JPS5999005A - Bypass valve test device in turbine bypass system - Google Patents

Abstract

PURPOSE:To control a thermal stress generated in a bypass valve casing at the time of the bypass valve testing by an arrangement in which the valve is temporarily held stationary after it is slightly opened, and once the differential temperature between the inner and outer wall metals of the bypass valve casing became within the tolerance, the valve opening is enlarged. CONSTITUTION:At the time of valve testing, feeding a valve test start signal 13 into a control device 12 will cause a valve test signal 17 to be sent from a valve test signal generator 25 to a valve actuating section 11, and a bypass valve 8 starts opening. When its opening reaches to the set value, the valve test signal 17 is terminated by a valve opening signal 16. Under such conditions, the inner wall of the bypass valve casing is gradually heated by a very small amount of steam through the valve 8, and the temperature of the outer wall is also risen. If the temperature signal 14 of said inner wall metal is higher than a specified value 19 and if the difference between inner and outer wall metal temperature signals 14, 15 determined by a comparison device 22 is within a specified value 23, a signal is outputted from an AND circuit 24 so that the valve test signal 17 may be again delivered to open the bypass valve 8.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a bypass valve testing device for a turbine bypass system used in a nuclear power plant or the like.

[Technical Background of the Invention] In nuclear power plants, when there is a load cutoff due to an accident in the system, the imbalance between the output of the C1 steam turbine and the output of the photoelectric machine is detected, and a control valve installed at the steam turbine inlet is activated. At the same time, the bypass valve installed in front of the control valve is suddenly closed, allowing the steam sent from the reactor to pass through the bypass line without passing through the turbine.
I try to send them to Fundenza. This is to reduce the impact on the reactor and protect the reactor by allowing the steam trapped by the sudden closing of the control valve to flow into the bypass line.

By providing such a bypass system, if an accident occurs on the system side, the reactor can be operated continuously without scramming (emergency shutdown), and the system can be kept free of pressure above the reactor pressure.
This can improve the reliability of nuclear power plants.

However, in such a bypass system, if the bypass valve does not suddenly close due to a schedule or some other reason, the nuclear coupler will stop, so to prevent this, periodic We conduct open/close tests on bypass valves to prevent sticking and confirm operation. This bypass valve operation test is to be carried out periodically, and it is assumed that the
It rotates about 0 times. This is a very large number of times compared to the estimated 700 times that the bypass valve is actually used due to system accidents such as those mentioned above.

[Problems in the background art] When the bypass valve operates rapidly (steam flows in quickly, a large amount of thermal stress is generated in the downstream part of the valve. Since the bypass valve goes from fully open to fully open in about 10 seconds, a large amount of thermal stress is generated in the bypass valve during the test.On the other hand, if the valve test time is lengthened to suppress the generation of thermal stress, the capacitor side This also has the disadvantage of having an adverse effect on the reactor side.

[Object of the Invention] The present invention has been made in order to eliminate the above-mentioned inconveniences in the background art. The object of the present invention is to provide a bypass valve test device for a turbine bypass system that can shorten test time and reduce the effects on the reactor and capacitor.

[Summary of the Invention] A bypass valve test device for a turbine bypass system according to the present invention includes a bypass valve provided in a bypass line that bypasses a turbine, a valve drive unit that opens and closes the bypass valve, and a casing of the bypass valve. Inputs the metal temperature signal of the inner and outer walls and the valve opening degree signal, and outputs the -C valve test signal to the valve drive mechanism during the valve test to slightly open the bypass valve, and then temporarily stops the opening operation. and a control device that opens the bypass valve again after the temperature difference between the inner and outer wall metals of the bypass valve casing reaches a predetermined value.

[Embodiments of the Invention] Hereinafter, embodiments of the present invention and their operations will be explained with reference to the drawings.

In Fig. 1, a steam pipe 2 installed at the outlet of a nuclear reactor 1 is branched into a line 4 that continues to a turbine 3 and a line 5 that bypasses the turbine 3. A steam stop valve 6 and a control valve 7 for controlling the amount of steam inflow are installed. In addition, a bypass valve 8 is installed in the bypass line 5, and downstream of the bypass valve 8, a pressure reduction,
A temperature reducing device 9 is provided. The downstream side of the turbine 3 and the pressure reduction/temperature reduction device 9 is connected to a condenser 1o.

Bypass valve 8 is driven by valve drive section 11 . The control device 12 inputs a valve test start signal 13, a bypass valve casing inner wall metal temperature signal 14, a bypass valve casing outer wall metal temperature signal 15, and a valve opening signal 16, and performs a valve test () toward the valve drive unit 11 (). Outputs signal 17.

FIG. 2 does not show a specific example of the control device 12, and the comparator 1
8 sends a signal 21 to an AND circuit 20 using the bypass valve casing inner wall metal temperature signal 14 and temperature set value signal 19 as manual input. Further, the comparator 22 receives the bypass valve casing inner wall metal temperature signal 14, the bypass valve casing outer wall metal temperature signal 15, and the temperature difference setting value signal 23 as inputs, and sends a signal 24 to the AND circuit 20. AND circuit 2o
When inputting signals 21 and 24, it sends a signal 26 to the valve tester 1 to the signal generator 25. This valve output signal generator 25
is the signal 26, the valve test start signal 13 and the valve opening signal 16
When input, the valve test signal 17 is outputted to the valve driving section 11.

Next, the operation of the test apparatus of the present invention configured as described above will be explained.

When starting a valve test, a valve test start signal 13 is generated, a signal is sent to the valve test signal generator 25, and a valve test signal generator 25 sends a C valve test open signal to the valve drive unit 11. 18 will be sent. As a result, the bypass valve 8 starts to open, but when the preset opening degree is reached, the valve opening degree signal 16
The valve test signal 17 is stopped by this, and the bypass valve 8 is temporarily stopped at that opening degree. In this case, the bypass valve 8 is stopped in a slightly open state, so that a small amount of steam flows through the bar pass valve 8.
continues to flow downstream. Therefore, the temperature of the inner wall of the bypass valve casing gradually increases, and the metal temperature of the outer wall of the bypass valve casing also rises accordingly, so that the temperature difference between the inner and outer surfaces of the metal does not become too large and excessive thermal stress does not occur. When the bypass valve casing inner wall metal temperature exceeds a preset value, the comparator 18 turns on the AND circuit 20.
The comparator 22 sends a signal 21 to the AND circuit 20 if the temperature difference between the inside and outside metals at that time falls within the set value. As a result, the AND condition of the AND circuit 20 is met and the signal 26 is output. Valve test generator 25
When receiving the signal 26, the valve test signal 17, which had been stopped by the valve opening signal 16, is sent to the valve drive unit 11 again. As a result, the bypass valve 8 will close and the valve test will continue.

The above-mentioned changes in valve opening degree and changes in internal and external metal temperatures are shown in FIGS. 3 and 4. As shown in FIG. 3, 1. t Since the bypass valve 8 suddenly changes from fully open to fully open, the valve S-loak S changes linearly, and the bypass valve casing inner wall metal temperature rapidly rises.

Therefore, the bypass valve casing outer wall metal temperature To cannot follow the temperature To, and the inner and outer metal temperature difference ΔT becomes large, and a large transient thermal stress is generated. On the other hand, according to the present invention, as shown in FIG.
Is the C1 bypass valve casing inner wall metal temperature Ti gradual when the valve is slightly opened and the valve opening is maintained at the same opening from time t1 to C2? W lff1 l=increases, so the bypass valve casing outer wall metal temperature TO sufficiently follows, and the temperature difference ΔK becomes small.

After time C2, even if the valve is opened rapidly, the metal temperature has already risen considerably, so the metal temperature difference Δ between the inner and outer surfaces does not become that large, and no large thermal stress is generated.

[Effects of the Invention] As explained above, the present invention opens the valve slightly during the valve test of the bypass valve, temporarily stops the valve movement, and confirms that the temperature difference between the inner and outer wall metals of the bypass valve casing falls within the allowable value. Since the valve is configured to have a large opening degree, it is possible to suppress thermal stress generated in the bypass valve casing during a bypass valve operation test. In addition, because the valve opening is slightly opened, the downstream part of the bypass valve will be injected, so the amount of steam flowing downstream of the valve will be small, and therefore the impact on the -C condenser and reactor side will be small. Become.

Therefore, according to the present invention, it is possible to perform a test without applying large thermal stress to the bypass valve, and it is possible to contribute to improving the reliability of the bypass valve and, by extension, of the nuclear power plant 1 and the entire nuclear power plant 1.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of a nuclear power plant equipped with a bypass valve test device in the turbine bypass system of the present invention, Fig. 2 is a circuit diagram showing a specific example of the control device in J3 of the present invention, and Fig. 3 is a conventional system diagram. A graph showing the relationship between the valve stroke and the temperature of the inner and outer metal surfaces of the bypass valve casing according to the valve test method, and FIG. Guaru. 1... Reactor 2... Steam pipe 3... Turbine 4... Line 5... Bypass line 6... Main steam stop valve 7... Control valve 8... Bypass valve 9... Pressure reduction and temperature reduction device 10... Densor 11... Valve drive unit 12...Control device 13...Valve test start signal 14...Bypass valve casing inner wall metal temperature signal 15...Bypass valve casing outer wall metal temperature Signal 16... Valve fai 1 degree signal 17... Valve test signal 18.22... Comparator 19... Temperature set value signal 20... AND circuit 23...Temperature difference set value signal 25...Valve test 1-Signal generator representative patent attorney
Suyama Sa - Figure 1 13 Figure 2 [13 Figure 3 Start of Figure 4 Valve t, t2 =

Claims (2)

[Claims] (1) A bypass valve installed in a bypass line that bypasses the turbine, and whether this bypass valve is connected to I? fl A valve drive unit that drives the bypass valve to close, a metal temperature signal of the inner and outer walls of the casing of the bypass valve, and a valve opening degree signal are input, and a valve test signal is output to the valve drive mechanism during a valve test to drive the bypass valve. and a control device that once stops the opening operation after being slightly opened, and then opens the bypass valve again after the temperature difference between the inner and outer wall metals of the bypass valve casing reaches a predetermined value. A bypass valve test 1 for a turbine bypass system characterized by: (2) The control m11 device inputs a comparator that inputs the casing inner wall metal temperature signal and temperature set value number of the bypass valve, and inputs the casing inner wall metal temperature signal, casing outer wall metal temperature signal, and temperature difference set value signal of the bypass valve. An AND circuit that inputs the outputs of both comparators, the output of this AND circuit, the valve opening signal, and the valve dest start signal, and outputs the valve dest signal. Bypass valve test training L for a turbine bypass system according to claim 1, characterized in that it is comprised of a