JP2001041193A - Pump with self-liquid fluid bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the maintenance for lubrication and shaft sealing by forming a rotating wear ring fitted into the shroud part of an impeller out of a material having excellent seizure resistance, and supporting a rotor by means of dynamic fluid of self-liquid fluid produced by operating a pump. SOLUTION: A multiple stage centrifugal pump, having an impeller 2 fitted onto a pump shaft 1 forming a rotor, is provided with a stationary wear ring 10 and a rotating wear ring 9 so that they may face with a clearance S therebetween, with the former fitted onto the inner-periphery surface of an inner casing 6 and the latter formed out of a material having excellent seizure resistance and fitted onto the outer periphery surface of the shroud part 8 of the impeller 2. When the pump is rotated, axial flow by a pressure difference across it and circumferential flow by the rotation occur in the clearance S. The axial flow, out of those occurring in the clearance S, acts dominantly, so that the part between both wear rings 10, 9 serves as a leaky seal by means of self-liquid of the pump, thus it is possible to keep fluid dynamics in a stable condition for stable driving condition of the pump.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a multistage centrifugal pump, and more particularly to a multistage centrifugal pump having a self-fluid bearing.

[0002]

2. Description of the Related Art As shown in FIG. 2, a conventional pump of this type houses a rotor in which a plurality of impellers 2 are mounted on a pump shaft 1 in a pump casing 3, and the pump shaft 1 extends to the outside of the pump casing 3. And is supported by an oil-lubricated bearing 4 outside the pump casing 3.

[0003] Oil-lubricated bearings require maintenance of lubricating oil, and large-sized bearings require a lubricating oil supply device. Further, in the case of oil-lubricated bearings, a bearing enclosure 5 is also required to hold the lubricating oil, and the number of parts is increased.

Further, a pump shaft 1 is connected to a pump casing 3
So that the pump shaft becomes longer
For this reason, the overall length of the pump is long. In the figure, reference numeral 6 denotes an inner casing that partitions the impeller 2 into split chambers, and is fixed to an inner surface of the pump casing 3. Reference numeral 7 denotes a thrust bearing fitted to the discharge side end of the pump shaft 1 and supported by the pump casing 3 to receive a thrust load applied to the pump shaft 1.

FIG. 3 is an enlarged view showing the relationship between the impeller 2 and the inner casing 6. A rotation-side wear ring 9 is fitted on the outer peripheral surface of the shroud portion 8 of the impeller 2, and faces the fixed-side wear ring 10 attached to the inner peripheral surface of the inner casing 6. In the figure, reference numeral 11 denotes a pump suction port, and 12 denotes a pump discharge port.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a compact multi-stage centrifugal pump by reducing the number of parts of the pump, improving the maintainability of the pump, shortening the pump shaft and shortening the overall length of the pump. Aim.

[0007]

SUMMARY OF THE INVENTION In a pump having a rotor having an impeller mounted on a pump shaft, a rotating wear ring fitted to a shroud portion of the impeller is made of a material having excellent seizure resistance. The gap between the ring and the fixed-side wear ring attached to the inner peripheral surface of the inner casing is defined as a small gap, and the dynamics of the self-liquid fluid generated in the gap between the rotating-side wear ring and the fixed-side wear ring by operation of the pump. The rotor was supported by fluid force.

Further, the rotating side wear ring is made of an engineering plastic material having excellent seizure resistance. Further, the gap between the rotating side wear ring and the fixed side wear ring was set to a minute gap of 0,065 to 0,165 mm.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of a pump according to the present invention. Parts that are the same as the conventional parts described with reference to FIG. 2 are given the same numbers, and detailed descriptions thereof are omitted. In the figure, 13 is a shortened pump shaft,
As compared with the conventional type shown in FIG. 2, the lubrication bearing 4 is not supported by the oil-lubricated bearing 4 outside the pump casing 3 and is shortened accordingly.

The impeller 2 is mounted on the pump shaft 13 to form a rotor. Inner casing 6
The fixed-side wear ring 10 attached to the inner peripheral surface of the impeller 2 and the rotating-side wear ring 9 fitted to the outer peripheral surface of the shroud portion 8 of the impeller 2 face each other with a gap S therebetween. In addition,
The gap S indicates a gap on one side.
× 2.

In this configuration, when the pump is stopped, the rotor is mounted on the rotating side wear ring 9 of the impeller 2.
Are supported on the fixed-side wear ring 10 of the inner casing 6 and are stationary. At this time, the lower gap S has disappeared, and the upper gap S has increased. Activating the pump, that is, rotating the rotor,
The gap S between the fixed-side wear ring 10 and the rotation-side wear ring 9 has an axial flow due to a differential pressure between before and after the gap S,
The rotation causes a circumferential flow.

In the conventional type, the gap between the rotor and the fixed part is 0, 1 so that the rotor does not come into rotational contact with the fixed part.
It was set to about 25 to 0.275 mm. In the present invention, the gap S is an extremely thin gap of about 0,065 to 0,165 mm. The flow generated in the gap S is dominated by the axial flow, and acts as a leak-type seal between the fixed-side wear ring 10 and the rotation-side wear ring 9 by the pump's own liquid. As a characteristic, a bearing effect and a whirling prevention effect occur.

That is, a dynamic fluid force is generated to guide the axis of the rotor to the center of the fixed-side wear ring 10, and the rotor starts to float. Then, if the axis of the rotor is guided to the center of the fixed-side wear ring 10, if steady operation is started in that state, the dynamic fluid force is stabilized, and a stable operation state of the pump is obtained.

When the operation of the pump is stopped, immediately before the stop, the pressure difference between the front and rear of the fixed-side wear ring 10 and the rotating-side wear ring 9 and the rotation speed of the rotor are reduced, so that the rotation of the fixed-side wear ring 10 and the rotation of the fixed-side wear ring 10 are reduced. The dynamic fluid force in the gap S with the side wear ring 9 decreases, the rotor gradually sinks, and the rotating side wear ring 9 comes into contact with the fixed side wear ring 10 and stops. When the rotor is stopped, the rotor returns to a state in which the rotating wear ring 9 of the impeller 2 rides on the fixed wear ring 10 of the inner casing 6 and stops.

Note that only the rotation-side wear ring 9 may be fitted, and the fixed-side wear ring may be omitted. At that time, the gap between the rotation-side wear ring 9 and the inner peripheral surface of the inner casing 6 is S, and the rotation-side wear ring 9 rides on the inner peripheral surface of the inner casing 6 and stops. The radial load is supported by the dynamic fluid force of the pump's own liquid, while the thrust load is supported by the balance disk 14. The means for supporting the thrust load is a conventionally used technique.

In the present invention, the rotating body and the fixed portion are in contact with each other immediately before starting and stopping, so that seizure is easily caused. For this reason, the gap S is set to a minute gap of about 0,065 to 0,165 mm so as to quickly increase the dynamic fluid force in the gap S between the fixed-side wear ring 10 and the rotation-side wear ring 9. The rotation side wear ring 9 is made of a material having excellent seizure resistance, for example, an engineering plastic material (PEEK polyetheretherketone, etc.).

[0017]

According to the present invention, in the liquid pump, the rotor is supported by the dynamic fluid force of the own liquid fluid in the gap between the fixed-side wear ring and the rotating-side wear ring. This eliminates the need for support by oil-lubricated bearings, reduces the number of parts, and simplifies maintenance of lubrication and shaft seals. Also,
Because the oil-lubricated bearing outside the pump casing is not used, the pump shaft can be shortened, and the overall length of the pump can be shortened and the pump can be made compact.

[Brief description of the drawings]

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

FIG. 2 is a sectional view of a conventional pump.

FIG. 3 is an enlarged view showing a relationship between an impeller and an inner casing.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Pump shaft 2 Impeller 3 Casing 4 Oil lubricated bearing 5 Bearing enclosure 6 Inner casing 7 Thrust bearing 8 Impeller shroud part 9 Rotation side wear ring 10 Fixed side wear ring 11 Pump suction port 12 Pump discharge port 13 Pump shaft 14 Balance disk S Gap

Claims (3)

[Claims] 1. A pump having a rotor in which an impeller is mounted on a pump shaft, wherein a rotation-side wear ring fitted to a shroud portion of the impeller is made of a material having excellent seizure resistance, and the rotation-side wear ring and an inner casing are provided. The gap between the fixed-side wear ring and the fixed-side wear ring attached to the inner peripheral surface of the rotor is set as a small gap, and the rotor is driven by the dynamic fluid force of the self-liquid fluid generated in the gap between the rotary-side wear ring and the fixed-side wear ring by operation of the pump. A pump having a self-fluid bearing. 2. An engineering plastic is used as a material having excellent seizure resistance.
A pump having the self-fluid bearing described in the above. 3. A pump having a self-fluid bearing according to claim 1, wherein a gap between the rotating side wear ring and the fixed side wear ring is set to be 0,065 to 0,165 mm.