JP2972298B2 - Vertical pump - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a vertical pump installed in a water absorption tank,
In particular, the pumping operation is enabled even when the water level in the water absorption tank is low, and is suitable as, for example, a vertical shaft pump that performs a preliminary standby operation provided for draining water during rainfall,
The present invention relates to a pump that can be used for a pump management operation in normal times.

[Prior art] With the progress of urbanization in recent years, the amount of inflow to the rainwater drainage pump station has rapidly increased due to an increase in rainwater impervious area and the like. For this reason, in the event of rainfall, a preparatory standby operation type vertical shaft pump that predicts the amount of water flowing into a pump station and the arrival time in advance and operates the pump from a state where the pump well water level is lower than a specified water level has been put to practical use.

As described in Japanese Patent Application Laid-Open No. 63-90697, this type of conventional vertical shaft pump has a pump-specific water pressure level corresponding to the lowest water level (LWL) below which the water is sucked when the pump is submerged. An impeller is provided at a position slightly higher than the pump specific portion, and when the water level becomes lower than the water level corresponding to the above minimum water level, a vacuum break is performed to make the wheel idle, and the water is dropped to prevent drainage operation. .

Another conventional vertical shaft pump is disclosed in
As described in Japanese Patent Publication No. 0097, the impeller is located at a position lower than the water level of the water absorption tank, a through hole is provided near the inlet of the impeller, and the through hole is connected to a pipe. It is known that the other end is provided with an opening in a water absorption tank near a level where the impeller is submerged.

Further, as another conventional example, there is one disclosed in Japanese Utility Model Laid-Open No. 2-4993. This is because, when the pump is in air, the vertical shaft pump may vibrate when the bearings are not supplied with water. A vibration damper is provided, and the shaft is pressed against a bearing by centrifugal force of the vibration damper as the shaft whirls, thereby suppressing vibration.

[Problems to be solved by the invention]

Normally, in order to perform the preliminary standby operation based on rainfall information and the like, since the storage effect of the water suction tank and the sewer increases, it is desirable that the drainage operation can be performed at the lowest possible water level,
In addition, setting the flow rate to an appropriate value according to the water level in the water absorption tank is effective in preventing vortices and reducing surges in the water absorption tank, and enables stable operation of the pump.

However, among the above prior arts, Japanese Unexamined Patent Publication (Kokai) No. 63-90697 and Japanese Utility Model Laid-Open No. 2-4993 do not consider draining operation at a water level lower than the minimum water level. The drainage operation cannot be performed at a water level lower than the known minimum water level of 1.4 to 1.7 times the water level.

According to the conventional technique described in Japanese Unexamined Utility Model Application Publication No. 63-15097, if the water level of the water absorption tank falls below the level of the opening, air is sucked in from the opening, and the pumping action of the pump gradually decreases as the water level decreases. Therefore, the pumping operation can be performed at a low water level, and the transition to the idling state does not suddenly occur.For example, the pump idles and waits before a sudden inflow into the water suction tank occurs. It seems that this is suitable for a pump that performs a so-called advance standby operation.

In this type of vertical pump, the lower the water level in the water absorption tank, the higher the intake air volume from the through hole provided in the suction bell mouth, and the lower the drain water volume. This is difficult to perform, and the imbalance force between the air and water in the impeller causes the imbalance force to be greater than in conventional pumps. In addition, the water level during the drainage operation with the intake air is considerably lower than that during the normal drainage operation of the pump. Therefore, the submerged portion of the pump casing is small, and the damping performance is reduced. Therefore, it has been found that there is a problem that vibration is generated due to the fact that stable intake is not performed during the intake operation, the volume imbalance between the air and water in the impeller, and the reduction in vibration damping of the pump. In particular, when the natural frequency of the pump is close to the rotation speed of the pump, there is a problem that resonance occurs and very large vibration occurs.

SUMMARY OF THE INVENTION An object of the present invention is to provide a vertical shaft pump capable of suppressing vibration generated during an intake operation in which a drain operation is performed while performing intake.

Another object of the present invention is to adjust the natural frequency of the pump so that the natural frequency of the pump body does not resonate with the rotational speed of the pump in order to suppress the vibration that occurs during the suction operation in which the drain operation is performed while suctioning air. It is an object of the present invention to obtain a vertical shaft pump that can perform the operation.

[Means for solving the problem]

In order to achieve the above object, the vertical pump according to the present invention is provided such that the water level during the operation of the pump is below the position corresponding to the lowest water level (LWL) below which the air is sucked from the suction bell mouth of the pump casing. The pump impeller, the suction hole provided in the pump casing below the impeller, and one end connected to the suction hole and the other end open to the atmosphere at a level higher than the maximum water level of the pump suction tank. A suction pipe provided in the pump casing and located below the suction hole and acting as a resistance to water in the water absorption tank, wherein the vibration damping body is a plurality of dividable members. It is characterized in that the weight of the vibration damper can be changed to thereby prevent resonance.

Another feature of the present invention is that the impeller of the vertical shaft pump is located below a position where the water level during the operation of the pump is less than or equal to a minimum water level at which the air is sucked from the suction bell mouth of the pump casing. An intake hole is provided in a pump casing below the impeller, an intake pipe having one end connected to the intake hole and the other end opened to the atmosphere is provided, and the thickness of the suction bell mouth is reduced by a pump casing other than the suction bell mouth. The vertical pump is configured to be larger than the wall thickness.

[Action]

Since the damping member is provided at a position lower than the intake hole, the damping member is always immersed in water even during an intake operation in which vibration is likely to occur. Therefore, when the pump main body vibrates, the vibration damper also vibrates at the same time, and receives a large resistance of water, so that a vibration damping action is generated. Therefore, an action of suppressing the pump vibration generated during the intake operation by the vibration damper is obtained.

In addition, by configuring the vibration damping body with a plurality of dividable members, the natural frequency of the lower part of the pump casing can be adjusted, and the natural frequency of the pump body is reduced due to a decrease in the water level in the storage tank. Therefore, the occurrence of resonance can be prevented.

In addition, by increasing the thickness of the suction bell mouth and increasing its weight, the natural frequency of the suction bell mouth can be changed and resonance can be avoided.

〔Example〕

Hereinafter, an embodiment of a vertical pump according to the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of the present invention and is a sectional view showing the structure of a bowl portion of a vertical stand-by type vertical shaft pump. A suction bell mouth 3 of the pump casing is connected below the casing liner 2 of the pump casing 4 containing the impeller 1.

An intake hole 5 is provided near the lower portion of the impeller 1, an intake pipe 6 is provided in connection with the intake hole 5, and an intake air amount adjusting valve (not shown) is provided at the other end of the intake pipe 6. Forming a control device.

Further, a plurality of vibration dampers 7 are attached to the bell mouth 3 so as to be located from the vicinity of the intake hole 5 to a lower portion, and the bell mouth 3 acts as a resistance to water in the water absorption tank and suppresses vibration. I have.

Now, when the water level in the water absorption tank drops and the water level when the pump is submerged is below this level, the minimum water level (LW
L) The intake air amount is adjusted so that the intake port 5 becomes negative pressure when it becomes less than or equal to L). When the water level falls below the LWL, air starts to be sucked in from the intake hole 5, and the inside of the impeller 1 enters an intake operation state in which a mixed flow of water and air is formed. For this reason, the unbalance force increases, and in the conventional pump, during the intake operation, the number of submerged parts is reduced, and the resistance to water is reduced, and the pump is liable to vibrate. On the other hand, in the present invention, even at the lowest water level (LWL), the resistance to water is large because the damping body 7 is immersed in the underwater part, and the water acts as a cushioning material to produce a vibration damping effect. Vibration can be suppressed even if the balance force is somewhat large.

This is because, as shown in FIGS. 2 and 3, when the underground part of the vertical pump (the part below the pump mounting position) vibrates in the primary mode, the water level becomes low and the length of the submerged part of the pump is reduced. When l decreases, the damping effect due to the resistance of the water to the vibration of the pump, that is, the damper effect, decreases. Therefore, vibration is likely to occur, and the amplitude increases. In order to prevent this, in this embodiment, the vibration is reduced by providing a resistor (vibration damper) for vibration in water in the submerged part under the pump casing.

This damping body is not a mere rib which is necessary for the bellmouth in terms of strength, and as shown in FIG. 1, it is required to have a size of 1.5 to 2 times or more the diameter of the intake hole 5 of the bellmouth. is there.

FIGS. 4 and 5 show a modification of the embodiment of FIG. 1 of the present invention, in which a vibration damper 7 is mounted below the suction bell mouth 3 and flows into the impeller. This shows an embodiment in which a rectifying plate 8 for rectifying the flowing water is provided. As shown in FIG. 5, the current plate 8 is arranged in a cross shape.
It is supported by the four columns 7a, and the bellmouth 3 is
Mounted on

When the water level decreases and the intake starts, the flow at the inlet of the impeller is not always uniform. Depending on the suction conditions, turbulence may occur, resulting in instability of the amount of air suction and imbalance of water and air in the impeller. Vibration increases. In this embodiment, since the damper having the rectifying plate 8 is suspended from the bell mouth 3, the flow near the impeller inlet is rectified, the intake air amount is stabilized, and the vibration can be reduced.

 This damping effect has been confirmed by model tests and the like.

Further, as in the above-mentioned embodiment, when the pump vibrates, the vibration damping body having the flow regulating plate 8 also acts as a resistance to water and also performs a vibration reducing action.

In addition, the leading standby operation type vertical shaft pump has a wider operation range than the conventional pump, and the width of the maximum operation water level and the minimum operation water level is wide, so the submersion depth changes depending on the water level, and the natural frequency of the underground part below the pump support changes I do. For this reason, the rotation speed and the natural frequency are more likely to coincide with each other than in the conventional pump, and there is a possibility that the vibration will increase due to resonance when the imbalance force at the time of air suction is superimposed. In the present invention, since the vibration damper 7 is composed of a plurality of members, for example, by changing the number of mounting plates 9 or changing the number and thickness of the columns 7a, the superposition is changed, the natural frequency is adjusted, and resonance occurs. I try to avoid it. In this embodiment, the current plate 8a is connected to the suction bell mouth 3
The rectification and vibration damping effects of the blade inlet are also provided inside the blades, thereby further improving the vibration reduction effect.

FIG. 6 shows an embodiment in which the vibration damper 7 is provided with a strainer 10 for the water flowing into the impeller. The strainer 10 is attached to a lower part of the bell mouth 3. In the present embodiment, at a pumping station where there is a large amount of dust, dust is removed, and vibration is reduced by imparting vibration damping properties by the resistance of water in the strainer 10.

In both of the embodiments shown in FIGS. 7 and 8, resonance is avoided by changing the weight on the suction side.

FIG. 7 shows an example of adjusting the natural frequency by increasing the thickness and increasing the weight of the bell mouth 3.

FIG. 8 shows that a plurality of plates 11 are placed on the bell mouth 3 and
The natural frequency is adjusted by adjusting the weight.

FIG. 9 is an overall view of a vertical shaft pump showing still another embodiment of the present invention.
It is configured so that it can be fixedly mounted to 12. The intake pipe 6 can be of a different thickness, and the natural frequency of the underground part of the pump can be changed by the intake pipe. Therefore, the intake pipe 6
By changing the number or thickness of the bell mouth, the rigidity and weight of the bell mouth can be changed to adjust the natural frequency, thereby avoiding resonance and reducing vibration. Further, it is possible to always apply a tensile force to the intake pipe 6 and adjust the natural frequency according to the magnitude of the tensile force by providing a plurality of intake pipes in the circumferential direction of the bell mouth.

As described above, according to the present embodiment, even at the lowest operating water level (LWL), the damping body is present in the submerged portion, and the structure that also serves as the rectifying plate is used, so that the intake air pressure is reduced. The balance can be reduced, and the vibration can be reduced in the entire operation range of the preceding standby operation type vertical pump.

In addition, resonance can be avoided by changing the natural frequency by adjusting the weight of the suction bell mouth portion, providing a plurality of intake pipes, and the like, so that the vibration generation factor can be reduced.

〔The invention's effect〕

According to the present invention, since the vibration damping member is provided below the intake hole provided in the pump casing, the vibration damping member is immersed in water even during the suction operation in which the drain operation is performed while sucking air. There is an effect that the generated pump vibration can be suppressed by the vibration damper.

Also, by changing the weight and rigidity of the suction bell mouth so that its natural frequency can be changed, there is an effect that the vibration generated during the suction operation can be prevented from increasing due to resonance.

[Brief description of the drawings]

FIG. 1 is a sectional view of a pump bowl portion showing one embodiment of the present invention, FIGS. 2 and 3 are diagrams each illustrating a vibration mode of a vertical shaft pump due to fluctuations in water level, and FIG. 4 is a modification of the present invention. FIG. 5 is a sectional view of a pump bowl portion showing an example, FIG. 5 is a view taken along line VV of FIG. 4, and FIGS. 6 to 9 show another embodiment of the present invention. FIG. 8 to FIG. 8 are sectional views of the pump bowl portion, respectively, and FIG. 9 is an overall front view of the vertical shaft pump. DESCRIPTION OF SYMBOLS 1 ... Impeller, 2 ... Casing liner, 3 ... Suction bell mouth, 4 ... Pump casing, 5 ... Suction hole, 6
…… Intake pipe, 7… Damper, 8… Rectifier plate, 9… Mounting plate, 10… Strainer, 11… Plate, 12… Support.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F04D 29/66 F04D 13/00 F04D 29/44

Claims (2)

(57) [Claims] 1. A pump impeller provided below a position corresponding to a minimum water level at which air is sucked from a suction bell mouth of a pump casing when a water level during operation of the pump is lower than the impeller. An intake pipe provided in the pump casing below, an intake pipe having one end connected to the intake port and the other end opened to the atmosphere at a level higher than the highest water level of the pump water tank, and provided in the pump casing. A damping body positioned below the intake hole and acting as a resistance to water in the water absorption tank, and the weight of the damping body can be changed by configuring the damping body with a plurality of dividable members. Characterized in that the vertical shaft pump is configured to prevent resonance. 2. The impeller of a vertical shaft pump is positioned below a position corresponding to a minimum water level at which air is sucked from a suction bell mouth of a pump casing when the water level during the operation of the pump is lower than this. An intake port is provided in a pump casing below the intake port, an intake pipe having one end connected to the intake port and the other end open to the atmosphere is provided, and the thickness of the suction bell mouth is changed to the thickness of a pump casing other than the suction bell mouth. A vertical pump characterized by having a larger configuration.