JPH01142204A - Valve rod gap abnormality detecting device of steam governing valve - Google Patents

Abstract

PURPOSE:To facilitate maintenance managing work by detecting the quantity of state for leaking steam from the valve stem gap of a steam governing valve and comparing the detected quantity of state with the quantity of state at a normal time to diagnose the presence of abnormal of the gap of the valve stem and displaying the result of the diagnosis. CONSTITUTION:An orifice 15 serving as a detector A for valve of state is provided on the way of a high pressure leak-off piping 10 for discharging, outside a system, steam which leaks from the gap 9a of the valve stem of a steam governing valve and a pre-orifice pressure sensor 16 is connected to its upper stream side. The output signal of the sensor 16 together with the output signal of a steam chamber temperature sensor are input to a calculator B to calculate the flow as the quantity of state of leaking steam by a built-in flow calculation circuit 19. At the time of the operation of a turbine, the calculated leaking steam flow and the signal of the quantity of state read out from a leaking steam quantity memory 20 at a normal time are compared with a each the through a comparing circuit C to diagnose the presence of abnormal gap of the valve stem for displaying its result of diagnosis on a state display unit D.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a valve stem gap abnormality detection device for a steam control valve used in a steam turbine or the like.

(Prior Art) A steam control valve is used in a steam turbine plant to adjust the flow rate of steam supplied to a steam turbine.

This steam control valve is generally formed integrally with the high pressure casing 1 of the steam turbine, as shown in FIG. A steam chamber 2 through which steam flows is formed in the high-pressure casing 1, a valve seat 3 is provided at the bottom of the steam chamber 2, and a valve body 4 is configured to be seated on the valve seat 3. The valve body 4 is integrally fixed to the lower end of a valve stem 5, and the valve stem 5 has a bush 7 fitted into a valve cover 6.
．． 8 is inserted. The valve stem 5 is guided by a bush 7.8 and assembled so that it can move up and down inside the steam chamber 2. Valve stem gaps 9a and 9b are formed between the valve stem 5 and the bushing 7.8, and high pressure leak-off piping is provided for discharging steam leaking through the respective valve stem gaps 9a and 9b to the outside of the system. 10 and low pressure leak-off piping 11 are provided.

The opening and closing operations of the steam control valve configured as described above are performed by transmitting the reciprocating motion of an oil cylinder (not shown) as the rotational motion of the cam 12. The rotation of the cam 12 causes the lever 13 to rotate vertically about its fulcrum 13a. The vertical movement of the lever 13 is transmitted to the valve rod 5 via the spring 14, and the valve rod 5 moves up and down the valve body 4 to adjust the opening degree of the steam control valve. The steam that has entered the steam chamber 2 passes through the gap between the valve body 4 and the valve seat 3, flows in the direction of the arrow, and is supplied to the steam turbine at a predetermined flow rate.

Here, the valve stem gaps 9a and 9b formed between the valve stem 5 and the bushing 7.8 are used to reduce the amount of steam leaking as much as possible, and also to enable smooth vertical movement of the valve stem 5. It is designed to the minimum necessary dimensions and manufactured and adjusted with high precision.

(Problems to be Solved by the Invention) However, after the turbine starts operating, the valve stem gaps 9a and 9b increase over time due to mutual friction between the valve stem 5 and the bushing 7.8. Valve stem gap 9a.

When 9b increases, the amount of leaked steam increases and the amount of steam to be discharged from the leak-off pipe 10.11 increases. If the valve stem gap 9 increases too much, the steam discharge capacity of the leak-off piping 10, 11 will be exceeded, so there is a risk of steam leaking from the upper part of the bush 8.

In addition, due to the increase in the valve stem gap 9, the seating of the valve body 4 against the valve seat 3 deteriorates, causing vibrations in the entire steam control valve and bending of the valve stem 5, making it difficult to accurately adjust the steam amount. There is a possibility that it will become possible.

Therefore, during periodic inspections of the steam turbine, it is necessary to disassemble the steam control valve, measure the valve stem clearance 9, and confirm that the measured value is always maintained within an appropriate range. If an abnormal increase in the valve stem clearance 9 is found, the valve stem 5 or bushing 7.8 is replaced with a new one.

As described above, it is impossible to measure the valve stem clearance 9 of the steam control valve during turbine operation, and it is only confirmed by measurements during periodic inspections. Therefore, whether or not there is any abnormality in the valve stem gap 9 is checked only during periodic inspections or when a specific problem such as a steam leak occurs. Therefore, there were problems in maintenance management, such as delays in early detection of failure locations and a great deal of labor required for repair and maintenance.

The present invention has been made to solve the above problems, and even during operation of a turbine plant, it is possible to automatically detect the presence or absence of an abnormality in the valve stem clearance of a steam control valve, An object of the present invention is to provide a valve stem clearance abnormality detection device for a steam control valve that facilitates maintenance management.

[Structure of the invention]

(Means for Solving the Problems) A valve stem gap abnormality detection device for a steam control valve according to the present invention includes a state value detector and a state value detector for detecting a state value of steam leaking from a valve stem gap of a steam control valve. An arithmetic unit that calculates the state quantity from the state signal from the detector, a comparator circuit that compares the state quantity signal from the arithmetic unit with the state quantity under normal conditions, and an abnormality in the valve stem clearance depending on the magnitude of the output signal of the comparator circuit. The present invention is characterized by comprising a diagnosis display device that diagnoses the presence or absence of the disease and displays the diagnosis result.

(Function) In the valve stem gap abnormality detection device for a steam control valve configured as described above, a state value such as pressure or temperature of steam leaking from the valve stem gap is detected by a state value detector. The state signal from the state value detector is input to the calculator, where state quantities such as steam flow rate are calculated.

The state quantity signal from the arithmetic unit is input to a comparator circuit, where it is compared with the state fllffi, such as the flow rate of leaked steam in a normal state. The output signal of the comparison circuit is input to a diagnostic display. If the output signal from the comparison circuit is larger than a predetermined value, the diagnostic display device diagnoses that there is an abnormality in the valve stem gap and displays a message to that effect.

According to the above configuration, it is possible to automatically and accurately detect the presence or absence of an abnormality in the valve stem clearance of the steam control valve even during operation of the turbine plant, and it is possible to quickly respond to equipment abnormalities, and the turbine This has the effect of significantly reducing plant maintenance work.

(Example) Hereinafter, an example of the present invention will be described with reference to the accompanying drawings. The valve stem gap abnormality detection device for a steam control valve in this embodiment focuses on the fact that when the valve stem gap changes, the amount of steam leaking from the corresponding part changes, and measures the amount of leaked steam,
The measured value is compared with a reference value for the leakage steam amount allowed under normal conditions, and the presence or absence of an abnormality in the valve stem gap is detected based on the magnitude of the difference.

That is, the valve stem gap abnormality detection device for a steam control valve according to the embodiment shown in FIG.
5, a pre-orifice pressure sensor 16, and a steam chamber temperature sensor 17. is provided. Further, a steam chamber temperature sensor 17 for detecting the temperature of steam flowing into the steam chamber 2 is provided at the top of the steam control valve.

The steam leaking from the valve stem gap 9a is transferred to the high pressure leak-off pipe 1.
0 and is guided via orifice 15 to sealed steam header 18 . When the leaked steam passes through the orifice 15, the pressure of the leaked steam on the primary side of the orifice is detected by the pre-orifice pressure sensor 16.

The state values of the steam pressure and temperature detected by the orifice front pressure sensor 16 and the steam chamber temperature sensor 17 are input to the computing unit B as shown in FIG. Arithmetic unit B calculates the flow rate as a state quantity of leaked steam from the above state value using a built-in flow rate calculation circuit 19.

On the other hand, the valve stem gap value under normal conditions, that is, the leakage steam amount in a state where the valve stem gap value is adjusted to the designed value, is stored in advance in the normal status leakage steam master storage device H20.

The leakage steam flow rate calculated by the calculator B during turbine operation is compared in the comparison circuit C with the state quantity signal from the normal leakage steam amount storage @20. The output signal of this comparison circuit C is input to the diagnostic display device WD,
Here, depending on the magnitude of the output signal from the comparison circuit C, the presence or absence of an abnormality in the valve stem gap is self-diagnosed, and the diagnosis result is displayed.

Furthermore, by similarly providing a status value detector or the like in the low pressure leak-off piping 11, it is possible to determine whether or not an abnormality has occurred in the valve stem clearance value using the same procedure.

According to this embodiment, even during operation of the turbine plant, the presence or absence of an abnormality in the valve stem clearance of the steam control valve is automatically and quickly displayed, making it possible to quickly respond to abnormalities in the steam control valve. Maintenance work for turbine plants can be significantly reduced, and plant reliability can be maintained over a long period of time.

Furthermore, since the valve stem gap abnormality detection device of this embodiment is configured with a simple detector and circuit, it can be easily adapted to existing equipment. That is, when implementing the system, there is no need to significantly modify the existing steam control valve, and a new one can be easily installed.

Next, a second embodiment of the present invention will be described with reference to FIG. In the embodiment shown in FIG.
In addition, a leak-off pipe temperature sensor 21 is provided to detect the pipe wall temperature of the high-pressure leak-off pipe 10.

When the valve stem gap 9a changes during operation of the steam control valve, the amount of steam leaking from the valve stem gap 9a changes, and this change in the amount of steam causes a change in the flow rate of steam flowing in the high pressure leak-off pipe 10, Additionally, changes in flow rate cause changes in heat transfer coefficients, resulting in differences in pipe wall temperatures. The pipe wall temperature in this state is detected by the leak-off pipe temperature sensor 21, and compared with the pipe wall temperature as a state quantity under normal conditions,
When the temperature difference exceeds a predetermined value, it is diagnosed that an abnormality has occurred, and the diagnosis result is automatically displayed.

As shown in the embodiment shown in FIG. 1, the system not only detects changes in the amount of leaked steam caused by changes in the valve stem clearance and diagnoses whether or not there is an abnormality in the valve stem clearance, but also detects the presence or absence of an abnormality in the valve stem clearance, as shown in the embodiment shown in FIG. It is also possible to detect the presence or absence of an abnormality in the valve stem gap by detecting a change in the pipe wall temperature of the off-piping 10, 11 as the amount of leaked steam changes.

Next, a third embodiment of the present invention will be described with reference to FIG. In the valve stem gap abnormality detection device for a steam control valve according to the present embodiment, the state value detector A is connected to an orifice installed in the leak-off piping and a pre-orifice pressure sensor 16 disposed on the primary side of the orifice. , a steam chamber temperature sensor 17 that detects the temperature of steam flowing into the steam chamber, and a steam chamber pressure sensor 22 that detects the pressure inside the steam chamber. and a flow rate calculation circuit 19 that calculates steam ore based on the temperature signal from the steam chamber temperature sensor 17, a steam enthalpy calculation circuit 23 that calculates steam enthalpy based on the temperature signal and a pressure signal from the steam chamber pressure sensor, and a steam chamber pressure A valve stem gap back calculation circuit 24 is provided for back calculating the valve stem gap based on the pressure signal from the sensor and the steam flow rate and steam enthalpy.

According to this embodiment, the enthalpy of steam is calculated from the state values such as the pressure and temperature of the steam flowing into the steam chamber 2, and the flow rate of leaked steam flowing through the leak-off piping 10.11 is calculated by the flow rate calculation circuit 19. Ru.

Furthermore, the valve stem gap back calculation circuit 24 uses the steam pressure in the steam chamber and the leakage steam flow rate passing through the orifice together with the enthal.
The valve stem clearance value is calculated backwards by

The back-calculated current gap value and the valve stem gap design value 25 are compared in the comparison circuit C, and furthermore, the diagnosis display device indicates that the valve stem gap is determined when the difference between the gap value and the design value exceeds a predetermined value. It is diagnosed that an abnormality has occurred.

According to this embodiment, the steam chamber pressure sensor 22 is added to the configuration shown in FIG. 2, and the valve stem clearance value is calculated by correcting the leakage steam flow rate using the steam state value. Compared to the example, the valve stem clearance value can be calculated with higher accuracy, and the accuracy of detecting the presence or absence of abnormality is also significantly improved.

Although all of the above embodiments have been described by taking as an example a steam control valve installed in a steam turbine, the present invention can be similarly applied to other main valves such as a bleed air control valve.

〔Effect of the invention〕

As explained above, according to the valve stem gap abnormality detection device for a steam control valve according to the present invention, the amount of steam leaking from the valve stem gap is automatically measured from its state value, and the valve stem gap during operation of the steam turbine is automatically measured. Changes in the gap can be monitored at any time, and the presence or absence of an abnormality in the valve stem gap can be accurately determined. As a result, accidents such as steam leaks can be prevented, it is also possible to predict when parts such as bushings and valve stems will be replaced, and it is possible to quickly respond to abnormalities, greatly reducing maintenance work for turbine plants. , the reliability of turbine plants can be significantly improved.

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing one embodiment of the present invention, and Fig. 2 is a system diagram showing an embodiment of the present invention.
FIG. 3 is a system diagram showing the second embodiment of the present invention; FIG. 4 is a block diagram showing the third embodiment of the present invention; FIG. 5 1 is a sectional view showing a general configuration of a steam control valve. DESCRIPTION OF SYMBOLS 1... High pressure casing, 2... Steam chamber, 3... Valve seat, 4... Valve body, 5... Valve stem, 6... Valve lid, 7.
8... Bush, 9.9a, 9b... Valve stem gap, 1
0...High pressure leak off piping, 11...Low pressure leak off piping, 12...Cam, 13...Lever, 13a.
...Fully point, 14... Spring, 15... Orifice, 16... Orifice front pressure sensor, 17... Steam chamber temperature sensor, 18... Seal steam header, 19...
...Flow rate calculation circuit, 20...Normal leakage steam amount storage device, 21...Leak-off tube humidity sensor, 22...Steam chamber pressure sensor, 23...Steam enthalpy calculation circuit,
24... Valve stem gap back calculation circuit, 25... Valve stem gap design value, A... Status value detector, B... Arithmetic unit, C...
Comparison circuit, D...Diagnostic display device. Representative Patent Attorney Nori Chika Ken Shu Kanshu Komaru Ken Figure 2 〆8 Figure 4

Claims (1)

[Claims] 1. A state value detector that detects the state value of steam leaking from the valve stem gap of a steam control valve, a computing unit that computes a state quantity from a state signal from the state value detector, and a computing unit. A comparison circuit that compares a state quantity signal from the valve with a state quantity in a normal state, and a diagnostic display device that diagnoses whether there is an abnormality in the valve stem gap based on the magnitude of the output signal of the comparison circuit and displays the diagnosis result. A valve stem clearance abnormality detection device for a steam control valve, characterized by: 2. The status value detector consists of an orifice installed in the leak-off piping, a pressure sensor in front of the orifice installed on the primary side of the orifice, and a steam chamber temperature sensor that detects the temperature of steam flowing into the steam chamber. A valve stem gap abnormality detection device for a steam control valve according to claim 1. 3. The valve stem gap abnormality detection device for a steam control valve according to claim 1, wherein the state value detector comprises a temperature sensor that detects the pipe wall temperature of the leak-off pipe. 4. The status value detector includes an orifice installed in the leak-off pipe, a pressure sensor in front of the orifice installed on the primary side of the orifice, a steam chamber temperature sensor that detects the temperature of steam flowing into the steam chamber, and a steam chamber temperature sensor that detects the temperature of steam flowing into the steam chamber. The calculator includes a steam chamber pressure sensor that detects the pressure in the room, and a flow rate calculation circuit that calculates the steam flow rate based on the pressure signal from the orifice front pressure sensor and the temperature signal from the steam chamber temperature sensor, and the temperature signal. and a steam enthalpy calculation circuit that calculates steam enthalpy based on the pressure signal from the steam chamber pressure sensor, and a valve stem gap back calculation circuit that calculates the valve stem gap based on the pressure signal from the steam chamber pressure sensor, the steam flow rate, and the steam enthalpy. A valve stem gap abnormality detection device for a steam control valve according to claim 1.