JP2000027786A - Vertical shaft pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the draining operation at a water level lower than the lowest water level without generating the harmful swirl by controlling the capacity of a pump in response to the water level. SOLUTION: In order to perform the advanced waiting operation at a water level lower than the lowest water level (WL 1), a vane 1 of the pump is arranged at a position lower than the lowest water level. A suction pipe 10 having one end always opened in the atmospheric air is communicated with the inside of a pump casing 4 under the vane 1, and when the pressure inside of the pump casing 4 is lowered in response to the lowering of the water level air is sucked into the pump casing through the suction pipe 10, and since the practical quantity of the pumped water of the pump is reduced in response to the sucked variable of the air, generation of harmful swirl can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vertical pump of a pumping station which performs a preparatory standby operation provided for draining water during rainfall, and which can also be used for pump management operation in normal times. About.

[0002]

2. Description of the Related Art A conventional apparatus is disclosed in JP-A-63-90697.
As described in the publication, when the water level at the time of submersion of the pump is lower than this, an impeller is provided at a position slightly above a pump specific part corresponding to the lowest water level for sucking air, and the lowest water level When the water level becomes lower than the corresponding water level, there is a type in which the vacuum is broken to make the wheel idle, and the water is dropped to prevent the drainage operation.

Further, as described in Japanese Patent Application Laid-Open No. 63-134897, when the storage capacity of the water absorption tank cannot be sufficiently secured against sudden fluctuations in the amount of rainwater, the pump is operated in a standby mode. In order to prevent the occurrence of inconvenience due to the air suction vortex that occurs when the water level falls below the minimum water level, the intake passage for supplying air is connected between the pump impeller and the bell mouth. Then, when the water level falls below the impeller inlet level, the intake valve provided in the intake passage is opened, and air is sent into the inlet of the impeller, thereby causing the water in the suction bellmouth to drop by vacuum breakage. It has been proposed that the pump be operated in the air.

[0004]

Normally, in order to perform the preliminary standby operation based on rainfall information or the like, it is necessary to start the drainage operation at the lowest possible water level in order to increase the storage effect of the water absorption tank and the sewer. It is desirable to set the flow rate to an appropriate value according to the water level in the water absorption tank, which is effective against vortex prevention and surge phenomenon in the water absorption tank, and enables stable operation of the pump.

However, in the former prior art, no consideration is given to draining operation at a water level lower than the minimum water level.
Drainage operation cannot be performed at a water level lower than the known minimum water level of 1.7 times.

Further, in the latter prior art, since the impeller is disposed above the minimum water level, even if the water level rises from a low water level, pumping starts until the impeller reaches the position. Therefore, the storage capacity of the water absorption tank cannot be sufficiently increased. Further, when the water level reaches the position of the impeller, pumping is suddenly started, and the load on the pump is rapidly increased, and the water level in the water absorption tank fluctuates greatly, causing a problem of surge phenomenon in the water absorption tank. Similarly, when the water level drops during pumping and drops below the minimum water level, the suction valve is opened and the vacuum at the suction bellmouth is broken, so pumping is suddenly stopped. This allows
The problem of surge phenomenon of the water absorption layer occurs.

An object of the present invention is to enable drainage operation at a water level lower than the minimum water level without generating harmful eddies.

[0008]

According to the vertical pump of the present invention, which solves the above-mentioned problems, the water level during the pumping operation is lower than the water level corresponding to the lowest water level at which air is sucked from the suction bell mouth. In a vertical shaft pump that performs preliminary standby operation from a low water level, an impeller of a pump disposed below a position corresponding to the lowest water level, one end is communicated with a pump casing below the impeller, and the other end is always open to the atmosphere. And a suction pipe.

In this case, a part of the intake pipe is provided with an intake air amount adjusting valve for adjusting the amount of intake air, and the other end of the intake pipe is opened to the atmosphere at the upper end in the water absorption tank. Can be provided.

[0010] A pipe having one end connected to the intake pipe and the other end connected to the discharge side of the pump casing, and a valve provided on the pipe may be provided. In this case, it is preferable to provide a discharge valve on the discharge side of the pump casing, and connect the other end of the pipe to the pump casing between the discharge valve and the impeller. Instead of this pipe, a water supply device for supplying water to the intake pipe and a pipe having one end connected to the intake pipe and the other end connected to the water supply apparatus may be provided.

[0011]

Since the position of the impeller of the pump is lower than the minimum water level, the preliminary standby operation with pumping can be performed even at a level lower than the minimum water level. Since the intake pipe is always open to the atmosphere, the water level at which the pressure at the position where the intake pipe communicates with the pump casing during operation of the pump (hereinafter, referred to as an intake pipe communication part) becomes equal to or higher than the atmospheric pressure. However, if the water level drops during the operation of the pump, the pressure in the intake pipe communication section decreases as the water level decreases, so that air is sucked into the intake pipe communication section via the intake pipe, and the amount of intake air Increases as the water level decreases, and the actual pumping rate of the pump decreases as the amount of intake air increases. In other words, if the water level drops, the pumping amount of the pump will decrease accordingly, so even if the water level is lower than the minimum water level, air can be sucked in through the intake pipe to prevent air from being drawn from the suction bell and pumping is possible. And abnormal vibration and noise can be prevented.

[0012] In addition, if the intake is performed at a water level equal to or lower than the minimum water level, the storage capacity of the water absorption tank can be fully utilized, and at the start of pumping and at the time of pumping stop, the pumping amount is controlled by the intake air. Since the flow rate is less than the flow rate, sudden start and stop of pumping can be mitigated, and surge phenomenon of the water absorption tank can be mitigated, so that stable operation can be performed.

If the height position of the communication portion of the intake pipe is set so as to start suction from the intake pipe into the pump casing below the water level corresponding to the minimum water level during the pumping operation of the vertical shaft pump, the minimum water level is obtained. When the water level reaches or exceeds the level, the intake is stopped, and the pumping with the normal pump capacity can be performed. In addition, since the intake pipe is always open to the atmosphere above the maximum water level, it does not sink into the water of the water absorption tank, preventing clogging and blockage of the water absorption pipe due to dust floating in the water, Stable intake operation can be secured.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, a suction bell 3 of a pump casing is connected to a lower part of a casing liner 2 of a pump casing 4 in which an impeller 1 is housed, and a pumping pipe, which is a part of the pump casing 4, is provided above. 5 and the discharge elbow 6 are connected to form a vertical pump. On the discharge side of the discharge elbow 6, a discharge pipe 7 and a discharge valve 8 are provided. In addition, an intake hole 9 is provided near the lower portion of the impeller 1, an intake pipe 10 is provided in connection with the intake hole 9, an intake air amount adjustment valve 11 is provided in the intake pipe 10, and an intake port of the intake pipe 10 is provided. Numeral 12 constitutes a flow control device installed in the water absorption tank. The intake hole 9 is provided at a position where the air is not sucked from the intake hole 9 at the conventional minimum water level, that is, at the minimum water level WL1 at which the air is sucked from the suction bell 3 below this water level. The static pressure P (m) at the intake hole 9 is represented by the following equation.

[0016]

(Equation 1)

Here, Po: atmospheric pressure (10.3 m), Ba: saturated vapor pressure (0.3 m), L: distance from the water surface to the intake hole (m), hs: pump head suction head loss head (m) ), V: Flow velocity (m) of the liquid handled in the suction hole portion In Formula 1, if the static pressure P in the suction hole 9 becomes larger than Po-Ba, suction is not performed. Therefore, if the relationship of Expression 2 is set, no intake is performed.

[0018]

(Equation 2)

That is, if the intake holes 9 are provided below the conventional minimum water level WL1 by the following equation 3, the water level becomes
Since the intake is not performed in the range A of WL1 or more, the drainage operation can be performed with a predetermined pump capacity.

[0020]

(Equation 3)

On the other hand, in the range B where the water level is lower than WL1, since L decreases in the equation (1), P becomes smaller than the atmospheric pressure, and air is taken. Since the intake amount is given an appropriate loss by the intake amount control valve 11, the intake amount is adjusted in accordance with the water level to control the flow rate. In range B, the water level is
In the case of WL2, since P is slightly lower than the atmospheric pressure, the intake air amount is small, and the flow rate of the pump is also slightly reduced. In this case, since the submersion depth S1 of the pump is sufficient for the pump flow at this time, no vortex is generated. When the water level is WL3, P decreases almost in proportion to the decrease in the water level, so that P becomes smaller than the atmospheric pressure, the intake air volume increases, the flow rate of the pump decreases significantly, and vortices occur even at the submergence depth S2. It can be a flow rate that does not occur. When the water level is WL4, the intake air amount becomes 15% to 20% of the pump flow rate, so that pumping is not possible and the idle operation state is set. The level of the inlet of the suction bell is designed so that the immersion depth S3 at this time has a length that does not generate a vortex at the flow rate immediately before the pumping becomes impossible. Note that the opening of the intake air amount control valve 11 is constant in the entire range in which the water level fluctuates. Even at a level lower than the conventional minimum water level WL1, no vortex is generated, and safe operation without abnormal vibration or noise can be performed. At the water level where the impeller 1 that shifts from idling operation to drain operation is slightly submerged and at the water level slightly higher than the water level WL4 that shifts from drain operation to idle operation, the flow rate of the pump is controlled to about half of the predetermined flow rate by suction. Therefore, the change in flow rate at the start and the end of drainage is small, the surge phenomenon can be reduced, and the pump can be operated stably. In addition, 20 is a bottom wall of the water absorption tank.

FIGS. 2 and 3 show an embodiment in which a plurality of vertical shaft pumps shown in FIG. 1 are installed. FIG. 2 shows an example in which the impeller positions of the respective pumps are provided at the same level. In this case, although the surge phenomenon is alleviated by controlling the flow rate of each pump as described above, the drainage start water level WL5 and the drainage stop water level WL4 are the same for all the pumps, and the flow rates of a plurality of pumps are simultaneously controlled. Drainage or drainage is stopped, and the surge phenomenon of the water absorption tank may become a problem. Further, a sudden load change may adversely affect the power supply equipment.

FIG. 3 is an improved example of the example of FIG. 2. In this embodiment, each pump is located at a different position of the impeller, and the drain start water level and the drain stop water level of each pump are different. . No. No. 1 pump, No. No. 2 pump, No. Three
The pump drain start water level and drain stop water level are WL
51, WL41, WL52, WL42, WL53, WL
43. When the water level rises due to flooding and reaches WL51, No. One pump starts draining. At this time, No. 2,
No. The three pumps are still idling. When the water level further rises and reaches WL52, No. No. 2 pump starts draining, and when it reaches WL53, No. 3 pumps start draining. In this way, the state is sequentially shifted from the idling operation state to the drainage operation, so that abrupt drainage can be prevented, a rapid drop in water level does not occur, and a surge phenomenon can be mitigated. Further, a sudden change in load can be avoided. On the other hand, considering the situation where the water level decreases, when the water level becomes WL43, No. Only the three pumps shift from the drain operation to the idling state first, and the following WL42, W
No. L41 as the water level decreased. 2 pumps, N
o. Shift to one pump and idling operation state. Therefore, a sudden stop of drainage can be prevented, a rapid rise in water level does not occur, a surge phenomenon can be mitigated, and a load fluctuation can be mitigated. As described above, since the surge phenomenon and the load fluctuation can be reduced, the pump can be stably operated.

Next, with reference to FIG. 4, a method of backwashing with the self liquid when the intake pipe 10 is blocked by foreign matter such as dust will be described. An intake pipe 1 is provided to a vertical pump having a configuration as shown in FIG.
0 and the discharge pipe 7 of the pump casing were connected by a pipe 14, and the pipe 14 was provided with a valve 13. In a state where the water level is equal to or higher than the drainage start water level WL5, the discharge valve 8 is throttled within a range where the prime mover of the pump does not overload. At this time, the normally closed valve 13 is opened, and high-pressure water of the pump is caused to flow through the intake pipe 10 so that the intake pipe 1 is closed.
Foreign matter stuck in 0 can be backwashed. In FIG. 4, the intake pipe 10 and the discharge pipe 7 are connected by a pipe, but the intake pipe 10 and the discharge elbow 6 of the pump casing may be connected.

Next, a backwash method using tap water, treated water, filtered water, or the like when the intake pipe 10 is blocked by foreign matter such as dust will be described with reference to FIG. In a vertical shaft pump as shown in FIG. 1, a part of an intake pipe 10 and a water supply device 15 are connected by a pipe 14 and a valve 13 is provided in the pipe 14. At this time, the water level may be in any state. Water is fed from the water supply device 15, the normally closed valve 13 is opened, and high-pressure water flows from the water supply device 15 to the water suction pipe 10, so that foreign substances in the suction pipe 10 can be backwashed.

As described above, according to the vertical shaft pump of the present invention, automatic and appropriate suction can be performed in accordance with the water level, so that the "pump suction portion loss +
The drainage operation can be performed to a water level as low as the distance of the “intake hole section velocity head”, and vortex generation and air entrapment from the lower end of the suction bell can be prevented. In addition, since sudden start and stop of drainage can be alleviated, surge phenomenon of the water absorption tank can be alleviated, and stable pump operation can be performed.

In the embodiment shown in FIG. 1, since the suction port of the suction pipe is opened to the atmosphere above the water absorption tank, the odor in the water absorption tank does not leak to the air above the pump through the suction pipe. Also, even if the handling liquid flows backward from the intake pipe due to an erroneous operation of the operation, it does not leak to the outside.

In the embodiment shown in FIG. 3, when a plurality of pumps are installed, the positions of the impellers of the vertical shaft pumps are shifted vertically so as to make a difference in the water level at which the drainage operation starts. When the water level rises due to flooding, drainage is started one by one in accordance with the rise of the water level. When the water level falls and the system shifts to the standby operation, the system sequentially shifts to the idling operation standby. Therefore, all pumps perform drainage operation at the same time,
Since it does not shift to the idling operation standby, the surge phenomenon of the water absorption tank can be prevented, and the load fluctuation can be reduced.
There is an effect that stable operation can be performed.

According to the embodiment shown in FIG. 4, when the suction pipe is blocked by foreign matter such as dust, the pump can be backwashed with high-pressure water by operating the pump with the discharge valve closed or throttled. This has the effect that foreign matter in the intake pipe can be easily removed.

In the embodiment shown in FIG. 5, when the intake pipe is clogged with foreign matter such as dust, high pressure water is supplied from the water supply device to the water supply device, so that the embodiment shown in FIG. Foreign matter can be removed, and backwashing of the intake pipe is possible regardless of the water level of the water absorption tank.

In the embodiment shown in FIG. 4, since the intake pipe is backwashed with its own liquid, there is an effect that the apparatus can be simplified.

[0032]

According to the present invention, drainage operation can be performed at a water level lower than the minimum water level without generating harmful swirls.

[Brief description of the drawings]

FIG. 1 is a side view showing an embodiment of a vertical pump according to the present invention.

FIG. 2 is a side view of an embodiment of a pumping station provided with a plurality of other embodiments of the vertical pump according to the present invention.

FIG. 3 is a side view showing a pumping station according to the embodiment of FIG. 2;

FIG. 4 is a side view showing still another embodiment of the vertical pump according to the present invention.

FIG. 5 is a side view showing a modification of the embodiment of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Impeller 2 Casing liner 3 Suction bell 4 Pump casing 5 Pumping pipe 6 Discharge elbow 7 Discharge pipe 8 Discharge valve 9 Intake hole 10 Intake pipe 11 Intake amount adjustment valve 12 Suction port 13 Valve 14 Pipe 15 Water supply device

Claims (3)

[Claims] 1. A vertical shaft pump that performs a preliminary standby operation from a water level lower than a water level corresponding to a minimum water level at which air is sucked from a suction bell mouth when a water level during a pumping operation is lower than the lowest water level. A pump impeller disposed below the corresponding position, and an intake pipe having one end communicating with the inside of a pump casing below the impeller and having the other end constantly open to the atmosphere, and A vertical shaft pump wherein a height position at which the intake pipe communicates with the inside of the pump casing is set so that the intake pipe draws air into the pump casing at a water level equal to or lower than a minimum water level. 2. The vertical shaft pump according to claim 1, wherein
A vertical shaft pump wherein the other end of the intake pipe is provided at a position equal to or higher than the highest water level in the water absorption tank and is always open to the atmosphere. 3. A vertical axis pump which performs a preliminary standby operation from a water level lower than a water level corresponding to a lowest water level at which air is sucked from a suction bell mouth when the water level during the pumping operation is lower than the lowest water level. A vertical shaft pump comprising: a pump impeller disposed below a corresponding position; and an intake pipe having one end communicating with the inside of a pump casing below the impeller and having the other end always open to the atmosphere.