JPH08327010A - Water hammer preventing apparatus for water supply system - Google Patents

Abstract

PURPOSE: To prevent the self-evaporation of feed water in a deaerator downflow tube and a water storage tank when a load shut-off or an plant single operation occurs. CONSTITUTION: A noncondensible gas filling tube 12 for filling noncondensible gas in a deaerator 1 is connected via a gas injection control valve 13. A pressure oscillator 14 for detecting the pressure in the deaerator 1 is installed. The pressure signal of the oscillator 14 is input to a controller 15, which calculates the pressure drop rate for a specified time in the deaerator 1, compares it with the maximum pressure drop rate at the time of preset normal stopping. When the drop rate is abnormally large, the valve 13 is opened, and the pressure drop rate in the deaerator 1 is controlled to the specified rate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water hammer prevention device used by being incorporated in a boiler water supply system of a power generation turbine plant.

[0002]

2. Description of the Related Art FIG. 6 is a diagram showing a conventional boiler water supply system used in a power generation turbine plant. In the figure, the condensate from the low-pressure feed water heater (not shown) is the deaerator 1
Inside, it is heated and deaerated by the extracted steam from the extraction pipe 3, and flows into the lower water storage tank 2. Then, it is sent to the high-pressure feed water heater through the deaerator downcomer pipe 4a, the shutoff valve 5a, the water supply booster pump 6a, the connecting pipe 7a, and the water supply pump 8a.
Water is supplied to a boiler (not shown).

At the time of starting the plant, in order to remove a large amount of air dissolved in the boiler feed water, the deaerator downcomer 4a
Deaerator circulation pump using deaerator circulation pipe 9 branched from
By operating 10 the boiler feedwater circulates in the deaerator 1 and air is removed.

Generally, the water supply pump is divided into a plurality of units, and in addition to the water supply pump 8a system, a deaerator downcomer pipe 4a, a shutoff valve 5b, a water supply booster pump 6b, a connecting pipe 7b, a water supply pump 8b, etc. Is installed. These pumps are driven by steam turbines and electric motors,
Generally, steam turbine drive is used for regular use, and electric motor drive is used for emergency use.

[0005]

When the load on the steam turbine decreases during plant operation, the pressure in the deaerator 1 decreases almost in proportion to this load, and the supply of water in the water storage tank 2 also changes to the internal pressure. Follow the saturation temperature. However, when the load suddenly decreases due to load shedding / in-house operation alone, the supply of turbine extraction steam to the deaerator 1 also sharply decreases, so the internal pressure also sharply decreases. And the feed water in the deaerator downcomer 4 is left at the temperature before the load change, and remains at the saturation temperature of the in-vessel pressure. Therefore, the water supply in the water storage tank 2 and the deaerator downcomer 4 self-evaporates,
The water supply containing the bubbles may reach the water supply booster pump 6a. In the water supply pump 8a system in operation, this water supply flows continuously as it is and is sucked into the water supply booster pump 6a to cause no abnormality, but in the pipe of the water supply pump 8b system which is stopped as a standby machine, a water hammer phenomenon (hereinafter (Referred to as “hammer”) occurs, and the vibration damages the piping system, and disables the water supply booster pump 6b and the water supply pump 8b that are stopped. Water containing bubbles in the water storage tank 2 may make the level control of the water storage tank 2 unstable.

Therefore, in the conventional feed pump, the deaerator circulation pump 10 is operated or the pressure drop in the deaerator 1 is performed in order to replace the feed water in the deaerator downcomer pipe 4 in a specific load range. In order to make the rate as low as possible, auxiliary steam is introduced from the auxiliary steam pipe 11 to prevent troubles in the water supply pump 8b system.

However, if an attempt is made to prevent such a water hammer in the conventional water supply system,
The capacity of the deaerator circulation pump 10 originally installed for the purpose of bleeding air at startup is insufficient, and the intended effect cannot be obtained. In addition, since there is a restriction on the amount of auxiliary steam, it is not possible to completely prevent troubles caused by water containing bubbles, and water hammer may occur in the piping of the water supply pump 8b system that is in standby as a standby machine, The water supply booster pump 6b and the water supply pump 8b may be unable to start.

Therefore, an object of the present invention is to prevent water-hammer of a water supply system which surely prevents self-evaporation of the water supply in the deaerator downcomer pipe and the water storage tank when a load shedding / independent operation in the station occurs. To provide.

[0009]

The invention according to claim 1 is
A water tank that communicates with a deaerator and a deaerator downcomer that guides the water supply in the water tank to a water supply pump, including a gas injection control valve that injects non-condensable gas into the deaerator. A non-condensable gas injection pipe is provided, and the non-condensable gas is injected into the deaerator by opening the gas injection control valve when the load is cut off or the island is operated independently.

Further, the invention according to claim 2 is characterized in that the gas injection control valve is provided with a control means for controlling the injection of the non-condensable gas in accordance with the rate of decrease of the pressure in the deaerator during a normal stop.

Further, the invention according to claim 3 is characterized in that the gas injection control valve comprises control means for controlling the injection of the non-condensable gas in accordance with the pressure difference between the deaerator internal pressure and the feed water pump inlet pressure. To do.

Further, the invention according to claim 4 is characterized in that the gas injection control valve comprises a control means for controlling the injection of the non-condensable gas by the opening signal of the extraction check valve. Further, the invention according to claim 5 is characterized in that an initial gas injection control valve is provided in parallel with the gas injection control valve in the path of the non-condensable gas injection pipe.

[0013]

The gas injection control valve of the non-condensable gas injection pipe connected to the deaerator is fully opened when, for example, the load is cut off or the in-house isolated operation signal is given. Therefore, the non-condensable gas flows into the deaerator through the non-condensable gas injection pipe, and the internal pressure of the non-condensable gas rises before it largely drops. By avoiding this pressure drop, it is possible to prevent the water supply from self-evaporating in the deaerator and the water storage tank.

The gas injection control valve is normally controlled according to the pressure drop rate of the deaerator at the time of stop or according to the differential pressure between the deaerator internal pressure and the feed water pump inlet pressure. Moreover, you may control by the opening degree signal of the extraction check valve. This can increase the internal pressure while keeping the time delay to a minimum.

Further, the initial gas injection control valve is a control valve having a high opening / closing speed, and is opened at the initial stage when the load is cut off, for example. Then, the gas injection control valve may be opened when the internal pressure becomes stable. By doing so, the non-condensable gas can be introduced into the deaerator without time delay.

[0016]

1 is a diagram showing a boiler water supply system showing an embodiment of the present invention. In FIG. 1, a non-condensable gas injection pipe 12 for injecting a non-condensable gas into the deaerator 1 is a gas injection control valve
A pressure transmitter 14 for detecting the pressure inside the deaerator 1 is installed. This pressure transmitter
The pressure signal of 14 is input to the controller 15, and the pressure drop rate within the specified time in the deaerator 1 of the actual machine is calculated, and it drops abnormally compared with the preset maximum pressure drop rate during normal stop. When the rate is large, the gas injection control valve 13 is opened to control the rate of pressure drop in the deaerator 1 to the specified rate.

FIG. 2 is an explanatory view of the control of the gas injection control valve 13 in FIG. The gas injection control valve 13 is the pressure drop in the deaerator 1 of the actual machine taken in the controller 15 and the preset maximum depressurization rate in the deaerator during normal stop, that is, the maximum load drop rate during normal stop. The pressure drop rate in the deaerator is compared with that in the deaerator 1, and the pressure control in the deaerator 1 is started at the time when the drop rate is not considered during normal stop. Prevents self-evaporation in tank 2 and prevents water hammer reliably, and water tank 2
Maintains good water level control.

FIG. 3 is a diagram showing a boiler water supply system showing another embodiment of the present invention. In FIG. 3, a noncondensable gas injection pipe 12 for injecting a noncondensable gas is connected to the deaerator 1 via a gas injection control valve 13. Also deaerator 1
And pressure transmitters 14, 16a, 16b are installed at the inlets of the water supply booster pumps 6a, 6b, respectively, through pipes,
The pressures inside the deaerator 1 and the lower part of the deaerator downcomer pipe 4, that is, the inlet of the water supply booster pump 6 are detected. When these detection signals enter the controller 15 and the differential pressure value calculated as the differential pressure falls below a specified value, the controller 15 causes the gas injection control valve 13
The deaerator 1 is controlled so that the differential pressure value becomes constant.
It is designed to control the internal pressure of. As a result, the internal pressure of the deaerator 1 can always be kept higher than the pressure at the lower part of the deaerator downcomer pipe 4, that is, the inlet of the water booster pump 6 by a certain value or more, and the deaerator downcomer pipe 4 and the water storage tank 2 can be maintained. The self-evaporation is prevented, the water hammer is surely prevented, and the water level control of the water storage tank 2 is well maintained.

Further, another embodiment of the present invention will be described.
In FIG. 4, the control start timing of the gas injection control valve is set to the deaerator internal pressure drop rate of the above embodiment (FIG. 1) and the deaerator internal pressure and deaerator of another embodiment (FIG. 3). Instead of starting with the differential pressure signal at the bottom of the downcomer pipe, the opening signal of the extraction check valve is used. In each of the above embodiments, the control start timing is detected by the pressure signal. However, in the case of the pressure signal, detection delay occurs, so that when the amount of heating steam supplied to the deaerator 1 decreases, the extraction check valve operates immediately. The opening signal allows the initial injection of non-condensable gas.

Further, an embodiment different from the above will be described. In FIG. 5, a noncondensable gas injection pipe 12 for injecting a noncondensable gas is connected to the deaerator 1, and the noncondensable gas injection pipe 12 has a gas injection control valve 13 and an initial gas injection control valve 16 Are installed in parallel. Since the initial gas injection control valve 17 is installed for the purpose of assisting the delay of the opening operation time of the gas injection control valve 13, the signal of the controller 15 is received and the valve is opened for a certain period of time to inject the non-condensable gas without delay. Is possible. This can prevent the occurrence of flash in the deaerator downcomer 4 and the water storage tank 2.

In each of the above embodiments, the non-condensable gas injection pipe 12 is connected to the deaerator 1 by a single connection port. However, if the injection ports are attached at two or more places, the non-condensed gas is not formed. It is possible to maintain a uniform pressure distribution in the deaerator 1 during injection.

Further, by switching the injection of the non-condensable gas and the injection of the auxiliary steam at a specified time, the pressure deviation between the deaerator 1 and the deaerator downcomer pipe 4 becomes very small, and a stable state is reached. Then, the original heating and degassing operation is started, and the non-condensable gas can be smoothly discharged to the outside of the system.

[0023]

As is apparent from the above description, the present invention can prevent self-evaporation of water supply in the deaerator downcomer and the water storage tank, can reliably prevent water hammer, and can control the water level of the water storage tank. Can be kept good.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of a water hammer prevention device according to the present invention.

FIG. 2 is an explanatory view showing a control method of a gas injection control valve in FIG.

FIG. 3 is a system diagram showing another embodiment of the present invention.

FIG. 4 is a configuration diagram showing a control circuit of the present invention.

FIG. 5 is a system diagram showing another embodiment of the present invention.

FIG. 6 is a system diagram showing a conventional boiler water supply system.

[Explanation of symbols]

1 Deaerator 2 Water storage tank 3 Turbine extraction pipe 4 Deaerator downcomer pipe 5 Shutoff valve 6 Water supply booster pump 7 Communication pipe 8 Water supply pump 9 Deaerator circulation pipe 10 Deaerator circulation pump 11 Deaerator auxiliary steam pipe 12 Non-condensable gas injection pipe 13 Gas injection control valve 14 Pressure transmitter 15 Controller 16 Pressure transmitter 17 Gas injection initial control valve

Claims (5)

[Claims] 1. A non-condensing gas is injected into the deaerator in a water storage tank communicating with the deaerator, and a deaerator downcomer that guides the water supply in the water storage tank to a water supply pump. Provide a non-condensable gas injection pipe with a gas injection control valve,
A water hammer prevention device for a water supply system, characterized in that the gas injection control valve is opened to inject non-condensable gas into the deaerator when the load is cut off and the island is operated independently. 2. The water supply system according to claim 1, wherein the gas injection control valve includes control means for controlling the injection of the non-condensable gas in accordance with the rate of decrease of the pressure in the deaerator during normal stop. Water hammer prevention device. 3. The gas injection control valve comprises control means for controlling the injection of non-condensable gas according to the differential pressure between the internal pressure of the deaerator and the inlet pressure of the feed water pump. Water hammer prevention device for water supply system. 4. The water hammer prevention device for a water supply system according to claim 1, wherein said gas injection control valve comprises a control means for controlling the injection of the non-condensable gas by an opening signal of the extraction check valve. 5. The water hammer prevention device for a water supply system according to claim 1, wherein an initial gas injection control valve is provided in parallel with the gas injection control valve in a path of the non-condensable gas injection pipe.