JP3765595B2 - Shaft seal of impeller shaft of vertical centrifugal pump - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to an improvement in a shaft seal applied to an impeller shaft in a vertical centrifugal pump such as a canned motor type.
[0002]
[Prior art]
In general, the shaft seal 12 of the impeller shaft 10 in a vertical centrifugal pump (see FIG. 3) such as a canned motor type moves in a direction perpendicular to the rotation sleeve 14 fixed to the impeller shaft 10 and the diffuser cover 18. It is configured by a floating system including a fixed side liner ring 16 that is attached, that is, a system in which the fixed side liner ring 16 is slidably brought into contact with the rotation of the rotary sleeve 14. Therefore, according to such a configuration, the shaft seal 12 operates satisfactorily because an excessive force is not applied between the rotating side sleeve 14 and the stationary side liner ring which are both components. And at the same time a long life can be achieved.
[0003]
[Problems to be solved by the invention]
However, the shaft seal of the impeller shaft of the conventional vertical centrifugal pump has the following basic problems.
[0004]
That is, in general, the shaft seal of the impeller shaft is required to have both functions of sealing performance during pump operation and air bleedability (exclusion of retained gas in the pump) at the time of starting the pump. The seal could not achieve both functions at the same time.
[0005]
In FIG. 3, when the pump is started, the gas staying in the back surface portion 22 of the impeller 20 is removed into the motor portion 24. On the other hand, during the pump operation, the handling liquid (cooling liquid) in the motor portion 24 on the high pressure side is removed. , (See dotted arrows) must prevent the impeller back surface portion 22 on the low pressure side from entering, but both functions are related to the sealing performance of the shaft seal 10 (that is, the rotating sleeve 14 and the stationary liner ring). Both of which are dependent on the size of the gap between the sliding contact and the seal 16 and act in opposition to each other (that is, when the gap increases, the air venting is promoted but the sealing performance is hindered, while the gap is When it becomes smaller, the sealing performance is promoted but the air bleeding performance is hindered), and therefore it is impossible to achieve the sealing performance and the air bleeding performance at the same time. In addition, it is clear that a decrease in air bleeding performance generally impedes pump operation performance, and a decrease in sealing performance significantly impairs pump efficiency, particularly in the high speed operation region.
[0006]
Therefore, an object of the present invention is to provide a shaft seal of an impeller shaft of a vertical centrifugal pump that can simultaneously achieve both functions of air bleeding at the time of starting the pump and sealing performance during the operation of the pump.
[0007]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the present invention comprises a rotary sleeve fixedly attached to an impeller shaft of a vertical centrifugal pump according to the present invention and a fixed liner ring attached to a diffuser cover so as to be movable in a direction perpendicular to the axis. In the floating type shaft seal, the fixed-side liner ring is formed so as to be movable in the axial direction as well as the direction perpendicular to the axis, and a seal portion of the fixed-side liner ring with respect to the diffuser cover is formed on the liner ring. It is formed by an upper seal ring and a lower seal ring provided inside the diffuser cover so as to be held in the vertical direction, and the rotation side sleeve has a sliding contact gap with the fixed side liner ring of 0.02 to 0.08 mm. The sliding contact seal surface is set to a range of about the motor part from the back of the pump when the pump is started. Characterized by forming a thread groove pump mechanism for pumping the axial rotation direction of travel, to make the intrusion prevention from the pump back part to the pump back part of the pumped fluid within the air vent and the motor section of the motor of the And
[0008]
[Action]
Therefore, according to the present invention, the air bleeding property at the time of starting the pump is due to the pumping action of the thread groove pump mechanism on the sliding contact seal surface of the rotating side sleeve, and the sealing property during the pump operation is the same as that of the fixed side liner ring. Both good seal performance (due to narrowing of the sliding seal gap with the rotating sleeve) and reliable seal contact with the diffuser cover seal ring (due to the pressure difference between the upper and lower pressure of the liner ring) can be achieved well. It becomes possible.
[0009]
【Example】
Next, embodiments of the shaft seal of the impeller shaft of the vertical centrifugal pump according to the present invention will be described in detail with reference to the accompanying drawings. For convenience of explanation, the same components as those of the conventional configuration shown in FIG. 3 are denoted by the same reference numerals, and detailed description thereof is omitted.
[0010]
First, the basic structure of the shaft seal of the present invention is the same as the conventional structure (FIG. 3). That is, as shown in FIG. 3, the shaft seal 12 of the present invention is basically configured by a floating system including a rotation side sleeve 14 on the impeller shaft 10 side and a fixed side liner ring 16 on the diffuser cover 18 side. Has been.
[0011]
However, in the present invention, in the above configuration, as shown in FIGS. 1 and 2, the fixed-side liner ring 16 is arranged in the direction perpendicular to the axis of the impeller shaft 10 and the shaft with respect to the diffuser cover 18 via the rotation stop pin 30. Mounted so that it can move in any direction. Further, a seal portion for the diffuser cover 18 is formed inside the diffuser cover 18 by upper and lower seal rings 32 and 34 provided so as to hold the liner ring 16 vertically in the axial direction. Further, the rotation-side sleeve 14 sets the sliding contact gap c with the fixed-side liner ring 16 as small as possible (preferably in a range of about 0.02 to 0.08 mm). The sliding contact seal surface 14a (FIG. 2) is configured to form a pump mechanism having a thread groove 36 that performs a pumping action in the direction of axial rotation.
[0012]
Therefore, according to the present invention, at the time of pump start-up, that is, the removal of the staying gas 26 in the pump back surface portion 22 into the motor portion 24 is ensured by the pump action of the pump mechanism comprising the thread groove 36. Clearly it can be achieved. On the other hand, the sealing performance during the operation of the pump, that is, the function of preventing the handling liquid (cooling liquid) in the motor section 24 on the high pressure side from entering the impeller back surface section 22 on the low pressure side is good for the fixed side liner ring 16. Due to the sealing performance (due to the narrowing of the sliding contact seal gap c) and the reliable seal contact with the lower seal ring 34 of the diffuser cover 18 (due to the pressure difference between the upper and lower portions 24, 20 with respect to the liner ring 16), It can be achieved well.
[0013]
As a result, the operation performance and efficiency of the pump can be greatly improved. It is obvious that the sealing of the liner ring 16 can be achieved by the upper seal ring 32 when the pressure of the impeller back surface portion 22 becomes higher than the pressure of the motor portion 24 when the pump is stopped.
[0014]
Although the present invention has been described with reference to the preferred embodiments, the present invention is not limited to the above-described embodiments, and many design changes can be made without departing from the spirit of the present invention. Further, the centrifugal pump to which the present invention can be applied is not limited to the canned motor type described above, and can be similarly applied to the impeller shafts of various pumps.
[0015]
【The invention's effect】
As described above, the floating type of the vertical type centrifugal pump according to the present invention includes a rotating sleeve fixedly attached to the impeller shaft and a fixed side liner ring attached to the diffuser cover so as to be movable in a direction perpendicular to the axis. In the shaft seal, the fixed-side liner ring is formed so as to be movable in the same axial direction as the axis-perpendicular direction, and the seal portion of the fixed-side liner ring with respect to the diffuser cover is arranged vertically in the axial direction. It is formed by an upper seal ring and a lower seal ring provided inside the diffuser cover so as to hold, and the rotation side sleeve has a sliding contact seal gap with the fixed side liner ring in a range of about 0.02 to 0.08 mm. And the sliding contact seal surface has a shaft from the back of the pump to the motor when the pump is started. By forming the screw groove pump mechanism for rolling pumping the traveling direction, has a pump back part to perform and intrusion prevention to the pump back part of the pumped fluid within the air vent and the motor unit to the motor unit Therefore, the air releasing performance at the start of the pump is due to the pumping action of the thread groove pump mechanism on the sliding contact seal surface of the rotating sleeve, and the sealing performance during the pump operation is a good sealing performance (rotating) Both the sliding contact seal gap with respect to the side sleeve and the reliable seal contact with the seal ring of the diffuser cover (due to the pressure difference between the upper and lower pressures of the liner ring) can achieve both well.
[0016]
Therefore, according to the present invention, in this type of vertical centrifugal pump, it is possible to greatly improve the poor operating performance and efficiency which have been regarded as problems in the past.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an essential part showing an embodiment of a shaft seal of an impeller shaft of a vertical centrifugal pump according to the present invention.
2 is a front view showing a sliding surface of a rotation side sleeve in the shaft seal shown in FIG. 1. FIG.
FIG. 3 is a cross-sectional side view of an essential part showing a general floating type shaft seal of an impeller shaft of a canned motor type vertical centrifugal pump.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Impeller shaft 12 Shaft seal 14 Rotation side sleeve 14a Sliding contact seal surface 16 Fixed side liner ring 18 Diffuser cover 20 Impeller 22 Pump back surface (impeller back surface)
24 Motor part 26 Stagnant gas 30 Rotation stop pin 32 Upper seal ring 34 Lower seal ring 36 Thread groove c Sliding contact seal gap

Claims (1)

In a floating type shaft seal comprising a rotary sleeve fixedly attached to an impeller shaft of a vertical centrifugal pump and a fixed liner ring movably attached to a diffuser cover in a direction perpendicular to the shaft, the fixed liner ring is In addition to being formed so as to be movable in the axial direction as well as in the direction perpendicular to the axis, a seal portion of the fixed side liner ring with respect to the diffuser cover is provided inside the diffuser cover so as to hold the liner ring up and down in the axial direction. The rotating side sleeve is formed by an upper seal ring and a lower seal ring, and the sliding contact seal gap with the fixed side liner ring is set in a range of about 0.02 to 0.08 mm, and the sliding contact seal surface There is a pump action in the direction of shaft rotation from the back of the pump to the motor when the pump is started. By forming a groove pump mechanism, the axis of the impeller shaft of the vertical centrifugal pump, characterized in that the pump back part performs the intrusion prevention to the pump back part of the pumped fluid within the air vent and the motor unit to the motor unit sticker.

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