JPS6039848B2 - Main steam valve control system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a main steam valve control system used in a nuclear power plant, that is, one main steam valve having a preceding valve operated by a preceding valve starting device, and a main steam valve having a preceding valve operated by a preceding valve starting device. The present invention relates to a main steam valve control system that includes a plurality of main steam valves without preceding valves that are operated via interlocking switching valves.

It is well known that in a steam turbine, in order to supply a large amount of steam, a plurality of main steam stop valves are installed in a main steam pipe before a steam control valve. The outlet of each main steam stop valve is connected to the inlet of the steam control valve, and in the downstream portion of the main steam stop valve, the outlet chamber behind the valve seat is communicated by a pressure equalizing pipe. Therefore, even if any main steam stop valve is closed, the back of the valve seat is connected by the foot pressure pipe, so the outlet chamber is common to each main steam stop valve, and if the other main steam stop valves are open, all Steam is supplied to the steam control valve. Or, even if the other check valves are closed, if one main stop valve is open and the steam control valve is closed, the pressure in each stop valve and the wake section after the valve seat control will increase. Since the main steam stop valve mentioned above is an unbalanced type and cannot open against the full pressure drop, one of the multiple main steam stop valves has a built-in advance valve that is operated by a motor-driven advance valve activation device. has been done.

By stroking this preceding valve and allowing steam to flow, the downstream part of the main steam stop valve and the steam control valve are warmed at the beginning of operation, and the downstream part of the valve necessary to open the main steam stop valve is heated. The pressure in the area can be increased. The other main steam stop valves do not have lead valves and are operated in either the fully open or fully closed position and are controlled by air switching valves operated by lead valve actuators. A typical example of a secondary main steam valve control system will be described with reference to FIG. 1. During operation of a steam turbine, main steam stop valves 1 and 2 are in the fully open position as shown.

When starting the steam turbine, in order to open the main steam stop valve 1 (hereinafter referred to as the main valve) that incorporates the preceding valve 3, the preceding valve starting device 4 is used.
and open the advance valve 3. That is, the control motor 6 is driven to rotate the main shaft 5 via the worm mechanisms 7 and 9 and the friction clutch 8, and the lead screw 10 is moved in the x direction.
The torque shaft 13 and bell crank 14 are stroked. This stroke of the bell crank 14 is transmitted to the input end of the floating lever 15, and the lowering of this input end causes the pilot valve 21 to also be lowered, so that the control oil B is supplied from the supply boat d through the oil path 22 to the hydraulic cylinder 24. flows into the lower piston chamber 20 of the piston 19 against the spring 18.
is raised to open the preceding valve 3 via the valve stem 23.
The lift of the valve stem 23 is transferred to the floating lever 15 via the restoring arm 16.

This operation returns the pilot valve 21 to the on-port position, so that the preceding valve 3 is stopped from further stroking. In this way, as the input end of the floating lever descends throughout the entire stroke of the preceding valve 3, the valve stem 2
3 strokes.

When the pilot valve 3 is in the fully closed position and the input end of the floating lever 15 strokes downward relative to the stopper 17, the pilot valve 21 is held at the off port position, so that the master valve The piston 19 strokes until the piston 1 is fully closed. The advance valve starting device 4 is provided with an air switching valve 11 for performing necessary automatic control.

When the valve body 33 is pressed by the operation of the operating lever 12 linked to the advance starting device 4, the switching valve 11 switches the air. When the advance valve starting device 4 is in the closed position, the operating lever 12 is separated from the valve body 33, so the operating air A flows through the supply port a of the switching valve 11 and further flows through the common pipe 32 via the outlet b. , after flowing in from the exhaust port g of each test electromagnetic valve 25 of each other main steam stop valve 2 that does not have a preceding valve, passes through the outlet f and flows from the supply port i of the test air cylinder 28 to the upper part of the piston 27. Inflow. Since the piston 27 is lowered by this incoming air, the test pilot valve 30 is also lowered via the piston rod 29, so the boat h of the pilot valve 30 is closed. Therefore, the control oil B is not supplied to the hydraulic cylinder 24, so the main steam stop valve 2 is closed by the spring 18. Next, when the advance valve 3 reaches the fully open position by moving the advance start blind pupil 4 in the opening direction (x direction), the operating lever 12 moves the switching valve 1
The first valve body 33 is pressed and held in the illustrated state.

For this reason, the transmission of the operating air A between the inlet a and the outlet b is cut off, and at the same time the exhaust port c and the outlet b are removed, so that the operating air that was being supplied to each test air cylinder 28 is released from the exhaust port. emitted into the atmosphere from c. Above air cylinder 2
When the air in the test pilot valve 30 is discharged, the oil leakage C flows into the lower part of the test pilot valve 30, and the test pilot valve 3
Since boat h is opened by raising boat h, control oil B is
, and flows into the piston lower chamber 203 of the hydraulic cylinder 24a via the oil passage 31.

At this time, since the preceding valve 3 is already fully open, the pressure at the wake of each main steam stop valve 2 that does not have a preceding valve has increased, so the steam force acting on the valve stem 23a due to steam pressure and Since the piston 19a is raised against the force of the spring 18a, the valve 2 is fully opened via the valve 23a. During operation of the steam turbine, a valve closing test of each main steam stop valve 2 in the test system is carried out periodically (one for each valve 2 individually).

That is, when the test electromagnetic valve 25-1 is energized, its piston 26 is moved in the Y direction, so the operating air A flows in from the inlet boat e, passes through the outlet boat f and the boat i of the air cylinder 28-1, and is then used for testing. air cylinder 2
It flows into 8-1. Therefore, the upper air pressure of the piston 27 overcomes the hydraulic pressure at the lower part of the test pilot valve 30 and lowers the valve 30 from the boat h, so that the control of the piston lower chamber 20a of the hydraulic cylinder 24a is controlled by the boat h The oil is discharged from the upper artificial oil row of the valve 30. Therefore, the piston 19a is lowered by the force of the spring 18a, and the main steam stop valve 2 is closed via the valve shank 23a. If the test solenoid valve 25-1 is demagnetized when the valve 2 is closed, the solenoid valve 25-1
The inlet boat e of -1 is closed, and at the same time the outlet boat f and the exhaust boat g are vented, so the air that has been supplied so far is released into the atmosphere from the outlet C of the switching valve 11 through the common pipe 32. Ru.

When the operating air is discharged from the test air cylinder 28, the test pit valve 30 is returned to its normal position by the lower hydraulic pressure, and the hydraulic cylinder 24a is again operated with hydraulic pressure, so the main steam stop valve 2 is fully opened. . As mentioned above, in the conventional control system, the supply and discharge of operating air for testing are performed through a common piping. If a foreign object gets caught in the solenoid valve or the solenoid valve is jammed, and an abnormal condition occurs in which the solenoid valve stops at an intermediate opening, the inlet boat e, outlet boat f, and exhaust boat g of the solenoid valve will not be able to communicate with each other. be done.

For this reason, operating air is supplied to the switching valve 11 via the test air cylinder 28 and the common piping 32, but if the amount of leakage is large due to the relationship between the displacement of the switching valve 11 and the amount of leakage from the solenoid valve 25-1. In this case, the common line 32 has pressure and operates the test air cylinders of the other main stop valves, so that the valves close simultaneously. However, in order to reduce the sudden pressure rise inside the reactor, nuclear reactors have a scram system that stops the reactor if multiple main steam stop valves open at the same time in excess of a certain value. It has the disadvantage of causing the reactor to scram.

The present invention aims to eliminate the above-mentioned drawbacks and provide a main steam valve control system that improves the safety and reliability of nuclear power plants. The present invention is characterized in that the same number of main steam valves without preceding valves are provided, and the main steam valves without preceding valves and the switching valves are connected to each other by separate test systems.

An embodiment of the present invention will be described below with reference to the drawings.

Among the symbols in FIG. 2, the same symbols as those in FIG. 1 indicate the same or corresponding parts. In Figure 2, 11-1
- 11-3 are air switching valves (hereinafter referred to as switching valves) having valve bodies 33-1 to 33-3, respectively; 12-1 to 12-3;
has one end facing the valve bodies 33-1 to 33-3, and
Torque shaft 13 whose other end is connected to bell crank 14
a, the intermediate portion thereof is connected to a torque shaft 13b connected to the advance starting device 4, respectively.

25-1 to 25-3 are test electromagnetic valves installed in piping 32-1 to 32-3 that connect the switching valves 11-1 to 11-3 and the test air cylinders 28-1 to 28-3, respectively. , 34-1 to 34-3 are test solenoid valves 25
11 to 25 and 3 are test relief solenoid valves connected in series.

The rest of the structure is the same as that shown in FIG. 1, so the explanation will be omitted. Since this embodiment is configured as described above, when the advance starting device 4 is driven, the operating levers 12-1 to 12-3 are simultaneously operated via the torque shaft 13b connected thereto, and the valve body of each switching valve is activated. 33-1 to 33-3 are moved, and the operation air is passed through each piping 32-1 to 32-3 and test solenoid valves 25-1 to 25-3 to test air cylinders 28-1 to 28-3. Each will be summarized.

For this reason, test pie. Shut valve 30 and hydraulic cylinder 2
4a, it is possible to reliably perform interlock control of each main steam valve 2 without a preceding valve at the time of startup. In this case, the pilot valve 21, the hydraulic cylinders 24, 24
3. The functions of the test solenoid valves 25-1 to 25-3, the air cylinders 28-1 to 28-3, and the test pilot valves 30-1 to 30-13 are the same as those in the case of Fig. 1, so we will explain them here. Omitted. In this embodiment, the test solenoid valve 25-1
~25-3 and test relief solenoid valves 34-1 to 34-3 are connected in series, and each piping 32-1 to 32-3 is connected in series.
Since both the solenoid valves 25 and 34 connected to each of the piping 32-1 to 32-3 are simultaneously excited and operated, the operating air A flows into the test relief solenoid valve 34 from the inlet j and the outlet. k is sent to the test solenoid valve 25, flows into the test air cylinder 2 through the inlet e, and passes through the outlet f.
His grandchild was donated to the 8th.

By operating the air cylinder 28, a valve closing test of the main steam valve 2 having no preceding valve can be performed via the test pilot valve 30 and the hydraulic cylinder 24a. When the solenoid valves 25 and 34 are simultaneously demagnetized at the end of the test, the operating air is discharged from the exhaust port g of the test solenoid valve 25 through the pipe 32 to the atmosphere from the exhaust port C of the switching valve 11. In this case, even if the test solenoid valve 25 fails, if the test relief solenoid valve 34 is normal, the test relief solenoid valve 3
Since the outlet k of 4 is closed, there is no possibility that operating air will be supplied to the test air cylinder 28. Conversely, if the test solenoid valve 26 is normal even if the test relief solenoid valve 34 fails, operating air will not be supplied to the test air cylinder 28 as described above, and the main steam valve 2 will return to the fully open position. . As described above, according to the present invention, even when the test electromagnetic valve is held at an intermediate level during the valve closing test, operating air can be released into the atmosphere through the switching valve.

Even if the pressure is maintained in the piping because the amount of leakage from the test solenoid valve is greater than the amount released into the atmosphere from the switching valve, other main steam valves that do not have preceding valves may be released at the same time. The closing operation can be prevented. In addition, in the present invention, the number of test solenoid valves is increased, so even if the test solenoid valves are held at an intermediate opening at the end of the test, if one of the solenoid valves operates normally, the operating air will be released into the atmosphere. This allows the test valve to be fully opened.

Therefore, it is possible to improve the safety and reliability of a nuclear power plant during valve closing tests to prevent valve sticking, which are performed periodically.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a conventional main steam valve control system, and FIG. 2 is a diagram showing an embodiment of the main steam valve control system of the present invention. DESCRIPTION OF SYMBOLS 1, 2... Main steam valve, 3... Leading valve, 4... Leading valve starting device, 11... Switching valve, 12... Operating lever, 2
6, 34... Solenoid valve for test, 32... Piping. Figure 'Figure 2

Claims (1)

[Claims] 1. One main steam valve having a preceding valve operated by a preceding valve starting device, and a plurality of main steam valves having no preceding valve operated via an air switching valve linked to the preceding valve starting device. In the main steam valve control system, the switching valves are provided in the same number as the main steam valves without a preceding valve, and the switching valves are provided with an actuating lever that is linked to the preceding valve starting device, and The main steam valve without a preceding valve and the air switching valve are connected by separate test systems, and this test system is provided with a plurality of test solenoid valves connected in series. Main steam valve control system.