JPH0133720B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a water hammer prevention device in a liquid pipe.

(Prior art) When fluid flows through a pipe, such as a sewage pipe, when the pipe is rapidly fully opened or partially closed, the liquid flow in the pipe decelerates rapidly. As a result, the pressure at the front and rear of the closed part also suddenly increases or decreases significantly, respectively, resulting in a so-called water hammer, which can damage liquid pipes and other surrounding equipment, and cause noise and vibration. be aroused.

Conventionally, as a means to prevent such water hammer, air is sealed in the upper part of a closed pressure vessel, and an air tank for preventing water hammer, which has a water reservoir in the lower part, is placed upright in the pressure-feeding section of the liquid delivery pipe. A method of preventing water hammering is adopted in which a portion of the liquid is moved in and out of the air tank according to the level of pressure in the installation and liquid feeding pipe to maintain balance.

(Problem to be solved by the invention) However, the above-mentioned conventional water hammer prevention method
Since liquid and air are always allowed to coexist in the sealed air tank to prevent water hammer, the proportion of air dissolved in the liquid increases, especially under pressure, and the water level in the air tank increases due to the dissolution of air. When the amount of air increases and the amount of air decreases, the liquid in the air tank cannot be discharged, resulting in a disadvantage that it becomes impossible to prevent a sudden pressure drop in the liquid pipe, that is, it becomes impossible to prevent water hammer. Conventionally, on a small scale, a method was used to block the liquid and air from coming into contact with each other using a diaphragm, etc., but on a large scale,
A method is used to replenish the air that has been reduced by dissolution.

In the case of the latter method, especially when automating the process, it becomes necessary to check and control the water level and pressure in the air tank. However, under normal circumstances, the amount and pressure of liquid in the sewage pipes are constantly changing, and it is difficult to immediately adjust the pressure and water level of the stored liquid in the air tank in response to these changes. There was a problem.

Conventionally, attempts have been made to control this using a single-pole water level detector, but when using this, the sensor part of the detector is contaminated by the flowing liquid, resulting in a large fluctuation range. could only be roughly controlled. It is also possible to predict the amount of air dissolved in the air tank in advance and mix air into the air tank during feeding, or to send air into the air tank by timed operation. However, in this case as well, proper control was not possible when the fluctuation range of the amount of liquid sent through the liquid sending pipe or the pressure was relatively large.

The present invention has been made in view of the above-mentioned circumstances, and is a water hammer prevention device in a liquid supply pipe that can automatically maintain the water level in the water hammer prevention air tank at an optimal position for water hammer prevention. The purpose is to provide the following.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the first invention is provided with a pressure gauge, a differential pressure type water level gauge, and an air replenishment control valve, which is disposed in the middle of a liquid sending pipe. A sealed air tank for water hammer prevention equipped with an air supply pipe and an air release pipe with an air release control valve, and an analog signal value of the pressure in the air tank detected and sent by the pressure gauge. The optimum water level for water hammer prevention is calculated based on the above calculation result, and the value of this calculation result is compared with the analog signal value of the water level in the air tank detected and sent by the differential pressure type water level gauge. When the value is smaller than the water level analog signal value, the output signal opens the air replenishment control valve to replenish air into the air tank, and when the calculated value is larger than the water level analog signal value, and a computing unit configured to open the air release control valve and release the air in the air tank in response to an output signal, and to maintain the water level in the air tank at an optimal position to prevent water hammer. This is a water hammer prevention device in a liquid sending pipe.

In order to achieve the above object, the second invention provides a system in which a plurality of pumps are connected individually, the number of pumps being operated is controlled by a pump operation controller according to the water level on the liquid sending side. A sealed air tank for preventing water hammer, which is installed in the middle of one liquid sending pipe and equipped with a differential pressure type water level gauge and an air supply pipe with an air supply control valve, and the performance of the pump. The optimal water level for water hammer prevention for each number of pumps in operation is calculated in advance based on the number of pumps in operation and the design conditions of liquid sending pipes, etc., and is stored separately. The set water position selected by the digital signal indicating the number of pumps in operation is compared with the analog signal value of the water level in the air tank detected and sent by the differential pressure type water level gauge, and the set water level value is determined to be the water level. and a water level control calculator configured to open the air replenishment control valve according to the output signal to replenish air into the air tank when the output signal is smaller than the analog signal value of the water level in the air tank. This is a water hammer prevention device in a liquid sending pipe, characterized in that the water hammer is kept at an optimal position for preventing water hammer.

(Operation) Since the first invention is configured as described above,
When the water level and pressure in the air tank fluctuate, the calculator calculates the optimal water level for water hammer prevention based on the analog signal value of the pressure in the air tank sent from the pressure gauge, and uses this calculated value and the differential pressure formula. The analog signal value of the water level in the air tank detected and sent by the water level meter is compared, and if the value of the calculation result is smaller than the analog signal value of the water level, the output signal is used to control the air supply control valve. When the calculated value is greater than the water level analog signal value, the output signal opens the air release control valve to release air from the air tank. As a result, the water level in the air tank is automatically maintained at the optimal position to prevent water hammer.

Further, since the second invention is configured as described above, when the water level on the liquid sending side changes, the number of pumps in operation is controlled by the pump operation controller, and the amount of liquid sent in the liquid sending pipe changes. Waru. As described above, when the amount of liquid sent in the liquid sending pipe changes, the water level control calculator selects the optimal water level for the number of pumps in operation based on the digital signal of the number of pumps in operation sent from the pump operation controller. This set water level value is compared with the analog signal value of the water level in the air tank detected and sent by the differential pressure type water level meter, and if the set water level value is smaller than the analog signal value of the water level, the output signal is By opening the air replenishment control valve and replenishing air into the air tank, the water level in the air tank is adjusted to the set water level, which is optimal for preventing water hammering for each number of pumps in operation, calculated in advance. It is automatically held in the correct position.

(Example) Hereinafter, examples of the first invention and the second invention will be described in detail with reference to the drawings.

First, in FIG. 1 showing an embodiment of the first invention, numeral 1 is a pressure-resistant container-type sealed air tank for preventing water hammer, and is connected to a liquid feeding pipe 3 through a connecting pipe 2 in an inverted manner. Air is sealed in the air tank 1 by the liquid flowing into the air tank 1, and the water level 4 is balanced according to fluctuations in the pressure inside the liquid feeding pipe 3.

5 is a differential pressure type water level gauge, and the pressure sensing parts on both sides of the water level gauge 5 are connected to the upper and lower parts of the air tank 1 through a vent pipe 6 and a liquid passage pipe 7, respectively.
The pressure difference between the upper and lower parts of air tank 1 is water level 4
Since the flow of the liquid in the liquid passage pipe 7 is minute, there are few blockages due to dirt in the liquid, and there are few erroneous measurements. In addition, since the water level is measured by differential pressure, the air tank 1
It is not affected by fluctuations in the air pressure inside. The differential pressure type water level gauge 5 constantly detects the water level 4 in the air tank 1 as an analog value, converts this into an analog signal, and sends it to an arithmetic unit 12, which will be described later, via an input wiring 13. .

Reference numeral 10 denotes a pressure gauge, which is attached to the top wall of the air tank 1 through a connecting pipe 11. The pressure inside the air tank 1 is constantly detected as an analog value by the pressure gauge 10, and this is converted into an analog signal and sent to the input wiring 1.
5 to an arithmetic unit 12, which will be described later. Note that the same effect can be obtained even if the mounting position of the pressure gauge 10 is changed to the lower part of the air tank 1 or to the liquid feeding pipe 3. Further, a pressure value calculated from a predetermined water head calculation by providing a flow meter in the liquid sending pipe 3 can also be used as the pressure value in the air tank 1.

Reference numeral 12 denotes a calculator, which calculates water hammer prevention for this signal value based on the pressure analog signal value sent from the pressure gauge 10 via the input wiring 15 in accordance with the Boyle-Charles law. The optimum water level is calculated, and the value of this calculation result is compared with the analog signal value of the water level 4 in the air tank 1 sent from the differential pressure type water level gauge 5 via the input wiring 13. When it is smaller than the analog signal value, it is output and opens the air supply control valve 17 via the output wiring 16, and when the value of the calculation result is larger than the analog signal value of water level 4, it is output and connected to the output wiring 16. 18 to open a control valve 19 for air release. An example of the operation of the arithmetic unit 12 is shown in the block diagram of FIG.

20 is an air supply pipe that communicates the air supply control valve 17 and the upper part of the air tank 1; 21 is an air discharge pipe that communicates the air discharge control valve 19 and the upper part of the air tank 1; It is open to the atmosphere at the outlet.

Reference numeral 23 is an air compressor, which can be constantly supplied with air. The air compressor 23 is adapted to supply air into the air tank 1 via a conduit 24, an air supply control valve 17, and an air supply pipe 20. 25 is a safety valve attached to the top wall of the air tank 1.

Since the first invention is configured as described above,
At all times, the water level 4 in the air tank 1 is sent to the calculator 12 as an analog water level signal by the differential pressure type water level gauge 5 via the input wiring 13, and the pressure in the air tank 1 is sent to the calculator 12 by the pressure gauge 10. It is sent to the computing unit 12 via the input wiring 15 as an analog pressure signal.

When the pressure and water level in the air tank 1 fluctuate, the calculator 12 uses the pressure analog signal value sent from the pressure gauge 10 to determine the optimal water hammer prevention for this signal value according to the Boyle-Charles law. Calculate the water level of this calculation result and input wiring 13
The analog signal value of the water level 4 in the air tank 1 sent from the differential pressure type water level gauge 5 via the air tank 1 is compared.

When the value of this calculation result is smaller than the analog signal value of the water level 4, the calculator 12 outputs an output, opens the air replenishment control valve 17 via the output wiring 16, and connects the air compressor 23 to the conduit 24 for air replenishment. Air is supplied to the air tank 1 via the control valve 17 and the air supply pipe 20, and when the calculated value and the analog signal value of the water level 4 match, the output of the calculator 12 is stopped and the air is The replenishment control valve 17 is closed, and the replenishment of air into the air tank 1 is stopped. Further, when the value of the calculation result is larger than the analog signal value of the water level 4, the calculator 12 outputs an output, opens the air release control valve 19 via the output wirings 16 and 18, and connects the air tank 1 to the air release pipe. 21, the air release control valve 19, and the outlet 22 to release air into the atmosphere, and when the calculated value and the analog signal value of the water level 4 match, the output of the calculator 12 stops, and the air The release control valve 19 is closed and the release of air from the air tank 1 is stopped.

Note that the release of air can be omitted if the amount of mixed air during liquid feeding is small and the possibility of excessive supply of air is expected to be small.
In addition, the air in the air tank 1 is contracted or expanded by the temperature of the outside world, and the water level in the air tank 1 is
When the temperature is to be changed, a thermometer is installed on the top wall of the air tank 1 via a connecting pipe, and the temperature of the air in the air tank 1 is constantly detected as an analog value, and this is converted into an analog signal. The data may be sent to the arithmetic unit 12 via input wiring, and the water level control may be corrected based on the temperature factor.

As described above, the water level 4 in the air tank 1 for preventing water hammer is automatically maintained at the optimum position for preventing water hammer.

Next, in FIG. 2 showing an embodiment of the second invention, parts common to those in FIG.

27,... are a plurality of pumps arranged in parallel in the pump tank 26, and each pump 27,... is connected to one liquid feeding pipe 3 via each valve 28 and a common header 29. There is.

Reference numeral 30 denotes a pump operation controller, and the pump operation controller 30 controls the operation and startup of the pumps 27, . Detects the number of units as a digital value, converts it into a digital signal, and sends it to the water level control calculator 34 via the input wiring 15.
A stored water level, which will be described later, is selected and used as the set water level. Reference numeral 31 indicates a valve disposed at an appropriate position in the liquid feeding pipe 3, and reference numeral 32 indicates a safety valve.

On the other hand, instead of the calculation by the arithmetic unit 12,
The optimal water level for preventing water hammering for each number of pumps 27 in operation is determined in advance based on pump performance such as discharge amount and discharge pressure of the pumps 27 and the number of operating pumps, and design conditions such as the inner diameter, length, and head of the liquid sending pipe 3. is determined by calculation, and the water levels determined by this calculation are stored separately in the water level control calculator 34.

Since the second invention is configured as above,
At all times, the water level 4 in the air tank 1 is sent as an analog signal by the differential pressure type water level gauge 5 to the water level control calculator 34 via the input wiring 13, and the number of operating pumps 27 is sent to the pump operation controller 30. Therefore, it is sent as a digital signal to the water level control calculator 34 via the input wiring 15.
The water level is set based on the number of pumps in operation.

Then, when the number of operating pumps 27 changes according to fluctuations in the water level in the pump tank 26, that is, the water level on the liquid feeding side, the water level control calculator 34 receives the digital number of operating pumps sent from the pump operation controller 30. The stored water level is selected by the signal and set as the set water level, and this set water level value is compared with the analog signal value of the water level 4 in the air tank 1 sent from the differential pressure type water level gauge 5, and the set water level value is determined as the water level. When it is smaller than the analog signal value of 4, the water level control calculator 3
4 outputs, opens the air supply control valve 17 via the output wiring 16, and connects the air compressor 23 to the conduit 24.
Air is supplied to the air tank 1 via the air supply control valve 17 and the air supply pipe 20, and when the set water level value and the analog signal value of the water level 4 match, the output of the water level control calculator 34 is is stopped, the air supply control valve 17 is closed, and the supply of air into the air tank 1 is stopped.

Incidentally, when it is necessary to release the air in the air tank 1, the air is released in the same manner as in the first invention.

As described above, the water level in the water hammer prevention air tank 1 is automatically maintained at the set water level, that is, the optimal position for preventing water hammer for each number of operating pumps calculated in advance.

(Effects of the Invention) As is clear from the above explanation, according to the first invention and the second invention, changes in the pressure and water level in the air tank, the number of operating pumps, and the water level in the air tank, respectively, Correspondingly, it has become possible to provide a water hammer prevention device in a liquid supply pipe that can automatically and precisely control the water level in the air tank to maintain the optimum position for preventing water hammer.

[Brief explanation of drawings]

FIG. 1 is a system diagram of an embodiment of the first invention, FIG. 2 is a system diagram of an embodiment of the second invention, and FIG. 3 is a block diagram showing an example of the operation of the arithmetic unit in the first invention. 1: Closed air tank to prevent water hammer, 3: Liquid feed pipe,
4: Water level, 5: Differential pressure type water level gauge, 10: Pressure gauge, 1
2: Arithmetic unit, 13, 15: Input wiring, 16, 1
8: Output wiring, 17: Air supply control valve, 19:
Air release control valve, 26: pump tank, 27: pump, 30: pump operation controller, 33: inflow sensor, 34: water level control calculator.

Claims (1)

[Scope of Claims] 1. Disposed in the middle of a liquid sending pipe, and equipped with a pressure gauge, a differential pressure type water level gauge, an air supply pipe with an air supply control valve, and an air discharge pipe with an air discharge control valve. The optimum water level for water hammer prevention is calculated based on the sealed air tank for water hammer prevention that has been detected and the analog signal value of the pressure in the air tank detected and sent by the pressure gauge, and the water level that is optimal for water hammer prevention is calculated. The value is compared with the analog signal value of the water level in the air tank detected and sent by the differential pressure type water level gauge, and when the value of the calculation result is smaller than the analog signal value of the water level, the output signal is used. The air replenishment control valve is opened to supply air into the air tank, and when the value of the calculation result is greater than the water level analog signal value, the air release control valve is opened by the output signal to supply air. A water hammer prevention device in a liquid sending pipe, comprising a computing unit configured to release air from inside the tank, and maintaining the water level in the air tank at an optimum position for preventing water hammer. . 2 A pump operation controller controls the number of pumps operated according to the water level on the liquid sending side, and a plurality of pumps are arranged in the middle of a single liquid sending pipe that are individually connected. Based on the design conditions such as the performance and number of pumps in operation and the liquid supply pipe, etc. The optimum water level for preventing water hammering is calculated in advance for each number of pumps in operation, and is stored separately, and one of the stored water levels is selected based on a digital signal indicating the number of pumps in operation sent from the pump operation controller. Compare the set water level value and the analog signal value of the water level in the air tank detected and sent by the differential pressure type water level gauge,
and a water level control calculator configured to open the air replenishment control valve in response to the output signal to replenish air into the air tank when the set water level value is smaller than the water level analog signal value. . A water hammer prevention device in a liquid sending pipe, characterized in that the water level in the air tank is maintained at an optimum position for preventing water hammer.