Middle throttling sealing assembly and self-balancing multi-stage pump with same

Abstract

The utility model provides a middle throttling sealing assembly and a self-balancing multistage pump with the same, a throttling bush structure is formed by a middle throttling bush (52), a sealing partition plate (53), an axial O-shaped sealing ring (54) and a middle isolation bush (55) together, a throttling shaft sleeve structure is formed by a middle throttling shaft sleeve (51) and a spring (56) together, a balance leakage hole (59) of a water outlet section (7) is matched, and the balance leakage hole (59) of the water outlet section (7) is matched with the middle throttling bush (52), the sealing partition plate (53), the axial O-shaped sealing ring (54) and the middle isolation bush (55) together. A middle throttling sealing assembly (5) is formed by the front flow passing assembly (4) and the back flow passing assembly (8) and then installed in an inner cavity between the water outlet section (7) and the pump shaft (1), the left side end face of the middle throttling sealing assembly (5) is in contact with the end face of a final-stage impeller hub of the front flow passing assembly (4), and the right side end face of the middle throttling sealing assembly (5) is in contact with the end face of a final-stage impeller hub of the back flow passing assembly (8). According to the device, the pressure of a fluid medium in the middle throttling sealing assembly is dynamically adjusted, the volume loss of the pump is reduced, the jet effect and the excitation effect in throttling sealing are reduced, and the running stability of the whole machine is improved.

Description

Technical Field

[0001] This utility model relates to the field of self-balancing multistage pump technology, specifically to an intermediate throttling sealing assembly and a self-balancing multistage pump having the assembly. Background Technology

[0002] Self-balancing multistage pumps mainly consist of components such as inlet section, intermediate section, outlet section, secondary inlet section, forward guide vanes, reverse guide vanes, forward impeller, reverse impeller, pump shaft, transition pipe, and bearing housing. The impeller rotor components are symmetrically arranged, and the axial forces generated by each stage of the symmetrical impeller cancel each other out. This eliminates the need for a balancing disc structure, achieving automatic axial thrust balance and reducing malfunctions caused by balancing device failure. Furthermore, residual axial force is borne by the thrust bearing, improving the rigidity and critical speed of the pump rotor, resulting in smooth and reliable operation. In addition, self-balancing multistage pumps employ advanced hydraulic models, ensuring excellent impeller and guide vane alignment and eliminating balancing water leakage, resulting in low volumetric loss. Their operating efficiency is 2-3 percentage points higher than ordinary multistage pumps. Due to their superior performance, they are widely used in industries such as boiler feedwater, petrochemicals, coal chemicals, mine drainage, and urban water supply.

[0003] However, the outlet section of a self-balancing multistage pump contains high-pressure water at different pressures on both sides. To effectively prevent this high-pressure water from entering the outlet section from one side to the other, a throttling sealing structure consisting of an intermediate throttling shaft sleeve and an intermediate throttling bushing is typically used. This prevents fluid from flowing from the high-pressure chamber to the low-pressure chamber, thus achieving throttling sealing and maintaining pressure stability. However, the high-pressure water at different pressures on both sides of the outlet section creates a significant pressure difference between the high-pressure and low-pressure chambers. This results in a high-speed, high-pressure jet effect and a sealing fluid excitation effect when the fluid flows through the axial gap between the intermediate throttling shaft sleeve and the intermediate throttling bushing. This easily leads to flash evaporation of the fluid and sub-resonance instability of the rotor-seal mixing system, causing vibration and operational instability in the self-balancing multistage pump. It also increases the volumetric loss of the self-balancing multistage pump, directly affecting the overall operating efficiency.

[0004] Therefore, in order to mitigate the impact of the jet effect and sealing fluid excitation effect of the intermediate throttling seal on the operating stability and efficiency of the self-balancing multistage pump, and to improve the operating stability and efficiency of the self-balancing multistage pump, there is an urgent need for an intermediate throttling seal assembly and a self-balancing multistage pump with such an assembly. Utility Model Content

[0005] To address the aforementioned technical challenges, this invention proposes an intermediate throttling seal assembly structure. This assembly is then installed on a self-balancing multistage pump. By dynamically adjusting the fluid medium pressure within the intermediate throttling seal assembly, the volumetric losses of the self-balancing multistage pump are reduced, as are the jetting effect and sealing fluid vibration effect within the intermediate throttling seal, thereby improving its operational stability.

[0006] To achieve the above objectives, the technical solution adopted by this utility model is as follows: An intermediate throttling sealing assembly includes an intermediate throttling bushing, an intermediate throttling bushing, a sealing partition, an axial O-ring, an intermediate isolation bushing, a radial O-ring, a spring, and a balance leakage hole. Two intermediate throttling bushings are respectively installed on the high-pressure chamber end face and the low-pressure chamber end face of the water outlet section via bolts at their ends. The intermediate isolation bushing is installed between the two intermediate throttling bushings. The intermediate isolation bushing engages with the groove structure of the two intermediate throttling bushings through boss structures at both ends. Two sealed cavities are formed, and two sealing partitions are installed in the sealed cavities respectively. Two axial O-rings are set at both ends of the intermediate isolation bushing, and two radial O-rings are installed between the intermediate throttling bushing and the two end faces of the outlet section. Two intermediate throttling bushings are symmetrically arranged on both sides of the two intermediate throttling bushings, and the two intermediate throttling bushings are installed on the pump shaft by ordinary flat keys. The end faces between the two intermediate throttling bushings are respectively connected to the two ends of the spring. One end of the balance leakage hole is connected to the high pressure chamber of the outlet section, and the other end of the balance leakage hole is connected to the internal cavity of the outlet section.

[0007] Furthermore, the radial clearance between the intermediate throttling bushing and the intermediate throttling shaft sleeve is 0.08~0.15mm. Based on the specific parameters of the labyrinth seal structure, it is necessary to calculate the pressure drop and leakage of the labyrinth seal structure under different pressure differentials, and then determine the specific value of the radial clearance between the intermediate throttling bushing and the intermediate throttling shaft sleeve.

[0008] Furthermore, an annular boss structure is provided at the end face of the intermediate throttling bushing. The surface of the annular boss structure is clad with a hard alloy wear-resistant coating by plasma welding. The hard alloy wear-resistant coating is annular and has a thickness of 0.1~0.3mm. A labyrinth sealing structure is provided on the inner surface of the intermediate throttling bushing. The top of the groove of the labyrinth sealing structure is treated with nickel alloy plating to improve its anti-corrosion performance.

[0009] Furthermore, the longitudinal cross-section of the intermediate throttling bushing is L-shaped, and the end face where the intermediate throttling bushing mates with the intermediate throttling bushing is clad with a hard alloy wear-resistant coating by plasma welding. The hard alloy wear-resistant coating is annular and has a thickness of 0.1~0.3mm. A labyrinth seal structure is opened on the outer circular surface of the intermediate throttling bushing, and the top of the groove of the labyrinth seal structure is treated by plating nickel-chromium-tungsten alloy to improve its hardness and wear resistance.

[0010] Furthermore, the centerline of the balance leakage hole is horizontal, and the diameter of the balance leakage hole is 2~4mm.

[0011] A self-balancing multistage pump with an intermediate throttling seal assembly includes a pump shaft, a positive bearing housing assembly, an inlet section, a positive flow assembly, an outlet section, an intermediate throttling seal assembly, a positive-to-reverse stage connecting pipe, a reverse flow assembly, a secondary inlet section, a packing seal assembly, and a reverse bearing housing assembly. The inlet section, positive flow assembly, outlet section, reverse flow assembly, and secondary inlet section are sequentially mounted on the pump shaft and secured by several through-bars. The positive bearing housing assembly is bolted to the left end face of the inlet section. The packing seal assembly... The components and the reverse bearing assembly are bolted together and installed on the right end face of the secondary inlet section. One end of the positive and reverse stage connecting pipe is connected to the horizontal outlet of the outlet section, and the other end of the positive and reverse stage connecting pipe is connected to the horizontal inlet of the secondary inlet section. The intermediate throttling seal assembly is installed in the inner cavity between the outlet section and the pump shaft. The left end face of the intermediate throttling seal assembly is in contact with the end face of the last stage impeller hub of the positive flow assembly, and the right end face of the intermediate throttling seal assembly is in contact with the end face of the last stage impeller hub of the reverse flow assembly.

[0012] Furthermore, the inlet section, outlet section, and secondary inlet section are all equipped with base structures, located at the front, middle, and rear ends of the self-balancing multistage pump, respectively, providing multiple support structures for the large-span self-balancing multistage pump and improving the rigidity and stability of the entire machine.

[0013] Compared with the prior art, the intermediate throttling sealing assembly and the self-balancing multistage pump with the assembly provided by this utility model can greatly reduce the pressure of the fluid medium in the intermediate throttling sealing assembly through the dual pressure reduction operation of the radial clearance and axial clearance between the intermediate throttling bushing and the intermediate throttling shaft sleeve, avoid the erosion of the intermediate throttling sealing assembly by the high-speed fluid medium, and also effectively reduce the leakage of the intermediate throttling sealing assembly.

[0014] Through the dynamic adjustment structure of the two intermediate throttling bushings and springs, the axial clearance between the intermediate throttling bushings and intermediate throttling bushings can be adjusted in real time when the hard alloy wear-resistant coating is worn. It can also adjust the axial clearance between the two when the rotor system of the whole machine moves axially, so as to minimize the fluid medium in the high pressure chamber and low pressure chamber of the water outlet section from entering the intermediate throttling sealing assembly and reduce the leakage of the intermediate throttling sealing assembly.

[0015] Compared to the integrated throttling bushing and throttling liner, the throttling liner structure proposed in this invention consists of two intermediate throttling liners, two sealing baffles, two axial O-rings, and an intermediate isolation liner. The throttling bushing structure consists of two intermediate throttling liners and springs. Combined with the labyrinth seal structure, this establishes a structure with vibration absorption and damping functions, reducing the sealing fluid excitation force and jet effect of the fluid medium in the intermediate throttling seal assembly, and improving the rotor stability of the self-balancing multistage pump.

[0016] Furthermore, the intermediate throttling sealing assembly proposed in this invention is relatively easy to install and disassemble. In particular, when some structures of the intermediate throttling sealing assembly are damaged and need to be replaced, only the damaged structure needs to be replaced, which effectively reduces the operation and maintenance cost of the intermediate throttling sealing assembly. Attached Figure Description

[0017] Figure 1 This is an overall structural diagram of the present invention;

[0018] Figure 2 This is a schematic diagram of the intermediate throttling sealing assembly of this utility model.

[0019] The diagram is labeled as follows: 1: Pump shaft; 2: Positive bearing housing assembly; 3: Inlet section; 4: Positive flow assembly; 5: Intermediate throttling seal assembly; 51: Intermediate throttling bushing; 52: Intermediate throttling bushing; 53: Sealing baffle; 54: Axial O-ring seal; 55: Intermediate isolation bushing; 56: Spring; 57: Radial O-ring seal; 58: Hard alloy wear-resistant coating; 59: Balance leakage hole; 6: Positive and negative stage connecting pipe; 7: Outlet section; 71: Low-pressure chamber; 72: High-pressure chamber; 8: Reverse flow assembly; 9: Secondary inlet section; 10: Packing seal assembly; 11: Reverse bearing housing assembly. Detailed Implementation

[0020] In the description of this utility model, it should be noted that the terms "upper", "lower", "left", "right", "inner", "outer", "front end", "rear end", "both ends", "one end", "the other end", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0021] To make the technical problem to be solved, the technical solution and the implementation effect of this utility model clearer, the following is in conjunction with the appendix. Figure 1 and 2 An embodiment of the present invention will be further described below:

[0022] See appendix Figure 1 and 2 This utility model discloses an intermediate throttling sealing assembly, comprising an intermediate throttling bushing 51, an intermediate throttling bushing 52, a sealing partition 53, an axial O-ring seal 54, an intermediate isolation bushing 55, a radial O-ring seal 57, a spring 56, and a balance leakage hole 59. Two intermediate throttling bushings 52 are respectively installed on the end faces of the high-pressure chamber 72 and the low-pressure chamber 71 of the outlet section 7 via bolts at their ends. The intermediate isolation bushing 55 is installed between the two intermediate throttling bushings 52, and its end bosses cooperate with the groove structures of the two intermediate throttling bushings 52, forming two seals between the intermediate isolation bushing 55 and the two intermediate throttling bushings 52. The cavity has two sealing baffles 53 installed in it, two axial O-rings 54 set at both ends of the intermediate isolation bushing 55, two radial O-rings 57 installed between the intermediate throttling bushing 52 and the two end faces of the outlet section 7, two intermediate throttling bushings 51 symmetrically arranged on both sides of the intermediate throttling bushing 51, and the two intermediate throttling bushings 51 are installed on the pump shaft 1 by ordinary flat keys. The end faces between the two intermediate throttling bushings 51 are respectively connected to the two ends of the spring 56. One end of the balance leakage hole 59 is connected to the high pressure chamber 72 of the outlet section 7, and the other end of the balance leakage hole 59 is connected to the internal cavity of the outlet section 7.

[0023] As a preferred embodiment, see Appendix Figure 2The radial clearance between the intermediate throttling bushing 52 and the intermediate throttling shaft sleeve 51 is 0.08~0.15mm. The flow rate, head, speed and other parameters of different models of self-balancing multistage pumps directly determine the fluid medium pressure of the high-pressure chamber 72 and the low-pressure chamber 71 of the outlet section 7, which in turn leads to different fluid medium pressure differences on both sides of the intermediate throttling sealing assembly 5. In addition, the axial length of the intermediate throttling sealing assembly 5 of different models of self-balancing multistage pumps is also different. Therefore, it is necessary to calculate the pressure drop and leakage of the labyrinth seal structure under different pressure differences based on the specific parameters of the labyrinth seal structure, and then determine the specific value of the radial clearance between the intermediate throttling bushing 52 and the intermediate throttling shaft sleeve 51.

[0024] As a preferred embodiment, see Appendix Figure 2 The intermediate throttling bushing 52 has an annular boss structure at its end face. The surface of the annular boss structure is clad with a hard alloy wear-resistant coating 58 by plasma welding. The hard alloy wear-resistant coating 58 is annular and has a thickness of 0.1~0.3mm. The inner surface of the intermediate throttling bushing 52 has a labyrinth seal structure. The top of the groove of the labyrinth seal structure is treated with nickel alloy plating to improve its wear resistance.

[0025] As a preferred embodiment, see Appendix Figure 2 The intermediate throttling bushing 51 has an L-shaped longitudinal cross-section. The end face where the intermediate throttling bushing 51 mates with the intermediate throttling bushing 52 is clad with a hard alloy wear-resistant coating 58 by plasma welding. The hard alloy wear-resistant coating 58 is annular and has a thickness of 0.1~0.3mm. A labyrinth seal structure is opened on the outer circular surface of the intermediate throttling bushing 51. The top of the groove of the labyrinth seal structure is treated by plating nickel-chromium-tungsten alloy to improve its hardness and wear resistance.

[0026] Based on the fundamental principle of rotary dynamic seal friction, the labyrinth seal structure that matches the intermediate throttling bushing 52 and the intermediate throttling shaft sleeve 51 is coated with two different materials. This not only improves the wear resistance of both materials, but also prevents adhesion, tearing, or seizing during operation due to the small gap between the intermediate throttling bushing 52 and the intermediate throttling shaft sleeve 51. The choice of these two materials was determined after multiple experiments to obtain experimental data on Mohs hardness, wear rate, sealing excitation force, leakage rate and speed, pump flow rate and head. This data was then analyzed, the sealing structure was optimized, and the coating was precisely machined.

[0027] As a preferred embodiment, see Appendix Figure 2 The centerline of the balance leakage hole 59 is horizontal, and the diameter of the balance leakage hole 59 is 2~4mm.

[0028] See appendix Figure 1This utility model discloses a self-balancing multistage pump with an intermediate throttling seal assembly, comprising a pump shaft 1, a positive bearing housing assembly 2, an inlet section 3, a positive flow assembly 4, an outlet section 7, an intermediate throttling seal assembly 5, a positive-to-negative stage connecting pipe 6, a negative flow assembly 8, a secondary inlet section 9, a packing seal assembly 10, and a negative bearing housing assembly 11. The inlet section 3, positive flow assembly 4, outlet section 7, negative flow assembly 8, and secondary inlet section 9 are sequentially mounted on the pump shaft 1 and secured by several through-bars. The positive bearing housing assembly 2 is bolted to the left end face of the inlet section 3. The packing seal assembly 10 and the reverse bearing assembly 11 are jointly installed on the right end face of the secondary inlet section 9 by bolts. One end of the positive and negative stage connecting pipe 6 is connected to the horizontal outlet of the outlet section 7, and the other end of the positive and negative stage connecting pipe 6 is connected to the horizontal inlet of the secondary inlet section 9. The intermediate throttling seal assembly 5 is installed in the inner cavity between the outlet section 7 and the pump shaft 1. The left end face of the intermediate throttling seal assembly 5 is in contact with the end face of the last stage impeller hub of the positive flow assembly 4, and the right end face of the intermediate throttling seal assembly 5 is in contact with the end face of the last stage impeller hub of the reverse flow assembly 8.

[0029] As a preferred embodiment, see Appendix Figure 2 The inlet section 3, outlet section 7 and secondary inlet section 9 are all equipped with base structures, which are located at the front, middle and rear of the self-balancing multistage pump, respectively. This provides multiple support structures for the large-span self-balancing multistage pump, improving the rigidity and stability of the whole machine.

[0030] In this embodiment, after the self-balancing multistage pump with an intermediate throttling seal assembly is assembled, the spring 56 of the intermediate throttling seal assembly 5 is in an extended state, i.e., a stretched state. At this time, the hard alloy wear-resistant coating 58 of the intermediate throttling bushing 51 and the hard alloy wear-resistant coating 58 of the intermediate throttling bushing 52 are in contact. When the self-balancing multistage pump is started and running normally, the fluid medium pressure in the high-pressure chamber 72 of the outlet section 7 is almost twice the fluid medium pressure in the low-pressure chamber 71 of the outlet section 7. When the number of stages of the self-balancing multistage pump is odd, the pressure difference between the fluid medium in the high-pressure chamber 72 and the low-pressure chamber 71 of the outlet section 7 will be even greater. At this time, the pressure difference in the high-pressure chamber 72 of the outlet section 7 will be even greater. The fluid medium enters the inner cavity of the outlet section 7 along the balance leakage hole 59. Then, some of the fluid medium will enter the intermediate throttling sealing assembly 5 along the gap between the intermediate throttling sealing assembly 5 and the outlet section 7 or the gap inside the intermediate throttling sealing assembly 5. This will change the dry friction of the labyrinth seal structure between the intermediate throttling bushing 51 and the intermediate throttling bushing 52 into wet friction, thereby protecting the labyrinth seal structure. In addition, some of the fluid medium in the high pressure chamber 72 and the low pressure chamber 71 of the outlet section 7 will also enter between the hard alloy wear-resistant coating 58 of the intermediate throttling bushing 51 and the intermediate throttling bushing 52, thereby protecting the hard alloy wear-resistant coating 58.

[0031] As the hard alloy wear-resistant coating 58 of the intermediate throttling bushing 51 and intermediate throttling bushing 52 wears, on the one hand, under the action of the spring 56 of the intermediate throttling sealing assembly 5, the axial distance between the two intermediate throttling bushings 51 is reduced as much as possible. On the other hand, the fluid medium in the high-pressure chamber 72 and low-pressure chamber 71 of the outlet section 7 will enter the labyrinth seal structure along the gap between the hard alloy wear-resistant coatings 58. At this time, after the pressure reduction of the radial gap between the hard alloy wear-resistant coatings 58 of the intermediate throttling bushing 51 and intermediate throttling bushing 52 and the pressure reduction of the labyrinth seal structure, the fluid medium pressure between the intermediate throttling bushing 51 and intermediate throttling bushing 52 is less than the fluid medium pressure in the high-pressure chamber 72 and low-pressure chamber 71 of the outlet section 7. At this time, the intermediate throttling bushing 51 will be in the outlet section. Under the pressure of the fluid medium in the high-pressure chamber 72 and low-pressure chamber 71 of section 7, the axial clearance between the intermediate throttling bushing 51 and the intermediate throttling bushing 52 is further reduced, thereby reducing the leakage of the intermediate throttling sealing assembly 5. In addition, the sealing fluid between the intermediate throttling bushing 51 and the intermediate throttling bushing 52 experiences a sudden pressure drop after the pressure is reduced by the radial and axial clearances between the intermediate throttling bushing 51 and the intermediate throttling bushing 52. At the same time, compared with the integrated throttling bushing, the two intermediate throttling bushings 52, the axial O-ring seal 54, the sealing partition 53, the intermediate isolation bushing 55, and the fluid medium in the inner cavity of the water outlet section 7 together constitute a vibration absorption and damping structure, which greatly reduces the risk of sub-resonance instability of the rotor-seal hybrid system and improves the overall operating stability and reliability of the machine.

[0032] When axial movement occurs during the operation of the self-balancing multistage pump, the intermediate throttling bushing 51 of the intermediate throttling sealing assembly 5 will also dynamically adjust the axial clearance between the intermediate throttling bushing 52 in real time under the pressure of the spring 56 and the fluid medium in the high-pressure chamber 72 and low-pressure chamber 71 of the outlet section 7. This ensures that the leakage is not increased, while reducing the erosion and wear of the fluid medium in the high-pressure chamber 72 and low-pressure chamber 71 of the outlet section 7 on the intermediate throttling sealing assembly 5, thus extending the service life of the intermediate throttling sealing assembly 5.

[0033] The above are merely preferred embodiments of the present utility model and are not intended to limit the present utility model. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. An intermediate throttling sealing assembly, comprising an intermediate throttling bushing (51), an intermediate throttling bushing (52), a sealing partition (53), an axial O-ring seal (54), an intermediate isolation bushing (55), a radial O-ring seal (57), a spring (56), and a balance leakage hole (59), characterized in that: Two intermediate throttling bushings (52) are respectively installed on the end face of the high-pressure chamber (72) and the end face of the low-pressure chamber (71) of the outlet section (7) by bolts at the ends. An intermediate isolation bushing (55) is installed between the two intermediate throttling bushings (52). The intermediate isolation bushing (55) is engaged with the groove structure of the two intermediate throttling bushings (52) by the boss structure at both ends. Two sealed cavities are formed between the intermediate isolation bushing (55) and the two intermediate throttling bushings (52). Two sealing partitions (53) are respectively installed in the sealed cavities. Two axial O-rings (54) are set on the intermediate isolation bushing (55). At both ends, two radial O-rings (57) are installed between the intermediate throttling bushing (52) and the two end faces of the outlet section (7). Two intermediate throttling bushings (51) are symmetrically arranged on both sides of the two intermediate throttling bushings (51). The two intermediate throttling bushings (51) are installed on the pump shaft (1) by ordinary flat keys. The end faces between the two intermediate throttling bushings (51) are respectively connected to the two ends of the spring (56). One end of the balance leakage hole (59) is connected to the high pressure chamber (72) of the outlet section (7), and the other end of the balance leakage hole (59) is connected to the internal cavity of the outlet section (7).

2. The intermediate throttling sealing assembly according to claim 1, characterized in that: The radial clearance between the intermediate throttling bushing (52) and the intermediate throttling bushing (51) is 0.08~0.15mm.

3. The intermediate throttling sealing assembly according to claim 1, characterized in that: An annular boss structure is provided at the end face of the intermediate throttling bushing (52). The surface of the annular boss structure is clad with a hard alloy wear-resistant coating (58) by plasma welding. The hard alloy wear-resistant coating (58) is annular and its thickness is 0.1~0.3mm. A labyrinth seal structure is opened on the inner surface of the intermediate throttling bushing (52). The top of the groove of the labyrinth seal structure is treated by nickel plating alloy.

4. The intermediate throttling sealing assembly according to claim 1, characterized in that: The longitudinal cross-section of the intermediate throttling bushing (51) is L-shaped. The end face where the intermediate throttling bushing (51) and the intermediate throttling bushing (52) meet is clad with a hard alloy wear-resistant coating (58) by plasma welding. The hard alloy wear-resistant coating (58) is annular and has a thickness of 0.1~0.3mm. A labyrinth seal structure is opened on the outer circular surface of the intermediate throttling bushing (51). The top of the groove of the labyrinth seal structure is treated by plating nickel-chromium-tungsten alloy.

5. A self-balancing multistage pump with an intermediate throttling seal assembly, characterized in that: The system includes a pump shaft (1), a positive bearing housing assembly (2), an inlet section (3), a positive flow assembly (4), an outlet section (7), an intermediate throttling seal assembly as described in any one of claims 1-4, a positive and negative stage connecting pipe (6), a reverse flow assembly (8), a secondary inlet section (9), a packing seal assembly (10), and a reverse bearing housing assembly (11). The intermediate throttling seal assembly is installed in the inner cavity between the outlet section (7) and the pump shaft (1). The left end face of the intermediate throttling seal assembly is in contact with the end face of the last stage impeller hub of the positive flow assembly (4), and the right end face of the intermediate throttling seal assembly is in contact with the end face of the last stage impeller hub of the reverse flow assembly (8).

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