JP3905589B2 - Vibration prevention device for pump plant - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vibration prevention device for a pump plant.
[0002]
[Prior art]
In public-use pump plants, demand for large-capacity, large-depth pumps has increased rapidly in recent years. The reason is that the rivers around the city have become ceiling rivers, and rainwater does not flow through the river bottom but flows through underground drainage channels, which are released into the ocean. The pump used in this plant has a large capacity and a high head as compared with the conventional pump, so that the drive output is large and the pump has a high energy density.
[0003]
The frequency of the water column in the plant piping is a constant value depending on the length, size, pipe thickness, and fluid properties of the pipe, but the depth is large, so the distance of the pipe from the suction pipe end to the discharge pipe end of the pump is equal to or less than lead 10H _Z to a decrease in water column frequency becomes very long compared to the prior art.
[0004]
The problem here is the resonance phenomenon that occurs when the low frequency frequency of several hertz is close to the water column frequency of the pipeline among various vibration components generated from a pump with high energy density. This causes abnormally large vibration and noise to the entire plant piping. Conventionally, the occurrence of this abnormal vibration has been solved by remodeling the pump or piping.
[0005]
FIG. 2 is a front view of an example of a conventional deep pump plant. In the figure, H ₃ is a ground level, A is an electric motor chamber, 1 is an electric motor provided in the electric motor chamber, B is an intermediate bearing chamber, 2 is an intermediate bearing stand provided in the intermediate bearing chamber, and C is a pump. Chambers 3 are large depth pumps provided in the pump chamber. The drive shaft of the pump is connected to the deep pump 3 from the electric motor 1 through the intermediate bearing stand 2. Reference numeral 4 denotes a suction pipe provided on the suction side of the pump 3. A discharge pipe 7 is connected to the discharge side of the pump 3 through a check valve 5 and a discharge valve 6. The main part of the discharge pipe 7 rises vertically. H ₁ is the discharge level of the pump 3, and H ₂ is the top level of the discharge pipe 7. In the illustrated example, the level difference between H ₁ and H ₂ is 41 m. In general, the length of the discharge pipe 7 of this type of pump plant is very long. Reference numeral 8 denotes a vertical concrete base that supports the long discharge pipe 7 at the bottom, 9 denotes a side concrete base that supports the discharge pipe 7 from the side, and 10 denotes a top concrete base.
[0006]
In this pump plant, water is sucked in from the end of the suction pipe 4, energized by the pump 3, and discharged to the end of the discharge pipe 7. The height of the discharge end is a position higher than the ground level H ₃ .
[0007]
[Problems to be solved by the invention]
Among various vibration components generated from a pump with high energy density, if the low frequency frequency of several hertz is close to the water column frequency of the pipe line, a resonance phenomenon or self-excitation phenomenon occurs, and the entire pump plant piping is abnormal. Causes a lot of vibration and noise.
[0008]
Even if the resonance phenomenon or self-excited vibration is small, if there is a vibration generation source, the resonance phenomenon or self-excited vibration is generated in correlation with the water column frequency. In addition, the frequency of water column is an eigenvalue of piping, and once the equipment is manufactured, changing to a constant value means a major modification of the equipment, which is a very difficult problem.
[0009]
The present invention solves the above-described conventional problems, and aims to prevent resonance or self-excited vibration with a simple device.
[0010]
[Means for Solving the Problems]
The present invention solves the above-described problem, and includes a pump, a suction pipe that is continuous with the suction side and opens into water, and a long discharge pipe that is continuous with the discharge side and extends upward and opens into the atmosphere. In the plant vibration prevention device, an air intake provided in the suction pipe, an air intake pipe connected to the air intake and extending upward from the suction liquid level of the plant, and an opening of the air intake pipe It consists of an orifice that is provided near the end and whose opening area can be changed. The opening area of the orifice is changed in various ways to adjust the amount of air taken into the suction pipe, thereby adjusting the water column frequency of the discharge pipe. In addition, the present invention relates to a vibration prevention device for a pump plant characterized by preventing a resonance phenomenon or self-excited vibration.
[0011]
The water column frequency is an eigenvalue of the pipe, but can be changed depending on the content of bubbles mixed in the water column. Therefore, resonance or self-excited vibration can be prevented from occurring by changing the water column frequency so that the water column frequency does not coincide with or close to the pump frequency.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a partially enlarged front view of a large depth pump plant according to an embodiment of the present invention. In the figure, 11 is an air intake provided in the suction pipe 4, H is a suction liquid level, 12 is an air intake pipe that is connected to the air intake and extends to a position higher than the suction liquid level H. , 13 are orifices provided near the pipe end of the air intake pipe. Parts other than the above are the same as in the prior art (FIG. 2).
[0013]
When the pump 3 is operated in this plant, water is sucked from the suction pipe 4 and discharged from the discharge pipe 7. In this process, since the suction pipe 4 has a negative pressure, the air adjusted according to the opening area of the orifice 13 is sucked from the upper end of the air intake pipe 12 and sucked into the pump through the air intake 11. It is sucked into the pipe 4, mixed into the water in the suction pipe 4, and becomes bubbles and flows toward the discharge pipe 7 together with the water. The air column frequency of the piping changes due to air mixing.
[0014]
In general, the pressure wave propagation velocity (so-called sound velocity) in a liquid greatly varies depending on the bubble content. The greater the amount of bubbles, the lower the pressure wave propagation speed. As the pressure wave velocity decreases, the water column frequency also decreases. By appropriately selecting the orifice opening area, the amount of air mixing is changed, and the low frequency frequency of the pump, which is the source of vibration, is adjusted so that the frequency of the water column in the pump plant piping is not close to the value. Can be prevented from occurring.
[0015]
To change the orifice opening area, for example, orifices with various opening areas are prepared, and when resonance occurs, the orifices are sequentially replaced so that resonance does not occur, or openings with various opening areas are formed on one orifice plate. And an opening that does not cause resonance by sliding is selected.
[0016]
【The invention's effect】
In the vibration prevention device for a pump plant of the present invention, an air intake provided in the suction pipe, an air intake pipe connected to the air intake and extending upward from the suction liquid level of the plant, and the air It consists of an orifice that is provided near the open end of the intake pipe and whose opening area can be changed, and the amount of air taken into the suction pipe is adjusted by changing the opening area of the orifice in various ways, thereby the water column of the discharge pipe Since the resonance frequency or self-excited vibration can be prevented by adjusting the frequency, when pump vibration and water column vibration or self-excited vibration occurs, pump remodeling or plant piping remarkably remodeled. Without this, resonance or self-excited vibration can be easily avoided.
[Brief description of the drawings]
FIG. 1 is a partially enlarged front view of a large depth pump plant according to an embodiment of the present invention.
FIG. 2 is a front view of an example of a conventional large depth pump plant.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Electric motor 2 Intermediate bearing stand 3 Deep pump 4 Suction pipe 5 Check valve 6 Discharge valve 7 Discharge pipe 8 Vertical concrete stand 9 Side surface concrete stand 10 Top concrete stand 11 Air intake 12 Air intake pipe 13 Orifice H Suction liquid Surface level H ₁ Discharge level H ₂ Vertex level H ₃ Ground level A Motor room B Intermediate bearing room C Pump room

Claims (1)

An anti-vibration device for a pump plant comprising a pump, a suction pipe connected to the suction side and opening into the water, and a long discharge pipe connected to the discharge side and extending upward into the atmosphere. An air intake inlet, an air intake pipe connected to the air intake inlet and extending upward from the suction liquid level of the plant, and an opening area of the air intake pipe provided near the open end of the air intake pipe is changed. It is possible to adjust the amount of air taken into the suction pipe by changing the opening area of the orifice in various ways, thereby adjusting the water column frequency of the discharge pipe and preventing resonance phenomenon or self-excited vibration. A vibration prevention device for a pump plant.

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