JPH05231375A - Vertical shaft pump - Google Patents

Abstract

PURPOSE:To perform a transfer from air operation to pumping operation with no water hammer by providing a ventilating device in a suction port casing successively provided in line with a pump casing, and also arranging a small assist impeller connected to an impeller in this suction port casing. CONSTITUTION:In a vertical shaft pump 2 arranged in a pit 1, a suction port casing 4 of positioning a suction port 5 with a predetermined distance apart from a pit bottom surface is successively provided in line with a lower part of a pump casing 3. In this casing 4, an impeller 7 fixed to a drive shaft 8 extended through a barrel part 6a of a guide vane 6 in the pump casing 3 and a small assist impeller 9 fixed to the drive shaft 8 in the vicinity of the suction port 5 are arranged. In the suction port casing 4, a ventilating pipe 10 is opened to a lower position of the assist impeller 9 to interpose an opening/ closing valve 11 in the ventilating pipe 10. The opening/closing valve 11 is opened to flow air into the suction port casing 4, at the time of air operation, and on the other hand closed to start pumping at the time of pumping operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vertical shaft pump, and more particularly to a large pump.

[0002]

2. Description of the Related Art A conventional vertical shaft pump is provided with a suction port casing communicating with a pump casing and having an impeller arranged therein, and a discharge pipe, and is operated when a water level reaches a pumping start water level (RWL). Is configured to start. In addition, some pumps that can perform standby operation perform air operation by supplying air into the suction port casing until the water level reaches the pumping start water level (RWL), and the water level becomes the pumping start water level (RWL). When reaching, the supply of air into the suction port casing is stopped, water is sucked into the pump casing through the suction port casing by the suction action of the impeller, and the sucked water is discharged to the discharge pipe to perform the pumping operation.

[0003]

However, in the above-mentioned conventional configuration, when the operation in the air is changed to the pumping operation, the suction action of the impeller abruptly sucks up and sucks up the water in the suction port casing. There is a problem that water impinges on the impeller and gives an impact. Especially, in a large capacity pump, the impact is great and there is a problem that each part of the pump is affected by up thrust and the like.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a vertical shaft pump capable of shifting from the air operation to the pumping operation without giving a water hammer to the impeller and each part of the pump.

[0005]

In order to solve the above problems, a vertical shaft pump of the present invention is provided with a suction port casing forming a suction port in communication with a pump casing, and a ventilation device in communication with the suction port casing. An impeller and an auxiliary impeller having a smaller capacity than the impeller are arranged in the suction port casing, and the impeller and the auxiliary impeller are connected on the same drive shaft.

[0006]

With the above structure, when the water level is below the minimum water level at which pumping is started, the drive shaft is rotationally driven to rotate the impeller and the auxiliary impeller, and the vertical shaft pump is preliminarily standby-operated. At this time, air flows into the suction port casing through the ventilation device, and the vertical shaft pump operates in the air.

Then, when the water level rises to the minimum water level (LWL) corresponding to the auxiliary impeller, the inflow of air by the ventilation device is cut off and pumping is started. At this time, the suction action of the impeller causes a negative pressure in the suction port casing,
The water level rises in the suction port casing, but prior to the rise in the water level in the suction port casing, the auxiliary impeller auxiliaryly pumps up some water in the suction port casing to the impeller and The main pumping operation by the impeller is gradually started without giving the full load at once.

Therefore, when the impeller shifts from the air operation to the pumping operation, it is possible to mitigate the abrupt collision of the water in the suction port casing with the impeller, and to provide the up thrust to each part of the vertical pump. It is possible to reduce the influence of the above.

Further, in the main pumping operation, the pressure water pumped by the auxiliary impeller flows into the impeller, so that the impeller can be protected from cavitation. Further, in the state where the water level is at the lowest water level after the pumping is finished, the auxiliary impeller is rotated in the reverse direction to stir the remaining water, thereby preventing the generation of the bad odor due to decay.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, a vertical shaft pump 2 arranged in a pit 1 is provided with a suction port casing 4 below a pump casing 3, and a lower end opening of the suction port casing 4 is a suction port 5.
Therefore, it is separated from the bottom surface of the pit 1 by an appropriate distance.

A guide vane 6 is arranged inside the pump casing 3, and an impeller 7 is arranged inside the suction port casing 4. The drive vane 6 is arranged so as to penetrate the body portion 6a of the guide vane 6. The impeller 7 is connected and fixed in the middle of the shaft 8. In addition, an auxiliary impeller 9 is arranged inside the suction port casing 4 near the suction port 5, and the auxiliary impeller 9 is smaller in size and smaller in capacity than the impeller 7, and has a drive shaft. It is connected and fixed to the tip of 8. Further, a ventilation pipe 10 is opened in the suction port casing 4 below the auxiliary impeller 9, and an opening / closing valve 11 is interposed in the upper part of the ventilation pipe 10. A drive motor (not shown) is interlocked with the upper end of the drive shaft 8.

The operation of the above structure will be described below.
The minimum water level (LW
L) In the following states, the drive shaft 8 is rotationally driven to rotate the impeller 7 and the auxiliary impeller 9, and the vertical pump 2 is preliminarily standby-operated. In this state, the on-off valve 11 is opened, and the suction action due to the rotation of the auxiliary impeller 9 and the impeller 7 causes the air to flow into the suction port casing 4 through the ventilation pipe 10, and the vertical shaft pump 2 is in the air. Drive.

Then, when the water level in the pit 1 rises to the lowest water level (LWL) corresponding to the auxiliary impeller 9, the on-off valve 11 is closed to block the inflow of air into the suction port casing 4 and pump up the water. To start. At this time, the impeller 7
Due to the suction action, the inside of the suction port casing 4 becomes negative pressure, and the water level rises inside the suction port casing 4. However, before the rise of the water level in the suction port casing 4, the auxiliary impeller 9 pumps a part of the water in the suction port casing 4 to the impeller 7 so as to assist the impeller 7 once. The main pumping operation by the impeller 7 is gradually started in the state where the full load is not applied to.

Therefore, the water level in the suction port casing 4 reaches the main pumping start water level (RWL) and the impeller 7
When the operation shifts from the air operation to the pumping operation, it is possible to mitigate the sudden collision of the water inside the suction port casing 4 with the impeller 7, and to prevent the influence of up-thrust on each part of the vertical shaft pump 2. It can be reduced.

In this pumping operation, the pressure water pumped by the auxiliary impeller 9 flows into the impeller 7,
The impeller 7 can be protected from cavitation. Further, in a state where the water level is at the lowest water level (LWL) after the pumping is completed, the auxiliary impeller 9 is rotated in the reverse direction to stir the remaining water, thereby preventing the generation of a bad odor due to decay.

[0016]

As described above, according to the present invention, the auxiliary impeller removes a part of the water in the suction port casing before the water level in the suction port casing rises due to the suction action of the impeller. As the water is pumped to the auxiliary, the impact on the impeller caused by water collision can be mitigated when the impeller shifts from air operation to pumping operation, and the pressure water pumped by the auxiliary impeller can be reduced. The impeller can be protected from cavitation by flowing into.

[Brief description of drawings]

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

[Explanation of symbols]

 2 Vertical shaft pump 3 Pump casing 4 Suction port casing 7 Impeller 8 Drive shaft 9 Auxiliary impeller 10 Vent pipe

Claims (1)

[Claims] 1. A suction port casing forming a suction port is provided in communication with a pump casing, a ventilation device is provided in communication with the suction port casing, and an impeller and an auxiliary blade having a smaller capacity than an impeller are provided in the suction port casing. A vertical shaft pump, in which a wheel is arranged, and an impeller and an auxiliary impeller are connected and provided on the same drive shaft.