JP2909497B2 - Pump station - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pumping station having a plurality of vertical shaft pumps which are operated on standby in order to drain water during rainfall.

[0002]

2. Description of the Related Art As described in Japanese Patent Application Laid-Open No. 63-90697, a vertical shaft pump used in a conventional pumping station has a water level when the pump is submerged below the water level corresponding to a minimum water level for sucking air. An impeller is provided slightly above the pump specific part specific to the pump to be pumped, and when the water level becomes lower than the water level corresponding to the minimum water level, the pump is idled due to vacuum break, and the water is dropped to prevent drainage operation. There is something.

[0003]

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, the above-mentioned prior art does not consider draining operation at a water level lower than the minimum water level, and for example, a known minimum water level of 1.4 to 1.7 times the diameter from the suction port of the suction bell. Drainage operation cannot be performed at a water level lower than the level.

[0005] In particular, when a plurality of vertical pumps are installed in the same water absorption tank to perform preparatory standby operation, when the water level rises and reaches near the impeller position, the plurality of vertical pumps are activated. Since the drainage is started all at once, the water level in the water absorption tank changes rapidly, causing a surge phenomenon in the water absorption tank. In addition, a sudden load change causes a problem on power supply equipment.

An object of the present invention is to control the flow rate of a pump according to a water level lower than the minimum water level, thereby enabling a drain operation at a water level lower than the minimum water level without generating a harmful vortex. Another object of the present invention is to reduce the surge phenomenon of the water absorption tank.

[0007]

Pump station of the present invention to solve the above problems BRIEF SUMMARY OF THE INVENTION The other end one end of which communicates with the impeller below the pump casing is opened to the atmosphere, the pump luck
During rolling an intake pipe and the one end and the other end is Ru is always communicating state, the water level in the pumping operation, the lower, corresponding to the lowest water level that would sucks air from the suction bell mouth A plurality of vertical shaft pumps that perform preliminary standby operation from a water level lower than the water level are installed in the same water suction tank, and the impellers of the plurality of vertical shaft pumps are arranged at the same height position, and correspond to the minimum water level. It is characterized by being arranged below the position.

In this case, the height position at which the intake pipe communicates with the inside of the pump casing is set to a position at which suction starts from the intake pipe into the pump casing below a water level corresponding to the lowest water level during the pumping operation of the vertical shaft pump. Is preferred. For example, the distance from the water level corresponding to the lowest water level to the height position at which the intake pipe communicates with the inside of the pump casing is the sum of the head loss at the pump suction part and the velocity head at the communication part of the intake pipe. It is preferable to set it equal to or smaller than the sum.

[0009]

During operation of the pump, the pressure in the intake pipe communication section decreases as the water level decreases, so that the amount of intake air sucked into the intake pipe communication section via the intake pipe increases as the water level decreases. Therefore, the actual pumping amount of the pump decreases as the intake air amount increases. In other words, if the water level decreases, the pumping amount decreases accordingly, preventing air from being drawn in from the suction bell even at a water level lower than the minimum water level, enabling pumping and preventing abnormal vibration and noise. it can.

When the water level rises during the preceding standby operation to start pumping, or when the water level drops during pump operation and pumping stops, the pumping amount is controlled by the intake air and is smaller than a predetermined flow rate. The sudden start and stop of pumping can be reduced. As a result, the surge phenomenon of the water absorption tank can be reduced, and stable operation can be performed. In particular, the effect of alleviating the sudden pumping start and stop is effective when a plurality of vertical pumps are installed at the same level, thereby reducing the surge phenomenon and the sudden increase / decrease of the load on the power supply equipment. .

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 water level is minimized. Above the water level,
Position one end of the intake pipe communicates with the pump casing (hereinafter, referred to. Intake pipe communicating portion) pressure is above atmospheric pressure. Therefore, when the water level is equal to or higher than the minimum water level, no suction is performed, and water can be pumped with normal pumping capacity. However, if the water level is lower than the minimum water level, the pressure in the intake pipe communication section decreases as the water level decreases.Therefore, the amount of intake air sucked into the intake pipe communication section via the intake pipe depends on the decrease in the water level. And the same operation as described above is obtained.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows an embodiment of a pumping station according to the present invention. In this embodiment, three vertical pumps having the structure shown in FIG. 2 are installed in the same water absorption tank. As shown in FIG. Reference numerals 1 to 3 respectively denote a suction bell 3 of the pump casing connected to a lower side of the casing liner 2 of the pump casing 4 housing the impeller 1 and a pumping pipe 5 which is a part of the pump casing 4 to the upper side. The discharge elbow 6 is connected. 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, and an intake amount adjusting valve 11 is provided in the intake pipe 10. Further, the impeller positions of the respective vertical shaft pumps are arranged at the same height position, and are arranged below a position corresponding to the lowest water level. In addition, 20
Is the bottom wall of the water absorption tank.

The operation of the pump station constructed as described above will be described below. The vertical shaft pump starts draining (pumping) when the water level reaches near the position of the impeller 1. No. 1 pump, No. No. 2 pump, No. The drainage start water level WL5 of the three pumps is the same, and the drainage stop water level W
L4 is the same. If there is no intake pipe 10, when the water level rises due to water discharge and reaches WL5, all the vertical pump Nos. Nos. 1 to 3 start the drainage by shifting from the idling operation state to the drainage operation. On the other hand, considering the situation where the water level decreases, when the water level decreases to WL4, all the vertical pumps N
o. Nos. 1 to 3 shift to the idling operation state and stop drainage.

The fact that the present embodiment can reduce the surge phenomenon of the water absorption tank due to the sudden start of pumping and the like will be described with reference to the intake hole 9, the intake pipe 10, and the intake amount control valve 11, which are characteristic parts of the present invention. This will be described with reference to FIG.

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 below which the air is sucked from the suction bell 3. This minimum water level is generally from the inlet of the suction bell to 1.4 to its diameter.
At a water level lower than 1.7 times, it is said that an air suction vortex is generated and stable drainage operation cannot be performed.
The static pressure P (m) at the intake hole 9 is represented by the following equation.

[0017]

(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.

[0019]

(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.

[0021]

(Equation 3)

On the other hand, in the range B in which the water level is lower than WL1, since L decreases in 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 occurs. When the water level is WL3, P decreases almost in proportion to the decrease of 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 particular, as shown in FIG. The effect when 1-3 are installed is large.

On the other hand, consider a situation where the water level in the pumping station of FIG. 1 is reduced. When the water level becomes WL4, all vertical pump Nos. 1 to 3 shift from the drain operation to the idling state. However, if the water level decreases, the pressure in the communicating portion of the intake pipe 10 decreases as the water level decreases.
The amount of intake air sucked into the intake pipe communication portion through 0 increases as the water level decreases. Therefore, the actual pumping amount of the pump decreases as the water level decreases.
In addition, even at a water level lower than the minimum water level, air is prevented from being trapped from the suction bell, water can be pumped, and abnormal vibration and noise can be prevented.

As described above, at the start of pumping and at the time of pumping stop, the pumping amount is controlled by the intake air and is smaller than the predetermined flow rate.
Surge phenomenon of the water absorption tank can be mitigated, and stable operation can be performed. In particular, the effect of alleviating the sudden pumping start and stop is effective when a plurality of vertical pumps are installed at the same level, thereby reducing the surge phenomenon and the sudden increase / decrease of the load on the power supply equipment. .

[0025]

According to the present invention, an impeller is provided below the lowest water level, an intake port is provided in a pump casing below the impeller, and an intake pipe is connected to the intake port. Since the suction port is opened to the atmosphere, the suction flow rate of the pump can be controlled according to the water level in the water absorption tank.As a result, no vortex is generated even at a water level lower than the conventional minimum water level at which the vortex starts to occur. Since the drain operation can be continued, the preceding standby operation can be stably performed.

In particular, according to the present invention, the start of pumping and the stopping of pumping are gradually performed by the suction action, so that the surge phenomenon of the water suction tank and the sudden increase or decrease of the load on the power supply can be mitigated. This is effective when installing a plurality of vertical pumps.

[Brief description of the drawings]

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

FIG. 2 is a view for explaining the operation of the vertical pump of the embodiment shown in FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Impeller 2 Casing liner 3 Suction bell 4 Pump casing 5 Pumping pipe 6 Discharge elbow 9 Suction hole 10 Suction pipe 11 Suction volume adjustment valve 12 Suction port

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F04D 13/00 F04D 15/00

Claims (3)

(57) [Claims] 1. A one end in the impeller below the pump casing is communicated with the other end is opened to the atmosphere, during pump operation
Comprises an intake pipe and the one end and the other end is Ru is always communicating state, the water level in the pumping operation, the lower, less than the water level corresponding to the lowest water level that would sucks air from the suction bell mouth A plurality of vertical shaft pumps that perform preliminary standby operation from the water level are installed in the same water absorption tank, and the impellers of the vertical shaft pumps are arranged at the same height position,
A pump station arranged below a position corresponding to the minimum water level. 2. The pump station according to claim 1, wherein
A height position at which the intake pipe communicates with the inside of the pump casing is set to a position at which suction starts from the intake pipe into the pump casing at a water level equal to or lower than the minimum water level during the pumping operation of the vertical shaft pump. Pumping station. 3. The pump station according to claim 1 , wherein
The height position at which the intake pipe communicates with the inside of the pump casing is defined as a distance from a water level corresponding to the lowest water level, the sum of a loss head of a pump suction part and a velocity head at the communication part of the intake pipe. A pump station characterized in that it is set equal to or smaller than the sum.