff signal is given to the electric actuator, and the electric actuator applies a cutoff torque between the valve plug and the valve seat portion via the valve stem. An electrically driven control valve characterized by acting.   3. The electrically driven control valve according to claim 2, wherein the sensor for monitoring the physical quantity of the process fluid comprises a temperature sensor, a pressure sensor, or a flow rate sensor. In the electrically driven control valve that controls the valve opening by applying an operation signal from the control device to the electric actuator to drive the valve stem and moving the valve plug through the valve stem.
An electrically driven control valve, wherein a spring having a direction in which a closing torque is always applied is attached to the valve stem. In the electrically driven control valve that controls the valve opening by applying an operation signal from the control device to the electric actuator to drive the valve stem and moving the valve plug through the valve stem.
An electrically driven control valve, wherein a spring in a direction in which a shut-off torque is always applied to the valve seat portion is attached to a lower portion of the valve seat portion in the valve casing. A plant comprising the electrically driven control valve according to any one of claims 1 to 5.

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