JPH0861283A - Pumping plant - Google Patents

Abstract

PURPOSE: To relax the surge phenomenon to a water suction tank and the load fluctuation by a method wherein the positions of the impellers of a plurality of vertical shaft pumps installed in the water suction tank are vertically displaced from each other and a difference is produced between the drain starting levels of the plurality of the vertical shaft pumps. CONSTITUTION: The positions of impellers 1 of pumps No.1-No.3 are arranged in different height. Since a vertical shaft pump is started to drain water when a water level reaches the vicinity of the impeller 1, the drain starting water levels of the pumps No.1-No.3 are WL51-WL53, respectively. Namely, when a water level is raised owing to a flood to reach the WL51, the pump No.1 is started to drain water. In this case, the pumps No.2 and No.3 still maintain an idling state. When the water level is further raised to reach the WL52, the pump No.2 is started to drain water, and when it is raised up to reach the WL53, the pump No.3 is started to drain water. Since, in this way, transfer from the idling state, in order, to draining operation is effected, the rapid starting of drainage is prevented, the rapid lowering of the water level is also prevented, and the surge phenomenon is relaxed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a pump station for performing a stand-by standby operation of a vertical shaft pump for draining water discharged during rainfall, and more particularly to a pump station for providing a plurality of vertical shaft pumps in the same water tank.

[0002]

2. Description of the Related Art Generally, a vertical shaft pump in a conventional pumping station has a minimum water level that sucks air when the water level when the pump is submerged is below that, as described in JP-A-63-90697. A pump impeller is provided slightly above the pump specific part that is unique to the pump, and when the water level is lower than the lowest water level, the vacuum break breaks the pump into an idling state, causing water to drop and preventing drainage operation. Air is not entrained in the vortex and the vehicle is in standby operation ahead of time.

[0003]

However, in the above-mentioned prior art, when the preparatory standby operation is carried out while the water level is lower than the impeller position based on the rainfall information or the like, a plurality of vertical pumps are installed in the same water tank. No consideration has been given to the problem of installing the pump station to construct a pump station, and there is a problem that a surge phenomenon occurs in the water absorption tank. That is, when the vertical pump is operated in advance standby, it runs idle when the water level is low, but when the water level reaches the vicinity of the impeller, it starts draining rapidly. Therefore, if the impellers of multiple vertical pumps are placed at the same level in the same water absorption tank, and if those pumps are operated in advance standby based on the rainfall information, the water level in the water absorption tank will rise. When it reaches the vicinity of the impeller position, multiple pumps start draining all at once. Therefore, since the flow rate of a plurality of units is drained at once, a surge phenomenon occurs in the water absorption tank. Further, such a surge phenomenon in the water absorption tank causes an abrupt load change of the motor that drives the pump, and the load also suddenly increases in the power supply equipment, which is not preferable.

The problem to be solved by the present invention is to mitigate the surge phenomenon in the water absorption tank due to abrupt start of drainage in a pumping station where a plurality of vertical shaft pumps performing the preceding standby operation are installed in the same water absorption tank. is there.

[0005]

The above object is to provide an intake pipe, one end of which is connected to the inside of the casing below the pump impeller and the other end of which is open to the atmosphere. When the water level during pumping operation is lower than that, suction bell is provided. Multiple vertical shaft pumps that perform pre-standby operation from a water level lower than the water level equivalent to the lowest water level that sucks air from the mouse are installed in the same water absorption tank,
Further, it is achieved by shifting the positions of the impellers of the plurality of vertical shaft pumps from each other in the vertical direction so that the drainage start water levels of the plurality of vertical shaft pumps are different from each other.

[0006]

As described above, the positions of the impellers of the vertical shaft pumps are vertically shifted from each other, and the water discharge starting water levels of the vertical pumps are made different from each other. , It will be done in stages on a pump-by-pump basis.

As a result, it is possible to prevent all the plurality of preceding standby operation pumps from starting draining at the same time, so that the surge phenomenon in the water absorption tank can be alleviated. This can reduce a sudden increase in load on the power supply equipment.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of a pumping station according to the present invention. In this embodiment, three vertical shaft pump Nos. 1 to N
o. The case where 3 is installed in the same water absorption tank is shown. As shown in the drawings, these vertical shaft pumps are each connected to a suction bell 3 of a pump casing below a casing liner 2 of a pump casing 4 accommodating an impeller 1, and
A pumping pipe 5 and a discharge elbow 6 which are a part of the pump casing 4 are connected to the upper side. Also,
An intake hole 9 is provided near the lower part of the impeller 1, and the intake hole 9
The intake pipe 10 is connected to the intake pipe 10, and the intake pipe 10 is provided with an intake amount adjusting valve 11. In addition, 20 is a bottom wall of the water absorption tank.

In particular, each pump No. 1-No. The positions of the impellers 3 of 3 are arranged at different height positions.

The operation of the pumping station constructed as above will be described below. The vertical shaft pump starts draining (pumping) when the water level reaches the vicinity of the position of the impeller 1. 1 pump, No. 1 2 pumps, no. The drainage starting water levels of the 3 pumps are WL51, WL52, and WL5, respectively.
It becomes 3.

That is, the water level rises due to the water discharge and WL51
No. 1 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 reaches No. 53 when it reaches WL53. Three
Pump starts draining. Since the idling operation state is sequentially shifted to the drainage operation in this way, a rapid drainage start can be prevented, a rapid drop in water level can be avoided, and a surge phenomenon can be mitigated. In addition, rapid changes in load can be avoided.

Next, although not a characteristic part of the present invention, the operation of the intake hole 9, the intake pipe 10 and the intake amount control valve 11 will be described with reference to FIG.

The intake hole 9 is provided at a position where the intake hole 9 is not inhaled at the conventional lowest water level level, that is, at the lowest water level WL1 for sucking air from the suction bell 3 below this water level. This minimum water level is generally from the suction port of the suction bell to 1.4
It is said to be 1.7 times, and at a water level lower than that, stable suction operation cannot be performed due to the generation of air suction vortices.
The static pressure P (m) at the intake hole 9 is expressed by the following equation.

[0015]

[Equation 1]

Where Po: atmospheric pressure (10.3 m), Ba: saturated vapor pressure (0.3 m), L: distance from water surface to intake hole (m), hs: head loss of pump casing suction part (m) ), V: Flow velocity (m) of the handled liquid in the intake hole portion In the number 1, if the static pressure P in the intake hole 9 is larger than Po-Ba, intake is not performed. Therefore, if the relationship of the equation 2 is set, intake is not performed.

[0017]

[Equation 2]

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

[0019]

(Equation 3)

On the other hand, in the range B where the water level is lower than WL1, L decreases in the equation 1, so that P becomes smaller than atmospheric pressure and intake is performed. Since an appropriate amount of intake air is given by the intake air amount control valve 11, an appropriate amount of intake air is taken 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 amount is small and the flow rate of the pump is also slightly decreased. In this case, since the submersion depth S1 of the pump is sufficient for the pump flow rate at this time, no vortex occurs. When the water level is WL3, P decreases almost in proportion to the decrease in the water level, so P becomes smaller than atmospheric pressure by that amount, the intake amount increases, the flow rate of the pump also decreases significantly, and vortices also occur at the submersion depth S2. A flow rate that does not occur can be used. When the water level is WL4, the amount of intake air is 15% to 20% of the pump flow rate, and pumping is impossible, resulting in idling operation. The submersion depth S3 at this time is designed such that the suction bell inlet level is such that a vortex does not occur at the flow rate immediately before the pumping is disabled. The opening degree of the intake air amount control valve 11 is constant in the entire range where the water level changes. Vortices do not occur even at the conventional minimum water level WL1 or less, and safe operation without abnormal vibration or noise becomes possible. The flow rate of the pump is controlled to about half of the predetermined flow rate by intake air at a water level at which the impeller 1 is slightly submerged from idle operation to drain operation and at a water level slightly higher than the water level WL4 at which drain operation is changed to idle operation. Therefore, there is little change in the flow rate at the start and stop of drainage, the surge phenomenon can be alleviated, and stable operation of the pump is possible.

On the other hand, consider a situation in which the water level drops at the pumping station of FIG. When the water level reaches WL43, No.
Only 3 pumps first shift from drainage to idle
As the water level decreases below WL42 and WL41, N
o. 2 pumps, no. 1 Pump and shift to idle operation. Therefore, it is possible to prevent a sudden stop of drainage, prevent a sudden rise in the water level, reduce the surge phenomenon, and reduce the load fluctuation.

As described above, according to the embodiment shown in FIG. 1, when a plurality of vertical pumps are installed in the same water tank, the impellers of the vertical pumps are arranged with their positions vertically shifted to perform drainage operation. Since the starting water level is set to be different, when the water level rises due to flooding, drainage starts one by one as the water level rises.On the other hand, when the water level drops and shifts to standby operation, it also sequentially shifts to idle operation standby. . Therefore, since all the pumps do not perform drainage operation at the same time or shift to idling operation standby, surge phenomenon in the water absorption tank can be prevented and load fluctuation can be reduced, so stable operation can be performed. There is an effect.

[0023]

According to the present invention, the positions of the impellers of a plurality of vertical pumps installed in the same water absorption tank are vertically shifted so as to make a difference in the drainage operation start water level. Even if those vertical pumps are operated in advance standby, drainage is started one by one as the water level rises, and all pumps do not start draining operation at the same time, so surge phenomenon in the water absorption tank can be prevented. In addition, it is possible to reduce load fluctuations on the power supply equipment.

[Brief description of drawings]

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

FIG. 2 is a diagram for explaining the operation of the vertical pump of FIG. 1 embodiment.

[Explanation of symbols]

 1 Impeller 2 Casing Liner 3 Suction Bell 4 Pump Casing 5 Pumping Pipe 6 Discharge Elbow 9 Intake Hole 10 Intake Pipe 11 Intake Volume Control Valve 12 Suction Port

Claims (1)

[Claims] 1. An intake pipe having one end communicating with the casing below the pump impeller and the other end being open to the atmosphere,
If the water level during pumping operation is lower than that, a plurality of vertical pumps that perform a preliminary standby operation from a water level lower than the water level corresponding to the lowest water level that sucks air from the suction bell mouth are installed in the same water absorption tank, and A pumping station, wherein the vane wheel positions of a plurality of vertical shaft pumps are vertically displaced from each other so that the drainage starting water levels of the plurality of vertical shaft pumps are different from each other.