JP2018165468A - Control system and control method of pump, and drainage system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control system and a control method of a pump which can perform drainage with high reliability even when a pump head is high, and to provide a drainage system.SOLUTION: A control system (20) of a pump (100) which performs operation irrespective of a water level includes: first detection means (21) which detects a water level of a water absorption tank (51); second detection means (22) which detects a water level of discharge destinations (4 and 52); and a control device (23) which controls a flow rate of the pump (100) so as to prevent shaft power over and cavitation from being generated based on the water level of the water absorption tank (51) and the water level of the discharge destinations (4 and 52).SELECTED DRAWING: Figure 4

Description

  The present invention relates to a pump control system and control method in a drainage station or the like, and a drainage system.

  In a drainage station that drains rainwater, the pump must be operated before the water level rises in order to prevent a delay in starting the pump in response to a sudden rise in the rainwater main line due to sudden heavy rain (so-called guerrilla heavy rain). A standby pump is used.

  Conventional leading stand-by pumps are mainly equipped with a relatively low pump head (total lift) of 20 m or less. However, with the recent urbanization, rainwater trunks have become deeper and pumps are often installed deep underground. Thereby, the case where the head of a pump becomes 30 m or more is increasing.

Japanese Patent Laying-Open No. 2005-320863

  An object of the present invention is to provide a pump control system and a control method, and a drainage system that can perform drainage with high reliability even when the pump head is high.

According to one aspect of the present invention, there is provided a pump control system that operates regardless of the suction water level, the first detection means for detecting the water level of the water absorption tank, and the second detection means for detecting the water level of the discharge destination. And a control device that controls the flow rate of the pump so that shaft power over and cavitation do not occur based on the water level of the water absorption tank and the water level of the discharge destination.
By controlling the flow rate of the pump based on the water level of the water absorption tank and the water level of the discharge destination, shaft power over and cavitation can be suppressed even when the pump head is high, and the reliability as a drainage facility is improved.

  The control device may control the flow rate of the pump by adjusting an opening degree of a discharge valve provided in a discharge pipe of the pump.

  The control device estimates an operating point when the pump makes a transition from a gas-water mixing operation to a steady operation based on the water level of the water absorption tank and the water level of the discharge destination, and determines the axis of the discharge amount at the estimated operating point. When power over or cavitation occurs, the flow rate of the pump may be controlled to be small.

  When the estimated discharge amount at the operating point is smaller than the discharge amount at which shaft power over or cavitation occurs, the control device may control the flow rate of the pump to be increased.

  The control device is based on the difference between the water level of the water absorption tank and the water level of the discharge destination, the pipeline resistance curve of the pump determined according to the flow rate of the pump, and the total head curve of the pump. The operating point may be estimated.

  The control device may perform control so that the flow rate of the pump becomes a target value less than a discharge amount at which the shaft power over or cavitation occurs.

According to another aspect of the present invention, there is provided a pump control system that operates regardless of the suction water level, the first detection means for detecting the water level of the water absorption tank, and the second for detecting the water level of the discharge destination. A control device for controlling the amount of gas fed into the intake pipe connected to the suction pipe of the pump based on the detection means and the water level of the water absorption tank and the water level of the discharge destination so that shaft power over and cavitation do not occur A control system is provided.
By controlling the amount of gas sent to the intake pipe connected to the suction pipe of the pump based on the water level of the water absorption tank and the discharge destination, shaft power overload and cavitation can be suppressed even when the pump head is high, Reliability is improved.

According to another aspect of the present invention, there is provided a pump control system that operates regardless of the suction water level, the first detection means for detecting the water level of the water absorption tank, and the second for detecting the water level of the discharge destination. Provided is a control system comprising detection means and a control device that controls the rotational speed of the impeller of the pump so that shaft power over and cavitation do not occur based on the water level of the water absorption tank and the water level of the discharge destination Is done.
By controlling the rotational speed of the pump impeller based on the water level of the water absorption tank and the water level of the discharge destination, shaft power over and cavitation can be suppressed even when the pump head is high, and reliability is improved.

  Moreover, according to another aspect of this invention, a drainage system provided with a pump and the said control system is provided.

  A plurality of the pumps may be provided, and the control system may control a pump that starts operation first when the discharge destination is dry.

  According to another aspect of the present invention, there is provided a control method for a pump that operates regardless of the suction water level, detecting the water level of the water absorption tank, detecting the water level of the discharge destination, A control method is provided that controls the flow rate of the pump so that shaft power over and cavitation do not occur based on the water level of the discharge destination.

  According to another aspect of the present invention, there is provided a control method for a pump that operates regardless of the suction water level, detecting the water level of the water absorption tank, detecting the water level of the discharge destination, A control method is provided for controlling the amount of gas fed into an intake pipe connected to the suction pipe of the pump so that shaft power over and cavitation do not occur based on the water level of the discharge destination.

  According to another aspect of the present invention, there is provided a control method for a pump that operates regardless of the suction water level, detecting the water level of the water absorption tank, detecting the water level of the discharge destination, A control method is provided for controlling the rotational speed of the impeller of the pump based on the water level of the discharge destination so that shaft power over and cavitation do not occur.

  Even when the pump head is high, overdrive force and cavitation can be suppressed, and the reliability of the pump can be improved.

The figure explaining the prior | preceding standby pump 100 installed in a drainage machine station, and its operation | movement. The figure which compares the pump 100 'with a low lift, and the pump 100 with a high lift. Performance curves of low lift pump 100 'and high lift pump 100. The figure which shows schematic structure of the drainage system which concerns on 1st Embodiment. The flowchart which shows operation | movement of the drainage system of FIG. Pump 100 in the drainage system of FIG. The figure which shows schematic structure of the drainage system which concerns on 2nd Embodiment. The flowchart which shows operation | movement of the drainage system of FIG. The performance curve of the pump 100 in the drainage system of FIG. The figure which shows schematic structure of the drainage system which concerns on 3rd Embodiment. The flowchart which shows operation | movement of the drainage system of FIG. The performance curve of the pump 100 in the drainage system of FIG.

  First, the preceding standby pump will be described. Next, a problem that occurs in the preceding standby pump having a high head and the cause of such a problem will be described. In addition, in this invention, in order to suppress the stench of stagnant water, when not performing drainage operation, the dry operation which drains a discharge pipe or a discharge water tank is assumed.

FIG. 1 is a diagram for explaining a preliminary standby pump 100 installed in a drainage station and its operation, and illustrates a preliminary standby pump 100 (hereinafter simply referred to as pump 100) of a full speed / full water level drainage operation method. . The standby standby pump 100 is desirably a vertical shaft type, but may be another type such as a horizontal axis type.
The pump 100 sucks water from the suction port 2a of the suction pipe 2 when the impeller 1 is rotated by a driving machine (not shown). In addition, an intake pipe 3 whose upper end is opened to the atmosphere is connected to the suction pipe 2 in the pump 100 so that air can flow into the suction pipe 2. The pump 100 operates as follows.

  As shown in FIG. 1A, “in-air operation” in which the impeller 1 rotates is performed even when the water level WL does not reach the suction port 2a. In this air operation, there is no air inflow from the intake pipe 3, the impeller 1 is rotating, but the discharge amount of the pump 100 is zero.

  As shown in FIG. 1B, when the water level WL reaches a predetermined air-water mixing operation start water level WL0, the “air-water mixing operation” is performed. The air / water mixing operation start water level WL0 corresponds to the lower end position of the impeller 1. In the air-water mixing operation, water is sucked up from the suction port 2a by the rotation of the impeller 1 and drained. When water is sucked up and the flow rate of water increases, the pressure in the suction pipe 2 near the connection portion of the intake pipe 3 decreases. Therefore, air flows from the intake pipe 3 into the suction pipe 2 due to the difference from the atmospheric pressure. Thus, the pump 100 discharges a mixture of water and air.

  As shown in FIG. 1C, when the water level WL reaches the steady operation water level WL1, the “steady operation” is performed. The steady operation water level WL1 is determined for each pump 100 according to the operating conditions (given conditions) of the drainage station. When the water level increases, the pressure in the suction pipe 2 near the connection portion of the intake pipe 3 increases due to the water pressure and balances with the atmospheric pressure. Thereby, air does not flow into the suction pipe 2 from the intake pipe 3. Therefore, the pump 100 drains water that does not contain air.

  FIG. 2 is a diagram comparing a pump 100 ′ with a low lift (low lift pump) and a pump 100 with a high lift (high lift pump). Comparing the two pumps 100 and 100 ', the pumps have the same size, but the depth of the pump is increased, so that the difference between the water level in the high-lift pump 100 and the water level in the discharge tank at the rated operation becomes large. On the other hand, when the discharge side is not filled and the discharge side water level is low when shifting from the air / water mixing operation to the steady operation, the actual head H2 is generally common to both pumps 100 and 100 '. Therefore, the actual lift H0 during rated operation and the actual lift difference H1 when shifting from the air / water mixing operation to the steady operation are larger in the high lift pump 100 than in the low lift pump 100 '.

  FIG. 3 is a performance curve of the low-lift pump 100 'and the high-lift pump 100. The horizontal axis represents the pump discharge amount, and the vertical axis represents the total pump head. As described above, when the discharge water level is low, the actual lifting range when shifting from the air-water mixing operation to the steady operation is common, and therefore the pipe resistance curve A until the shift to the steady operation is substantially common. On the other hand, since the actual head during normal operation is higher in the high head pump 100, the total head curve B1 of the high head pump 100 is located above the total head curve C1 of the low head pump 100 'on the vertical axis.

  Both the low-lift pump 100 'and the high-lift pump 100 have a discharge amount of 0 during the air operation, and the operating point A0 moves on the pipe resistance curve A when the air-water mixing operation starts. The operating point (discharge amount and total head) changes along the pipe resistance curve A in both the low head pump 100 ′ and the high head pump 100 until the transition from the air / water mixing operation to the steady operation (arrow F1). .

  In the low lift pump 100 ′, the air / water mixing operation is shifted to the steady operation at the intersection C <b> 2 between the total lift curve C <b> 1 and the pipe resistance curve A (hereinafter, this intersection C <b> 2 is referred to as a transition point C <b> 2). After shifting to steady operation, the operating point changes along the full lift curve C1 with the change of the actual lift (arrow F2). The operating point reaches the operating point C4 determined by the pipe resistance curve C3 at a predetermined point.

  In the high-lift pump 100, at the intersection B2 between the total lift curve B1 and the pipe resistance curve A, the air-water mixing operation is shifted to the steady operation (hereinafter, this intersection B2 is referred to as a transition point B2). After shifting to the steady operation, the operating point changes along the full lift curve B1 with the change of the actual lift (arrow F3). The operating point reaches an operating point B4 determined by the pipe resistance curve B3 at a predetermined point.

  Here, the discharge amount difference B between the transition point B2 in the high lift pump 100 and the operating point B4 at the main point is the discharge amount difference C between the transition point C2 in the low lift pump 100 ′ and the operating point C4 at the main point. Greater than. That is, in the high head pump 100, the ratio of the discharge amount at the transition point B2 is larger than the discharge amount at the main point.

  Generally, when the discharge amount exceeds a threshold determined by the shaft power curve during steady operation, shaft power over occurs. Further, cavitation occurs when the discharge amount exceeds a threshold determined by the required suction performance NPSH. Therefore, the high lift pump 100 has a problem that shaft power over and cavitation are likely to occur.

  When shaft power over occurs, the drive unit is overloaded, and in some cases, the drive unit may stop. However, it is not desirable to use a driving machine that expects a larger discharge amount than the discharge amount at the operation point B4 at the point of necessity, which increases the cost. Further, when cavitation occurs, the impeller 1 may be damaged and the reliability of the pump 100 may be reduced. However, since the required suction performance NPSH of the pump 100 is a value unique to the pump 100, it is difficult to suppress cavitation by improving the suction performance.

  Therefore, the pump 100 is controlled so that shaft power over and cavitation do not occur in the embodiment described below.

(First embodiment)
In the first embodiment, the pipe resistance curve is controlled by adjusting the discharge valve of the flow rate of the pump 100 to prevent overshaft power and cavitation.

  FIG. 4 is a diagram illustrating a schematic configuration of the drainage system according to the first embodiment. This drainage system is provided, for example, in a drainage station and drains water from a water absorption tank 51 to a discharge water tank 52, and includes a pump 100, a drive unit 11 such as a wound-type electric motor, and a control system 20. The control system 20 includes a water tank water level meter 21, a discharge destination water level meter 22, a control device 23 connected thereto, and the like.

  The pump 100 is a preceding standby type pump that operates regardless of the water level of the water absorption tank 51 in the drainage station. As described with reference to FIG. 1, the pump 100 discharges in addition to the impeller 1, the suction pipe 2, and the intake pipe 3. It has a pipe 4, a discharge valve 5, and the like. The discharge valve 5 is an electric valve whose opening degree is adjusted by, for example, the control device 23 and is provided in the discharge pipe 4. The flow rate increases as the opening degree of the discharge valve 5 increases, and the flow rate decreases as the opening degree decreases.

  The water tank water level meter 21 detects the water level (suction water level) of the water tank 51 and notifies the control device 23 of the detection result. The discharge destination water level meter 22 detects the water level (discharge water level) of the discharge pipe 4 or the discharge water tank 52 which is the discharge destination, and notifies the control device 23 of the detection result. In addition, the discharge destination water level meter 22 may not detect the water level directly but may detect the pressure. This is because the water level can be determined from the pressure.

  The control device 23 stores in advance a total head curve and a pipe resistance curve of the pump 100 described in FIG. And the control apparatus 23 controls flow volume (namely, pipe resistance) by adjusting the opening degree of the discharge valve 5, for example so that driving force over and cavitation may not generate | occur | produce according to a water absorption water level and a discharge water level.

Here, the pipeline resistance curve described in FIG. 3 depends on the actual head and the pipeline resistance. More specifically, the left end of the pipe resistance curve is determined by the actual head, and the shape of the pipe resistance curve is determined by the pipe resistance. The control device 23 grasps the relationship among the actual head, the pipe resistance, and the pipe resistance curve based on tests performed in advance. Further, the control device 23 can know the actual head from the difference between the discharge water level and the water absorption water level, and can also control the flow rate by adjusting the opening of the discharge valve 5.
Therefore, in this embodiment, the control apparatus 23 controls the discharge valve 5 as follows according to an actual head.

  FIG. 5 is a flowchart showing the operation of the drainage system of FIG. FIG. 6 is a performance curve of the pump 100 in the drainage system of FIG. Since the pump 100 of the present embodiment is a preceding standby pump, the operation is started regardless of the water level (step S1). Specifically, the discharge valve 5 is opened and the impeller 1 is rotating.

  The control device 23 sets the discharge valve 5 to the intermediate opening (step S2). This is because the opening of the discharge valve 5 can be increased or decreased according to the water level.

  Based on the detection result of the water tank water level meter 21, the control device 23 determines whether or not the water level in the water tank 51 is equal to or higher than a predetermined air-water mixing operation start water level WL0 (step S3). When it is less than the air-water mixing operation start water level WL0 (NO in step S3), since the pump 100 is in the air operation state, the control device 23 does not perform any special processing.

  When the water / water mixing operation start water level WL0 or higher (YES in step S3), the pump 100 is in the air / water mixing operation state. Also in this case, the control device 23 continues to monitor the water level in the water absorption tank 51. When the difference between the steady operation water level WL1 and the water level in the water absorption tank 51 is equal to or less than the threshold value β (YES in step S4), the control of the discharge valve 5 after step S5 is started. The threshold β is a constant that can be arbitrarily set. The reason for providing step S4 is that it is not always necessary to immediately start the control of the discharge valve 5 even when the water level in the water absorption tank 51 exceeds the air-water mixing operation start water level WL0, and when the water level approaches the steady operation water level WL1. This is to start control.

  In order to control the discharge valve 5, the control device 23 calculates the actual head from the difference between the two based on the detection results of the water tank water level meter 21 and the discharge destination water level meter 22 (step S5).

  Then, the control device 23 estimates the operating point at the time of transition from the air / water mixing operation to the steady operation from the calculated actual head and the current opening of the discharge valve 5 (step S6). Specifically, the control device 23 grasps the pipe resistance curve during steady operation from the actual head and the opening degree (pipe resistance) of the discharge valve 5. More specifically, the control device 23 grasps the left end of the pipeline resistance curve from the actual head, and grasps the shape (inclination) of the pipeline resistance curve from the opening degree of the discharge valve 5. And the control apparatus 23 makes the intersection of such a pipe line resistance curve and a known total lift curve the operating point at the time of steady operation transfer. In the example of FIG. 6, the control device 23 sets an intersection P1 between the pipe resistance curve A1 and the total lift curve B1 that is grasped from the actual lift and the opening degree of the discharge valve 5 at the time of transition from the air / water mixing operation to the steady operation. Estimated operating point.

  Returning to FIG. 5, the control device 23 determines whether or not the calculated discharge amount at the operating point exceeds the maximum discharge amount (step S7). The maximum discharge amount here is the maximum discharge amount at which neither shaft power over nor cavitation occurs, in other words, the smaller one of the discharge amounts at which shaft power over or cavitation occurs. ing.

  For example, when the operating point estimated in step S6 is the intersection P1 in FIG. 6, the discharge amount exceeds the maximum discharge amount (YES in step S7). If the water tank level rises as it is and shifts to steady operation, shaft power over or cavitation will occur. Therefore, the control device 23 sends an operation command for reducing the opening degree of the discharge valve 5 to the discharge valve 5 so that the discharge amount does not cause excessive driving force and cavitation. Thereby, the discharge valve 5 is controlled in the closing direction (step S8).

  As a result, since the flow rate is reduced, the pipeline resistance curve is changed in the direction in which the discharge amount is reduced (for example, the pipeline resistance curve in FIG. 6 is changed from A1 to A2). As a result, the operating point changes in a direction in which the discharge amount decreases (intersection points P1 to P2).

  On the other hand, when the operating point estimated in step S6 is the intersection P11 on the pipe resistance curve A11 in FIG. 6, the discharge amount is equal to or less than the maximum discharge amount (NO in step S7). In this case, shaft power over and cavitation do not occur even if the water level rises as it is and shifts to steady operation. However, in order to quickly fill the discharge water tank 52 or the discharge pipe and shift to the total drainage operation, it is desirable that the discharge amount of the pump 100 be as large as possible. Therefore, the control device 23 determines whether or not the discharge amount can be increased.

  That is, when the discharge valve 5 is not fully open (NO in step S9 in FIG. 5), the control device 23 determines whether or not the difference between the maximum discharge amount and the discharge amount at the operating point is equal to or less than a predetermined threshold value α. (Step S10). Here, the threshold value α is a constant that can be arbitrarily set.

  If it is equal to or less than the threshold value α (YES in Step S10), the control device 23 does not increase the opening of the discharge valve 5 because the discharge amount at the operating point is sufficiently close to the maximum discharge amount.

  On the other hand, if it is equal to or greater than the threshold value α (YES in step S10), the discharge amount at the operating point still has a sufficient margin with respect to the maximum discharge amount, so the control device 23 increases the opening of the discharge valve 5. An operation command is sent to the discharge valve 5. Thereby, the discharge valve 5 is controlled in the opening direction (step S11), and the flow rate is increased. As a result, the pipe resistance curve changes in the direction in which the discharge amount increases (for example, the pipe resistance curve in FIG. 6 changes from A11 to A12). As a result, the operating point changes in a direction in which the discharge amount increases (intersection points P11 to P12).

  After YES or S11 in the above steps S8 and S10, the control device 23 repeats the processes after step S3. Thereby, the opening degree of the discharge valve 5 becomes larger as the actual lift becomes higher as the water level of the discharge destination rises, and the discharge amount at the operating point at which the gas-water mixing operation shifts to the steady operation becomes a target value (less than the maximum discharge amount). For example, it is controlled to be 99% of the maximum discharge amount). As a result, the discharge amount at the operating point rises and falls near the target value, but does not exceed the maximum discharge amount. When the discharge valve 5 is fully opened (YES in step S9), the control device 23 ends the control of the discharge valve 5. As the water level in the discharge water tank 52 rises, the point where neither shaft power over nor cavitation occurs in the total head curve becomes the operating point, and the operation moves to steady operation, and then the operating point moves along the total head curve B1. Thus, the pump essential point P21 is reached (arrow F3).

  The control device 23 measures the suction water level, the discharge water level, the opening of the discharge valve 5 and the current value indicating the shaft power when the operation is shifted to the steady operation, and the discharge amount at the operation point at the time of the transition to the normal operation is the maximum discharge. If it is smaller than the amount, the control amount of the discharge valve 5 may be corrected so that the operating point is closer to the maximum discharge amount at the next control. The transition to steady operation can be determined from the water absorption level.

  Thus, in the first embodiment, the opening degree of the discharge valve 5 is adjusted so that shaft power over and cavitation do not occur while monitoring the actual head. Therefore, even when the head of the pump 100 is high, high reliability can be ensured. In addition, by setting the discharge amount to a target value less than the maximum discharge amount, the discharge water tank 52 or the discharge pipe can be quickly filled and the entire amount can be discharged, and the safety against flood damage is improved.

  Although only one pump is illustrated in FIG. 4, two or more pumps may be provided so that the pumps start operation sequentially. In that case, the above-described control may be performed for a pump that starts operation at least when the discharge water tank 52 or the discharge pipe is dry. When the second and subsequent units start operation, the discharge water tank 52 or the discharge pipe has already been filled and the actual lift is high, so that shaft power over and cavitation do not occur.

(Second Embodiment)
In the first embodiment described above, the opening degree of the discharge valve 5 is adjusted to control the pipe resistance curve so that shaft power over and cavitation do not occur. In contrast, in the second embodiment described below, gas is appropriately fed into the intake pipe 3 to control the total lift curve of the pump 100, thereby preventing shaft power over and cavitation from occurring. Hereinafter, a description will be given focusing on differences from the first embodiment.

  FIG. 7 is a diagram illustrating a schematic configuration of a drainage system according to the second embodiment. As a difference from the first embodiment shown in FIG. 4, the control system 20 includes a gas supply system 30 that supplies a gas such as air to the intake pipe 3. The gas supply system 30 includes a compressor 31, valves 32 and 33, and a flow meter 34.

  The intake pipe 3 is branched upward, and a compressor 31 is connected to one of the intake pipes 3 via a valve 32. In the present embodiment, the compressor 31 supplies a certain amount of gas, and the amount of gas injected into the intake pipe 3 is controlled according to the opening degree of the valve 32. The opening degree of the valve 32 is controlled by the control device 23. The amount of gas supplied from the compressor 31 may be directly controlled without providing the valve 32. The other branched side of the intake pipe 3 is opened to the atmosphere via a valve 33.

  Further, a flow meter 34 is provided below the branch point (on the side connected to the suction pipe 2), and the flow rate of the gas injected into the intake pipe 3 is measured. The measured value is input to the control device 23, and the control device 23 can grasp the gas injection amount.

  The total head curve described in FIG. 3 depends on the amount of gas injected into the intake pipe 3. In FIG. 3, when the gas is not injected, the total head curve B1. When the gas is injected, the pump 100 sucks not only water but also gas, so that the discharge amount is reduced. As a result, the total lift curve moves in the direction in which the discharge amount decreases (left side in the horizontal axis). The amount of movement increases as the amount of gas injected into the intake pipe 3 increases.

  The control device 23 grasps the relationship between the gas injection amount (in other words, the opening degree of the valve 32) and the total lift curve based on a test performed in advance. Therefore, the control device 23 controls the gas injection amount according to the actual head as follows.

  FIG. 8 is a flowchart showing the operation of the drainage system of FIG. Initially, it is assumed that the compressor 31 is not operating. FIG. 9 is a performance curve of the pump 100 in the drainage system of FIG. Since the pump 100 of the present embodiment is a preceding standby pump, the operation is started regardless of the water level (step S1).

  The control device 23 sets the valve 32 to the intermediate opening (step S2 '). This is because the opening degree of the valve 32 can be increased or decreased according to the water level. The control device 23 is set so that the valve 33 is completely opened.

  Based on the detection result of the water tank water level meter 21, the control device 23 determines whether or not the water level in the water tank 51 is equal to or higher than a predetermined air-water mixing operation start water level WL0 (step S3). When it is less than the air-water mixing operation start water level WL0 (NO in step S3), since the pump 100 is in the air operation state, the control device 23 does not perform any special processing.

  When the water / water mixing operation start water level WL0 or higher (YES in step S3), the pump 100 is in the air / water mixing operation state. Also in this case, the control device 23 continues to monitor the water level in the water absorption tank 51. When the difference between the steady operation water level WL1 and the water level in the water absorption tank 51 is equal to or less than the threshold value β (YES in step S4), the valve 33 is set to close and the compressor 31 is set to start control of the valve 32 after step S5. Operation starts (step S20).

  And the control apparatus 23 calculates an actual head from the difference of both based on the detection result of the water tank water level meter 21 and the discharge destination water level meter 22 (step S5).

  Then, the control device 23 estimates the operating point at the time of transition from the air / water mixing operation to the steady operation from the calculated actual head and the opening of the valve 32 (step S6 '). Specifically, the control device 23 sets the intersection of the pipeline resistance curve and the total lift curve during steady operation as determined from the actual lift and the opening degree of the valve 32 as the operation point during transition to steady operation. In the example of FIG. 9, the control device 23 sets an intersection P31 between the pipe resistance curve A1 and the total lift curve B1 grasped from the actual lift and the opening of the valve 32 at the time of transition from the air / water mixing operation to the steady operation. Estimated operating point.

  Returning to FIG. 8, the control device 23 determines whether or not the calculated discharge amount at the operating point exceeds the maximum discharge amount (step S7). The maximum discharge amount here is the maximum discharge amount at which neither shaft power over nor cavitation occurs, in other words, the smaller one of the discharge amounts at which shaft power over or cavitation occurs. ing.

  For example, when the operating point estimated in step S6 'is the intersection P31 in FIG. 9, the discharge amount exceeds the maximum discharge amount (YES in step S7). If the water tank level rises as it is and shifts to steady operation, shaft power over or cavitation will occur. Therefore, the control device 23 sends an operation command for increasing the opening degree of the valve 32 to the valve 32 so that the discharge amount does not cause excessive driving force and cavitation. Thereby, the valve 32 is controlled in the opening direction (step S8 ').

  As a result, since the amount of gas injected into the suction pipe 2 of the pump 100 through the intake pipe 3 increases, the total lift curve changes in a direction in which the discharge amount decreases (for example, the total lift curve in FIG. To B12). As a result, the operating point changes in the direction in which the discharge amount decreases (intersection points P31 to P32). The relationship between the amount of gas injected into the suction pipe 2 and the total head curve is registered in the control device 23 in advance.

  On the other hand, when the operating point estimated in step S6 'is the intersection P33 on the total lift curve B12 in FIG. 9, the discharge amount is not more than the maximum discharge amount (NO in step S7). In this case, shaft power over and cavitation do not occur even if the water level rises as it is and shifts to steady operation. However, in order to quickly fill the discharge water tank 52 or the discharge pipe and shift to the total drainage operation, it is desirable that the discharge amount of the pump 100 be as large as possible. Therefore, the control device 23 determines whether or not the discharge amount can be increased.

  That is, when the valve 32 is not fully closed (NO in step S9 ′ in FIG. 8), the control device 23 determines whether or not the difference between the maximum discharge amount and the discharge amount at the operating point is equal to or less than a predetermined threshold value α. Determine (step S10). Here, the threshold value α is a constant that can be arbitrarily set.

  If it is equal to or less than the threshold value α (YES in step S10), the discharge amount at the operating point is sufficiently close to the maximum discharge amount, so the control device 23 does not reduce the opening of the valve 32.

  On the other hand, if it is greater than the threshold value α (NO in step S10), the discharge amount at the operating point still has a margin with respect to the maximum discharge amount, so the control device 23 is an operation command for reducing the opening of the valve 32. Is delivered to the valve 32. As a result, the valve 32 is controlled to close (step S11 '), and the amount of gas injected into the intake pipe 3 is reduced. As a result, the pipeline resistance curve changes in the direction in which the discharge amount increases (for example, the total lift curve in FIG. 9 changes from B12 to B13). As a result, the operating point changes in the direction in which the discharge amount increases (intersection points P33 to P34).

  After YES or S11 'in the above steps S8' and S10, the control device 23 repeats the processes after step S3. As a result, the gas injection amount decreases as the actual head increases as the discharge level rises, and the discharge amount at the operating point at which the gas-water mixing operation shifts to the steady operation is less than the target value (for example, the maximum discharge amount). 99%). As a result, the discharge amount at the operating point rises and falls near the target value, but does not exceed the maximum discharge amount. When the water level in the water absorption tank 51 becomes less than the air-water mixing operation start water level WL0 in step S3 in the repetition, the control device 23 stops the compressor 31 and fully opens the valve 33.

  When the valve 32 is fully closed (YES in step S9 '), the control device 23 ends the control of the valve 32, stops the compressor 31 (step S21), and fully opens the valve 33 (step S22).

  Then, as the water level of the discharge water tank 52 rises, the point where neither shaft power over nor cavitation occurs in the total head curve becomes an operating point, and the operation point shifts to steady operation. It moves along the curve B1 and reaches the pump essential point P21 (arrow F3).

  The control device 23 measures the suction water level, the discharge water level, the opening of the valve 32, and the current value indicating the shaft power when the operation is shifted to the steady operation, and the discharge amount at the operation point at the time of the steady operation shift is the maximum discharge amount. If it is smaller, the control amount of the valve 32 may be corrected so that the operating point approaches the maximum discharge amount during the next control. The transition to steady operation can be determined from the water absorption level.

  As described above, in the second embodiment, the opening degree of the valve 32 is adjusted so that shaft power over and cavitation do not occur while monitoring the actual head. Therefore, even when the head of the pump 100 is high, high reliability can be ensured. Further, by setting the discharge amount to a target value less than the maximum discharge amount, the discharge pipe 4 or the discharge water tank 52 can be quickly filled and the entire amount can be transferred to the drainage operation, and the safety against flood damage is improved.

(Third embodiment)
In the second embodiment described above, gas is fed into the intake pipe 3 to control the total head curve of the pump 100. On the other hand, in the third embodiment described below, the total head curve of the pump 100 is controlled by adjusting the rotational speed of the impeller 1. Hereinafter, the difference from the second embodiment will be mainly described.

  FIG. 10 is a diagram illustrating a schematic configuration of a drainage system according to the third embodiment. As a difference from the second embodiment shown in FIG. 7, the control system 20 includes a rotation speed adjustment system 40 including a secondary resistor 41 and a drive unit 11. As the drive machine 11, a wire-wound motor that can reduce the starting current is suitable. The secondary resistor 41 is necessary for starting the driving machine 11, and for example, a metal resistor or a liquid resistor can be applied. The resistance value of the secondary resistor 41 is controlled by the control device 23. As the resistance value increases, the rotational speed of the drive unit 11 decreases and the rotational speed of the impeller 1 also decreases. Thereby, the discharge amount of the pump 100 decreases. As a result, the total lift curve moves in the direction in which the discharge amount decreases (left side in the horizontal axis).

  The control device 23 grasps the relationship between the resistance value of the secondary resistor 41 (in other words, the rotational speed of the drive unit 11 and the impeller 1) and the total head curve based on a test performed in advance. . Therefore, the control device 23 controls the rotation speed as follows according to the actual head.

  FIG. 11 is a flowchart showing the operation of the drainage system of FIG. FIG. 12 is a performance curve of the pump 100 in the drainage system of FIG. Here, the necessary NPSH and the shaft power differ from the first and second embodiments in that they change in proportion to the square and the cube of the rotational speed of the impeller 1, respectively.

  Since the pump 100 of the present embodiment is a preceding standby pump, the operation is started regardless of the water level (step S1).

  First, the control device 23 sets the resistance value of the secondary resistor 41 to an intermediate value (step S2 ″). This is because the resistance value of the secondary resistor 41 can be increased or decreased according to the water level.

  Based on the detection result of the water tank water level meter 21, the control device 23 determines whether or not the water level in the water tank 51 is equal to or higher than a predetermined air-water mixing operation start water level WL0 (step S3). When it is less than the air-water mixing operation start water level WL0 (NO in step S3), since the pump 100 is in the air operation state, the control device 23 does not perform any special processing.

  When the water / water mixing operation start water level WL0 or higher (YES in step S3), the pump 100 is in the air / water mixing operation state. Also in this case, the control device 23 continues to monitor the water level in the water absorption tank 51. When the difference between the steady operation water level WL1 and the water level in the water absorption tank 51 becomes equal to or less than the threshold value β (YES in step S4), the control of the secondary resistor 41 after step S5 is started.

  In order to control the secondary resistor 41, the control device 23 calculates the actual head from the difference between the two based on the detection results of the water tank water level meter 21 and the discharge destination water level meter 22 (step S5).

  Then, the control device 23 estimates the operating point at the time of transition from the air / water mixing operation to the steady operation from the calculated actual head and the resistance value of the secondary resistor 41 (step S6 ″). Specifically, the control device 23 intersects the pipeline resistance curve with the total lift curve during steady operation that is grasped from the actual lift and the resistance value of the secondary resistor 41 (that is, the rotational speed of the impeller 1). Is the operating point at the time of transition to steady operation. In the example of FIG. 12, the control device 23 changes the intersection P41 between the pipe resistance curve A1 and the total lift curve B1 obtained from the actual lift and the resistance value of the secondary resistor 41 from the air-water mixing operation to the steady operation. Estimated operating point at the time of transition.

  Returning to FIG. 11, the control device 23 determines whether or not the calculated discharge amount at the operating point exceeds the maximum discharge amount (step S7). The maximum discharge amount here is the maximum discharge amount at which neither shaft power over nor cavitation occurs, in other words, the smaller one of the discharge amounts at which shaft power over or cavitation occurs. ing.

  For example, when the operating point estimated in step S6 ″ is the intersection P41 in FIG. 12, the required NPSH at this rotational speed is the curve N1, and the shaft power curve is the curve D1, the discharge amount exceeds the maximum discharge amount. (YES in step S7). If the water tank level rises as it is and shifts to steady operation, shaft power over and cavitation will occur. Therefore, the control device 23 sends an operation command for increasing the resistance value of the secondary resistor 41 to the secondary resistor 41 so that the discharge amount does not cause excessive driving force and cavitation. As a result, the resistance value of the secondary resistor 41 is controlled to increase (step S8 ').

  As a result, since the rotational speed of the impeller 1 decreases, the total lift curve changes in a direction in which the discharge amount decreases (for example, the total lift curve in FIG. 12 changes from B1 to B21). As a result, the operating point changes in the direction in which the discharge amount decreases (intersection points P41 to P42). Further, as the rotational speed decreases, the required NPSH and the shaft power change in a direction that decreases (for example, the required NPSH in FIG. 12 changes from the curve N1 to the curve N2, and the shaft power curve changes from the curves D1 to D2).

  On the other hand, when the operating point estimated in step S6 '' is the intersection P43 on the total head curve B21 in FIG. 12, the required NPSH at this rotational speed is the curve N2, and the shaft power curve is the curve D2, the discharge amount Is below the maximum discharge amount (NO in step S7). In this case, shaft power over and cavitation do not occur even if the water level rises as it is and shifts to steady operation. However, in order to quickly fill the discharge water tank 52 or the discharge pipe and shift to the total drainage operation, it is desirable that the discharge amount of the pump 100 be as large as possible. Therefore, the control device 23 determines whether the rotation speed of the impeller 1 can be increased.

  That is, when the rotation speed of the impeller 1 is not the maximum (NO in step S9 ″ in FIG. 11), the control device 23 determines that the difference between the maximum discharge amount and the discharge amount at the operating point is equal to or less than a predetermined threshold value α. Whether or not (step S10). Here, the threshold value α is a constant that can be arbitrarily set.

  If it is equal to or less than the threshold value α (YES in step S10), the discharge amount at the operating point is sufficiently close to the maximum discharge amount, so the control device 23 does not reduce the rotation speed.

  On the other hand, if it is equal to or greater than the threshold value α (YES in step S10), the discharge amount at the operating point still has a sufficient margin with respect to the maximum discharge amount, so the control device 23 decreases the resistance value of the secondary resistor 41. Is sent to the secondary resistor 41. As a result, the secondary resistor 41 is controlled to decrease (Step S11 ″), and the rotational speed of the impeller 1 increases. As a result, the pipeline resistance curve changes in the direction in which the discharge amount increases (for example, the total lift curve in FIG. 12 changes from B21 to B22). As a result, the operating point changes in the direction in which the discharge amount increases (intersection points P43 to P44). Further, the required NPSH and the shaft power change in the direction of increasing (for example, the required NPSH in FIG. 12 changes from the curve N2 to the curve N3, and the shaft power curve changes from the curves D2 to D3).

  After the above steps S8 ", S10 YES or S11", the control device 23 repeats the processes after step S3. As a result, the higher the actual head as the discharge level rises, the higher the rotational speed of the impeller 1, and the target value (for example, the discharge amount at the operating point at which the steam-water mixing operation shifts to the steady operation is less than the maximum discharge amount) , 99% of the maximum discharge amount). As a result, the discharge amount at the operating point rises and falls near the target value, but does not exceed the maximum discharge amount.

  When the rotational speed of the impeller 1 reaches the maximum (YES in step S9 ″), the control device 23 ends the control of the secondary resistor 41.

  Then, as the water level of the discharge water tank 52 rises, the point where neither shaft power over nor cavitation occurs in the total head curve becomes an operating point, and the operation point shifts to steady operation. It moves along the curve B1 and reaches the pump essential point P21 (arrow F3).

  The control device 23 measures the suction water level, the discharge water level, the resistance value of the secondary resistor 41, and the current value indicating the shaft power when the operation is shifted to the steady operation. If the discharge amount is smaller than the maximum discharge amount, the control amount of the secondary resistor 41 may be corrected so that the operating point approaches the maximum discharge amount at the next control. The transition to steady operation can be determined from the water absorption level.

  As described above, in the third embodiment, by adjusting the resistance value of the secondary resistor 41 and controlling the rotational speed of the impeller 1, it is possible to suppress overdrive force and cavitation.

  The embodiment described above is described for the purpose of enabling the person having ordinary knowledge in the technical field to which the present invention belongs to implement the present invention. Various modifications of the above embodiment can be naturally made by those skilled in the art, and the technical idea of the present invention can be applied to other embodiments. Therefore, the present invention should not be limited to the described embodiments, but should be the widest scope according to the technical idea defined by the claims.

DESCRIPTION OF SYMBOLS 1 Impeller 2 Suction pipe 2a Suction port 3 Intake pipe 4 Discharge pipe 5 Discharge valve 11 Driver 20 Control system 21 Water absorption tank water level meter 22 Discharge destination water level meter 23 Controller 30 Gas supply system 31 Compressors 32, 33 Valve 40 Rotational speed Adjustment system 41 Secondary resistor 51 Water absorption tank 52 Discharge water tank 100 Advance standby pump

Claims (13)

A pump control system that operates regardless of the suction water level,
First detection means for detecting the water level of the water absorption tank;
Second detection means for detecting the water level of the discharge destination;
And a control device that controls the flow rate of the pump so that shaft power over and cavitation do not occur based on the water level of the water absorption tank and the water level of the discharge destination.   The control system according to claim 1, wherein the control device controls a flow rate of the pump by adjusting an opening degree of a discharge valve provided in a discharge pipe of the pump.   The control device estimates an operating point when the pump makes a transition from a gas-water mixing operation to a steady operation based on the water level of the water absorption tank and the water level of the discharge destination, and determines the axis of the discharge amount at the estimated operating point. The control system according to claim 1, wherein when the power over or cavitation occurs, control is performed so that the flow rate of the pump is reduced.   4. The control according to claim 3, wherein the control device controls the flow rate of the pump to be increased when a discharge amount at the estimated operating point is smaller than a discharge value at which shaft power over or cavitation occurs by a predetermined value or more. system.   The control device is based on the difference between the water level of the water absorption tank and the water level of the discharge destination, the pipeline resistance curve of the pump determined according to the flow rate of the pump, and the total head curve of the pump. The control system according to claim 3, wherein the operating point is estimated.   The control system according to any one of claims 1 to 5, wherein the control device controls the flow rate of the pump to be a target value less than a discharge amount at which the shaft power over or cavitation occurs. A pump control system that operates regardless of the suction water level,
First detection means for detecting the water level of the water absorption tank;
Second detection means for detecting the water level of the discharge destination;
A control device for controlling the amount of gas fed into the intake pipe connected to the suction pipe of the pump so that shaft power over and cavitation do not occur based on the water level of the water absorption tank and the water level of the discharge destination Control system. A pump control system that operates regardless of the suction water level,
First detection means for detecting the water level of the water absorption tank;
Second detection means for detecting the water level of the discharge destination;
And a control device that controls the rotational speed of the impeller of the pump so that shaft power over and cavitation do not occur based on the water level of the water absorption tank and the water level of the discharge destination.   A drainage system comprising a pump and the control system according to any one of claims 1 to 8. Comprising a plurality of said pumps;
The drainage system according to claim 9, wherein the control system controls a pump that starts operation first when the discharge destination is dry. A pump control method that operates regardless of the suction water level,
Detect the water level in the water tank,
Detect the water level at the discharge destination,
A control method for controlling the flow rate of the pump based on the water level of the water absorption tank and the water level of the discharge destination so that shaft power over and cavitation do not occur. A pump control method that operates regardless of the suction water level,
Detect the water level in the water tank,
Detect the water level at the discharge destination,
A control method for controlling an amount of gas fed into an intake pipe connected to an intake pipe of the pump based on a water level of the water absorption tank and a water level of the discharge destination so that shaft power over and cavitation do not occur. A pump control method that operates regardless of the suction water level,
Detect the water level in the water tank,
Detect the water level at the discharge destination,
A control method of controlling the rotational speed of the impeller of the pump so that shaft power over and cavitation do not occur based on the water level of the water absorption tank and the water level of the discharge destination.