JPH0315086B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a device for suppressing the hammering phenomenon that occurs in a water pump minimum flow line for a steam power engine in a power generation plant.

[Prior art]

FIG. 1 is a system diagram of a water pump minimum flow line commonly used in the past.

Hot water supplied from a low-pressure feedwater heater is pressurized to over 100 atmospheres by a water supply pump 1, and is supplied to a nuclear reactor (boiler in the case of a thermal power plant) via an electric valve 2. On the other hand, in order to ensure the minimum flow rate of the water supply pump and prevent the occurrence of a shut-off operation state, a minimum flow line as described below is provided between the discharge side of the water supply pump 1 and the condenser 4. That is, the above-mentioned minimum flow line sequentially connects the minimum flow valve 5, the drain pipe 10, the orifice 6, and the drain pipe 9 to the drain pipe 7 which is branched and communicated with the water supply pump outlet water supply pipe 3, and this drain pipe 9 The above-mentioned minimum flow valve 5, which is connected to the condenser 4, is opened by the valve opening signal 8 transmitted by starting the water supply pump 1, and when the minimum flow valve 5 is in the open state, The drain flow rate flowing through this minimum flow line is mainly controlled by the orifice 6.

During normal operation, the water discharged from the water supply pump 1 is hot water heated by the low-pressure water heater, so the drain pipe 9 connects the orifice 6 and the condenser 4. The fluid flowing through the drain pipes 10 and 7 on the upstream side of the orifice 6 flows as a single-phase flow because the orifice 6 has the minimum flow path area. However, in the above-mentioned initial state of drain water flow, the drain accumulated in the drain pipe 10 comes into contact with hot water and is heated by opening the minimum flow valve 5, and is accelerated to a two-phase flow state. It then passes through the drain pipe 10 and the orifice 6. At this time, since the two-phase fluid is a fluid that undergoes a phase change, a two-phase flow hammering phenomenon occurs due to repeated boiling and condensation within the pipe. Also,
When the flow pattern of this two-phase flow becomes similar to a slag flow, unstable flow occurs and a hammering phenomenon occurs intermittently. Furthermore, when the condensate in this two-phase flow state changes to a single-phase flow and collides with the orifice 6, a hot water hammering phenomenon occurs. These series of hammering phenomena occur in the orifice 6.
This causes a sudden increase in the internal pressure of the drain located upstream of the drain, and depending on its size, it can damage the orifice or drain piping, causing a reduction in the reliability of the plant.

[Purpose of the invention]

An object of the present invention is to improve the reliability of the plant by suppressing the rapid pressure rise caused by the various hammer-in phenomena that occur when starting up the above-mentioned water pump minimum flow line.

[Summary of the invention]

In order to achieve the above object, the suppression control device of the present invention installs an orifice on the downstream side and a minimum flow valve on the upstream side of the drain piping connecting the water supply piping at the outlet of the power supply pump and the condenser. In the minimum flow line, which is connected to each other and opens the minimum flow valve in response to a valve opening signal issued by starting the water supply pump, a temperature detector and a pressure detector are installed in the drain piping upstream of the minimum flow valve. The present invention is characterized in that a pressure detector is provided in the drain pipe on the downstream side of the minimum flow valve, and a computing unit is provided that controls opening and closing of the minimum flow valve based on the output signals of each of the above-mentioned detectors.

[Embodiments of the invention]

FIG. 2 shows an improved embodiment in which the present invention is applied to the conventional minimum flow line (FIG. 1) described above to suppress the hammering phenomenon, and the same drawing reference numbers as in FIG. 1 are given. water supply pump 1, electric valve 2, outlet water supply piping 3, condenser 4, minimum flow valve 5, orifice 6, and drain piping 7, 9,
Reference numeral 10 designates the same or similar structural members as in the conventional device.

Drain piping 7 on the upstream side of the minimum flow valve 5
A temperature detector 11 and a pressure detector 12 are provided, a pressure detector 13 is provided in the drain pipe 10 on the downstream side of the minimum flow valve 5, and an arithmetic unit 19 for hammering control is provided. 11
Signal output 14 of pressure sensor 12, signal output 1 of pressure sensor 12
5, a signal output 16 of the pressure detector 13, and a minimum flow valve opening signal 17 transmitted by activation of the water supply pump 1 are input to the computing unit 19.

The arithmetic unit 19 has the configuration and functions described in detail later with reference to FIG. 3, performs arithmetic operations based on input signals, and controls the opening and closing of the minimum flow valve 5 so as to suppress the hammering phenomenon.

FIG. 3 is a block diagram showing one example of a specific configuration of the arithmetic unit 19 described above.

A signal selector 38 is provided at the output section that provides the valve opening signal 18 from the calculator 19 to the minimum flow valve 5, and selects either the signal output of the predetermined opening setting device 37 or the signal output of the adder 36. It is structured to selectively switch and output. The above switching operation is performed by the output signal of the comparator 35.

The adder 36 described above outputs a signal 2 to the arithmetic unit 23.
2 and the signal output 31 of the optimal valve gradual opening operation signal calculator 32 are added and output.

The arithmetic unit 23 described above is equipped with an initial opening degree setting device 21, and upon receiving the above-mentioned minimum flow valve opening signal 17 (sent by starting the water pump), a preset initial opening degree setting device 21 is activated. Upon receiving the output, it outputs an initial setting valve opening signal 22. The value of this initial setting valve opening degree signal 22 is set so that when the minimum flow valve 5 opens, high flow rate condensate repeatedly boils and condenses and induces a pressure increase due to two-phase flow hammering as much as possible. The opening degree of the minimum flow valve 5 is given as follows.

With this configuration, the minimum flow valve opening signal 17 is directly input to the minimum flow valve 5 and immediately fully opened, unlike in the conventional device, without inducing hammering.
The minimum flow valve opening signal 17 is converted into an initial setting valve opening signal 22 by a computing unit 23 to produce an effect of suppressing hammering at the initial stage of opening the valve.

On the other hand, the optimal valve gradual opening operation signal calculator 32 that outputs the optimal gradual opening signal 31 to be input to the heater 36 includes a gradual valve opening time setting device 29 and a gradual valve opening value setting device 30, and includes a gradual valve opening time setting device 29 and a gradual valve opening value setting device 30. The valve gradual opening start signal 27 transmitted in this manner is input, and an appropriate initial valve opening degree and a command signal for gradually increasing the valve opening degree are transmitted in order to suppress hammering. As shown in the graph in the block diagram, this optimum valve gradual opening operation signal calculator 32 receives the valve gradual opening start signal 27 and then calculates the value Δt ₁ given by the valve gradual opening time setting device 29.
After seconds, the valve opening given by the valve gradual opening value setting device 30
It is configured to generate a signal output corresponding to A _V2 .

The configuration for transmitting the above-mentioned gradual valve opening start signal 27 is as follows.

The arithmetic unit 24 receives the signal output 14 of the temperature detector 11.
It has a function of calculating a saturated steam pressure signal 25 corresponding to the detected temperature. Thereby, the detected temperature information T of the drain is converted into the saturated vapor pressure P _V and provided to the comparator 28 .
This comparator 28 is equipped with a differential pressure setting device 26, which turns ON when ΔP ₁ > _PV −P ₂ and issues a valve gradual opening start signal 27 . However, ΔP ₁ is the setting value of the differential pressure setting device 26, P ₂
is the drain pressure represented by the output signal 16 of the pressure detector 13 provided downstream of the minimum flow valve 5. With this configuration, it is possible to detect that the differential pressure between the drain saturated steam pressure on the upstream side of the minimum flow valve and the drain pressure on the downstream side of the minimum flow valve has become ΔP ₁ or less, thereby reducing the risk of hammering. It is possible to start increasing the opening degree of the minimum flow valve 5 without any delay.

The comparator 35 that sends the switching command 34 to the signal selector 38 described above is equipped with a differential pressure setting device 33, and is equipped with a pressure sensor 1 on the upstream side of the minimum flow valve 5.
The signal output 15 representing the detected value P ₁ of the pressure sensor 13 on the downstream side is compared with the signal output 16 representing the detected value P ₂ of the pressure detector 13 on the downstream side, and when ΔP ₂ > P ₁ - P ₂ is reached, it turns ON and switches. A command 34 is issued. However, ΔP ₂ is a value set in the differential pressure setting device 33. With this configuration, it is possible to detect that the differential pressure between the upstream drain pressure and the downstream drain pressure of the minimum flow valve 5 has become ΔP ₂ or less, and the minimum flow valve can be closed without the risk of hammering. 5 can be opened to a predetermined opening degree. The above-mentioned predetermined opening degree is given in advance by a predetermined valve opening degree setting device 37. When the differential pressure becomes ΔP ₂ or less and the switching command 34 is issued, the signal selector 38 is activated and a signal output corresponding to the set value A _{V 3} of the predetermined valve opening setting device 37 is output to the minimum flow valve 5. . Therefore, the above switching command 34
is a signal indicating the start of a switching operation to a predetermined valve opening degree A _V3 .

To summarize the above operations and summarize them over time, when the minimum flow valve opening signal 17 is transmitted by starting the water supply pump, the operation of the calculator 23 first causes the initial state to be set so that there is no risk of hammering. It is converted into a signal 22 giving the opening degree.

This opens the minimum flow valve 5 slightly.

Next, the saturated vapor pressure upstream of the minimum flow valve
When the difference between P _V and the pressure P ₂ on the downstream side becomes less than ΔP ₁ , the valve gradual opening start signal 27 is transmitted, and the valve gradually opens at a speed determined by the optimum valve gradual opening operation signal calculator 32. The degree of opening is increased.

And the pressure on the downstream side above the minimum flow valve
When the difference between P ₁ and P ₂ becomes ΔP ₂ or less, the valve opening degree is switched to a preset value A _V3 and a steady operating state is established.

FIG. 4 is a system diagram showing an example of application of the present invention.
This application example simplifies the configuration of the hammer ring suppression computing unit 19 of the embodiment shown in FIG. A program valve opening calculator 40 is provided. A block diagram of this program valve opening computing unit 40 is shown in FIG.

The program valve opening degree calculator 40 shown in this figure is an extremely simplified version of the hammering suppression calculator 19 shown in FIG. 3, and as will be described in detail later.
An intermediate configuration between the configuration of FIG. 3 and the configuration of FIG. 5 (partial simplification of the configuration of FIG. 3) is also possible.

The calculation mechanism simplified in this way is applicable when the operating conditions of the power plant are almost constant, that is, when the drain temperature and pressure of the minimum flow line are almost constant when the minimum flow valve 5 is opened. It is configured so that
The valve opening pattern suitable for the above-mentioned certain conditions is set without actually measuring the drain temperature and pressure, and the performance start operation is automatically controlled in accordance with this pattern.

In this example, the program valve opening calculation unit 40
As shown in the graph, starting from time t ₀ when the minimum flow valve opening signal 17 is input, the valve opening A _V1 after time t ₁ , the valve opening A _V2 after time t ₂ , and time.
After t ₃ , the valve opening control signal 4 is set so that the valve opening becomes A _V3 .
1 is emitted.

42 is a time t ₁ setting device, 43 is a time t ₂ setting device, and 44 is a time t ₃ setting device.

21 is the initial opening A _V1 setting device, 30 is the valve gradual opening value
The A _V2 setting device 37 is a setting device for the predetermined valve opening A _V3 .

As in this example, it is equipped with an initial opening setting device, a gradual valve opening value setting device, a predetermined valve opening setting device, and a timer device,
If a computing unit is provided that transmits a predetermined pattern of valve opening control signals using the valve opening signal 17, this computing unit can replace some or all of the components of the computing unit shown in FIG. The configuration of the device of the present invention can be simplified.

〔Effect of the invention〕

As described in detail above, the control device of the present invention includes an orifice installed on the downstream side of the drain piping connecting the water supply piping at the outlet of the power plant water pump and the condenser.
Minimum flow valves are connected to each other on the upstream side, and the minimum flow valves are opened by the valve open signal issued by the start of the water pump.In the minimum flow line, temperature is detected in the drain piping on the upstream side of the minimum flow valves. By providing a pressure detector and a pressure detector, and also providing a pressure detector in the drain pipe downstream of the minimum flow valve, and providing a computing unit that controls opening and closing of the minimum flow valve based on the signal output of each of the above detectors, It is possible to suppress the hammering phenomenon that occurs when the water supply pump minimum flow line is started, and to prevent a shocking sudden rise in the pressure inside the drain pipe, which greatly contributes to improving the reliability of the power plant.

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing a conventional minimum flow line, Fig. 2 is a system diagram of a minimum flow line equipped with an embodiment of the hammering suppressing device of the present invention, and Fig. 3 is a system diagram of the arithmetic unit of the above embodiment. FIG. 4 is a system diagram of an applied example of the present invention, and FIG. 5 is a block diagram of an arithmetic unit of the above applied example. 1... Water supply pump, 2... Electric valve, 4... Condenser, 5... Minimum flow valve, 6... Orifice, 7, 9, 10... Drain piping, 11... Drain temperature detector, 12 , 13...Drain pressure detector, 19...Hammering suppression control calculator, 2
3, 32... Calculator, 24... Saturated steam pressure calculator, 28, 35... Comparison calculator, 36... Adder, 38... Selector, 26, 29, 30, 33...
...Setter, 40...Program valve opening calculator, 4
2, 43, 44... Setting device.

Claims (1)

[Claims] 1. In order to ensure the minimum flow rate of the feed water pump that sends hot water from the low-pressure feed water heater of the power plant to the next stage, a minimum flow valve is installed between the outlet side of the feed water pump and the condenser. In a control device for a power plant water feed pump minimum flow line, which is connected via a power supply pump and opens the minimum flow valve in response to a start signal of the water feed pump, the minimum flow valve is gradually opened while the minimum flow valve is initially opened. A hammering suppression control device for a minimum flow line of a water supply pump in a power generation plant, characterized in that a control device for suppressing hammering due to the generation of two-phase flow downstream of a minimum flow valve is provided. 2. The control means according to claim 1, wherein the control means controls the gradual opening amount based on the detected pressure values on the upper and downstream sides of the minimum flow valve and the detected temperature values on the upstream side. Hammering suppression control device for power plant water supply pump minimum flow line. 3. The hammering suppression control device for a power plant water supply pump minimum flow line according to claim 1, wherein the control means controls the gradual opening amount according to a preset program.