Operational method for pump system and the pump system

Abstract

To provide an operational method for a pump system for enabling the operation start of a main pump to be reliably executed by reliably exhausting air from a pump casing.SOLUTION: The operational method for the pump system includes a step of starting a main pump 5 in the state of closing a discharge valve 27 connected to the discharge side of a pump casing 6 to start the operation of a vacuum pump 7, a step of opening a bypass valve 41 provided in a bypass pipe 40 extending from the pump casing 6 to a duction tank 1, to the extent of an intermediate opening, and a step of counting a predetermined first standby time after it is detected that the pump casing 6 is filled with water, closing the bypass valve 41 after the passage of the predetermined first standby time, and then fully opening the discharge valve 27.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a pump system including a main pump that transfers water from a suction tank to a discharge tank and a vacuum pump that exhausts air from a pump casing of the main pump, and more particularly to a method for starting the pump system. [Background technology]

[0002] In conventional suction-type horizontal shaft pump systems, a vacuum pump draws air into the pump casing, and a full-water detector detects that the pump is full. The electric motor driving the horizontal shaft pump (main pump) is then started. This type of operation results in a large pump torque (torque required to rotate the pump rotor) at startup, making it necessary to select a drive system capable of generating sufficient starting torque. This type of drive system requires a large starting current to generate a large starting torque, so expensive electric motors and starting methods must be used to suppress this starting current.

[0003] As mentioned above, when a motor with a large starting current is used, a momentary voltage drop can occur in the power supply system that supplies the power. To solve this problem, it is necessary to use a wound-type motor with a complex structure, an expensive starting device (such as an inverter or a Condolfer starter), or to install a separate voltage drop compensation device. This is because each power company that supplies power sets limits on voltage drop in the system, taking into consideration the impact on other power consumers, and if a facility deviates from these limits, the facility is required to install equipment that meets the limits.

[0004] To address these issues, a pump system and operating method using a gas-liquid separator and a swirl prevention plate is provided, as shown in Patent Document 1. Patent Document 1 provides a technique for discharging air from the pump casing using a vacuum pump while the main pump is operating. This technique reduces the starting current of the electric motor, making it possible to provide an inexpensive and simple horizontal shaft pump. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-256769 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the method described in Patent Document 1 has the problem that during the filling process after dry start, the air inside the casing is not completely sucked in, leaving a small amount of air, reducing the head of the main pump. In other words, because the density of a water-air mixture is low, pump performance is significantly reduced, and the main pump is unable to discharge water. This problem is likely to occur when high water pressure is applied to the discharge pipe of the main pump. For example, this problem can occur when the water level in the discharge tank is higher than the outlet of the discharge pipe, or when part of the discharge pipe is higher than the impeller of the main pump.

[0007] Therefore, the present invention provides a pump system operating method that can reliably discharge air from the pump casing, thereby reliably starting up the main pump, and a pump system that can perform such an operating method. [Means for solving the problem]

[0008] In one aspect, a method for operating a pump system includes a main pump that transfers water from a suction tank to a discharge tank, a gas-liquid separation mechanism provided in a pump casing of the main pump, a swirl prevention plate that prevents swirling flow within the pump casing, and a vacuum pump connected to the pump casing via the gas-liquid separation mechanism and that discharges air from the pump casing, the method comprising: starting the main pump with a discharge valve connected to the discharge side of the pump casing closed; starting the operation of the vacuum pump; opening a bypass valve provided in a bypass pipe extending from the pump casing to the suction tank to an intermediate opening; counting a predetermined first waiting time after detecting that the pump casing is full of water; closing the bypass valve after the predetermined first waiting time has elapsed; and then fully opening the discharge valve.

[0009] In one aspect, the operating method further includes, after closing the bypass valve and before fully opening the discharge valve, determining whether the pressure inside the pump casing exceeds a predetermined target pressure, and when the pressure inside the pump casing exceeds the predetermined target pressure, fully opening the discharge valve. In one aspect, the operating method further includes, when the pressure in the pump casing is lower than the predetermined target pressure, opening the bypass valve, counting a predetermined second waiting time, closing the bypass valve after the predetermined second waiting time has elapsed, and then determining again whether the pressure in the pump casing has risen to the predetermined target pressure. In one embodiment, the operating method further includes stopping operation of the vacuum pump after the pump casing is detected to be full of water and before the predetermined first waiting time is counted. In one aspect, the operating method further includes closing the bypass valve, opening the discharge valve to an intermediate opening, and then stopping operation of the vacuum pump, and fully opening the discharge valve after stopping operation of the vacuum pump. In one embodiment, the operating method further includes stopping operation of the vacuum pump after the discharge valve is fully opened.

[0010] In one aspect, the operating method further includes executing a management operation mode after operation of the main pump has stopped, in which the management operation mode starts the main pump with the discharge valve and the bypass valve closed, starts operation of the vacuum pump, opens the bypass valve to an intermediate opening, and after full water is detected in the pump casing, stops operation of the vacuum pump and then fully opens the bypass valve. In one aspect, the operating method further includes performing a drainage operation using the main pump with the discharge valve fully open, and when the water level in the suction tank drops during the drainage operation of the main pump and reaches a first low-flow rate operating level, determining a first operating point within a range between a predetermined minimum continuous operation flow rate and a flow rate at an operating point during the drainage operation of the main pump, determining a first opening degree of the discharge valve corresponding to the first operating point, and changing the opening degree of the discharge valve from fully open to the first opening degree, and when the water level in the suction tank further drops and reaches a second low-flow rate operating level, determining a second operating point within a range between the predetermined minimum continuous operation flow rate and the flow rate at the operating point during the drainage operation of the main pump, determining a second opening degree of the discharge valve and a third opening degree of the bypass valve corresponding to the second operating point, and changing the opening degree of the discharge valve from the first opening degree to the second opening degree, and changing the opening degree of the bypass valve from fully closed to the third opening degree.

[0011] In one aspect, a pump system is provided that includes: a main pump that transfers water from a suction tank to a discharge tank; a gas-liquid separation mechanism provided in a pump casing of the main pump; a swirl prevention plate that prevents swirling flow within the pump casing; a vacuum pump connected to the pump casing via the gas-liquid separation mechanism and that exhausts air from the pump casing; a discharge valve connected to the discharge side of the pump casing; a bypass pipe extending from the pump casing to the suction tank; a bypass valve provided in the bypass pipe; a full-water detector that detects when the pump casing is full of water; and an operation control unit that controls operation of the main pump, the vacuum pump, the discharge valve, and the bypass valve, wherein the operation control unit is configured to start the main pump with the discharge valve closed, initiate operation of the vacuum pump, open the bypass valve to an intermediate opening, count a predetermined first waiting time after the pump casing is detected to be full of water, close the bypass valve after the predetermined first waiting time has elapsed, and then fully open the discharge valve.

[0012] In one aspect, the operation control unit is configured to determine whether the pressure inside the pump casing exceeds a predetermined target pressure after closing the bypass valve and before fully opening the discharge valve, and to fully open the discharge valve if the pressure inside the pump casing exceeds the predetermined target pressure. In one aspect, the operation control unit is configured to open the bypass valve when the pressure inside the pump casing is lower than the predetermined target pressure, count a predetermined second waiting time, close the bypass valve after the predetermined second waiting time has elapsed, and then determine again whether the pressure inside the pump casing has risen to the predetermined target pressure. In one embodiment, the operation control unit is configured to stop operation of the vacuum pump after the pump casing is detected to be full of water and before the predetermined first waiting time is counted. In one aspect, the operation control unit is configured to close the bypass valve, then open the discharge valve to an intermediate opening, then stop operation of the vacuum pump, and after stopping operation of the vacuum pump, fully open the discharge valve. In one aspect, the operation control unit is configured to stop operation of the vacuum pump after fully opening the discharge valve.

[0013] In one aspect, the operation control unit is configured to execute a management operation mode after operation of the main pump stops, and the management operation mode is an operation in which, with the discharge valve and the bypass valve closed, the main pump is started, operation of the vacuum pump is initiated, the bypass valve is opened to an intermediate opening, and after full water is detected in the pump casing, operation of the vacuum pump is stopped, and then the bypass valve is fully opened. In one aspect, when the water level in the suction tank drops to a first low-flow rate operating level during drainage operation of the main pump, the operation control unit is configured to determine a first operating point within a range between a preset minimum continuous operation flow rate and a flow rate at an operating point during drainage operation of the main pump, determine a first opening degree of the discharge valve corresponding to the first operating point, and change the opening degree of the discharge valve from fully open to the first opening degree; and when the water level in the suction tank further drops to a second low-flow rate operating level, determine a second operating point within a range between the preset minimum continuous operation flow rate and the flow rate at the operating point during drainage operation of the main pump, determine a second opening degree of the discharge valve and a third opening degree of the bypass valve corresponding to the second operating point, change the opening degree of the discharge valve from the first opening degree to the second opening degree, and change the opening degree of the bypass valve from fully closed to the third opening degree. [Effects of the Invention]

[0014] After the main pump and vacuum pump start operating, the bypass valve is opened. The air and water mixture in the pump casing is discharged through the bypass pipe into the suction tank. Eventually, the air in the pump casing is removed and the pump casing is filled with water. The discharge valve is then opened. With the pump casing filled with water, the main pump can perform its original pumping performance, allowing it to perform normal drainage operation. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a schematic diagram illustrating an embodiment of a pump system. [Figure 2] 2 is a flowchart illustrating an embodiment of a method for operating the pump system shown in FIG. 1. [Figure 3] 10 is a flowchart illustrating another embodiment of a method for operating the pump system shown in FIG. [Figure 4] 10 is a flowchart illustrating yet another embodiment of a method for operating the pump system shown in FIG. [Figure 5] FIG. 2 is a schematic diagram illustrating an embodiment of the installation of the pump system shown in FIG. 1. [Figure 6] 1. FIG. 4 is a schematic diagram showing another embodiment of the installation of the pump system shown in FIG. [Figure 7] 1. FIG. 4 is a schematic diagram showing yet another embodiment of the installation of the pump system shown in FIG. [Figure 8] 1. FIG. 4 is a schematic diagram showing yet another embodiment of the installation of the pump system shown in FIG. [Figure 9] 1 is a flow chart illustrating an embodiment of a managed operation of a pump system. [Figure 10] 4 is a graph illustrating the operating points of the main pump. [Figure 11] 4 is a graph illustrating the operating points of the main pump. [Figure 12] 10 is a flowchart of a low water volume operation of the main pump. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing one embodiment of a pump system. The pump system includes a main pump 5 that discharges water from a suction tank 1 and transfers it to a tank (not shown), and a vacuum pump 7 that exhausts air from a pump casing 6 of the main pump 5. The main pump 5 is a horizontal shaft pump such as a mixed flow pump or an axial flow pump. More specifically, the main pump 5 includes a rotating shaft 11 that extends horizontally, an impeller 12 connected to the rotating shaft 11, a pump casing 6 that houses the impeller 12, and a driver 15 that rotates the rotating shaft 11. Examples of the driver 15 include an electric motor or a combination of an electric motor and a reducer.

[0017] The pump casing 6 has an impeller casing 17 in which the impeller 12 is disposed, a curved pipe 18 connected to the suction side of the impeller casing 17, and a discharge pipe 19 connected to the discharge side of the impeller casing 17. The rotating shaft 11 extends horizontally through the curved pipe 18. The main pump 5 further has a suction pipe 22 extending into the suction sump 1. The suction pipe 22 is connected to the suction side of the curved pipe 18 and extends downward from the curved pipe 18. The suction pipe 22 has a suction port 23 at its lower end, which is submerged in the water in the suction sump 1. The pump casing 6, impeller 12, and driver 15 are disposed above the suction sump 1.

[0018] The main pump 5 further includes a discharge valve 27 connected to the discharge side of the pump casing 6, and a transfer pipe 30 connected to the discharge valve 27. The discharge valve 27 is connected to the discharge pipe 19 of the pump casing 6. The transfer pipe 30 is connected to the discharge pipe 19 of the pump casing 6 via the discharge valve 27. The transfer pipe 30 is provided to discharge the water pressurized by the main pump 5 and transfer it to a tank (not shown).

[0019] The pump system further includes a bypass pipe 40 extending from the pump casing 6 to the suction tank 1, and a bypass valve 41 provided in the bypass pipe 40. The connection position of the bypass pipe 40 and the pump casing 6 is downstream of the impeller 12 and upstream of the discharge valve 27 in the water flow direction. That is, one end of the bypass pipe 40 is connected to the discharge pipe 19 of the pump casing 6. In this embodiment, one end of the bypass pipe 40 is connected to a side portion of the discharge pipe 19. In another embodiment, one end of the bypass pipe 40 may be connected to the bottom or top of the discharge pipe 19. The other end of the bypass pipe 40 forms a fluid outlet 42 that opens in the suction tank 1. The fluid outlet 42 is submerged in the water in the suction tank 1.

[0020] During the discharge operation of the main pump 5, the bypass valve 41 is closed, the discharge valve 27 is open, and the impeller 12 is rotated by the driver 15. Water in the suction tank 1 is sucked up through the suction pipe 22 and flows into the pump casing 6. The rotating impeller 12 discharges the water from the pump casing 6 and transfers it to the discharge tank (not shown) through the discharge valve 27 and the transfer pipe 30. The pump system is equipped with a suction water level detector 45 that detects the water level in the suction tank 1.

[0021] The pump system includes a gas-liquid separation mechanism 46 and a swirl prevention plate 47. The gas-liquid separation mechanism 46 and the swirl prevention plate 47 are provided on the upper wall of the pump casing 6 and are located upstream of the impeller 12. In this embodiment, the gas-liquid separation mechanism 46 and the swirl prevention plate 47 are provided on the upper wall of the curved pipe 18. The swirl prevention plate 47 is fixed to the lower part of the gas-liquid separation mechanism 46 and is disposed inside the pump casing 6.

[0022] The swirl prevention plate 47 acts to block the swirling flow (water film) that occurs on the inner wall of the pump casing 6 when the pump is started, preventing water from flowing into the intake line 51, which will be described later, and the gas-liquid separation mechanism 46 acts to separate the gas-liquid mixture (gas-liquid two-phase flow) into gas and liquid, creating an air pocket near the intake port of the intake line 51, which will be described later. The configurations and operations of the gas-liquid separation mechanism 46 and the swirl prevention plate 47 are described in Patent Document 1 (JP 2011-256769 A) and are publicly known, so detailed description thereof will be omitted.

[0023] The pump system includes an intake device 50 for creating a vacuum in the pump casing 6 when the main pump 5 starts. The intake device 50 includes an intake line 51 connected to the pump casing 6, a vacuum pump 7 connected to the intake line 51, a full-water detector 52 and an intake valve 54 provided in the intake line 51, and a pressure measuring device 53 disposed on the secondary side (discharge side) of the impeller 12. The intake line 51 is connected to a gas-liquid separation mechanism 46 and is connected to the pump casing 6 via the gas-liquid separation mechanism 46. During a drainage operation of the main pump 5, the intake valve 54 is closed. The full-water detector 52 is a device for detecting when the pump casing 6 is filled with water. The pressure measuring device 53 is configured to measure the pressure inside the pump casing 6. In one embodiment, the gas-liquid separation mechanism 46 and the anti-swirl plate 47 are not provided, and the intake line 51 is connected to the upper wall of the pump casing 6.

[0024] The pump system further includes an operation control unit 60 that controls the operation of the main pump 5 and the suction device 50. The driver 15, discharge valve 27, suction water level detector 45, bypass valve 41, pressure measuring instrument 53, suction valve 54, vacuum pump 7, and full-water detector 52 are electrically connected to the operation control unit 60. The operation of the driver 15, discharge valve 27, bypass valve 41, suction valve 54, and vacuum pump 7 is controlled by the operation control unit 60. The operation control unit 60 starts and stops the main pump 5 based on the detection result of the water level in the suction sump 1 sent from the suction water level detector 45. More specifically, when the water level in the suction sump 1 reaches a start water level SL, the operation control unit 60 starts the main pump 5, and when the water level in the suction sump 1 reaches a stop water level LL, the operation control unit 60 stops the operation of the main pump 5.

[0025] The operation control unit 60 is composed of at least one computer. The operation control unit 60 includes a storage device 60a that stores a program for controlling the operation of the pump system, and a processor 60b that executes calculations according to instructions included in the program. The storage device 60a includes a main storage device such as a random access memory (RAM) and an auxiliary storage device such as a hard disk drive (HDD) or a solid state drive (SSD). Examples of the processor 60b include a CPU (central processing unit) and a GPU (graphics processing unit). However, the specific configuration of the operation control unit 60 is not limited to these examples.

[0026] Next, a method for operating the pump system will be described with reference to a flowchart of FIG. In step S101, with the discharge valve 27 and the bypass valve 41 closed, the operation control unit 60 issues a command to the driver 15 to start the main pump 5. The discharge valve 27 is fully closed. The bypass valve 41 is also fully closed, but may be slightly open.

[0027] In step S102, the operation control unit 60 opens the intake valve . In step S103, the operation control unit 60 issues a command to the vacuum pump 7 to start operating the vacuum pump 7. A vacuum is created within the pump casing 6, and the water in the suction tank 1 begins to rise up the suction pipe 22. When the water reaches the impeller 12 of the main pump 5, a swirling flow of the water-air mixed fluid is created within the pump casing 6. In step S104, the operation control unit 60 opens the bypass valve 41 to an intermediate opening. When the bypass valve 41 is opened to an intermediate opening, the bypass valve 41 is in a so-called half-open state. By opening the bypass valve 41 to an intermediate opening, the main pump 5 can be started with low torque.

[0028] In step S105, when the full water detector 52 detects that the pump casing 6 is filled with water, it sends a full water detection signal indicating that the pump casing 6 is filled with water to the operation control unit 60. In one embodiment, instead of using the full water detector 52, the operation control unit 60 may detect that the pump casing 6 is filled with water based on a comparison between the current supplied to the electric motor of the driver 15 and a threshold value. In another embodiment, a flow meter may be provided in the bypass pipe 40, and the operation control unit 60 may detect that the pump casing 6 is filled with water based on a comparison between a measurement value of the flow meter and a threshold value.

[0029] In step S106, the operation control unit 60 closes the intake valve 54 after detecting that the pump casing 6 is filled with water. In step S107, the operation control unit 60 stops the operation of the vacuum pump 7. Most of the air in the pump casing 6 has been exhausted by the vacuum pump 7 through the suction line 51, but it is assumed that a certain amount of air remains in the pump casing 6. Therefore, a mixed fluid of air and water exists in the pump casing 6. This mixed fluid of air and water is sent to the suction tank 1 through the bypass pipe 40 by the rotation of the impeller 12.

[0030] In step S108, the operation control unit 60 starts a timer (not shown) provided in the operation control unit 60 and counts a predetermined first waiting time. This predetermined first waiting time is the time required for the remaining air, together with the water, to be discharged from the pump casing 6 through the bypass pipe 40. This first waiting time is determined in advance based on factors such as the configuration and size of the main pump 5. In step S109, after a predetermined first waiting time has elapsed, the operation control unit 60 fully closes the bypass valve 41.

[0031] In step S110, the operation control unit 60 receives the measured value of the pressure inside the pump casing 6 from the pressure measuring instrument 53 and determines whether the pressure inside the pump casing 6 exceeds a predetermined target pressure. The target pressure is the pressure when the main pump 5 is performing a normal drainage operation under conditions where no air is present inside the pump casing 6. When the pressure inside the pump casing 6 exceeds the target pressure, it can be determined that the residual air inside the pump casing 6 has been removed. Therefore, when the pressure inside the pump casing 6 exceeds the target pressure, the operation control unit 60 fully opens the discharge valve 27 (step S111). This causes the main pump 5 to perform a drainage operation.

[0032] When the pressure inside the pump casing 6 is lower than the target pressure, it is determined that air still remains inside the pump casing 6. Therefore, when the pressure inside the pump casing 6 is lower than the target pressure, the operation control unit 60 fully opens the bypass valve 41 in step S112.

[0033] In step S113, the operation control unit 60 counts a predetermined second waiting time. This second waiting time may be the same as or different from the first waiting time in step S108. After the second waiting time has elapsed, the process flow returns to step S109, and the operation control unit 60 repeats the operations from step S109 onwards. That is, the operations from step S109 onwards are repeated until the discharge valve 27 is fully opened in step S111.

[0034] 2, the discharge valve 27 is opened after the air is expelled from the pump casing 6. The main pump 5, whose pump casing 6 is filled with water, can perform its original pumping performance, and therefore can perform normal drainage operation.

[0035] Fig. 3 is a flowchart illustrating another embodiment of the method for operating the pump system shown in Fig. 1. Operations of this embodiment that are not specifically described are the same as those described with reference to Fig. 2, and therefore, redundant descriptions will be omitted.

[0036] Steps S201 to S205 are the same as steps S101 to S105 in FIG. In step S206, the operation control unit 60 starts a timer (not shown) provided in the operation control unit 60, and counts a predetermined first waiting time. In step S207, after a predetermined first waiting time has elapsed, the operation control unit 60 fully closes the bypass valve 41. In step S208, it is determined whether the pressure inside the pump casing 6 exceeds a predetermined target pressure.

[0037] In step S209, when the pressure inside the pump casing 6 exceeds the target pressure, the operation control unit 60 opens the discharge valve 27 to an intermediate opening. When the discharge valve 27 is opened to an intermediate opening, the discharge valve 27 is in a so-called half-open state. In step S210, the operation control unit 60 closes the intake valve . In step S211, the operation control unit 60 stops the operation of the vacuum pump 7. In step S212, the operation control unit 60 fully opens the discharge valve 27. This causes the main pump 5 to perform a drainage operation.

[0038] If the pressure inside the pump casing 6 is lower than the target pressure in step S208, the operation control unit 60 fully opens the bypass valve 41 in step S213. In step S214, the operation control unit 60 counts a predetermined second waiting time. This second waiting time may be the same as or different from the first waiting time in step S206. After the second waiting time has elapsed, the process flow returns to step S207, and the operation control unit 60 repeats the operations from step S207 onwards. That is, the operations from step S207 onwards are repeated until the discharge valve 27 is fully opened in step S212.

[0039] 3, the vacuum pump continues to operate until immediately before the discharge valve 27 is fully opened. Even if water begins to fall inside the pump casing 6 due to a backflow of air from the transfer pipe 30, the vacuum pump 7 operates to remove the air, and the main pump 5 can perform a draining operation.

[0040] Fig. 4 is a flowchart illustrating another embodiment of the method for operating the pump system shown in Fig. 1. Operations of this embodiment that are not specifically described are the same as those described with reference to Fig. 3, and therefore, redundant descriptions will be omitted.

[0041] Steps S301 to S308 are the same as steps S201 to S208 in FIG. In step S309, the operation control unit 60 fully opens the discharge valve 27. This causes the main pump 5 to perform a drainage operation. In step S310, the operation control unit 60 closes the intake valve . In step S311, the operation control unit 60 stops the operation of the vacuum pump 7. Steps S312 and S313 are the same as steps S213 and S214 in FIG.

[0042] 4, the vacuum pump continues to operate even after the discharge valve 27 is fully opened. Even if water begins to fall inside the pump casing 6 due to a backflow of air from the transfer pipe 30, the vacuum pump 7 operates to remove the air, and the main pump 5 can perform a draining operation.

[0043] The embodiment of the method for operating the pump system described with reference to Figures 2 to 4 is particularly effective when starting the main pump 5 while the water pressure of the discharge tank is applied to the outlet of the transfer pipe 30 connected to the main pump 5. The embodiment described below is an example to which the above embodiment of the method for operating the pump system is applied. However, the above embodiment of the method for operating the pump system can also be applied to embodiments other than the embodiment described below.

[0044] 5 is a schematic diagram showing one embodiment of the installation of the pump system shown in FIG. 1. A transfer pipe 30 connected to a discharge valve 27 extends horizontally to the discharge tank 2. A flap valve (check valve) 65 is provided at the outlet of the discharge tank 2. The symbol NWL represents the design water level (normal water level) in the discharge tank 2, the symbol HWL represents the highest water level in the discharge tank 2, the symbol LWL represents the lowest water level in the discharge tank 2, and the symbol UWL represents the lowest water level in the discharge tank 2.

[0045] At water levels NWL, HWL, and LWL, the water pressure in the discharge tank 2 is applied to the flap valve 65. In the conventional start-up method disclosed in Patent Document 1, the vacuum pump 7 and the main pump 5 are started with the discharge valve 27 open, causing a water-air mixture to flow through the transfer pipe 30. Because the water-air mixture has a low specific gravity, the discharge pressure in the transfer pipe 30 may be lower than the water pressure in the discharge tank 2. In this case, the main pump 5 fails to start and does not enter normal drainage operation. In this regard, according to the embodiment described with reference to Figures 2 to 4, the discharge valve 27 is opened after the air is expelled from the pump casing 6, allowing the main pump 5 to transfer high-pressure water to the discharge tank 2 through the transfer pipe 30.

[0046] At the water level UWL, part of the flap valve 65 is exposed above the water surface. In the conventional start-up method disclosed in Patent Document 1, the vacuum pump 7 and the main pump 5 are started with the discharge valve 27 open, which can allow air to enter the main pump 5 through the transfer pipe 30 via a tiny gap in the flap valve 65, making it difficult to create a vacuum in the pump casing 6. As a result, the main pump 5 sometimes fails to start. In this regard, according to the embodiment described with reference to Figures 2 to 4, the vacuum pump 7 is started with the discharge valve 27 closed, so the vacuum pump 7 can create a vacuum in the pump casing 6.

[0047] FIG. 6 is a schematic diagram showing another embodiment of the installation of the pump system shown in FIG. 1. In the embodiment shown in FIG. 6, the transfer pipe 30 is inclined downward from the discharge valve 27. The suction pipe 22, the pump casing 6, and the transfer pipe 30 together form a siphon. The symbol NWL1 represents the design water level (normal water level) in the discharge tank 2 when the suction pipe 22, the pump casing 6, and the transfer pipe 30 together form a siphon, and the symbol NWL2 represents the design water level (normal water level) in the discharge tank 2 when the suction pipe 22, the pump casing 6, and the transfer pipe 30 do not form a siphon. The operating method of the embodiment described with reference to FIGS. 2 to 4 can start the main pump 5 at any of the water levels NWL1, NWL2, HWL, LWL, and UWL.

[0048] Fig. 7 is a schematic diagram showing another embodiment of the installation of the pump system shown in Fig. 1. In the embodiment shown in Fig. 7, a portion of the transfer pipe 30 is raised upward so that the transfer pipe 30 can climb over the side wall of the discharge tank 2. In this embodiment, a flap valve 65 is not provided, and the outlet 66 of the transfer pipe 30 faces downward. The very low water level UWL is located lower than the outlet 66 of the transfer pipe 30.

[0049] The discharge pressure of the main pump 5 must be high enough to allow water to pass through the top of the transfer pipe 30. Therefore, the design water level (NWL) of the main pump 5 is higher than the top of the transfer pipe 30. Because the pressure of the air-water mixture discharged from the main pump 5 is lower than the pressure of the water, the air-water mixture may not be able to pass through the top of the transfer pipe 30. In this case, the main pump 5 fails to start and does not perform normal drainage operation. In this regard, according to the embodiment described with reference to FIGS. 2 to 4, the discharge valve 27 opens after air is expelled from the pump casing 6, so the main pump 5 can transfer high-pressure water through the transfer pipe 30 to the discharge tank 2. Furthermore, the operating method of the embodiment described with reference to FIGS. 2 to 4 allows the main pump 5 to start regardless of the water level (HWL, LWL, or UWL).

[0050] 8 is a schematic diagram showing another embodiment of the installation of the pump system shown in FIG. 1. In the embodiment shown in FIG. 8, a portion of the transfer pipe 30 is raised upward so that the transfer pipe 30 can overcome the embankment. In this embodiment, a flap valve 65 is not provided, and the outlet 66 of the transfer pipe 30 faces downward. The design water level NWL of the main pump 5 is located higher than the top of the transfer pipe 30. The extremely low water level UWL is located lower than the outlet 66 of the transfer pipe 30.

[0051] 2 to 4, the discharge valve 27 is opened after air is removed from the pump casing 6, so that the main pump 5 can discharge high-pressure water through the transfer pipe 30 and transfer it to the tank 2. Furthermore, the operating method of the embodiment described with reference to FIGS. 2 to 4 can start the main pump 5 regardless of whether the water level is HWL, LWL, or UWL.

[0052] Next, we will explain the maintenance and operation of the pump system. The pump system is an emergency facility that is operated when the river water level rises above the danger level due to heavy rain or other reasons. Therefore, it is required that the main pump 5 can be reliably started in an emergency. Conversely, the main pump 5 is not operated during non-flood seasons, so maintenance and management of the main pump 5 is required during non-flood seasons. Specifically, maintenance and operation is required about once a month during non-flood seasons when there is little water in the suction tank 1. However, if the main pump 5 sucks water from the suction tank 1, the water level in the suction tank 1 will drop and the main pump 5 will no longer be able to be operated.

[0053] Therefore, the management operation of the main pump 5 is carried out according to the embodiment described below. Figure 9 is a flowchart illustrating one embodiment of the management operation of the pump system. In step S401, while the main pump 5 is stopped, the user switches the operation mode of the pump system from the normal drainage operation mode to the managed operation mode by operating a selector switch (not shown) provided in the operation control unit 60. In the normal drainage operation mode, the main pump 5 is started according to the embodiment described with reference to Figures 2 to 4.

[0054] In step S402, the operation control unit 60 issues a command to the driver 15 to start the main pump 5 while the discharge valve 27 and the bypass valve 41 are closed. In step S403, the operation control unit 60 opens the intake valve . In step S404, the operation control unit 60 issues a command to the vacuum pump 7 to start operating the vacuum pump 7. A vacuum is created within the pump casing 6, and the water in the suction tank 1 begins to rise up the suction pipe 22. When the water reaches the impeller 12 of the main pump 5, a swirling flow of the water-air mixed fluid is created within the pump casing 6. In step S405, the operation control unit 60 opens the bypass valve 41 to an intermediate opening degree. The mixed fluid of water and air is sent to the suction tank 1 through the bypass pipe 40.

[0055] In step S406, when the full water detector 52 detects that the pump casing 6 is filled with water, it sends a full water detection signal indicating that the pump casing 6 is filled with water to the operation control unit 60. In one embodiment, instead of using the full water detector 52, the operation control unit 60 may detect that the pump casing 6 is filled with water based on a comparison between the current supplied to the electric motor of the driver 15 and a threshold value. In another embodiment, a flow meter may be provided in the bypass pipe 40, and the operation control unit 60 may detect that the pump casing 6 is filled with water based on a comparison between a measurement value of the flow meter and a threshold value.

[0056] In step S407, the operation control unit 60 closes the intake valve 54 after detecting that the pump casing 6 is filled with water. In step S408, the operation control unit 60 stops the operation of the vacuum pump 7. In step S409, the operation control unit 60 fully opens the bypass valve 41. This causes water to return from the pump casing 6 through the bypass pipe 40 to the suction tank 1. That is, the water circulates between the suction tank 1 and the main pump 5. According to this embodiment, the water level in the suction tank 1 does not drop while the main pump 5 is operating, so that the maintenance operation of the main pump 5 can be performed for only the required time.

[0057] During rainfall during the flood season, if the water level in the suction tank 1 exceeds SL (see Figure 1), the main pump 5 performs drainage operation. However, the amount of rainfall is not constant, and the amount of water flowing into the suction tank 1 fluctuates. If drainage operation continues when the amount of water flowing into the suction tank 1 decreases, the water level in the suction tank 1 will drop. When the water level in the suction tank 1 falls below LL (see Figure 1), the main pump 5 will stop operating. However, it may continue operating by detecting the drop in the water level in the suction tank 1 and throttling the discharge valve 27 to reduce the discharge flow rate. This is to prevent the water level in the suction tank 1 from rising again after the main pump 5 has stopped, which would require the main pump 5 to be restarted. However, the main pump 5 has a preset minimum continuous operating flow rate (minimum flow), and throttling the discharge valve 27 too much will cause the pump to operate below the minimum flow, ultimately shutting down the main pump 5.

[0058] Therefore, in the embodiment described below, if the water level in the suction tank 1 drops while the main pump 5 is performing drainage operation, the opening of the discharge valve 27 is reduced to perform the first small water volume operation, and if the water level in the suction tank 1 drops further, the opening of the discharge valve 27 is maintained small while the bypass valve 41 is opened to perform the second small water volume operation. The water level in the suction tank 1 is detected by the suction water level detector 45 shown in Figure 1.

[0059] FIG. 10 is a graph illustrating the operating points of the main pump 5. Symbol SC1 is the piping loss curve when the discharge valve 27 is fully open. When the discharge valve 27 is fully open, the main pump 5 operates at operating point P1, which is the intersection of the pump performance curve and the piping loss curve SC1. Operation at operating point P1 is the normal drainage operation of the main pump 5. Therefore, the bypass valve 41 is fully closed.

[0060] When the water level in the suction tank 1 drops and reaches the first low-flow operating water level, the operation control unit 60 determines an operating point P2 from the actual head of the main pump 5 (the difference between the water level in the discharge tank 2 and the water level in the suction tank 1), the pump performance curve, and the piping loss curve. The operating point P2 is an operating point within the range between the minimum continuous operation flow rate (minimum flow) and the flow rate of the operating point P1 during the drainage operation of the main pump 5. The first low-flow operating water level is lower than the starting water level SL shown in Figure 1 and higher than the stop water level LL (see Figure 1). The operation control unit 60 determines a piping loss curve SC2 that passes through the operating point P2.

[0061] The operation control unit 60 determines a first opening degree of the discharge valve 27 for operating the main pump 5 at the operating point P2. More specifically, the operation control unit 60 determines the opening degree of the discharge valve 27 that corresponds to the piping loss curve SC2. Then, the operation control unit 60 changes the opening degree of the discharge valve 27 from fully open to the first opening degree. As a result, the main pump 5 performs a first low-flow rate operation that corresponds to the first opening degree of the discharge valve 27. The operating point P2 is an operating point of the main pump 5 in a state where the discharge valve 27 is open at the first opening degree and the bypass valve 41 is closed. The piping loss curve SC2 is a piping loss curve when the discharge valve 27 is at the first opening degree.

[0062] When the water level in the suction tank 1 further drops and reaches the second low-flow operating level, the operation control unit 60 determines an operating point P3 based on the actual head of the main pump 5, the pump performance curve, and the piping loss curve. The operating point P3 is within a range between the minimum continuous operation flow rate (minimum flow) and the flow rate at the operating point P1 during the main pump 5's drainage operation. The second low-flow operating water level is lower than the first low-flow operating water level and higher than the stop water level LL (see FIG. 1). The operation control unit 60 determines a piping loss curve SC3 that passes through the operating point P3. The operating point P3 is the operating point of the main pump 5 when both the discharge valve 27 and the bypass valve 41 are open to a certain degree. Therefore, the piping loss curve SC3 is a composite curve of the piping loss curve when only the discharge valve 27 is open to a certain degree and the piping loss curve when only the bypass valve 41 is open to a certain degree.

[0063] The operation control unit 60 determines the second aperture of the discharge valve 27 and the third aperture of the bypass valve 41 for operating the main pump 5 at the operating point P3. More specifically, the operation control unit 60 determines the second aperture of the discharge valve 27 and the third aperture of the bypass valve 41 that correspond to the piping loss curve SC3. The operation control unit 60 then changes the aperture of the discharge valve 27 from the first aperture to the second aperture, and changes the aperture of the bypass valve 41 from fully closed to the third aperture. As a result, the main pump 5 performs the second low-flow operation corresponding to the second aperture of the discharge valve 27 and the third aperture of the bypass valve 41. In the second low-flow operation, water flows through both the discharge valve 27 and the bypass valve 41. This prevents the total flow rate of the main pump 5 from falling below the minimum flow Min, while avoiding the need to stop and restart the main pump 5.

[0064] FIG. 12 is a flowchart of the low water volume operation of the main pump 5 described with reference to FIGS. In step S501, during the drainage operation of the main pump 5, the suction water level detector 45 (see FIG. 1) detects that the water level in the suction tank 1 has dropped and reached the first small water volume operation water level. In step S502, the operation control unit 60 determines an operating point P2 from the actual head of the main pump 5 (the difference between the water level in the discharge tank 2 and the water level in the suction tank 1), the pump performance curve, and the piping loss curve. In step S503, the operation control unit 60 determines a first opening degree of the discharge valve 27 for operating the main pump 5 at the operating point P2. In step S504, the operation control unit 60 changes the opening degree of the discharge valve 27 from the full open state to the first opening degree, causing the main pump 5 to perform the first low water volume operation.

[0065] In step S505, when the water level in the suction tank 1 further drops and reaches the second low-flow operating water level, the operation control unit 60 determines the operating point P3 from the actual head of the main pump 5, the pump performance curve, and the piping loss curve. In step S506, the operation control unit 60 determines the second opening degree of the discharge valve 27 and the third opening degree of the bypass valve 41 for operating the main pump 5 at the operating point P3. In step S507, the operation control unit 60 changes the opening degree of the discharge valve 27 from the first opening degree to the second opening degree, and changes the opening degree of the bypass valve 41 from fully closed to the third opening degree. As a result, the main pump 5 performs the second low water volume operation.

[0066] The above-described embodiments have been described for the purpose of enabling a person of ordinary skill in the art to practice the present invention. Various modifications of the above-described embodiments would be obvious to a person skilled in the art, and the technical concept of the present invention may be applied to other embodiments. Therefore, the present invention is not limited to the described embodiments, but is to be interpreted in the broadest scope in accordance with the technical concept defined by the claims. [Explanation of symbols]

[0067] 1. Suction tank 2 Discharge tank 5 Main pump 6 Pump casing 7. Vacuum pump 11 Rotation axis 12 impeller 15 Drive 17 Impeller casing 18 Bent pipe 19 Discharge pipe 22 Suction pipe 23 Intake port 27 Discharge valve 30 Transfer pipe 40 Bypass pipe 41 Bypass valve 42 Fluid outlet 45 Suction water level detector 50 Intake system 51 Intake line 52 Full water detector 53 Pressure measuring instrument 54 Intake valve 60 Motion control section 65 Flap valve (check valve) 66 Outlet

Claims

1. A method for operating a pump system including a main pump that discharges water from a suction tank to a tank, a gas-liquid separation mechanism provided in a pump casing of the main pump, a swirl prevention plate that prevents swirl flow within the pump casing, and a vacuum pump that is connected to the pump casing via the gas-liquid separation mechanism and that exhausts air from the pump casing, The main pump is started with a discharge valve connected to the discharge side of the pump casing closed, Start the operation of the vacuum pump, a bypass valve provided in a bypass pipe extending from the pump casing to the suction tank is opened to an intermediate opening degree; After the pump casing is detected as being full of water, a predetermined first waiting time is counted; After the predetermined first waiting time has elapsed, the bypass valve is closed, and then A method for operating a pump system, comprising fully opening the discharge valve.

2. the method further includes determining whether a pressure in the pump casing exceeds a predetermined target pressure after closing the bypass valve and before fully opening the discharge valve; 2. The method for operating a pump system according to claim 1, wherein the discharge valve is fully opened when the pressure in the pump casing exceeds the predetermined target pressure.

3. When the pressure in the pump casing is lower than the predetermined target pressure, the bypass valve is opened; Counting a predetermined second waiting time, After the predetermined second waiting time has elapsed, the bypass valve is closed, and then 3. The method of operating a pump system according to claim 2, further comprising again determining whether the pressure in the pump casing has risen to the predetermined target pressure.

4. 2. The method for operating a pump system according to claim 1, further comprising stopping operation of the vacuum pump after the pump casing is detected as being full of water and before the predetermined first waiting time is counted.

5. After closing the bypass valve, the discharge valve is opened to an intermediate opening, and then further comprising stopping operation of the vacuum pump; 2. The method for operating a pump system according to claim 1, further comprising the step of fully opening the discharge valve after stopping the operation of the vacuum pump.

6. The method of operating a pump system according to claim 1 , further comprising stopping operation of the vacuum pump after the discharge valve is fully opened.

7. The operating method further includes executing a managed operation mode after the operation of the main pump is stopped; The management operation mode is Starting the main pump with the discharge valve and the bypass valve closed; Start the operation of the vacuum pump, Open the bypass valve to an intermediate opening, After the pump casing is detected to be full of water, the operation of the vacuum pump is stopped, and then The method for operating a pump system according to claim 1 , further comprising fully opening the bypass valve.

8. The operating method includes performing a drainage operation by the main pump with the discharge valve fully open, When the water level in the suction tank drops to a first low-flow-rate operating level during the drainage operation of the main pump, a first operating point is determined that is within a range between a preset minimum continuous operation flow rate and a flow rate at an operating point during the drainage operation of the main pump; determining a first opening degree of the discharge valve corresponding to the first operating point; changing the opening degree of the discharge valve from full opening to the first opening degree; When the water level in the suction tank further drops and reaches a second low-flow-rate operating level, a second operating point is determined that is within a range between the preset minimum continuous operating flow rate and the flow rate at the operating point during the drainage operation of the main pump; determining a second opening degree of the discharge valve and a third opening degree of the bypass valve corresponding to the second operating point; 2. The method for operating a pump system according to claim 1, further comprising changing an opening degree of the discharge valve from the first opening degree to the second opening degree, and changing an opening degree of the bypass valve from fully closed to the third opening degree.

9. a main pump that transfers water from the suction tank to the discharge tank; a gas-liquid separation mechanism provided in a pump casing of the main pump; a swirl prevention plate for preventing swirl flow in the pump casing; a vacuum pump connected to the pump casing via the gas-liquid separation mechanism and configured to discharge air from the pump casing; a discharge valve connected to the discharge side of the pump casing; a bypass pipe extending from the pump casing to the suction tank; a bypass valve provided in the bypass pipe; a water-fill detector for detecting a full water state in the pump casing; an operation control unit that controls operations of the main pump, the vacuum pump, the discharge valve, and the bypass valve; The operation control unit With the discharge valve closed, the main pump is started, Starting the vacuum pump; Open the bypass valve to an intermediate opening, After the pump casing is detected as being full of water, a predetermined first waiting time is counted; After the predetermined first waiting time has elapsed, the bypass valve is closed, and then The pump system is configured to fully open the discharge valve.

10. The operation control unit After closing the bypass valve and before fully opening the discharge valve, determining whether or not the pressure in the pump casing exceeds a predetermined target pressure; The pump system according to claim 9 , wherein the discharge valve is configured to be fully open when the pressure in the pump casing exceeds the predetermined target pressure.

11. The operation control unit When the pressure in the pump casing is lower than the predetermined target pressure, the bypass valve is opened; Counting a predetermined second waiting time, After the predetermined second waiting time has elapsed, the bypass valve is closed, and then The pump system of claim 10 , further configured to again determine whether the pressure in the pump casing has risen to the predetermined target pressure.

12. 10. The pump system according to claim 9, wherein the operation control unit is configured to stop operation of the vacuum pump after the pump casing is detected to be full of water and before the predetermined first waiting time is counted.

13. The operation control unit After closing the bypass valve, the discharge valve is opened to an intermediate opening, and then Stopping the operation of the vacuum pump; The pump system of claim 9 , wherein the discharge valve is fully opened after the vacuum pump is stopped.

14. The pump system according to claim 9 , wherein the operation control unit is configured to stop operation of the vacuum pump after the discharge valve is fully opened.

15. the operation control unit is configured to execute a managed operation mode after the operation of the main pump is stopped, The management operation mode is Starting the main pump with the discharge valve and the bypass valve closed; Start the operation of the vacuum pump, Open the bypass valve to an intermediate opening, After the pump casing is detected to be full of water, the operation of the vacuum pump is stopped, and then The pump system according to claim 9 , wherein the bypass valve is fully opened.

16. The operation control unit When the water level in the suction tank drops to a first low-flow-rate operating level during the drainage operation of the main pump, a first operating point is determined that is within a range between a preset minimum continuous operation flow rate and a flow rate at an operating point during the drainage operation of the main pump; determining a first opening degree of the discharge valve corresponding to the first operating point; changing the opening degree of the discharge valve from full opening to the first opening degree; When the water level in the suction tank further drops and reaches a second low-flow-rate operating level, a second operating point is determined that is within a range between the preset minimum continuous operating flow rate and the flow rate at the operating point during the drainage operation of the main pump; determining a second opening degree of the discharge valve and a third opening degree of the bypass valve corresponding to the second operating point; 10. The pump system according to claim 9, wherein the opening degree of the discharge valve is changed from the first opening degree to the second opening degree, and the opening degree of the bypass valve is changed from fully closed to the third opening degree.

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