Multifunctional double-mechanical-seal shaft head force balancing structure

Abstract

The utility model relates to a multifunctional double-mechanical-seal shaft head force balancing structure which comprises a lower sealing cavity composed of a lower sealing structure, an upper sealing cavity composed of an upper sealing structure, a motor cooling cavity located between the upper sealing cavity and the lower sealing cavity, and a water return assembly. The upper sealing cavity and the lower sealing cavity are connected through a water return assembly, and the upper sealing cavity, the lower sealing cavity and the motor cooling cavity are connected through a water return assembly. The upward thrust F1 generated by the lower locking nut in the lower sealing structure is equal to the downward thrust F2 generated by the upper locking nut in the upper sealing structure, and the shaft head force generated under any inlet pressure is balanced. The double-mechanical-seal shaft head force balancing structure can balance shaft head force generated under any inlet pressure, improve the stress state of a bearing, prolong the service life of the bearing, provide cooling water for a motor, reduce the number of pipelines of a pump set and facilitate improvement of stability and reliability of operation of a centrifugal pump.

Description

Technical Field

[0001] The utility model relates to an adaptive balance device for the shaft head force of a centrifugal pump, in particular to a shaft head force balance structure with double mechanical seals. Background Art

[0002] The centrifugal pump adopts an impeller cantilever structure, and the shaft end of the centrifugal pump is directly immersed in the medium. Due to the action of the high pressure of the inlet medium of the centrifugal pump, a large upward shaft head force will be generated, and this shaft head force cannot be balanced by the structure of the centrifugal pump itself. At present, a bearing structure that can withstand large axial thrust is generally used to solve the problem of shaft head force balance. The limitations of this structure are reflected in the following aspects:

[0003] Only larger bearings can be selected, which not only increases the space size, but also the vibration and noise of the bearings themselves are relatively large, which is not conducive to reducing the volume and running at low noise; the overall shaft of the centrifugal pump is under pressure, generating a large bending deflection, which makes the running stability of the centrifugal pump worse; due to the limitation of the structural space, small bearings will bear large axial thrust, shortening the bearing life, which is not conducive to improving the reliability of the centrifugal pump; the mechanical seal of the pump needs to bear the dual effects of high pressure and particulate impurities or crystal particles in the medium at the same time, and is easy to be damaged.

[0004] At present, the shaft head force adaptive balance device (patent number: ZL202221865534.7) balances the shaft head force by an external balance device and controlling the cavity area, but the layout of this scheme is relatively complex and has high requirements for the design of the balance device. Therefore, it is necessary to propose a simple and reliable shaft head force balance device to improve the adaptability and reliability of the water pump working scenario. Summary of the Invention

[0005] The utility model aims to provide a multi-functional shaft head force balance structure with double mechanical seals, which can balance the shaft head force generated under any inlet pressure, improve the bearing force state, extend the bearing life, and at the same time provide cooling water for the motor, reduce the number of pump group pipelines, and is conducive to improving the running stability and reliability of the centrifugal pump.

[0006] To achieve the above object, the technical solution of the utility model is: a multi-functional shaft head force balance structure with double mechanical seals, which includes a lower seal cavity composed of a lower seal structure, an upper seal cavity composed of an upper seal structure, a motor cooling cavity located between the upper seal cavity and the lower seal cavity, and a return water assembly. The upper seal cavity and the lower seal cavity are connected through the return water assembly, and the upper seal cavity, the lower seal cavity and the motor cooling cavity are respectively connected through the return water assembly; the upward thrust F1 generated by the lower locking nut in the lower seal structure is equal to the downward thrust F2 generated by the upper locking nut in the upper seal structure, so as to balance the shaft head force generated under any inlet pressure.

[0007] Further, the lower sealing structure includes a lower mechanical seal, a pump bracket, an impeller, a pump body, an O-ring I, and a lower locking nut. A lower mechanical seal is provided between the shaft of the impeller and the pump bracket. The pump bracket and the pump body are sealed and connected by an O-ring I. The impeller is fixedly connected to the shaft of the impeller with a lower locking nut.

[0008] Further, the lower mechanical seal is used to seal the medium after work done by the impeller in the lower sealing cavity, establish high-pressure water higher than the shaft head force, and connect it to the motor cooling cavity through a return pipe.

[0009] Further, the upper sealing structure includes an upper locking nut, a balance cover, an upper mechanical seal, an O-ring II, a balance bracket, and a water throwing ring. An upper mechanical seal is provided between the rotating shaft bushing of the water throwing ring and the balance bracket and is fixed with an upper locking nut. The balance cover and the balance bracket are sealed and connected by an O-ring II.

[0010] Further, the upper mechanical seal is used to seal the high-pressure water after passing through the motor cooling cavity in the upper sealing cavity and connect it to the pump inlet flange through a return pipe.

[0011] Further, the water throwing ring is used to throw the leaked seawater into the liquid collecting tank at the top of the motor and drain it through the motor drain hole.

[0012] Further, the return pipe assembly is composed of a return pipe connecting the lower sealing cavity and the motor cooling cavity, a return pipe connecting the motor cooling cavity and the upper sealing cavity, and a return pipe connecting the upper sealing body and the pump body inlet flange.

[0013] The beneficial effects of the present utility model are as follows:

[0014] The present utility model balances the shaft head force generated by the centrifugal pump under any inlet pressure, greatly improves the bearing stress state, cools the motor at the same time, reduces the number of pump group pipelines, and is beneficial to improving the operation stability and reliability of the centrifugal pump. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a schematic diagram of the multi-functional double mechanical seal shaft head force balance structure of the present utility model;

[0016] Figure 2 is a schematic diagram of the lower mechanical seal structure of the present utility model;

[0017] Figure 3 is a schematic diagram of the upper mechanical seal structure of the present utility model. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] The present utility model will be further described below with reference to the drawings and embodiments.

[0019] As Figures 1 to 3As shown in the figure, the multi-functional double mechanical seal shaft head force balance structure of the present utility model includes a lower seal cavity composed of a lower seal structure 21, an upper seal cavity composed of an upper seal structure 20, a motor cooling cavity located between the upper seal cavity 20 and the lower seal cavity 21, and a return water assembly. The upper seal cavity and the lower seal cavity are connected by the return water assembly respectively, and the upper seal cavity, the lower seal cavity and the motor cooling cavity are also connected by the return water assembly. The upward thrust F1 generated by the lower locking nut 6 in the lower seal structure 21 is equal to the downward thrust F2 generated by the upper locking nut 7 in the upper seal structure 20, which can balance the shaft head force generated under any inlet pressure, improve the bearing force state, increase the bearing life, and at the same time provide cooling water for the motor, reduce the number of pump group pipelines, and is beneficial to improving the stability and reliability of the centrifugal pump operation.

[0020] The high-pressure water in the lower seal cavity enters the upper seal cavity after passing through the motor cooling cavity. The medium can not only wash and cool the lower mechanical seal, but also cool the motor; the high-pressure water in the upper seal cavity enters the water pump inlet through the return water pipe, which can not only release the energy of the medium after the impeller does work, but also wash and cool the upper mechanical seal; the medium pressures in the upper seal cavity and the lower seal cavity are basically the same. During design, it is ensured that the upper locking nut and the lower locking nut are exactly the same, and the acting forces on the upper and lower shaft heads are basically the same, so as to realize the adaptive adjustment of the pump shaft head force during the pressure change process.

[0021] As Figure 2 shown in the figure, the lower seal structure 21 includes a lower mechanical seal 1, a pump bracket 2, an impeller 3, a pump body 4, an O-ring 5, a lower locking nut 6, etc. The lower mechanical seal 1, the pump bracket 2, the impeller 3, the pump body 4, the lower locking nut 6 and the O-ring 5 form a lower seal cavity. The shaft of the impeller 3 is sealed and connected to the pump bracket 2 through the lower mechanical seal 1, the pump bracket 2 and the pump body 4 are sealed and connected by the O-ring 5, and the impeller 3 is fixedly connected to the shaft of the impeller 3 by the lower locking nut 6. The lower mechanical seal 1 seals the medium after the impeller 3 does work in the lower seal cavity, establishes high-pressure water slightly higher than the shaft head force, and is connected to the motor cooling cavity through the return water pipe.

[0022] As Figure 3 shown in the figure, the upper seal structure 20 includes an upper locking nut 7, a balance cover 8, an upper mechanical seal 9, an O-ring 10, a balance bracket 11, a water throwing ring 12, etc. The upper mechanical seal 9, the balance cover 8, the balance bracket 11, the upper locking nut 7 and the O-ring 10 form an upper seal cavity. The rotating shaft bushing of the water throwing ring 12 is sealed and connected to the balance bracket 11 through the upper mechanical seal 9 and fixed by the upper locking nut 7, and the balance cover 8 and the balance bracket 11 are sealed and connected by the O-ring 10. The high-pressure water in the lower seal cavity enters the upper seal cavity after passing through the motor cooling cavity. The medium can not only wash and cool the lower mechanical seal, but also cool the motor; the high-pressure water in the upper seal cavity enters the water pump inlet through the return water pipe, which can not only release the energy of the medium after the impeller does work, but also wash and cool the upper mechanical seal.

[0023] The medium pressures in the upper sealing cavity and the lower sealing cavity are basically the same. During design, it is ensured that the upper and lower locking nuts are exactly the same, and the forces acting on the upper and lower shaft heads are basically the same, so as to realize the adaptive adjustment of the pump shaft head force during the pressure change process.

[0024] The water return assembly is composed of the first water return pipe assembly 22, the second water return pipe assembly 23, and the third water return pipe assembly 24. As Figure 1 shown, the first water return pipe assembly 22 connects the lower sealing cavity and the motor cooling cavity, the second water return pipe assembly 23 connects the motor cooling cavity and the upper balance cavity, and the third water return pipe assembly 24 connects the upper sealing cavity and the pump inlet. When the medium circulates, on the one hand, it can cool the motor, and on the other hand, it can flush the upper mechanical seal and the lower mechanical seal, cool the mechanical seal, and prevent sediment deposition.

[0025] As Figure 2 shown, the force analysis of the lower sealing cavity:

[0026] When the pressure at the pump inlet is high, the lower locking nut 6 generates an upward thrust F1:

[0027] F1 = P1 × A1

[0028] P1—the pressure at the inlet of the centrifugal pump, A2—the area of the lower locking nut.

[0029] As Figure 3 shown, the force analysis of the upper sealing cavity:

[0030] When the pressure at the pump inlet is high, the upper locking nut 7 generates a downward thrust F2:

[0031] F2 = P2 × A2

[0032] P2—the sum of the pressure at the inlet of the centrifugal pump and the head of the water pump, A2—the area of the upper locking nut.

[0033] By controlling the area ratio of the lower locking nut 6 and the upper locking nut 7, F2 > F1 can be achieved. When the pump inlet pressure P1 increases, P2 also increases. Since the area ratio is fixed, that is, F2 / F1 is a constant C, therefore, during the process of the pump inlet pressure change, the pressure in the balance cavity can realize adaptive adjustment.

[0034] During design, according to the actual pump inlet pressure parameters, reasonably design the area of the locking nut and the type of mechanical seal, so that F1 = F2, and the shaft head force generated by the high pressure at the inlet of the centrifugal pump can be balanced.

[0035] The water throwing ring 12. When the mechanical seal is damaged and leaks, the leaked seawater will be thrown into the liquid collecting tank at the top of the motor by the water retaining ring and discharged through the motor drain hole, protecting the motor bearing and winding and improving the reliability of the water pump.

Claims

1. A multi-functional double mechanical seal shaft head force balance structure, characterized in that: It includes a lower sealing cavity composed of a lower sealing structure, an upper sealing cavity composed of an upper sealing structure, a motor cooling cavity located between the upper sealing cavity and the lower sealing cavity, and a return water assembly. The upper sealing cavity and the lower sealing cavity, and the upper sealing cavity, the lower sealing cavity and the motor cooling cavity are respectively connected through the return water assembly; in the lower sealing structure, the upward thrust F1 generated by the lower locking nut is equal to the downward thrust F2 generated by the upper locking nut in the upper sealing structure, balancing the shaft end force generated under any inlet pressure.

2. The multi-functional double mechanical seal shaft head force balance structure according to claim 1, wherein: The lower sealing structure includes a lower mechanical seal, a pump bracket, an impeller, a pump body, an O-ring I, and a lower locking nut. A lower mechanical seal is provided between the shaft of the impeller and the pump bracket. The pump bracket and the pump body are sealed and connected by the O-ring I. The impeller is fixedly connected to the shaft of the impeller by the lower locking nut.

3. The multi-functional double mechanical seal shaft head force balance structure according to claim 2, characterized in that: The lower mechanical seal is used to seal the medium after the work done by the impeller in the lower sealing cavity, establish high-pressure water higher than the shaft end force, and connect it to the motor cooling cavity through a return water pipe.

4. The multi-functional double mechanical seal shaft head force balance structure according to claim 1, characterized in that: The upper sealing structure includes an upper locking nut, a balance cover, an upper mechanical seal, an O-ring II, a balance bracket, and a water throwing ring. An upper mechanical seal is provided between the rotating shaft bushing of the water throwing ring and the balance bracket and is fixed by the upper locking nut. The balance cover and the balance bracket are sealed and connected by the O-ring II.

5. The multi-functional double mechanical seal shaft head force balance structure according to claim 4, wherein: The upper mechanical seal is used to seal the high-pressure water after passing through the motor cooling cavity in the upper sealing cavity and connect it to the water pump inlet flange through a return water pipe.

6. The multi-functional double mechanical seal shaft head force balance structure according to claim 4, characterized in that: The water throwing ring is used to throw the leaked seawater into the liquid collecting tank at the top of the motor and drain it through the motor drain hole.

7. The multi-functional double mechanical seal shaft head force balance structure according to claim 1, wherein: The return water pipe assembly is composed of a return water pipe connecting the lower sealing cavity and the motor cooling cavity, a return water pipe connecting the motor cooling cavity and the upper sealing cavity, and a return water pipe connecting the upper sealing body and the pump body inlet flange.

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