JP2012122418A - Preceding standby operation pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a preceding standby operation pump capable of reducing vibrations.SOLUTION: The preceding standby operation pump includes: a casing 4 having a suction port which opens in a suction water tank; an impeller disposed in the casing 4; an air introduction pipe 15 for air-water mixing which lowers the water discharge amount by discharging water in an air-water mixed state while introducing air into the casing 4 below the impeller in such a state that a water level in the suction water tank is the lowest level or less; and a resistor 14 disposed below the impeller in the casing 4, wherein an opening part 17 communicated into the casing 4 from the air introduction pipe 15 for air-water mixing is located on the upstream side S1 of the swirling direction A of water swirling along the inner periphery of the casing 4 with respect to the resistor 14.

Description

  The present invention relates to a preceding standby operation pump including an air / water mixing air introduction pipe.

  Conventionally, as for this type of prior standby operation pump, for example, as shown in FIGS. 12 and 13, there is an advance standby operation pump 63 including an air / water mixing air introduction pipe 61 and a drainage blocking air introduction pipe 62. . An impeller 66 is disposed in the casing 64 of the pump 63 via a main shaft 65.

  The air / water mixing air introduction pipe 61 is formed in an inverted U shape, and introduces air into the casing 64 below the impeller 66 when the water absorption level WL of the suction water tank 67 is equal to or lower than the minimum water level WL1. It is for air-water mixing operation that reduces the amount of drainage by pumping water. Also, two air / water mixing air introduction pipes 61 are provided, and first openings 68 communicating from one end 61 a of each air / water mixing air introduction pipe 61 into the casing 64 are provided at two locations of the casing 64. Is formed. The other end 61b of each air / water mixing air introduction pipe 61 is provided so as to be submerged and closed when the water absorption level WL of the suction water tank 67 rises to the lowest water level WL1.

  In addition, the drainage cutoff air introduction pipe 62 is formed in an inverted U-shape, and the water / water mixing operation is performed, so that the suction level WL of the suction water tank 67 becomes the drainage cutoff level WL2 lower than the lowest level WL1. Occasionally, it is for drainage blocking operation in which drainage is blocked by introducing air into the casing 64 below the impeller 66. A second opening 69 communicating with the inside of the casing 64 from the one end 62 a of the drainage blocking air introduction pipe 62 is formed in the casing 64. The other end 62b of the drainage cutoff air introduction pipe 62 is provided so as to be submerged and closed when the water absorption level WL of the suction water tank 67 rises to the drainage cutoff water level WL2.

Hereinafter, an operation method of the preceding standby operation pump 63 will be described.
The pump 63 is started when the water absorption level WL of the suction water tank 2 rises to the drainage cutoff water level WL2 and the other end 62b of the drainage cutoff air introduction pipe 62 is submerged and closed. Until the pump 63 is started and the water absorption level WL rises to the drainage start water level WL3, the impeller 66 is idling in the air.

  When the water absorption level WL rises and reaches the drainage start water level WL3, the impeller 66 starts pumping and begins to drain, but at this time, the other end 61b of the air / water mixing air introduction pipe 61 is opened without being submerged. Since the air is sucked into the casing 64 from the first opening 68 through the air / water mixing air introduction pipe 61 and the impeller 66 pumps up the air together with water, the amount of drainage is rated. Drainage is started in a state where it is lower than the amount of drainage, thereby starting the air-water mixing operation.

  In this air-water mixing operation state, when the water absorption level WL further rises and reaches the lowest water level WL1, the other end 61b of the air-water mixing air introduction pipe 61 that has been kept open until then is submerged. Since it is closed and air is not sucked from the first opening 68, drainage at the rated drainage amount is started, and thus, full operation is started.

  Thereafter, when the water absorption level WL starts to fall and falls below the lowest water level WL1, the other end 61b of the air / water mixing air introduction pipe 61 that has been kept closed until then is opened without being submerged. Inhalation of air into the casing 64 from the opening 68 is started, and the full-volume operation shifts to the air-water mixing operation.

  When the water-absorbing level WL is further lowered by the air-water mixing operation, the air suction amount gradually increases, and instead the water amount gradually decreases, so that the drainage amount gradually decreases. Then, when the water absorption level WL further decreases and falls below the drainage cutoff water level WL2, the other end 62b of the drainage cutoff air introduction pipe 62 that has been kept closed until then is opened without being submerged. As a result, air is also sucked into the casing 64 from the second opening 69 through the drainage blocking air introduction pipe 62, the mixing ratio of water and air becomes very high, and the impeller 66 can suck water. The drainage stops. That is, the operation is switched from the air / water mixing operation to the drainage cutoff operation.

  The preceding standby operation pump 63 as described above is disclosed, for example, in Patent Document 1 below.

JP 2010-121480 A

  However, in the conventional type, when the air is introduced into the casing 64 from the air / water mixing air introduction pipe 61 and drained in the air / water mixed state in the air / water mixing operation, the pump 63 is vibrated greatly. appear. If this vibration is left unattended, the pump 63 may be adversely affected, but there is a problem that it is difficult to reduce the vibration.

  An object of this invention is to provide the prior | preceding standby operation pump which can reduce the vibration at the time of air-water mixing operation.

In order to achieve the above object, the preceding standby operation pump according to the first aspect of the present invention has a casing having a suction opening at the lower end opened in the suction water tank, an impeller provided in the casing, and a water level in the suction water tank. An air / water mixing air introduction pipe for reducing the amount of drainage by draining in the air / water mixing state while introducing air into the casing below the impeller in the state below the first predetermined water level,
A resistor is provided below the impeller in the casing,
An opening communicating with the inside of the casing from the air / water mixing air introduction pipe is located upstream of the resistor in the swirling direction of the water swirling along the inner periphery of the casing.

  According to this, when the impeller rotates in a state where the water level in the suction water tank is equal to or lower than the first predetermined water level, air is introduced from the air-water mixing air introduction pipe into the casing through the opening, and the blade Since the car pumps up water while sucking in air together with water, the drainage is started in a state where the drainage amount is lower than the rated drainage amount, thereby starting the air-water mixing operation.

  In such a gas-water mixing operation, a swirling flow of water that swirls in the same direction as the rotation direction of the impeller is generated in the casing, and the swirling flow collides with the resistor, thereby causing a resistance opposite to the swirling direction. The pressure on the upstream side of the body is higher than the pressure on the downstream side. For this reason, the pressure on the upstream side of the resistor becomes resistance, and the air in the air / water mixing air introduction pipe hardly flows into the casing from the opening. Therefore, the air introduced into the casing from the opening through the air-water mixing air introduction pipe is introduced little by little without rapidly increasing or decreasing. Thereby, a big fluctuation | variation does not arise in an air-water mixing state, and a vibration is reduced.

In the preceding standby operation pump in the second invention, a plurality of resistors are provided in the circumferential direction in the casing,
A plurality of openings are provided corresponding to each resistor.

  According to this, since external air is gradually introduced into the casing through the plurality of openings through the air / water mixing air introduction pipe, the air / water mixing state is less likely to be changed, and vibration is further reduced. The

In the preceding standby operation pump according to the third aspect of the present invention, the resistor is formed in a ten shape when viewed from the rotational axis of the impeller and is provided in the casing.
According to this, vibration is further reduced.

  The preceding standby operation pump of the fourth invention introduces air into the casing below the impeller and drains the water when the water level in the suction tank is equal to or lower than a second predetermined water level lower than the first predetermined water level. It is provided with an air introduction pipe for blocking the drainage.

  According to this, when the water level in the suction water tank drops below the second predetermined water level, external air is introduced into the casing at once from the drainage air introduction pipe, and the mixing ratio of water and air becomes very high. The impeller can no longer suck in water, and drainage from the pump stops. Thereby, it can switch from an air-water mixing operation to drainage interception operation, and can prevent the vibration resulting from an air-water mixing state.

  As described above, according to the present invention, when the air-water mixing operation is performed, the water pressure upstream of the resistor becomes resistance, and the air in the air-water mixing air introduction pipe hardly flows into the casing from the opening. Therefore, external air is gradually introduced into the casing from the opening through the mixing air introduction pipe, thereby reducing vibration.

It is a longitudinal cross-sectional view of the advance standby operation pump in the 1st Embodiment of this invention. FIG. 2 is a plan view of the preceding standby operation pump. It is a cross-sectional view of a preceding standby operation pump. It is a XX arrow line view in FIG. It is a cross-sectional view of the preceding standby operation pump in the second embodiment of the present invention. It is a cross-sectional view of the preceding standby operation pump in the third embodiment of the present invention. It is a cross-sectional view of the preceding standby operation pump in the fourth embodiment of the present invention. It is a cross-sectional view of the preceding standby operation pump in the fifth embodiment of the present invention. It is a XX arrow line view in FIG. Flow coefficient and vibration of the preceding standby operation pump according to the fifth embodiment of the present invention, the preceding standby operation pump not provided with the resistor, and the preceding standby operation pump in which the resistor is positioned downstream as a comparative example. It is a graph which shows the relationship with ratio. It is a cross-sectional view of a preceding standby operation pump as a comparative example for comparison with the preceding standby operation pump of the fifth embodiment of the present invention. It is a longitudinal cross-sectional view of the conventional prior standby operation pump. It is a cross-sectional view of a preceding standby operation pump.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
First, a first embodiment will be described with reference to FIGS.

  Reference numeral 1 denotes a preceding standby operation pump. The preceding standby operation pump 1 is, for example, a vertical shaft pump that discharges water 3 such as rainwater that has flowed into a suction water tank 2 of a pump station. The casing 4 of the pump 1 includes a straight tubular pumping pipe 5, a pump casing 6 (a part of the casing 4) connected to the lower end of the pumping pipe 5, and a suction pipe 7 ( A part of the casing 4) and a discharge elbow 8 connected to the upper end of the pumping pipe 5. A suction port 9 that opens in the suction water tank 2 is formed at the lower end of the suction pipe 7.

  An impeller 11 is provided in the pump casing 6 via a rotatable main shaft 10. The impeller 11 is attached to the lower part of the main shaft 10. The upper end side of the main shaft 10 passes through the discharge elbow 8 and protrudes to the outside of the casing 4, and is connected to a rotary drive mechanism 12 made of an electric motor or the like.

  On the inner peripheral surface of the suction pipe 7, four (a plurality of) first resistor bodies 14 having a rib shape (flat plate shape) projecting inward in the radial direction are provided. In the present embodiment, these first resistors 14 are provided at intervals of 90 ° in the circumferential direction in the suction pipe 7 and are located below the impeller 11.

Further, the preceding standby operation pump 1 is provided with four (a plurality of) air / water mixing air introduction pipes 15 and one drainage blocking air introduction pipe 16.
Each air-water mixing air introduction pipe 15 is formed in an inverted U shape, and the impeller 11 is in a state where the water absorption level WL in the suction water tank 2 is equal to or lower than the lowest water level WL1 (an example of a first predetermined water level). The air-water mixing operation is to reduce the amount of drainage by draining (pumping) water while introducing air into the suction pipe 7 below. Further, a plurality of first openings 17 are formed in the suction pipe 7 so as to communicate with the inside of the suction pipe 7 from one end 15 a of each air / water mixing air introduction pipe 15. That is, one end 15 a of each air / water mixing air introduction pipe 15 is connected to each first opening 17.

  As shown in FIG. 3, these first openings 17 are located on the upstream side S <b> 1 in the swirling direction A of the water 3 swirling along the inner periphery of the suction pipe 7 with respect to each first resistor 14. is doing. The turning direction A is the same as the rotation direction of the impeller 11. Further, as shown in FIG. 1, the other end 15b of each air / water mixing air introduction pipe 15 is submerged and blocked when the water absorption level WL in the suction water tank 2 rises to the lowest water level WL1. Is provided.

  Further, the drainage cutoff air introduction pipe 16 is formed in an inverted U-shape, and performs an air-water mixing operation, so that the drainage cutoff level WL2 (first level) in which the water absorption level WL in the suction water tank 2 is lower than the minimum water level WL1. An example of the second predetermined water level) For a drainage cutoff operation in which the drainage is shut off by introducing air into the suction pipe 7 below the impeller 11 when it becomes below. A second opening 18 is formed in the suction pipe 7 so as to communicate with the suction pipe 7 from one end 16 a of the drainage cutoff air introduction pipe 16. That is, one end 16 a of the drainage blocking air introduction pipe 16 is connected to the second opening 18. As shown in FIG. 1, the other end 16b of the drainage cutoff air introduction pipe 16 is provided so as to be submerged and blocked when the water absorption level WL of the suction water tank 2 rises to the drainage cutoff water level WL2. ing. Further, a drainage start water level WL3 is set between the lowest water level WL1 and the drainage cutoff water level WL2.

Hereinafter, the operation method of the preceding standby operation pump 1 will be described.
As shown in FIG. 1, the pump 1 is started when the water absorption level WL in the suction water tank 2 rises to the drainage cutoff water level WL2 and the other end 16b of the drainage cutoff air introduction pipe 16 is submerged and closed. . As a result, the impeller 11 rotates via the main shaft 10 and the impeller 11 idles in the air until the water absorption level WL rises to the drainage start water level WL3.

  When the water absorption level WL rises and reaches the drainage start water level WL3, the impeller 11 starts pumping and starts draining. At this time, the pressure in each first opening 17 is lowered by the flow of the water 3 on the inflow side of the impeller 11 and becomes lower than the atmospheric pressure. Further, since the other end 15b of each air / water mixing air introduction pipe 15 is kept open without being submerged, the suction pipe 7 is passed through each air / water mixing air introduction pipe 15 through each first opening 17. Since air is sucked in and the impeller 11 pumps water (drainage) while sucking air together with the water 3, drainage is started with the drainage amount (pumped water amount) lower than the rated drainage amount. Is started.

  In such an air-water mixing operation, as shown in FIG. 3, a swirling flow 20 of water 3 swirling in the same direction as the rotation direction of the impeller 11 is generated in the suction pipe 7. By hitting each first resistor 14, the pressure on the upstream side S1 of each first resistor 14 facing the turning direction A becomes higher than the pressure on the downstream side S2. For this reason, the pressure on the upstream side S <b> 1 of each first resistor 14 becomes a resistance, and the air in each air / water mixing air introduction pipe 15 does not easily flow into the suction pipe 7 from each first opening 17. Become. Therefore, the air introduced into the suction pipe 7 from the first openings 17 through the air / water mixing air introduction pipes 15 is introduced little by little without rapidly increasing or decreasing. Thereby, a big fluctuation | variation does not arise in an air-water mixing state, and a vibration is reduced.

  In the air / water mixing operation state, as shown in FIG. 1, when the water absorption level WL further rises and reaches the lowest water level WL <b> 1, other air / water mixing air introduction pipes 15 that have been kept open until then. Since the end 15b is submerged and closed, and air is not sucked from each first opening portion 17, drainage at the rated drainage amount is started, and thus, full operation is started.

  Thereafter, when the water absorption level WL starts to fall and falls below the minimum water level WL1, the other end 15b of each air-water mixing air introduction pipe 15 that has been kept closed until then is opened without being submerged. The suction of the air from the first opening 17 into the suction pipe 7 is started, and the whole amount operation is shifted to the air / water mixing operation.

  Also in such an air-water mixing operation, the water pressure on the upstream side S1 of each first resistor 14 becomes resistance as shown in FIG. Since it is difficult for air to flow into the suction pipe 7 from the first openings 17, external air passes through the mixing air introduction pipes 15 and enters the suction pipe 7 from the first openings 17. It is introduced little by little, which reduces vibrations.

  When the water absorption level WL is further lowered by the air-water mixing operation, the air suction amount gradually increases, and instead the water amount gradually decreases, so that the amount of drainage (pumped water amount) gradually decreases. Then, as shown in FIG. 1, when the water absorption level WL is further lowered and falls below the drainage cutoff water level WL2, the other end 16b of the drainage cutoff air introduction pipe 16 that has been kept closed until then is submerged. Without being released.

  At this time, since the pressure of the second opening 18 is lowered by the flow of the water 3 on the inflow side of the impeller 11 and is lower than the atmospheric pressure, the second opening 18 is passed through the drainage cutoff air introduction pipe 16. The air is sucked into the suction pipe 7 from 18 at once, the mixing ratio of the air to the water 3 becomes very high, the impeller 11 cannot suck the water 3, and the drainage (pumped water) from the pump 1 is discharged. Stop. Thereby, it can switch from an air-water mixing operation to drainage interception operation (standby operation), and can prevent vibration resulting from an air-water mixing state.

(Second Embodiment)
Next, a second embodiment will be described with reference to FIG.
One rib-like (flat plate-like) second resistor 25 is provided on the inner peripheral surface of the suction pipe 7 so as to project radially inward. The second resistor 25 is located below the impeller 11. The second opening 18 is located on the downstream side S <b> 2 in the swirl direction A of the water 3 with respect to the second resistor 25.

Hereinafter, the operation of the above configuration will be described.
When the water absorption level WL is lower than the drainage cutoff water level WL2 and the other end 16b of the drainage cutoff air introduction pipe 16 is opened, air also enters the suction pipe 7 through the drainage cutoff air introduction pipe 16 from the second opening 18. Sucked into.

  At this time, the swirling flow 20 of the water 3 generated in the suction pipe 7 collides with the second resistor 25, so that the pressure on the downstream side S2 of the second resistor 25 facing the swirling direction A is upstream. The pressure is lower than the pressure on the side S1. For this reason, the air in the drainage blocking air introduction pipe 16 easily flows into the suction pipe 7 from the second opening 18. Accordingly, external air is introduced into the suction pipe 7 from the second opening 18 through the drainage shutoff air introduction pipe 16 at a stretch, and thus, from the air / water mixing operation to the drainage shutoff operation (standby operation). You can switch to

  In the second embodiment, the second resistor 25 is provided separately from the first resistor 14, but the second resistor 25 is not provided separately, and upstream of the first resistor 14. A first opening 17 is formed on the side S1, a second opening 18 is formed on the downstream side S2 of the first resistor 14, and the first resistor 14 is shared with the second resistor 25. May be.

  In the first and second embodiments, as shown in FIGS. 3 and 5, four first resistors 14, four air / water mixing air introduction pipes 15, and four first openings are provided. However, the present invention is not limited to four, four, and four, but a combination of the first resistor 14, the air / water mixing air introduction pipe 15, and the first opening 17. The number may be plural or singular other than the above. For example, the structure branched to the some 1st opening part 17 from one air-water mixing air introduction pipe | tube 15 may be sufficient.

  Moreover, in the said 1st and 2nd embodiment, although the 1st resistor 14 was made into the square flat plate shape, it is not limited to such a shape, Convex shape (such as resistance) ( For example, the cross-sectional shape may be a triangle or a circle).

  In the first and second embodiments, one drainage blocking air introduction pipe 16 and one second opening 18 are provided, but a plurality of them may be provided. In response to this, a plurality of second resistors 25 may be provided.

(Third and fourth embodiments)
In the first and second embodiments, as shown in FIGS. 3 and 5, the first resistor 14 is provided at a right angle or a substantially right angle with respect to a tangent line in contact with the inner peripheral surface of the suction pipe 7. However, as a third embodiment, as shown in FIG. 6, the first resistor 14 may be entirely inclined from the upstream side S1 toward the downstream side S2. As a fourth embodiment, as shown in FIG. 7, the first resistor 14 is bent, and the radially inner end of the first resistor 14 is partially separated from the upstream side S1 on the downstream side. You may make it incline toward S2.

(Fifth embodiment)
Next, a fifth embodiment will be described with reference to FIGS.
The resistor 28 is located below the impeller 11, is formed in a ten shape when viewed from the rotation axis 29 of the impeller 11, and is provided in the suction pipe 7. The resistor 28 has four end portions 28 a to 28 d attached to the inner peripheral surface of the suction pipe 7. Each first opening 17 is located on the upstream side S <b> 1 in the swirling direction A of the water 3 with respect to each end 28 a to 28 d of the resistor 28. The second opening 18 is located on the downstream side S <b> 2 in the swirl direction A of the water 3 with respect to any end 28 a of the resistor 28.

Hereinafter, the operation of the above configuration will be described.
In the air-water mixing operation, the swirl flow 20 of the water 3 generated in the suction pipe 7 collides with the resistor 28, whereby the upstream side S1 of each end portion 28a to 28d of the resistor 28 facing the swirl direction A. Becomes higher than the pressure on the downstream side S2. For this reason, the pressure on the upstream side S1 of each of the end portions 28a to 28d becomes resistance, and the air in each air / water mixing air introduction pipe 15 does not easily flow into the suction pipe 7 from each first opening 17. . Therefore, the air introduced into the suction pipe 7 from the first openings 17 through the air / water mixing air introduction pipes 15 is introduced little by little without rapidly increasing or decreasing. Thereby, a big fluctuation | variation does not arise in an air-water mixing state, and a vibration is reduced. In addition, since the resistor 28 in the fifth embodiment has a ten shape, it can also serve as a reinforcing member for the suction pipe 7, and thus the effect of improving the strength of the suction pipe 7 can be obtained. It is done.

  Further, when the water absorption level WL is lower than the drainage cutoff water level WL2 and the other end 16b of the drainage cutoff air introduction pipe 16 is opened, air is also sucked from the second opening 18 through the drainage cutoff air introduction pipe 16. 7 is sucked into.

  At this time, the swirling flow 20 of the water 3 generated in the suction pipe 7 collides with the resistor 28, so that the pressure on the downstream side S2 of the end portion 28a of the resistor 28 facing the swirling direction A becomes the upstream side S1. The pressure is lower than the pressure. For this reason, the air in the drainage blocking air introduction pipe 16 easily flows into the suction pipe 7 from the second opening 18, and therefore, the external air passes through the drainage cutoff air introduction pipe 16 to the second. The opening 18 is introduced into the suction pipe 7 at a stroke, whereby it is possible to quickly switch from the air / water mixing operation to the drainage cutoff operation (standby operation).

The graph shown in FIG. 10 shows the vibration ratio with respect to the flow coefficient of the pump 1, with the horizontal axis indicating the flow coefficient and the vertical axis indicating the vibration ratio. The flow coefficient and the vibration ratio are defined by the following relational expressions, respectively.
Flow coefficient = Flow rate per unit time / Rated flow vibration ratio = Actual vibration value / Maximum vibration value The larger the flow coefficient value, the more the flow rate per unit time of the pump 1, and the vibration ratio value A larger value indicates that the actual vibration of the pump 1 is more intense.

  Of the plurality of graphs G1 to G3, a graph G1 indicated by a dotted line is data of a pump not provided with the resistor 28 as shown in FIG. Graphs G2 and G3 are data of a pump provided with a ten-shaped resistor 28 as shown in FIG. According to this, it can be seen that the vibration of the pump provided with the resistor 28 is reduced as compared with the vibration of the pump not provided with the resistor 28.

  Further, in the graph G2 indicated by the solid line, as shown in FIG. 8 in the fifth embodiment, the first opening 17 is located on the upstream side S1 with respect to the end portions 28a to 28d of the resistor 28. This is the data when positioned. Furthermore, the graph G3 indicated by the alternate long and short dash line is for comparison when the first opening 17 is positioned on the downstream side S2 with respect to the end portions 28a to 28d of the resistor 28, as shown in FIG. It is data. According to this, the vibration of the pump (see FIG. 8) in which the first opening 17 is positioned on the upstream side S1 as shown in the graph G2, the downstream of the first opening 17 as shown in the graph G3. It can be seen that this is reduced compared to the vibration of the pump (see FIG. 11) located on the side S2.

  In the pump of the comparative example shown in FIG. 11, the pressure on the downstream side S2 of each end portion 28a to 28d of the resistor 28 facing the turning direction A is lower than the pressure on the upstream side S1, so that each gas Air in the water mixing air introduction pipe 15 easily flows into the suction pipe 7 from each first opening portion 17, and therefore, external air passes through the inside of the air / water mixing air introduction pipe 15. A large amount flows into the suction pipe 7 from the opening 17 at once. This is thought to increase the vibration of the pump.

  In the fifth embodiment, as shown in FIG. 8, four air / water mixing air introduction pipes 15 and four first openings 17 are provided, but the number is limited to four and four, respectively. It is not limited to these, and a plurality or a single number other than these may be used.

In the fifth embodiment, one drainage blocking air introduction pipe 16 and one second opening 18 are provided, but a plurality of each may be provided.
In each of the above embodiments, a plurality of air / water mixing air introduction pipes 15 and a plurality of first openings 17 are provided. However, a plurality of one ends 15a of one air / water mixing air introduction pipe 15 are provided. May be branched to be connected to the plurality of first openings 17.

  In each of the above embodiments, the air / water mixing air introduction pipe 15 and the drainage blocking air introduction pipe 16 are each formed in an inverted U shape, but are not limited to an inverted U shape, Any shape that can introduce air below a predetermined water level (minimum water level WL1, drainage cutoff water level WL2) may be used. For example, the air / water mixing air introduction pipe 15 and the drainage blocking air introduction pipe 16 are each formed in a straight tube shape, and air is introduced into and stopped from the air / water mixing air introduction pipe 15 and the drainage blocking air introduction pipe 16. A valve that can be freely opened and closed may be provided.

  In each of the above embodiments, the diameter of the air / water mixing air introduction pipe 15 and the diameter of the drainage blocking air introduction pipe 16 may be the same or different. The diameter of the air / water mixing air introduction pipe 15 is preferably set to about 0.07 to 0.13 times the diameter of the discharge side (discharge elbow 8) of the preceding standby operation pump 1.

  In each of the above embodiments, as shown in FIG. 1, the second opening 18 is formed at a position higher than the first opening 17, but at the same height as the first opening 17. It may be formed, or may be formed at a position lower than the first opening 17.

  Further, when a plurality of the first openings 17 or the second openings 18 are formed, the first openings 17 or the second openings 18 may all be formed at the same height. Alternatively, all may be formed at different heights.

DESCRIPTION OF SYMBOLS 1 Preliminary standby operation pump 2 Suction water tank 3 Water 4 Casing 9 Suction port 11 Impeller 14 First resistor 15 Air / air mixing air introduction pipe 16 Drainage cutoff air introduction pipe 17 First opening 28 Resistor 29 Rotation Axis WL Water absorption level WL1 Minimum water level (first predetermined water level)
WL2 Drainage cutoff water level (second predetermined water level)
S1 upstream

Claims (4)

A casing having a suction port opened at the lower end in the suction water tank, an impeller provided in the casing, and air in the casing below the impeller when the water level in the suction water tank is equal to or lower than the first predetermined water level. Equipped with an air / water mixing air introduction pipe that reduces the amount of drainage by draining in the air / water mixed state while introducing,
A resistor is provided below the impeller in the casing,
An opening communicating with the inside of the casing from the air / water mixing air introduction pipe is positioned upstream of the resistor in the swirling direction of the water swirling along the inner periphery of the casing. Standby operation pump. A plurality of resistors are provided in the circumferential direction in the casing,
The preceding standby operation pump according to claim 1, wherein a plurality of openings are provided corresponding to each resistor. The preceding standby operation pump according to claim 1, wherein the resistor is formed in a ten shape when viewed from the rotational axis of the impeller and is provided in the casing. Equipped with a drainage shutoff air introduction pipe that shuts off drainage by introducing air into the casing below the impeller when the water level in the suction water tank falls below a second predetermined water level lower than the first predetermined water level. The preceding standby operation pump according to any one of claims 1 to 3, wherein the preceding standby operation pump is provided.

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