Single-stage impeller easy to disassemble and assemble and multi-stage centrifugal pump

Abstract

The invention discloses a single-stage impeller easy to disassemble and assemble and a multi-stage centrifugal pump, and aims to solve the problems that an existing single-stage impeller is difficult to disassemble independently and tedious to maintain. One end of an impeller body is designed to be a plane, the other end of the impeller body coaxially protrudes to form a stepped-shaft-shaped sealing boss, the sealing boss comprises a second sealing section with the large diameter and a first sealing section with the small diameter, and a first sealing ring and a second sealing ring are arranged on the second sealing section and the first sealing section respectively. The end face of the first sealing ring forms an annular disassembly acting face by means of the diameter difference. During disassembly, the tool can apply axial force based on the disassembly acting surface, the single-stage impeller is directly and independently pulled out in the axial direction, rapid sequential disassembly and assembly are achieved, and the maintenance efficiency is improved; meanwhile, the integrated sealing carcass shortens the force transmission arm, reduces the bending stress and bending moment of the root of the impeller, and enhances the structural reliability; the improvement only aims at a single-stage impeller, other component connectors of the pump body do not need to be changed, universality is high, and the multi-stage centrifugal pump can be widely applied to upgrading and new design of various multi-stage centrifugal pumps.

Description

Technical Field

[0001] This invention relates to the technical field of multistage centrifugal pumps in mechanical engineering, and particularly to a single-stage impeller and a multistage centrifugal pump that are easy to disassemble and assemble. Background Technology

[0002] A multistage centrifugal pump is a general-purpose mechanical device that uses multiple single-stage impellers connected in series to progressively increase the pressure of fluid. (See attached instruction manual.) Figure 1 and attached Figure 2 As shown, the structural principle of the segmental multistage centrifugal pump is as follows: the drive unit drives the pump shaft 1, which runs through the pump body, to rotate. Several single-stage impellers 2 are fixedly installed on the pump shaft. Each single-stage impeller consists of a front cover plate 3, a rear cover plate 4, and blades 5 sandwiched between them, forming a flow channel from the center to the outer edge. Fluid is drawn in through the inlet 6 of the first single-stage impeller. After gaining kinetic and pressure energy in the high-speed rotating single-stage impeller, it is thrown into the stationary guide vanes 8 fixed in the segment 7 (middle section of the casing). The guide vanes are used to convert part of the fluid's kinetic energy into static pressure energy and guide it in an orderly manner to the inlet of the next single-stage impeller. The single-stage impellers, guide vanes, and segments are sequentially connected to form a booster unit. The entire segmental multistage centrifugal pump is composed of multiple such booster units connected in series by bolts 9 and driven by a single pump shaft, forming a complete multistage booster system.

[0003] To achieve a pressure seal, please refer to the instruction manual. Figure 2 and attached Figure 3 Appendix to Chinese Patent CN205101239U Figure 2 And the appendix to Chinese patent CN105697382A Figure 1 As shown, existing single-stage impellers typically have a front sealing boss 10 and a rear sealing boss 11 protruding at both ends (i.e., the outer sides of the front and rear cover plates), with a sealing ring 12 installed on the sealing boss. Correspondingly, a sealing ring 13 is also provided in the inner hole of the adjacent segment and the inner hole of the guide vane. However, because the sealing ring is directly set on the outer side of the impeller cover plate and close to the root of the blade, the outer surface of the sealing boss is smooth and continuous, lacking a surface for disassembly tools to grip or for direct force application. When maintenance is required, operators cannot apply effective axial tension to the single-stage impeller itself to remove it from the pump shaft. The usual maintenance procedure is to first remove the entire stage assembly, including the target single-stage impeller, the corresponding guide vane, and its segments, from the pump as a whole, and then perform a time-consuming and labor-intensive disassembly operation externally. This results in low maintenance efficiency, increased downtime, and increased labor costs.

[0004] In summary, the existing sealing structure design of segmental multistage centrifugal pump impellers makes it difficult to disassemble single-stage impellers independently, resulting in poor equipment maintainability. Therefore, it is necessary to improve the structure of single-stage impellers to achieve convenient and independent disassembly and assembly of the impellers while ensuring sealing performance. Summary of the Invention

[0005] In view of the above-mentioned shortcomings of the existing technology, the purpose of this invention is to solve the technical problem of the difficulty in independent disassembly of the impeller in the segmental multistage centrifugal pump due to structural limitations, and to provide an easy-to-disassemble single-stage impeller and multistage centrifugal pump, which can achieve the effect of quick and independent disassembly and assembly of the impeller, thereby simplifying the maintenance process and improving the maintainability of the equipment.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] A single-stage impeller that is easy to disassemble and assemble includes an impeller body, on which a sealing boss is formed by protrusion on one axial end face; the sealing boss is stepped shaft-shaped and includes a first sealing section and a second sealing section, the second sealing section is located between the first sealing section and the impeller body, the diameter of the second sealing section is larger than the diameter of the first sealing section, a second sealing ring is fixedly sleeved on the second sealing section, a first sealing ring is fixedly sleeved on the first sealing section, the first sealing ring and the second sealing section have an axial distance, and the end face of the first sealing ring facing the second sealing section serves as the disassembly surface.

[0008] Furthermore, the sealing boss is coaxial with the impeller body, and the end face of the first sealing section is provided with a shaft hole that coaxially penetrates the sealing boss and the impeller body.

[0009] Furthermore, the impeller body has a flow channel inside, one end of which extends to the end face of the second sealing section and forms an inlet, and the other end extends to the outer peripheral surface of the impeller body and forms an outlet.

[0010] Furthermore, there is an axial gap between the end face of the first sealing ring and the first sealing section.

[0011] Furthermore, a mounting portion is formed by a radial protrusion on the outer circumferential surface of the first sealing section. The mounting portion has an axial distance from the second sealing section, and the end face of the first sealing ring facing the second sealing section is flush with the end face of the mounting portion facing the second sealing section.

[0012] The present invention also includes an easily detachable multistage centrifugal pump, which includes a pump shaft and multiple booster units. Each booster unit includes guide vanes, segments, and easily detachable single-stage impellers as described above. A first inlet ring is provided in the inner hole of the guide vane, and the guide vane is fixed inside the segment. The segment has an annular partition extending radially inward, and a second inlet ring is provided in the inner hole of the annular partition. The pump shaft passes through the shaft hole of the single-stage impeller and is fixedly connected. The impeller body is located between the corresponding guide vane and the annular partition of the segment in the adjacent booster unit. A sealing boss passes through the inner holes of the segments and guide vanes in the adjacent booster unit. The end face of the first sealing segment abuts axially with the single-stage impeller of the adjacent booster unit. The first sealing ring is sealed and engaged with the first inlet ring in the adjacent booster unit, and the second sealing ring is sealed and engaged with the second inlet ring in the adjacent booster unit.

[0013] Compared with the prior art, the present invention has the following advantages:

[0014] 1. This invention integrates and reconstructs the sealing bosses on both sides of the existing single-stage impeller into a stepped shaft-like structure on the same side, with the end face of the first sealing ring on it forming the disassembly action surface. During maintenance, the tool can directly apply axial tension to the single-stage impeller based on this disassembly action surface, allowing it to be removed from the pump shaft and guide vanes individually and sequentially. This avoids the cumbersome process of disassembling the impeller, guide vanes, and sections as a whole in the existing structure, thus improving the maintainability and maintenance efficiency of the equipment.

[0015] 2. The present invention shortens and moves forward the existing long cantilever rear sealing boss and integrates it into the stepped shaft-shaped sealing boss. This shortens the lever arm from the impeller force-bearing body to the main force transmission section, reduces the bending stress and alternating bending moment at the impeller root, makes the torque transmission more direct, and improves the impeller's fatigue resistance and long-term structural reliability.

[0016] 3. The improvements of this invention focus on the core rotating component, the single-stage impeller, without changing the interface form of stationary components such as guide vanes and segments. Therefore, this invention has good adaptability to various multistage centrifugal pumps (such as segmental and double-casing pumps) that use sealing rings and mouth rings for interstage sealing. It is highly versatile, facilitates the upgrading and transformation of existing pump types and the design of new pumps, and has broad technology transferability and market application potential.

[0017] 4. The easy-to-disassemble single-stage impeller described in this invention can also be used in volute-type multistage centrifugal pumps, so that the stepped surface that mates with the retaining ring is located in the first sealing section. Since the first sealing section has more inlets protruding from the end face of the second sealing section, the operation is not limited by the impeller inlet size when using tools to disassemble and assemble the retaining ring, thus making disassembly and assembly more convenient. Attached Figure Description

[0018] To make the purpose, technical solution, and advantages of the invention clearer, the invention will now be described in further detail with reference to the accompanying drawings:

[0019] Figure 1 This is a schematic diagram of the structure of a segmental multistage centrifugal pump in the background art;

[0020] Figure 2 for Figure 1 Enlarged view of point A in the middle;

[0021] Figure 3 This is a schematic diagram of the structure of an existing single-stage impeller in the background art;

[0022] Figure 4 This is a schematic diagram of the structure of the multi-stage centrifugal pump described in Example 1;

[0023] Figure 5 for Figure 4 Enlarged view of point B in the middle;

[0024] Figure 6 This is a schematic diagram of the easily detachable single-stage impeller described in Example 1;

[0025] Figure 7 This is a schematic diagram of the existing volute multistage centrifugal pump described in Example 2;

[0026] Figure 8 This is a schematic diagram of the structure of a volute-type multistage centrifugal pump using an easily disassembled single-stage impeller in Example 2.

[0027] The components include: pump shaft 1, single-stage impeller 2, front cover plate 3, rear cover plate 4, blades 5, inlet 6, section 7, guide vane 8, bolt 9, front sealing boss 10, rear sealing boss 11, sealing ring 12, and inlet ring 13; impeller body 14, sealing boss 15, first sealing section 16, second sealing section 17, second sealing ring 18, first sealing ring 19, disassembly working surface 20, shaft hole 21, outlet 22, mounting part 23, first inlet ring 24, annular partition 25, and second inlet ring 26; volute 27, mounting cavity 28, volute flow channel 29, and retaining ring 30. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to represent selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0030] It should be noted that similar reference numerals and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the figures, or the orientation or positional relationship commonly used when the product is in use. They are only for the convenience of describing the invention 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 the invention. Furthermore, the terms "first," "second," and "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance. In addition, the terms "horizontal," "vertical," etc., do not indicate that the component is required to be absolutely horizontal or suspended, but can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted. In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0031] Example 1:

[0032] See Figure 6 A single-stage impeller that is easy to disassemble and assemble includes an impeller body 14. A sealing boss 15 is formed on one axial end face of the impeller body 14. In this embodiment, the other axial end face is a plane. The sealing boss 15 is in the shape of a stepped shaft and includes a first sealing section 16 and a second sealing section 17. The second sealing section 17 is located between the first sealing section 16 and the impeller body 14. The diameter of the second sealing section 17 is larger than the diameter of the first sealing section 16. A second sealing ring 18 is fixedly sleeved on the second sealing section 17. A first sealing ring 19 is fixedly sleeved on the first sealing section 16. The first sealing ring 19 and the second sealing section 17 have an axial distance. The end face of the first sealing ring 19 facing the second sealing section 17 serves as the disassembly surface 20.

[0033] The easily detachable single-stage impeller of the present invention integrates the sealing bosses on both sides of the existing impeller to the same side and designs it as a stepped shaft, consisting of a first sealing section 16 and a second sealing section 17 with different diameters; the smaller diameter first sealing section 16 is used to extend into the inner hole of the guide vane 8 in the adjacent booster unit, and the first sealing ring 19 on it (usually fixed by welding) forms a seal with the first opening ring 24 in the inner hole of the guide vane 8; the larger diameter second sealing section 17 is used to extend into the inner hole of the segment 7 in the adjacent booster unit, and the second sealing ring 18 on it (also usually fixed by welding) forms a seal with the second opening ring 26 in the inner hole of the segment 7;

[0034] First, the end face of the first sealing ring 19 facing the second sealing section 17 naturally forms an annular step due to the difference in their diameters, serving as the disassembly surface 20 for axial force. When disassembly is required, after removing the previous stage booster unit, maintenance tools (such as pullers) can directly act on the disassembly surface 20 to apply axial tension to the single-stage impeller, thereby pulling the single-stage impeller out separately from the pump shaft 1 and the corresponding guide vane 8. This achieves truly independent and sequential disassembly and assembly, avoiding the cumbersome process of disassembling the single-stage impeller, guide vane 8, and section 7 as a whole under the existing structure, thus improving maintenance efficiency.

[0035] Secondly, the existing impeller has a relatively long rear sealing boss, which is equivalent to a cantilever beam extending from the impeller body 14. The keyway for installing the sealing ring and transmitting torque is located at the end of this cantilever, resulting in a long driving force transmission path and a large lever arm, generating significant bending stress and additional bending moment. The present invention shortens the axial distance from the impeller body 14 (the force-bearing body) to the keyway (if provided) or main force-bearing section on the first sealing section 16 by moving the sealing function forward and integrating it into the stepped shaft-shaped sealing boss 15. The shortening of the lever arm directly reduces the bending stress and alternating bending moment at the root of the impeller body 14, making the torque transmission between the impeller body 14 and the pump shaft 1 more direct and efficient. This improves the ability of the single-stage impeller to resist fatigue damage during long-term operation and enhances structural reliability.

[0036] Furthermore, the improvements of this invention focus on the sealing boss of the single-stage impeller, without making any radical changes to the interface form of stationary components (such as guide vanes 8 and segments 7). Whether it is a segment 7 type multistage centrifugal pump or a double-casing multistage centrifugal pump, as long as it adopts the basic structure of multiple single-stage impellers connected in series and sealing between stages through sealing rings and mouth rings, the single-stage impeller proposed in this invention can be directly adapted and applied. Therefore, this invention can be widely applied to the upgrading and transformation of most existing multistage centrifugal pumps and the design of new pumps, and has great technology transfer value and market application potential.

[0037] See Figure 6The sealing boss 15 is coaxial with the impeller body 14, and the end face of the first sealing section 16 is provided with a shaft hole 21 that coaxially penetrates the sealing boss 15 and the impeller body 14. In this way, it is clear that the sealing boss 15 is coaxial with the impeller body 14 and is provided with a through shaft hole 21, which ensures that the single-stage impeller can be accurately fitted onto the pump shaft 1 and transmit torque through connecting parts such as keys, thus ensuring the functional basis of the single-stage impeller as a rotating component.

[0038] See Figure 6 The impeller body 14 has a flow channel inside. One end of the flow channel extends to the end face of the second sealing section 17 and forms an inlet 6, while the other end extends to the outer circumferential surface of the impeller body 14 and forms an outlet 22. This clarifies that the inlet 6 of the flow channel is located at the end face of the second sealing section 17, and the outlet 22 is located at the outer circumferential surface of the impeller body 14. This indicates that the larger diameter second sealing section 17 not only serves as a component of the mechanical seal and disassembly structure but also constitutes the water inlet boundary of the impeller flow channel. This ensures that while the single-stage impeller is structurally innovative, its core fluid pressurization function is retained and realized. It also shows that this improvement scheme is an inheritance and optimization of the existing single-stage impeller structural design, rather than a disruptive change to it.

[0039] See Figure 6 The end faces of the first sealing ring 19 and the first sealing section 16 have an axial gap. This requires that a certain axial gap be maintained between the end faces of the first sealing ring 19 and the first sealing section 16 (i.e., the end away from the impeller body 14) to prevent rigid contact or interference between the end face of the first sealing ring 19 and the adjacent impeller body 14 during assembly or operation. This not only ensures that each single-stage impeller can be compactly connected in series on the pump shaft 1, but also ensures that the gap seal between the first sealing ring 19 and the first inlet ring 24 is not disturbed in the designed position and throughout the entire operation, thereby maintaining the necessary sealing performance.

[0040] See Figure 6 A mounting portion 23 is formed by a radial protrusion on the outer peripheral surface of the first sealing section 16. The mounting portion 23 has an axial distance from the second sealing section 17. The end face of the first sealing ring 19 facing the second sealing section 17 is flush with the end face of the mounting portion 23 facing the second sealing section 17. In this way, a radially protruding mounting portion 23 is provided on the outer peripheral surface of the first sealing section 16, which provides a precise axial positioning reference for the first sealing ring 19 (usually fixed by welding). When the first sealing ring 19 is welded and installed, its end face can be made flush with the end face of the mounting portion 23, thereby ensuring that the first sealing ring 19 is fixed in the designed axial position. This is crucial for controlling the sealing gap between it and the first sealing ring 24.

[0041] Please see Figure 4 and Figure 5This embodiment also includes an easily detachable multistage centrifugal pump. The multistage centrifugal pump is segmental and includes a pump shaft 1 and multiple booster units. Each booster unit includes a guide vane 8, a segment 7, and an easily detachable single-stage impeller as described above. A first inlet ring 24 is provided in the inner hole of the guide vane 8. The guide vane 8 is fixed inside the segment 7. The segment 7 has an annular partition 25 extending radially inward. A second inlet ring 26 is provided in the inner hole of the annular partition 25. The pump shaft 1 passes through the shaft hole 21 of the single-stage impeller and is fixedly connected. The impeller body 14 is located between the corresponding guide vane 8 and the annular partition 25 of the segment 7 in the adjacent booster unit. The sealing boss 15 passes through the inner holes of the segment 7 and the guide vane 8 in the adjacent booster unit. The end face of the first sealing section 16 abuts against the axial direction of the single-stage impeller of the adjacent booster unit. The first sealing ring 19 is sealed and engaged with the first inlet ring 24 in the adjacent booster unit. The second sealing ring 18 is sealed and engaged with the second inlet ring 26 in the adjacent booster unit.

[0042] In this way, the easily disassembled single-stage impeller of the present invention is applied to a complete segmental multistage centrifugal pump. The impeller body 14 is located between the guide vane 8 of the current stage and the annular partition 25 of the segment 7 of the adjacent stage. The stepped sealing boss 15 extends into the inner hole of the segment 7 and the guide vane 8 of the adjacent stage, and forms a clearance fit with the first inlet ring 24 of the guide vane 8 and the second inlet ring 26 of the segment 7 through the first sealing ring 19 and the second sealing ring 18, respectively. This allows the advantage of independent disassembly based on the single-stage impeller to be realized at the pump level. During maintenance, the corresponding single-stage impeller can be pulled out separately by using the disassembly action surface 20 formed by the first sealing ring 19 when disassembling the booster unit step by step, without having to disassemble the entire booster unit first. This improves the maintainability of the equipment, reduces the overall maintenance cost, and reflects the ultimate application value of the present invention.

[0043] Example 2:

[0044] In addition to the segmental multistage centrifugal pump mentioned in the background technology and Example 1, there is also the volute multistage centrifugal pump. The radially split structure of an existing volute multistage centrifugal pump is as follows: Figure 7 As shown, it mainly includes a volute 27, a pump shaft 1, and multiple existing single-stage impellers as described in the background art (see...). Figure 3The volute 27 is a radially split structure, consisting of an upper shell and a lower shell fastened together by bolts (not shown in the figure). The volute 27 has a cavity that extends spirally along the axial direction. The cavity includes axially alternating mounting cavities 28 and volute flow channels 29. The pump shaft 1 passes through the cavity. Each single-stage impeller is arranged one-to-one in each mounting cavity 28. The single-stage impellers are synchronously rotated and mounted on the pump shaft 1. Fluid is drawn in through the inlet 6 of the first single-stage impeller. After gaining kinetic and pressure energy in the high-speed rotating single-stage impeller, it is thrown into the volute flow channel 29. The volute flow channel 29 converts part of the fluid's kinetic energy into static pressure energy and guides it in an orderly manner to the inlet 6 of the next single-stage impeller.

[0045] In a segmental multistage centrifugal pump, all impellers, guide vanes, and segments are axially bolted together into a tight, rigid, monolithic column with virtually no possibility of relative movement. Figure 2 and Figure 5 As shown, each single-stage impeller transmits the clamping force through axial contact; however, for a volute-type multistage centrifugal pump, the pump shaft 1 and its multiple single-stage impellers are installed as a whole, suspended and placed in the lower casing, with each single-stage impeller needing to be independently positioned in its corresponding mounting cavity 28; therefore, as Figure 7 As shown, in a volute-type multistage centrifugal pump, retaining rings 30 are axially spaced on the pump shaft 1. On the single-stage impeller, a stepped surface is formed between the end face where the inlet 6 is located and the inner hole, which is used to cooperate with the retaining rings 30, thereby restricting the axial movement of the single-stage impeller; however, as Figure 7 As shown, in existing single-stage impellers, the retaining ring 30 is flush with or lower than the end face of the impeller inlet 6. When using tools to install or remove the retaining ring, it is easily limited by the inlet size of the impeller.

[0046] This embodiment is a volute-type multistage centrifugal pump. This volute-type multistage centrifugal pump uses a single-stage impeller that is easy to disassemble and assemble, as described in Embodiment 1. Figure 8 As shown, the stepped surface for engaging with the retaining ring 30 is located in the first sealing section 16. The first sealing section 16 has a large number of inlets 6 protruding from the end face of the second sealing section 17. When using tools to disassemble and assemble the retaining ring, the operation is not limited by the inlet size of the impeller. Compared with the existing volute multistage centrifugal pump that uses a single-stage impeller, the disassembly and assembly of the single-stage impeller in this volute multistage centrifugal pump is more convenient.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit the technical solutions. Those skilled in the art should understand that any modifications or equivalent substitutions to the technical solutions of the present invention without departing from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A single stage impeller which is easily disassembled, characterized by: The impeller body includes a sealing boss protruding from an axial end face of the impeller body; the sealing boss is in the shape of a stepped shaft and includes a first sealing section and a second sealing section, the second sealing section is located between the first sealing section and the impeller body, the diameter of the second sealing section is greater than that of the first sealing section, a second sealing ring is fixedly sleeved on the second sealing section, a first sealing ring is fixedly sleeved on the first sealing section, the first sealing ring has an axial spacing from the second sealing section, and an end face of the first sealing ring facing the second sealing section serves as a dismounting surface.

2. The easily detachable single stage impeller as claimed in claim 1, wherein: The sealing boss is coaxial with the impeller body, and an axial hole is formed in the end face of the first sealing section and penetrates the sealing boss and the impeller body.

3. The easily detachable single stage impeller as claimed in claim 2 wherein: The impeller body has a flow channel inside, one end of the flow channel extends to an end face of the second sealing section and forms an inlet, and the other end of the flow channel extends to an outer peripheral surface of the impeller body and forms an outlet.

4. The easily detachable single stage impeller as claimed in claim 2 wherein: The first sealing ring has an axial spacing from the end face of the first sealing section.

5. The easily removable single stage impeller as claimed in claim 4 wherein: A plurality of mounting portions are radially protruding from an outer peripheral surface of the first sealing section, the mounting portions have an axial spacing from the second sealing section, and an end face of the first sealing ring facing the second sealing section is flush with an end face of the mounting portions facing the second sealing section.

6. A multi-stage centrifugal pump of the removable type, characterized in that: The pump shaft and a plurality of booster units are included, the booster unit includes a guide vane, a segment and the easily dismountable single-stage impeller as claimed in any one of claims 2-5; a first ring is arranged in an inner hole of the guide vane, the guide vane is fixed inside the segment, the segment has an annular partition plate extending radially inwardly, and a second ring is arranged in an inner hole of the annular partition plate; the pump shaft passes through the axial hole of the single-stage impeller and is fixedly connected, the impeller body is located between the guide vane and the annular partition plate of the segment of the adjacent booster unit, the sealing boss passes through the inner holes of the segment and the guide vane of the adjacent booster unit, the end face of the first sealing section axially abuts against the single-stage impeller of the adjacent booster unit, the first sealing ring is in sealing cooperation with the first ring of the adjacent booster unit, and the second sealing ring is in sealing cooperation with the second ring of the adjacent booster unit.

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