JP2009203806A - Preceding standby operation pump and method for operating same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a preceding standby operation pump capable of reliably shutting off pumping when it is desired to shut off pumping and inhibiting vibration and generation of swirl. <P>SOLUTION: The preceding standby operation pump 1 includes a first air charge port 21b for dropping drain water quantity by pumping by introducing air into a casing 3 below an impeller 11 while water suction level WL is not higher than the lowest water level LWL, and a second air charge port 22b for shutting off pumping by introducing air into the casing 3 below the impeller 11 when the water suction level gets to pumping shut off water level SWL lower than the lowest water level LWL, and includes air pipes 21, 22 providing communication between two kinds of air charge ports 21b, 22b and an inside of the casing 3. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a prior standby operation pump installed in a suction water tank or the like of a drainage station and an operation method thereof.

Conventionally, a casing having a suction port opened in the suction water tank at the lower end, an impeller disposed inside the casing, and pumping water while introducing air into the casing below the impeller reduces the amount of drainage. There are known vertical shaft pumps having an air supply port for mixing air and water, that is, prior standby operation pumps (see Patent Documents 1 and 2, etc.).
JP 2004-239215 A JP 2006-291900 A

  However, it has been difficult to introduce an appropriate amount of air using only the air / water mixing inlet. That is, when an air pipe capable of introducing a sufficient amount of air for shutting off pumping at a predetermined water level is installed at the time of air-water mixing operation, the air-water mixing operation introduces an excessive amount of air and increases vibrations. There is a possibility of blocking pumping above the water level. However, with an air pipe that reduces the amount of air that can be introduced, even if the water level in the suction tank drops to the level at which it is desired to block the pumping, the pumping may not be blocked. In order to cut off the pumping, the vibration sometimes increased. When the vibration level of the pump increases, it is necessary to increase the strength of the pump accordingly, which may increase the weight of the pump. Further, when the pump weight increases, it may be necessary to increase the floor strength of the drainage station that covers the upper surface of the suction water tank and suspends the pump.

  The preceding standby operation pump of the present invention includes a casing having a suction port opened in the suction water tank at a lower end, an impeller disposed inside the casing, and a state in which the water level of the suction water tank is equal to or lower than a first predetermined water level. A first air supply port for reducing the amount of drainage by pumping water while introducing air into the casing below the impeller, and a second predetermined level in which the water level of the suction water tank is lower than the first predetermined level When the water level is reached, a second air supply port for blocking pumping is provided by introducing air into the casing below the impeller, and the two types of air supply ports and the inside of the casing are provided. It is characterized by including an air pipe to be communicated.

  Further, the operation method of the preceding standby operation pump of the present invention includes a casing having a suction port opened in the suction water tank at the lower end, an impeller disposed inside the casing, and first and second types of air supply. An air pipe that communicates between the two types of air supply ports and the inside of the casing, and in the casing below the impeller in a state where the water level of the suction water tank is equal to or lower than a first predetermined water level. An air-water mixing operation in which the amount of discharged water is reduced by pumping water while introducing air through the air pipe from the first air supply port, and the water level of the suction water tank is changed from the first predetermined water level by the air-water mixing operation. When the low second predetermined water level is reached, pumping is shut off by introducing air through the air pipe from the second air supply port into the casing below the impeller, and switching to pumping shut-off operation is performed. Features and That.

  The preceding standby operation pump of the present invention preferably employs the following configuration.

  An air / water mixing air pipe for communicating the first air supply port and the inside of the casing, and a pumping-off air pipe for communicating the second air supply port and the inside of the casing.

  The pumping-off air pipe is provided with opening / closing means.

  An air supply port of the pumping-off air pipe is provided so as to be submerged at the second predetermined water level.

  The opening position in the casing of the pumping-off air pipe is above the opening position in the casing of the air / water mixing air pipe.

  The opening position in the casing of the air / water mixing air pipe is above the opening position in the casing of the pumping-off air pipe.

  Pressure reducing means for reducing the fluid pressure in the vicinity of the opening of the pumping-off air pipe is provided on the inner surface of the casing.

  The pressure reducing means is a support member that fixes a lower end bearing of a main shaft to which the impeller is attached to an inner surface of the casing.

  The air supply port of the air / water mixing air pipe is provided so as to be submerged at the first predetermined water level.

  At least one of the pumping-off air pipe and the air-water mixing air pipe is formed in an inverted U-shape, and the suction head by the maximum negative pressure generated by the inverted U-shaped folded portion at the opening position in the casing of the air tube. Is set to a higher position.

  A vortex generation prevention plate is provided on the outer surface of the casing below the impeller.

  According to the preceding standby operation pump and the operation method of the present invention, it is possible to introduce an air amount sufficient for shutting off the pumping water only at the time of shutting off the pumping water, and to easily optimize the air amount introduced during the air-water mixing operation. Therefore, it is possible to suppress the generation of vortices and vibrations compared to the case where air is introduced only by the air / water mixing supply port. As a result, it is not necessary to increase the strength of the pump, it is possible to reduce the weight of the pump, and it may not be necessary to increase the floor strength of the drainage station.

  In the present invention, a pipe branched from one pipe may be used as the air pipe that communicates the two types of air inlets with the inside of the casing, but the first air inlet and the inside of the casing are in communication with each other. When equipped with an air / water mixing air pipe, and a pumping shut-off air pipe that allows the second air supply port and the casing to communicate with each other, the amount of air introduced at the time of air / water mixing operation and the amount of air introduced at the time of shutting off the pumping water are respectively It becomes easy to set and the above-mentioned effects can be easily realized.

  In addition, the air inlet of the pumping-off air pipe may be open to the atmosphere at all times, but if the pumping-off air pipe is provided with an opening / closing means, the pumping water will be discharged when the water level in the suction tank reaches the second predetermined water level. Since it can interrupt | block and it can prevent producing a variation in a pumping off water level, it can implement | achieve by promoting the said effect.

  The opening / closing means may be a valve, but if the air supply port of the pumping-off air pipe is provided to be submerged at a second predetermined water level (for example, a water level substantially equal to the pumping-off water level), this configuration becomes the opening / closing means. Since the air supply port of the pumping-off air pipe can be opened and closed by the water in the suction water tank, a control mechanism for opening and closing the air supply port of the pumping-off air pipe is not required.

  In addition, the vertical positional relationship between the opening position in the casing of the air / water mixing air pipe and the opening position in the casing of the pumping-off air pipe may be the same, but the opening position in the casing of the pumping-off air pipe is the same. When the air pipe is above the opening position in the casing of the air / water mixing air pipe, the air is efficiently and effectively sent to the casing below the impeller at the position close to the impeller when the pumping is shut off. Since it can be introduced (intake), when the water absorption level is lowered (during air-water mixing operation), it becomes easy to shut off pumping accurately and stably, and the air pipe for mixing air and water Since the opening position in a casing can be made lower, it becomes easy to make a pumping cutoff water level lower.

  On the other hand, if the opening position in the casing of the air / water mixing air pipe is above the opening position in the casing of the pumping-off air pipe, the negative pressure level by the impeller at the time of pumping off can be reduced. Hunting phenomenon due to slight fluctuations in the water level of the suction water tank (a phenomenon in which the pumping starts due to the water level rising due to the backflow from the casing to the suction water tank when the pumping shuts off, and the pumping shutoff due to the lowering of the water level alternately) .

  In addition, if pressure reducing means for reducing the fluid pressure near the opening of the pumping-off air pipe is provided on the inner surface of the casing, air can be stably introduced through the pumping-off air pipe, so that the pumping can be performed more reliably. It can be switched to shut-off operation.

  Further, the pressure reducing means has a protrusion on the inner surface of the casing provided in the vicinity of the upstream side in the impeller rotation direction of the opening position in the casing of the pumping-off air pipe or a recess in the inner surface of the casing provided in the opening position in the casing of the pumping-up air pipe However, if the support member fixes the lower end bearing of the main shaft to which the impeller is attached to the inner surface of the casing, the casing structure below the impeller can be simplified and the pump can be reduced in weight.

  Further, the air / water mixing air pipe may or may not be provided with an opening / closing means. However, if it is provided, the first predetermined water level, for example, the water level in the suction water tank is lower than that in the air / water mixing operation. In the vortex from the suction port of the casing, that is, the air level can be completely stopped by closing the air / water mixing air pipe by the opening / closing means at a water level equal to the lowest water level that sucks in air. Full operation at the rated drainage volume of the pump can be performed above the minimum water level that inhales air. In this case, when the air inlet of the air / water mixing air pipe is provided so as to be submerged at the lowest water level, this structure becomes an opening / closing means, and the air pipe for air / water mixing with the water in the suction water tank Can be opened and closed, so that a control mechanism or the like for opening and closing the air / water mixing air pipe is not required.

  In addition, at least one of the pumping-off air pipe and the air / water mixing air pipe is formed in an inverted U shape, and the reverse U-shaped folded portion is sucked by the maximum negative pressure generated at the opening position in the casing of the air tube. If it is set at a position higher than the head, water is sucked up by a height corresponding to the negative pressure generated at the open end in the casing of the air pipe during the pumping operation, and it becomes a balanced state, but the inverted U-shaped air Since water is not sucked up beyond the folded portion of the tube, it is possible to reduce the possibility that dust or the like is clogged from the air tube into the folded portion.

  In addition, if a vortex generation prevention plate is provided on the outer surface of the casing below the impeller, the generation of vortices can be further suppressed when the water level of the suction tank is a low level below the pumping cutoff water level. The water level can be further lowered, and the water can be discharged to a lower water level in the suction water tank.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view of a preceding standby operation pump showing a first embodiment, and FIG. 2 is a transverse sectional view of an air introduction portion in the pump.

  In FIGS. 1 and 2, a preceding standby operation pump 1 is a vertical pump that drains water such as rainwater flowing into the suction water tank 2 of the drainage station downstream.

  The casing 3 extending in the vertical direction includes a straight tubular pumping pipe 4, a pump casing 5 connected to the lower end of the pumping pipe 4, a suction pipe (suction bell) 6 connected to the lower end of the pump casing 5, and a pumping pipe. 4 and a discharge elbow 7 curved in the horizontal direction from the vertical direction, and having a suction port 8 at the lower end of the suction pipe 6 (lower end of the casing 3). 3 is connected to a discharge pipe (drainage pipe) 10.

  The impeller 11 is disposed in the pump casing 5 via the main shaft 13, and a plurality of guide blades 12 are disposed in the pump casing 5 above (downstream side) the impeller 11.

  The main shaft 13 extending in the vertical direction is supported at the center of the casing 3 via a plurality of bearings 14, 15, and 16, and the impeller 11 is attached to the vicinity of the lower end of the main shaft 13 so as to be integrally rotatable. The upper end side of the main shaft 13 penetrates the discharge elbow 7 in a rotatable and watertight manner and protrudes to the outside of the casing 3 and is connected to a rotation drive mechanism 17 including a drive source such as an engine and an electric motor and a speed reduction mechanism. .

  The lower end bearing 16 that supports the lower end of the main shaft 13 is fixed to the inner surface of the suction pipe 6 on the outer side of the impeller 11 just below (upstream side) via four (a plurality of) support plates 16a. The support plate 16a also serves as a guide plate that divides a passage between the outer surface of the opposed lower end bearing 16 and the inner surface of the suction pipe 6 at substantially equal intervals and guides water to flow in the axial direction. The outer surfaces of the remaining bearings 14 and 15 are also fixed to the inner surface of the pumped-up pipe 4 by similar support plates 14a and 15a.

  A flange 18 for installation is provided at the upper part of the casing 3, and a hole 20 through which the pump 1 below the flange 18 can be inserted is provided in the concrete floor 19 of the drainage pump station covering the upper surface of the suction water tank 2. The pump 1 is installed on the floor 19 via the flange 18 with the lower side of the flange 18 suspended in the suction water tank 2 through the hole 20.

  And in the state where the water level WL of the suction water tank 2 is below the minimum water level LWL which will be described later, the preceding standby operation pump 1 reduces the amount of drainage by pumping water while introducing air into the casing 3 below the impeller 11. When the water level of the suction water tank 2 is lower than the minimum water level LWL and becomes a pumping cutoff water level SWL, which will be described later, air is introduced into the casing 3 below the impeller 11. And two air pipes 21 and 22 (an example of an air pipe) for shutting off the pumped water for shutting off the pumped water, and the air pipes 21 and 22 are provided with opening and closing means 23 and 24, respectively. Yes.

  On the pipe wall of the suction pipe 6 (an example of the casing) below the impeller 11, a first opening (air inlet for air / water mixing; casing) that penetrates the inner / outer surface serving as an attachment portion of the air / water mixing air pipe 21. And a second opening (an intake port for pumping water; an opening in the casing) 26 serving as a mounting portion for the pumping-off air pipe 22.

  In the present embodiment, two (plural) first openings 25 are arranged at equal intervals at the same height position. One second opening 26 is provided with a height difference with respect to the first opening 25 and is disposed below the lower end of the impeller 11 and above the first opening 25. On the other hand, the circumferential positions are also different so that they do not overlap in the vertical direction. Moreover, the circumferential position of the second opening 26 is shifted in the circumferential direction with respect to the first opening 25 so as to be positioned at the approximate center between the two adjacent first openings 25. Therefore, in this embodiment, two (a plurality) air-water mixing air tubes 21 are provided.

  The air-water mixing air pipe 21 is bent and formed in an inverted U shape having a folded portion at the upper end, and the folded portion at the upper end is disposed above the floor 19. Then, both end portions are extended into the suction water tank 2 through the holes 20, and one end 21 a is connected to the first opening 25. Since the folding part is set at a position higher than the suction lift by the maximum negative pressure generated in the first opening 25 due to hot water, the water sucks up the folding part of the inverted U-shaped air pipe. Therefore, it is possible to reduce the possibility that dust and the like are clogged in the folded portion from the air pipe.

  Further, the tip 21b (the other end; an example of the first air supply port) of the air / water mixing air pipe 21 has a water level (hereinafter referred to as “water absorption level”) LW of the suction water tank 2 as a minimum water level LWL (described later). It is provided so as to be submerged when rising to an example of the first predetermined water level. Therefore, the tip 21b of the air / water mixing air pipe 21 is opened in the atmosphere until the water absorption level LW rises to the lowest water level LWL, and the air / water mixing air pipe 21 is held open. When the water level rises to the lowest water level LWL, it is blocked by the water in the suction water tank 2, and when the water absorption level LW is equal to or higher than the lowest water level LWL, the air / water mixing air pipe 21 is kept closed. That is, the opening / closing means 23 of the air / water mixing air pipe 21 is constituted by the tip 21 b of the air / water mixing air pipe 21.

  Similarly to the air / water mixing air pipe 21, the pumping-off air pipe 22 is bent into an inverted U shape having a folded portion at the upper end, and the folded portion at the upper end is disposed above the floor 19. Both end portions are extended into the suction water tank 2 through the holes 20, and one end 22 a is connected to the second opening 26. Since the folded portion is set at a position higher than the suction lift by the maximum negative pressure generated in the second opening 26 due to hot water, the water sucks up the folded portion of the inverted U-shaped air pipe. Therefore, it is possible to reduce the possibility that dust and the like are clogged in the folded portion from the air pipe.

  Further, when the tip 22b (the other end; one example of the second air supply port) of the pumping-off air pipe 22 rises to the pumping cutoff water level SWL (an example of the second predetermined water level) that the water absorption level LW will be described later on. To be submerged in water. Therefore, the tip 22b of the pumping-off air pipe 22 is opened in the atmosphere until the water absorption level LW rises to the pumping-off water level SWL, and the pumping-off air pipe 22 is held open. When the water level rises to the pumping cutoff water level SWL, it is blocked by water in the suction water tank 2 and when the water absorption level LW is equal to or higher than the pumping cutoff water level SWL, the pumping cutoff air pipe 22 is kept closed. That is, the opening / closing means 24 of the pumping-off air pipe 22 is constituted by the tip 22 b of the pumping-off air pipe 22.

  In the present embodiment, the two air / water mixing air pipes 21 and the pumped water blocking air pipe 22 are divided into the amount of air introduced from the two air / water mixing air pipes 21 and one pumped water blocking air pipe 22. The thing of the pipe diameter that the air quantity to introduce | transduces becomes substantially the same is used. Since there is one pumping cutoff air pipe 22 for the two air / water mixing air pipes 21, the diameter of each air / water mixing air pipe 21 is approximately 1 / of the pipe diameter of the pumping / water blocking air pipe 22. √2.

  On the inner surface of the suction pipe 6, a rib 27 is provided as a pressure reducing means for reducing the fluid pressure in the vicinity of the second opening 26 to block the flow in the impeller rotational direction. Here, as shown in FIG. 2, the four support plates 16a of the lower end bearing 16 are such that the outer end of one of the support plates 16a is rotated by the impeller of the second opening 26 when viewed from the axial direction. It is installed between the outer surface of the opposing lower end bearing 16 and the inner surface of the suction pipe 6 so that it may be connected with the inner surface of the suction pipe 6 in the direction (arrow A direction) upstream vicinity. Further, the four support plates 16a of the lower end bearing 16 have a lower end located above the first opening 25, an upper end located below the lower end of the impeller 11, and the first opening 25 is not included. The second opening 26 extends between the outer surface of the opposite lower end bearing 16 and the inner surface of the suction pipe 6 in a height range including the second opening 26. Therefore, the outer end portion of the support plate 16a connected to the inner surface of the suction pipe 6 in the vicinity of the upstream side of the second opening 26 in the impeller rotation direction is in the impeller rotation direction immediately before passing through the second opening 26. Block the flow. That is, the pressure reducing means 27 is constituted by an outer end portion of a support plate (rib) 16 a connected to the inner surface of the suction pipe 6 in the vicinity of the upstream side of the second opening 26 in the impeller rotation direction. In addition, the rib as a pressure reduction means is not limited to the said embodiment, The form etc. which protruded in the cantilever state to the inner surface of the casing may be sufficient.

  Of the four support plates 16a of the lower end bearing 16, the outer end of one of the support plates 16a has an inner surface of the suction pipe 6 in the vicinity of the upstream side of the second opening 26 in the impeller rotation direction when viewed from the axial direction. The outer ends of the two support plates 16a adjacent to the one support plate 16a, when viewed from the axial direction, the suction pipe in the vicinity of the upstream side of the first opening 25 in the impeller rotation direction. 6 will be connected to the inner surface of 6. In other words, the positional relationship in the circumferential direction between the openings 25 and 26 provided in the suction pipe 6 and the outer end portion of the support plate 16a of the lower end bearing 16 is upstream of the rotation direction of the impellers of the openings 25 and 26 when viewed from the axial direction. The outer end portion of the support plate 16a is positioned in the vicinity of the side.

  A vortex generation preventing plate 28 is provided on the outer surface of the suction pipe 6 between the suction port 8 and the first opening 25. The vortex generation preventing plate 28 is formed of a horizontal plate that is in surface contact with the water surface when the water absorption level LW is lowered to the vicinity of the pumping cutoff water level SWL. The horizontal plate is formed larger than the suction port 8 and smaller than the hole 20 of the floor 19. The vortex generation preventing plate 28 may be composed of a plurality of vertical plates provided radially on the outer surface of the suction pipe 6 below the first opening 25. Further, a horizontal plate or a vertical plate larger than the hole 20 may be used.

  Next, the relationship between the structure in the height direction of the preceding standby operation pump 1 and the water absorption level LW will be described with reference to FIG.

  First, the maximum water level HWL peculiar to the suction water tank 2 is set to the suction water tank 2 as the allowable water level.

  Below the highest water level HWL, the lowest water level LWL (the first predetermined water level), which is unique to the pump 1 (the pump here is a vertical shaft pump that does not include the air pipes 21, 22 and the vortex generation prevention plate 28). One example) is set. Below that, the minimum water level LWL corresponds to the water absorption level WL in which vortex, that is, air is sucked from the suction port 8 and vibration and noise are generated, and the operation cannot be continued. The pump 1 is operated by pumping water while reducing the amount of drainage while introducing air into the casing 3 below the impeller 11 through the air / water mixing air pipe 21, so that the water absorption level WL is lower than the lowest water level LWL. Therefore, the tip 21b of the air / water mixing air pipe 21 can be provided at a position that is open to the atmosphere at least when the water absorption level WL falls below the lowest water level LWL. It ’s fine. In the present embodiment, the air / water mixing air pipe 21 is also provided with an opening / closing means 23, and the opening / closing means 23 is constituted by a tip 21 b of the air / water mixing air pipe 21. Therefore, as described above, the tip 21b (an example of the first air supply port) of the air / water mixing air pipe 21 is provided so as to be submerged when the water absorption level LW rises to the lowest water level LWL. Until the LW rises to the lowest water level LWL, it is opened in the atmosphere and the air-water mixing air pipe 21 is kept open, and when the water absorption level LW rises to the lowest water level LWL, the water in the suction water tank 2 When the water absorption level LW is equal to or higher than the lowest water level LWL, the air / water mixing air pipe 21 is held closed.

  The impeller 11 is disposed below the lowest water level LWL. If it is the minimum water level LWL, it arrange | positions so that the whole impeller 11 or at least the lower end part of the impeller 11 may be submerged.

  A pumping start water level RWL is set below the lowest water level LWL. The pumping start water level RWL corresponds to the water absorption level WL at the lower end of the impeller 11, and the water absorption level WL that starts pumping first after the pump 1 is started (when there is no water in the casing 3 above the impeller 11). It is.

  A second opening 26 and pressure reducing means 27 (support plate 16a of the lower end bearing 16) are disposed below the pumping start water level RWL, and a first opening 25 is disposed below the second opening 26 and the pressure reducing means 27.

  A re-pumping start water level CWL is set below the pumping start water level RWL. The re-pumping start water level CWL corresponds to the water absorption level WL at the upper end of the first opening 25, and after water is drained and the pumping shut-off operation (standby operation) is performed (there is water in the casing 3 above the impeller 11). In this case, the water absorption level WL can be re-pumped.

  Below the re-pumping start water level CWL, a pumping cutoff water level SWL (an example of a second predetermined water level) is set. The re-pumping start water level CWL opens the pumping shut-off air pipe 22 by the opening / closing means 24 when the water absorption level WL is lowered from the first opening 25 in the air-water mixing operation, and the impeller 11 passes through the pumping shut-off air pipe 22. It is the water absorption level WL which introduce | transduces air in the lower casing 3 and interrupts pumping, and switches to pumping off operation. Therefore, as described above, the tip 22b (an example of the second air supply port) of the pumping-off air pipe 22 is provided so as to be submerged when the water absorption level LW rises to the pumping-off water level SWL. Until the LW rises to the pumping shut-off water level SWL, it is opened in the atmosphere and the pumping shut-off air pipe 22 is kept open, and when the water sucking level LW rises to the pumping shut-off water level SWL, When the water absorption level LW is equal to or higher than the pumping cutoff water level SWL, the pumping cutoff air pipe 22 is held in a closed state.

  When the pump 1 is operated at a low water level near the pumping cutoff water level SWL, vortices are likely to be generated, and vortex, that is, air is easily sucked. It is arranged on the outer surface of the suction pipe 6 between the first opening 26.

  A suction port 8 is disposed below the pumping cutoff water level SWL. For example, the suction port 8 is opened at a height position having a dimension substantially equal to the pipe diameter (inner diameter) of the pumped water pipe 4 that is the body portion of the casing 3 with respect to the bottom surface 2 a of the suction water tank 2.

  Next, the transition of the operation state (drainage state) of the preceding standby operation pump 1 will be described with reference to FIG.

  Since it is the advance standby operation pump 1, it starts before the water absorption level WL rises to the lowest water level LWL (an example of the first predetermined water level) based on rainfall information or the like. In the present embodiment, the water absorption level WL rises to the pumping cutoff water level SWL (an example of the second predetermined water level) due to water such as rainwater entering the suction water tank 2, and the pumping cutoff air pipe 22 is closed by the opening / closing means 24. The pump 1 is started.

  Until the water absorption level WL rises to the pumping start water level RWL after the pump 1 is started, the impeller 11 is idling in the air.

  When the water absorption level WL rises and reaches the pumping start water level RWL, the impeller 11 starts pumping and starts draining. At this time, the pressure in the first opening 25 part is the water on the inflow side of the impeller 11. It is lowered by the flow of air and becomes lower than atmospheric pressure. And since the front-end | tip 21b (an example of a 1st air supply opening) of the air pipe 21 for air-water mixing is hold | maintained by the opening-and-closing means 23, from the 1st opening 25 through the air pipe 21 for air-water mixing. Since air is sucked in and the impeller 11 pumps up water while sucking in air, drainage starts in a state where the drainage amount is lower than the rated drainage amount. That is, the air / water mixing operation is started.

  In the air-water mixing operation state, when the water absorption level WL further rises and reaches the lowest water level LWL (an example of the first predetermined water level), the tip 21b of the air-water mixing air pipe 21 that has been held open until then. (An example of the first air supply port) is closed by the opening / closing means 23, and air suction from the first opening 25 is eliminated, so that drainage at the rated drainage amount starts. That is, the start of full operation.

  If the water absorption level WL is further increased after the full operation, the full operation is continued.

  On the other hand, when the total amount of operation is started and the drainage amount of the pump 1 exceeds the inflow amount of water such as rainwater into the suction water tank 2, the water absorption level WL starts to fall and falls below the minimum water level LWL (an example of the first predetermined water level). The tip 21b (an example of the first air supply port) of the air / water mixing air pipe 21 that has been kept closed until then is opened by the opening / closing means 23, and the suction of air from the first opening 25 is started. Then, the whole operation shifts to the air / water mixing operation.

  When the water absorption level WL is further lowered by the air-water mixing operation, the air suction amount gradually increases in accordance with the decrease in the water absorption level WL, and instead the water amount gradually decreases, so the drainage amount gradually decreases. . Then, when the water absorption level WL further decreases, falls below the pumping start water level RWL and the re-pumping start water level CWL, and finally falls below the pumping cutoff water level SWL (an example of the second predetermined water level), it is held closed until then. The front end 22 b (an example of the second air supply port) of the pumped-up water blocking air pipe 22 is opened by the opening / closing means 24. Since the pressure in the second opening 26 is reduced by the flow of water on the inflow side of the impeller 11 and becomes a negative pressure lower than the atmospheric pressure, the pressure from the second opening 26 also passes through the pumping-off cutoff air pipe 22. Air is sucked in, the mixing ratio of water and air becomes very high, the impeller 11 cannot suck in water, and drainage stops. That is, the operation is switched from the air / water mixing operation to the pumping off operation. In addition, since air required for pumping off is sucked into the casing when a gap of a certain level or more is generated between the tip 22b of the pumping cutoff air pipe 22 and the water surface, pumping is actually shut off. The water level is slightly lower than the water level at which the tip 22b of the pumping-off air pipe 22 is submerged, but the water level including the pumping-off water level SWL in this specification is a water absorption level having a width including these. This is a concept representing WL.

  When the water absorption level WL rises during the pumping shut-off operation (standby operation), since there is water in the casing 3 above the impeller 11, the water absorption level WL is the pumping shut-off water level SWL (an example of the second predetermined water level). (The tip 22b of the pumping-off air pipe 22 that has been held open until then is closed by the opening / closing means 24, and air is not sucked from the second opening 26), and the re-pumping start water level CWL is reached. At the time of arrival, the impeller 11 starts pumping water while sucking in air (air sucked from the first opening 25 through the air / water mixing air pipe 21). The air-water mixing operation is resumed.

  In this way, the pump 1 can continue the operation between the idle operation after start-up and the empty operation after the drainage (pumping shut-off operation) and the full operation, regardless of the water absorption level WL. The transition between operation and full operation is smooth, and vortex generation, pump 1 vibration, and excessive change in shaft torque are suppressed.

  As is clear from the above, the casing 3 having the suction port 8 opened in the suction water tank 2 at the lower end, the impeller 11 disposed inside the casing 3, and the water absorption level WL are the lowest water level LWL (the first predetermined water level). An example) A tip 21b of an air / water mixing air pipe 21 for reducing the amount of drainage by pumping water while introducing air into the casing 3 below the impeller 11 in the following state (an example of a first air supply port) ), And when the water absorption level WL becomes the pumping cutoff water level SWL (an example of the second predetermined water level) lower than the minimum water level LWL, the pumping is shut off by introducing air into the casing 3 below the impeller 11. The tip 22b (an example of the second air supply port) of the pumping-off air pipe 22 for performing the operation is provided, and the tip 21b of the two kinds of air-water mixing air pipes 21 and the tip 22b of the pumping-off air pipe 22 and the casing Within 3 The front standby operation pump 1 of this embodiment having an air-water mixing air pipe 21 and a pumping-off air pipe 22 (an example of an air pipe) that communicate with each other, and a suction port 8 that opens in the suction water tank 2 at the lower end The casing 3, the impeller 11 disposed inside the casing 3, the tip 21 b of the air / water mixing air pipe 21, and the tip 22 b of the pumping-off air pipe 22 (of the first and second types of air inlets). 1), the air-water mixing air pipe 21 and the pumping-off air pipe 22 (air pipe) that connect the tip 21b of the air-water mixing air pipe 21 and the tip 22b of the pumping-off air pipe 22 to the inside of the casing 3 are provided. Air) is introduced into the casing 3 below the impeller 11 from the tip 21b of the air / water mixing air pipe 21 through the air / water mixing air pipe 21 in a state where the water absorption level WL is equal to or lower than the lowest water level LWL. Pumping water When the air-water mixing operation is performed and the water absorption level WL becomes the pumping cutoff water level SWL lower than the lowest water level LWL, the pumping cutoff is performed in the casing 3 below the impeller 11. In the preceding standby operation pump of the present embodiment that shuts off pumping by introducing air from the tip 22b of the air pipe 22 through the pumping shut-off air pipe 22 and switches to pumping shut-off operation, a sufficient amount of air for pumping off is pumped up. It can be introduced only at the time of shut-off and can easily optimize the amount of air introduced during the air / water mixing operation, which is more reliable than when air is introduced only by the tip 21b of the air / water mixing air pipe 21. Since the pumping can be shut off, vortex generation and vibration can be suppressed. As a result, there is a case where it is not necessary to increase the weight of the pump 1 without increasing the strength of the pump 1 or to increase the strength of the floor 19 of the drainage station.

  In the preceding standby operation pump of the present embodiment, the air / water mixing air pipe 21 for communicating the front end 21b of the air / water mixing air pipe 21 and the inside of the casing 3, the front end 22b of the pumping-off air pipe 22 and the inside of the casing 3 Therefore, the amount of air introduced at the time of the air-water mixing operation and the amount of air introduced at the time of shutting off the pumping can be easily set, and the above-described effects can be easily realized.

  In addition, since the pumping shut-off air pipe 22 is provided with the opening / closing means 24, the pumping can be shut off when the water absorption level WL becomes the pumping shut-off water level SWL, and variations in the pumping shut-off water level can be prevented. It can be realized with encouragement.

  Further, since the tip 22b of the pumping shut-off air pipe 22 is provided so as to be submerged at the pumping shut-off water level SWL, this configuration becomes the opening / closing means 24, and the tip 22b of the pumping shut-off air pipe 22 is made of water in the suction water tank 2. Since it can be opened and closed, a control mechanism or the like for opening and closing the tip 22b of the pumping-off air pipe 22 is not necessary.

  Further, since the tip 22b of the pumping shut-off air pipe 22 is provided so as to be submerged at the pumping shut-off water level SWL, this configuration becomes the opening / closing means 24, and the tip 22b of the pumping shut-off air pipe 22 is made of water in the suction water tank 2. Since it can be opened and closed, a control mechanism or the like for opening and closing the tip 22b of the pumping-off air pipe 22 is not necessary.

  Note that the air pipe whose opening position in the casing is closer to the impeller 11 sucks more air when the water level is low. Further, in order to shut off the pumping, it is necessary to break the contact between the impeller 11 and water by filling the cross section (passage) of the casing 3 below the impeller 11 with air. Considering that the air in the lower casing 3 moves upward, it is necessary to introduce a large amount of air in a short time. In the present embodiment, the position of the opening 26 in the casing 3 of the pumping-off air pipe 22 is above the position of the opening 25 in the casing 3 of the air-water mixing air pipe 21, so Since air can be efficiently and effectively introduced (intake) into the casing 3 at a position closer to the impeller 11 from the pumping-off air pipe 22, the accuracy in the water level lowering phase (during air-water mixing operation) The pumping can be shut off well and stably. Further, the pumping cutoff water level SWL has an element that is determined by the height of the opening 26 in the casing 3 of the air / water mixing air pipe 21 (if the height of the opening 26 is low, pumping is cut off at a lower water level). Therefore, when shutting off the pumping at a low water level, it is desirable that the position of the opening 26 in the casing 3 of the air / water mixing air pipe 21 is on the lower side. Since the position of the opening 25 in the casing 3 of the air / water mixing air pipe 21 can be made lower and lower than the position of the opening 26 in the casing 3 of the pumping-off air pipe 22, the pumping-off water level SWL can be further increased. It becomes easy to lower the water level. That is, the positional relationship between the position of the opening 25 in the casing 3 of the air / water mixing air pipe 21 and the position of the opening 26 in the casing 3 of the pumping-off air pipe 22 is suitable for shutting off the water at a low water level.

  Further, since the pressure reducing means 27 for reducing the fluid pressure in the vicinity of the opening 26 of the pumping-off air pipe 22 is provided on the inner surface of the casing 3, air can be stably introduced through the pumping-off air pipe 22. It is possible to switch to the pumping off operation more reliably.

  Further, since the pressure reducing means 27 is a support plate (rib) 16a (an example of a support member) that fixes the lower end bearing 16 of the main shaft 13 to which the impeller 11 is attached to the inner surface of the casing 3, the casing 3 below the impeller 11 is provided. The structure can be simplified and the pump 1 can be reduced in weight.

  In addition, since the air / water mixing air pipe 21 is provided with the opening / closing means 23, the air / water mixing operation is performed, and the air / water mixing air pipe 23 is closed by the opening / closing means 23 when the water absorption level WL is equal to or higher than the minimum water level LWL. The pump can be completely stopped, and the full operation at the rated drainage amount of the pump 1 can be performed at the minimum water level LWL or higher. Here, when the tip 21b of the air / water mixing air pipe 21 is provided so as to be submerged at the lowest water level LWL, this structure becomes the opening / closing means 23, and the water in the suction water tank 2 is used to form the air / water mixing air pipe 21. Since the tip 21b can be opened and closed, a control mechanism or the like for opening and closing the tip 21b of the air / water mixing air pipe 21 becomes unnecessary.

  Further, since the vortex generation prevention plate 28 is provided on the outer surface of the casing 3 below the impeller 11, the generation of vortices can be further suppressed when the water absorption level WL is a low water level equal to or lower than the pumping cutoff water level SWL. SWL can be lowered to a lower water level and drained to a lower water level in the suction water tank 2.

  Next, the preceding standby operation pump 1A of the second embodiment will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the same part as the prior | preceding standby operation pump 1 of 1st Example, and the overlapping description is abbreviate | omitted.

  In FIG. 3, the preceding standby operation pump 1 </ b> A includes a substantially straight tubular air / water mixing air pipe 21 </ b> A and a pumping-off air pipe 22 </ b> A. In the air / water mixing air pipe 21 </ b> A, the vicinity of the upper end is disposed above the floor 19. And it is extended in the suction water tank 2 through the hole 20, and the lower end 21 </ b> Aa is connected to the first opening 25. The air / water mixing air pipe 21A disposed above the floor 19 is bent in an inverted U shape, and the upper end 21Ab of the air / water mixing air pipe 21A faces downward and is always open to the atmosphere.

  On the other hand, the pumping cutoff air pipe 22 </ b> A is disposed above the floor 19 in the vicinity of the upper end. And it is extended in the suction water tank 2 through the hole 20, and the lower end 22 </ b> Aa is connected to the second opening 26. The pumping off air pipe 22A arranged above the floor 19 is provided with an on / off valve (solenoid valve) 24A as an opening / closing means, and the upper end 22Ab of the pumping off air pipe 22A is connected to the atmosphere via the on / off valve 24A. It is open inside.

  In addition, pressure reducing means 27 </ b> A is provided on the inner surface of the suction pipe 6 to reduce the fluid pressure in the vicinity of both the first opening 25 and the second opening 26. The pressure reducing means 27A is a support plate (rib) of the lower end bearing 16, and the relative position in the circumferential direction with respect to the first opening 25 and the second opening 26 at the outer end is the position shown in FIG. The end portion is constituted by the outer end portion of the support plate 16Aa having a height (vertical width) that covers the height range of the first opening 25 and the second opening 26 below the impeller 11.

  In the preceding standby operation pump 1A of the present embodiment, the same function as the preceding standby operation pump 1A of the first embodiment is exhibited by controlling the opening / closing valve 24A based on a water level sensor or the like that detects the water absorption level WL. Can do. However, the air / water mixing air pipe 21A is always open to the atmosphere.

  In addition, since the pressure reducing means 27A for reducing the fluid pressure in the vicinity of the openings of both the first opening 25 and the second opening 26 is provided, the air pipe for air-water mixing is also used for the first opening 25. Air can be stably introduced through 21A.

  Next, the preceding standby operation pump 1B of the third embodiment will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the same part as the advance standby operation pumps 1 and 1A of 1st and 2nd Example, and the overlapping description is abbreviate | omitted.

  In FIG. 4, the preceding standby operation pump 1 </ b> B has an upside down positional relationship with respect to the positional relationship between the first opening 25 and the second opening 26 of the preceding standby operation pumps 1 and 1 </ b> A of the first and second embodiments. A first opening 25B and a second opening 26B are provided. The first opening 25B is connected to one end 21a of the air / water mixing air pipe 21 (or one end 21Aa of the air / water mixing air pipe 21A), and the second opening 26B is connected to the pumping off air pipe 22. One end 22a (the end 22Aa of the pumping-off air pipe 22A is also acceptable).

  The preceding standby operation pump 1B of the present embodiment can exhibit the same function as the preceding standby operation pump 1A of the second embodiment.

  In the preceding standby operation pump 1B of the present embodiment, the position of the opening 25B in the casing 3 of the air / water mixing air pipe 21 or 21A is higher than the position of the opening 26B in the casing 3 of the pumping-off air pipe 22 or 22A. Therefore, the degree of negative pressure by the impeller 11 at the time of pumping off can be reduced, and hunting phenomenon due to slight water level fluctuation of the suction water tank 3 at the time of pumping off (due to backflow from the casing 3 to the suction water tank 2 at the time of pumping off) The phenomenon that the pumping start due to the rise of the water absorption level WL and the pumping interruption due to the decrease of the water absorption level WL are alternately repeated) is less likely to occur.

  Next, the preceding standby operation pump 1C of the fourth embodiment will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the same part as the prior | preceding standby operation pumps 1 to 1B of 1st thru | or 3rd Example, and the overlapping description is abbreviate | omitted.

  In FIG. 5, the preceding standby operation pump 1 </ b> C is provided with a concave portion 6 a having a concave inner surface and a convex outer surface at the first opening 25 portion and the second opening 26 portion in the pipe wall of the suction pipe 6. A first opening 25 and a second opening 26 are provided in each recess 6a. Each recess 6a becomes pressure reducing means 27C for reducing the fluid pressure in the vicinity of each opening 25, 26, and the air for mixing air and water and the pumping off air can be easily sucked by the pressure reducing means 27C. Then, by providing the openings 25 and 26 on the upstream wall surface 6q in the impeller rotation direction (arrow A direction), the fluid pressure is reduced as compared with the case where the openings 25 and 26 are provided on the bottom wall surface 6r of each recess 6a. The effect to do can also be enlarged. That is, the air / water mixing air and the pumping-off air can be stably introduced through the air / water mixing air pipe 21 and the pumping-off air pipe 22. Such pressure reducing means 27C can also be applied to a structure in which the lower end bearing 16 is not provided.

  Next, the preceding standby operation pump 1D of the fifth embodiment will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the same part as the prior | preceding standby operation pumps 1 thru | or 1C of 1st thru | or 4th Example, and the overlapping description is abbreviate | omitted.

  In FIG. 6, the preceding standby operation pump 1 </ b> D includes a U-shaped tube 30 branched from between the upper end folded portion of the pumping-off air tube 22 and the tip 22 b in order to prevent the hunting phenomenon. The U-shaped tube 30 has an upper surface and a distal end (opening) 30b of substantially horizontal base ends (branch ends) 30a at both ends (upper ends) at a closed water level YWL substantially equal to the water absorption level WL at the upper end of the second opening 26. The upper surface of the substantially horizontal folded portion 30c at the lower end is provided along the open water level XWL substantially equal to the pumped water cutoff water level SWL. Here, the tip 22b of the pumping-off air pipe 22 is disposed below the lower surface of the folded portion 30c of the U-shaped pipe 30, and the pumping-up air pipe 22 has two air supply ports with different heights, that is, The tip 30b of the U-shaped pipe 30 that is the upper air supply port and the tip 22b of the pumping-off air pipe 22 that is the lower air supply port are communicated with the second opening 26.

  When the water absorption level WL rises from the pumping cutoff water level SWL or lower, there is no water in the pipe, so air is sucked from the tip 30b of the U-shaped pipe 30 and the tip 22b of the pumping cutoff air pipe 22 to start the re-pumping water level. Even if the water absorption level WL rises to CWL and the tip 22b of the pumping shut-off air tube 22 is submerged, the air intake continues from the tip 30b of the U-shaped tube 30, and when the water level reaches YWL, the tip 30b of the U-shaped tube 30 Since it is closed by being submerged, the air is not sucked from the second opening 26, and the air-water mixing operation for sucking only the air from the first opening 25 is performed.

  That is, in the rising phase of the water absorption level WL from the pumping shutoff water level SWL or lower, the pumping shutoff air pipe 22 is held open in the atmosphere up to the closed water level YWL, and passes through the pumping shutoff air pipe 22 from the second opening 26. Air is sucked in and the pumping shut-off air pipe 22 is blocked at the closed water level YWL or higher, and air is not sucked from the second opening 26. Thus, the tip 30b of the U-shaped ring 30 functions as the opening / closing means 24 in the direction in which the water absorption level WL rises.

  On the other hand, when the water absorption level WL is lowered from the minimum water level LWL or higher, even if the water absorption level WL is lowered to the lowest water level LWL, both the tip 30b of the U-shaped pipe 30 and the tip 22b of the pumping-off air pipe 22 are submerged. is doing. When the closed water level YWL is reached, the tip 30b of the U-shaped tube 30 comes into the atmosphere, but the water accumulated on the tip 30b side of the U-shaped tube 30 cannot be drained, but if the water level is below the pumping cutoff water level SWL, If the water level is further lowered and the water surface is lowered from the upper part of the folded portion 30c of the U-shaped tube 30, air is sucked from the tip 30b of the U-shaped tube 30.

  That is, when the water absorption level WL from the minimum water level LWL is lowering, the pumping shut-off air pipe 22 is blocked up to the pumping shut-off water level SWL, air is not sucked from the second opening 26, and the pumping shut-off water level is Below SWL, the pumping-off air pipe 22 is held open in the atmosphere, and air is sucked from the second opening 26 through the pumping-off air pipe 22. Thus, when the water absorption level WL decreases, the folded portion 30 c of the U-shaped tube 30 functions as the opening / closing means 24.

  In the preceding standby operation pump 1D of the present embodiment, the pumping-off air pipe 22 is opened to the atmosphere at different water-absorbing levels WL when the water-absorbing level WL is raised and lowered, that is, when the water-absorbing level WL is lowered. At the water level SWL (open water level XWL), the pumping-off air pipe 22 is opened to the atmosphere. When the water absorption level WL rises, the pumping-off air pipe 22 is brought into the atmosphere at the closed water level YWL higher than the pumping-off water level SWL (open water level XWL). Since it is opened, even if the water absorption level WL rises to the re-pumping start water level CWL due to a reverse flow from the inside of the casing 3 to the suction water tank 2 when the pumping is shut off, pumping is not started and the pumping shut-off operation is continued. Therefore, the hunting phenomenon can be prevented.

  In the first to fifth embodiments, the description has been made with the configuration including the two air pipes for air-water mixing and pumping-off, but the sixth to eighth shown in FIGS. 7 to 9 are used. As in the preceding standby operation pumps 1E to 1G of the embodiment, the air pipe may be branched from the middle, or a hole may be made in the pipe wall of the air pipe so as to function as an air supply port.

  The preceding standby operation pump 1E of the sixth embodiment shown in FIG. 7 includes an air / water mixing air pipe 21E formed of an inverted U-shaped narrow pipe branched from the middle of the pumping-off air pipe 22. The air / water mixing air pipe 21E is provided such that the branch end 21Ea and the tip (an example of the first air supply port) 21Eb at both ends are submerged at the lowest water level LWL (an example of the first predetermined water level). Yes.

  The preceding standby operation pump 1F of the seventh embodiment shown in FIG. 8 includes an air / water mixing air pipe 21F formed of a short L-shaped thin tube branched from the middle of the pumping-off air pipe 22. The air / water mixing air pipe 21F is provided so as to be submerged at the lowest water level LWL (an example of a first predetermined water level) as a whole. That is, the tip (an example of the first air supply port) 21Fb is provided so as to be submerged at the lowest water level LWL (an example of the first predetermined water level).

  The preceding standby operation pump 1G of the eighth embodiment shown in FIG. 9 includes an air supply port 21Ga (an example of a first air supply port) opened directly in the middle of the pipe wall of the pumping-off air pipe 22. The air supply port 21Ga is disposed at a position where it is submerged at the lowest water level LWL (an example of a first predetermined water level).

  In the above embodiment, the example in which the opening in the casing is formed on the same surface as the inner wall of the casing has been described, but the air pipe is arranged so as to protrude inward from the inner surface of the casing, and the opening position of the air pipe is set. You may make it arrange | position to the center side rather than the wall surface of a casing. By doing so, air is easily sucked into the casing.

It is a longitudinal cross-sectional view of the advance standby operation pump which shows 1st Example of this invention. It is a cross-sectional view of the air introduction part in the preceding standby operation pump showing the first embodiment of the present invention. It is a longitudinal cross-sectional view of the preceding standby operation pump showing the second embodiment of the present invention. It is a longitudinal cross-sectional view of the preceding standby operation pump showing the third embodiment of the present invention. It is a cross-sectional view of the air introduction part in the preceding standby operation pump showing the fourth embodiment of the present invention. It is a longitudinal cross-sectional view of the advance standby operation pump which shows 5th Example of this invention. It is a principal part longitudinal cross-sectional view of the prior | preceding standby operation pump which shows 6th Example of this invention. It is a principal part longitudinal cross-sectional view of the advance stand-by operation pump which shows 7th Example of this invention. It is a principal part longitudinal cross-sectional view of the advance standby operation pump which shows 8th Example of this invention.

Explanation of symbols

1, 1A, 1B, 1C, 1D, 1E, 1F, 1G Advance standby operation pump 2 Suction water tank 3 Casing 8 Suction port 11 Impeller 13 Main shaft 16 Lower end bearing 16a Support plate (support member)
21 Air tube for air / water mixing 21b Tip (example of first air supply port)
22 Pumping shut-off air pipe 22b Tip (example of second air supply port)
23 Opening / closing means (for air / water mixing)
24 Opening / closing means (for pumping off)
25 1st opening 26 2nd opening 27 Rib (an example of pressure reduction means)
28 Vortex generation prevention plate

Claims (12)

  In the casing below the impeller in a state where the lower end of the casing has a suction port that opens in the suction water tank, the impeller disposed inside the casing, and the water level of the suction water tank below a first predetermined water level A first air supply port for reducing the amount of drainage by pumping water while introducing air, and the impeller when the water level of the suction water tank becomes a second predetermined water level lower than the first predetermined water level. A second air supply port for blocking pumping by introducing air into the lower casing is provided, and an air pipe is provided for communicating the two types of air supply ports with the inside of the casing. A preceding standby operation pump.   The air-water mixing air pipe for communicating the first air supply port and the inside of the casing, and a pumping-off air pipe for communicating the second air supply port and the inside of the casing. Pre-standby operation pump.   The preceding standby operation pump according to claim 2, wherein the pumping-off air pipe is provided with an opening / closing means.   The preceding standby operation pump according to claim 3, wherein an air supply port of the pumping-off air pipe is provided so as to be submerged at the second predetermined water level.   The preceding standby operation pump according to any one of claims 2 to 4, wherein an opening position in the casing of the pumping-off air pipe is higher than an opening position in the casing of the air / water mixing air pipe.   The preceding standby operation pump according to any one of claims 2 to 4, wherein an opening position in the casing of the air / water mixing air pipe is above an opening position in the casing of the pumping-off air pipe.   The preceding standby operation pump according to any one of claims 2 to 6, wherein pressure reducing means for reducing a fluid pressure in the vicinity of an opening of the pumping-off air pipe is provided on an inner surface of the casing.   The preceding standby operation pump according to claim 7, wherein the pressure reducing means is a support member that fixes a lower end bearing of a main shaft to which the impeller is attached to an inner surface of the casing.   The preceding standby operation pump according to any one of claims 2 to 8, wherein an air supply port of the air / water mixing air pipe is provided so as to be submerged at the first predetermined water level.   At least one of the pumping-off air pipe and the air-water mixing air pipe is formed in an inverted U-shape, and the suction head by the maximum negative pressure generated by the inverted U-shaped folded portion at the opening position in the casing of the air tube. The preceding standby operation pump according to any one of claims 4 to 9, which is set at a higher position.   The preceding standby operation pump according to any one of claims 1 to 10, wherein a vortex generation prevention plate is provided on an outer surface of the casing below the impeller.   A casing having a suction port opened in the suction water tank at the lower end, an impeller disposed inside the casing, and first and second types of air supply ports are provided, and the two types of air supply ports and the casing are provided. An air pipe that communicates with the inside, and air is introduced through the air pipe from the first air supply port into the casing below the impeller when the water level of the suction water tank is equal to or lower than the first predetermined water level. When the water level of the suction water tank becomes a second predetermined water level lower than the first predetermined water level by performing the air / water mixing operation in which the amount of discharged water is reduced by pumping water, and the water / water mixing operation is performed, the impeller A method for operating a preceding standby operation pump, wherein pumping is shut off by introducing air through the air pipe from the second air supply port into the casing below and switching to pumping shut-off operation.

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