High-reliability multi-stage centrifugal pump

Abstract

The invention discloses a high-reliability multi-stage centrifugal pump which comprises an outer cylinder body, a main shaft, a first-stage middle section, a flow guide body, a last-stage middle section, a pump cover and a suction side stuffing box body, wherein the first-stage middle section, the flow guide body and the last-stage middle section are coaxially mounted in the outer cylinder body, and impellers are mounted on the main shaft and matched with the first-stage middle section, the flow guide body and the last-stage middle section; the pump cover and the suction measuring stuffing box body are each provided with a bearing body, bearings are arranged in the bearing bodies and used for slewing bearing of the main shaft, stepped holes used for installation of shell sealing rings are formed in the first-stage middle section, the flow guide body and the last-stage middle section, impeller sealing rings are installed at the two ends of the impeller, and the impeller sealing rings are in running fit with the shell sealing rings. The balancing drum is installed on the main shaft and located at the position of the pump cover, the axis of the stepped hole has a downward eccentric distance ei in the plumb line direction relative to the outer circle axis of the corresponding first-stage middle section, the flow guide body and the last-stage middle section, and the eccentric distance ei = yi-yp.

Description

Technical Field

[0001] The present application relates to the technical field of centrifugal pumps, and in particular to a high-reliability multi-stage centrifugal pump. Background Art

[0002] Horizontal multi-stage centrifugal pumps are widely used, especially in working conditions that require high-pressure pumping. Multi-stage centrifugal pumps are used to pump media. In the existing technology, this type of centrifugal pumps are designed to have stepped holes for installing casing sealing rings on the first-stage middle section, the guide body, and the last-stage middle section to coincide with the theoretical axis of the main shaft. In order to increase the pumping pressure, multi-stage centrifugal pumps are generally designed to have more stages. Since multi-stage centrifugal pumps have a large number of impellers and a guide body structure must be set between the impellers at each stage, the length of the entire rotor is long, resulting in a large span between the bearings at both ends. Figure 1 As shown, the main shaft 1 will naturally form a relatively rigid theoretical axis 12 with a downward bending eccentricity under the action of its own weight and the weight of the impeller, that is, the actual axis 13 of the main shaft 1 is a flexible arc line bending downward, and under the same conditions, the more stages the multi-stage pump has, the greater the eccentricity phenomenon is, which is equivalent to generating a relatively large additional wear pressure on the lower side of the dynamic and static operating gaps (that is, the fitting between the casing sealing ring 8 and the impeller sealing ring 9), causing early wear of the fitting surface on the lower side of the operating gap. Since the fitting between the casing sealing ring 8 and the impeller sealing ring 9 becomes an approximate ellipse after wear, the upper gap of the fitting is large, resulting in increased volume loss of the pump, and reduced efficiency and head. The usual solution is to design the main shaft diameter to be larger to enhance the rigidity of the shaft and make the actual axis line 13 coincide with the theoretical axis line 12. However, this method will increase the cost and cannot be implemented due to the limitations of the impeller hydraulic structure. There is also a method of increasing the operating gap size to avoid collision and wear at the dynamic and static operating gaps (that is, the fitting between the casing sealing ring 8 and the impeller sealing ring 9), which will also increase the volume loss of the pump, and both efficiency and head will decrease. The applicant proposed this case through research and experiments. Summary of the Invention

[0003] The purpose of this application is to provide a high-reliability multi-stage centrifugal pump to solve the problems in the prior art.

[0004] To achieve the above-mentioned purpose, the present application provides the following technical solutions: a high-reliability multi-stage centrifugal pump, comprising an outer cylinder 4, a main shaft 1, a first-stage middle section 10, a guide body 7, and a final-stage middle section 11 coaxially mounted in the outer cylinder 4, wherein the guide body 7 has a plurality of impellers 6 arranged between the first-stage middle section 10 and the final-stage middle section 11, and the main shaft 1 is paired with the first-stage middle section 10, the guide body 7, and the final-stage middle section 11. The pump also includes a pump cover 5 and a suction-side stuffing box 19 respectively arranged at both ends of the outer cylinder 4, and the pump cover 5 and the suction-side stuffing box 19 are both equipped with shafts. The bearing body 2 is provided with a bearing 3 for slewing support of the main shaft 1. The first-stage middle section 10, the guide body 7, and the final-stage middle section 11 are all provided with a step hole 17 for installing the casing sealing ring 8. Impeller sealing rings 9 are installed at both ends of the impeller 6. The impeller sealing ring 9 and the casing sealing ring 8 are rotated together. It also includes a balance drum 22 installed on the main shaft 1 and located at the pump cover 5. The axis of the step hole 17 has a downward eccentricity e in the direction of the plumb line relative to the corresponding outer axis of the first-stage middle section 10, the guide body 7, and the final-stage middle section 11. i , the eccentricity e i =y i -y p ;y i is the eccentricity of the impeller 6 position on the main shaft 1 corresponding to the first-stage middle section 10, the guide body 7, and the final-stage middle section 11, y p is the eccentricity of the balance drum 22 on the main shaft 1; wherein,

[0005] , where G i a is the load position of the impeller 6; a i is the axial distance from the impeller 6 to one of the bearings 3 close to the balance drum 22; L is the distance between the two bearing 3 fulcrums; E is the elastic modulus of the material of the main shaft 1; J i is the average moment of inertia at the position of the impeller 6;

[0006] , where d i is the shaft diameter of the main shaft 1 at the position of the impeller 6;

[0007] , where G p a For the load position of the balance drum 22; a p is the axial distance from the balance drum 22 to the adjacent bearing 3; L is the distance between the two bearing 3 fulcrums; E is the elastic modulus of the material of the main shaft 1; J p is the average moment of inertia at the balance drum 22;

[0008] , where d p is the shaft diameter of the main shaft 1 at the balance drum 22.

[0009] Preferably, the guide body 7 includes radial guide vanes 701 and a guide body middle section 702 of an integrated structure; the guide body 7 is provided with an annular groove 703 on the end surface of one side of the radial guide vane 701, and an axially protruding convex ring 704 is provided on one side of the guide body middle section 702. The annular groove 703 and the convex ring 704 are coaxial with the outer circle of the guide body 7, and an interference fit of 0.005 to 0.03 mm is provided between the outer circle of the convex ring 704 of two adjacent guide bodies 7 and the corresponding inner wall of the annular groove 703.

[0010] Preferably, each of the step holes 17 on the guide body 7 has two respectively located on the guide body middle section 702 and the radial guide vane 701 , and the inner diameter of the step hole 17 located on the guide body middle section 702 is larger than the inner diameter of the step hole 17 located on the radial guide vane 701 .

[0011] Preferably, the guide body 7 is further provided with a pin hole position A and a pin hole position B, and the center of the pin hole position A is located on the extension line of the line connecting the center of the step hole 17 and the outer circle center of the guide body 7, the line connecting the center of the pin hole position B and the outer circle center of the guide body 7 and the line connecting the pin hole position A and the outer circle center of the guide body 7 have an angle 18, and the angle 18 is 40-50 degrees; the guide body 7 is provided with a short pin hole 15 and a long pin hole 16, the long pin hole 16 axially penetrates the guide body 7 and includes a large hole section 1601 and a small hole section 1602 that are coaxially connected, the short pin hole 15 is a countersunk hole and opens on the same side as the large hole section 1601, wherein the short pin holes 15 and the long pin holes 16 on two adjacent guide bodies 7 are alternately formed at the pin hole position A and the pin hole position B, respectively.

[0012] Preferably, the high-reliability multi-stage centrifugal pump further includes a positioning pin 14, which is used to pass through the large hole section 1601 and be sleeved into the small hole section 1602 and the short pin hole 15, so that all the step holes 17 are located on the same side relative to the outer circle center of the guide body 7.

[0013] Preferably, a plurality of through holes 21 are evenly distributed circumferentially on the guide body 7 and the final-stage middle section 11, and the axes of the through holes 21 are parallel to the outer circle axis of the guide body 7. A plurality of threaded holes 23 are provided on the first-stage middle section 10 corresponding to the through holes 21; it also includes a tensioning stud 20 that is passed through the through hole 21 and has external thread sections formed at both ends. The external thread section at one end of the tensioning stud 20 is screwed into the threaded hole 23, and the external thread section at the other end is exposed from the final-stage middle section 11 and is screwed with a nut 24. The tensioning stud 20 and the nut 24 are used to connect the first-stage middle section 10, the guide body 7 and the final-stage middle section 11 into a whole.

[0014] The beneficial effects of the present application are as follows: the high-reliability multi-stage centrifugal pump provided by the present application adopts an eccentric setting for the step holes for installing the casing sealing rings on the middle section of the first stage, the guide body, and the middle section of the last stage, so that the actual axis center line of the main shaft at the fitting point of the impeller sealing ring and the casing sealing ring of each impeller coincides with the center line of the step hole at the corresponding position, so that the main shaft works in its own flexible position, effectively reducing the collision and wear at the fitting point between the casing sealing ring and the impeller sealing ring, thereby ensuring the operation reliability of the multi-stage centrifugal pump. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A cross-sectional view of the high-reliability multi-stage centrifugal pump of the present application;

[0016] Figure 2 This is the main view of the diverter body of this application;

[0017] Figure 3 for Figure 2 Middle CC section view;

[0018] Figure 4 This is a rear view of the guide body of this application;

[0019] Figure 5 for Figure 4 Middle DD section view;

[0020] Figure 6 This is a schematic diagram for calculating the eccentricity of the high-reliability multi-stage centrifugal pump of this application. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0022] See also Figure 1-6A high-reliability multi-stage centrifugal pump provided in an embodiment of the present application is now described. The high-reliability multi-stage centrifugal pump includes an outer cylinder 4, a main shaft 1, a first-stage middle section 10 coaxially installed in the outer cylinder 4, a guide body 7, and a final-stage middle section 11. The guide body 7 has a plurality of impellers 6 arranged between the first-stage middle section 10 and the final-stage middle section 11. The main shaft 1 is paired with the first-stage middle section 10, the guide body 7, and the final-stage middle section 11. The pump cover 5 and the suction-side stuffing box body 19 are respectively arranged at both ends of the outer cylinder 4. The pump cover 5 and the suction-side stuffing box body 19 They are all equipped with a bearing body 2, in which a bearing 3 is installed for slewing support of the main shaft 1. The first-stage middle section 10, the guide body 7, and the final-stage middle section 11 are all provided with a step hole 17 for installing the casing sealing ring 8. Impeller sealing rings 9 are installed at both ends of the impeller 6. The impeller sealing ring 9 and the casing sealing ring 8 rotate together. It also includes a balance drum 22 installed on the main shaft 1 and located at the pump cover 5. The axis of the step hole 17 has a downward eccentricity e in the direction of the plumb line relative to the outer axis of the corresponding first-stage middle section 10, the guide body 7, and the final-stage middle section 11. i , eccentricity e i =y i -y p ;y i The eccentricity of the impeller 6 on the main shaft 1 corresponding to the first-stage middle section 10, the guide body 7, and the final-stage middle section 11, in mm; p is the eccentricity of the balance drum 22 on the main shaft 1, in mm;

[0023] , where G i The load at the impeller 6 position is in kgf; a i is the axial distance from the impeller 6 to a bearing 3 close to the balance drum 22, in cm; L is the distance between the two bearing 3 fulcrums, in cm; E is the elastic modulus of the main shaft 1 material, in kgf / cm 2 ;J i is the average moment of inertia of impeller 6, unit: kgf / cm 2 ;

[0024] , where d i The diameter of the main shaft 1 at the impeller 6 is in cm;

[0025] , where G p a For the load of the balance drum 22 position, the unit is kgf; a p is the axial distance from the balance drum 22 to the adjacent bearing 3, in cm; L is the distance between the two bearing 3 fulcrums, in cm; E is the elastic modulus of the main shaft 1 material, in kgf / cm 2 ;Jp is the average moment of inertia at the balance drum 22, in kgf / cm 2 ;

[0026] , where d p The diameter of the main shaft 1 at the balance drum 22, in cm.

[0027] According to the above structure provided in this embodiment, the high-reliability multi-stage centrifugal pump provided in this embodiment adopts an eccentric arrangement of the stepped holes 17 for mounting the casing sealing ring 8 on the first-stage middle section 10, the guide body 7, and the final-stage middle section 11, so that the actual axis centerline 13 of the main shaft 1 at the fitting point between the impeller sealing ring 9 of each impeller 6 and the casing sealing ring 8 coincides with the centerline of the stepped hole 17 at the corresponding position, so that the main shaft 1 operates in its own flexible position, effectively reducing the collision and wear at the fitting point between the casing sealing ring 8 and the impeller sealing ring 9, thereby ensuring the operational reliability of the multi-stage centrifugal pump; the principle of reducing the collision and wear at the fitting point between the casing sealing ring 8 and the impeller sealing ring 9 by adopting the above structure is as follows: when the shaft diameter of the main shaft 1, the distance between the bearings 3 as the fulcrum of rotation, and the load at the corresponding position on the main shaft 1 are determined, the maximum flexible eccentricity of the main shaft 1 at any position is determined. At this time, the actual rotation axis of the main shaft 1 is the actual axis centerline 13 of the flexible bending of the main shaft 1. Since the outer circle axes of the first-stage middle section 10, the guide body 7 and the final-stage middle section 11 are coaxial with the axes of the bearings 3 at both ends after assembly, each step hole 17 is designed to have an eccentric structure, so that the axial position of each step hole 17 after assembly coincides with the actual axial centerline 13 at the corresponding position of the main shaft 1. In this way, the bearing capacity of the main shaft 1 itself is fully utilized, that is, the rotation axis of the main shaft 1 at the impeller 6 is coaxial with the rotation axis of the impeller sealing ring 9 relative to the housing sealing ring 8, so that the fitting clearance between the impeller sealing ring 9 and the housing sealing ring 8 at the corresponding positions is uniform and does not wear eccentrically; it avoids the forced lifting and supporting effect of the step hole 17 on the actual axial centerline 13 of the main shaft 1 when the axial centerline of the step hole 17 is designed to be coaxial with the theoretical axial centerline 12 of the main shaft 1 in a rigid state in the traditional design, resulting in the main shaft 1 generating additional pressure on the lower side of the fitting surface of the impeller sealing ring 9 and the housing sealing ring 8, thereby causing collision and eccentric load wear, thereby effectively ensuring the operation reliability of the multi-stage centrifugal pump.

[0028] In another embodiment of this application, please refer to Figures 1 to 6The guide body 7 includes a radial guide vane 701 and a guide body middle section 702 of an integrated structure; an annular groove 703 is provided on the end face of the radial guide vane 701 on one side of the guide body 7, and an axially protruding convex ring 704 is provided on one side of the guide body middle section 702. The annular groove 703 and the convex ring 704 are coaxial with the outer circle of the guide body 7, and there is an interference fit of 0.005 to 0.03 mm between the outer circle of the convex ring 704 of two adjacent guide bodies 7 and the corresponding inner wall of the annular groove 703. Correspondingly, annular grooves 703 or convex rings 704 are also provided on the first-stage middle section 10 and the final-stage middle section 11, so that the first-stage middle section 10 and the guide body 7 as well as the guide body 7 and the final-stage middle section 11 can be completed. According to the above structure provided in this embodiment, the coaxiality between the first-stage middle section 10, each guide body 7, and the final-stage middle section 11 after assembly is ensured. At the same time, it is also ensured that the eccentricity directions of the step holes 17 on the first-stage middle section 10, each guide body 7, and the final-stage middle section 11 after assembly are in the same direction, and it is easy to disassemble and maintain.

[0029] In another embodiment of this application, please refer to Figures 1 to 6 , each step hole 17 on the guide body 7 has two respectively located on the middle section 702 of the guide body and the radial guide vane 701. The inner diameter of the step hole 17 located on the middle section 702 of the guide body is larger than the inner diameter of the step hole 17 located on the radial guide vane 701. Here, a casing sealing ring 8 installed in the step hole 17 at the middle section 702 of the guide body cooperates with an impeller sealing ring 9 installed on the hub side of the impeller 6, and a casing sealing ring 8 installed in the step hole 17 at the radial guide vane 701 cooperates with an impeller sealing ring 9 installed on the suction side of the impeller 6. The sealing ring 9 cooperates with each other; by designing the inner diameter of the step hole 17 on the middle section 702 of the guide body to be larger than the inner diameter of the step hole 17 on the radial guide vane 701, the sizes of the casing sealing ring 8 and the impeller sealing ring 9 are adapted to the impeller 6, effectively ensuring the stability of the multi-stage centrifugal pump; at the same time, the radial guide vane 701 and the middle section 702 of the guide body 7 are designed as an integrated structure, which improves the consistency of the position accuracy of the two step holes 17 on the same guide body 7, which is conducive to ensuring the assembly quality and improving the reliability of the multi-stage centrifugal pump.

[0030] In another embodiment of this application, please refer to Figures 1 to 6The guide body 7 is also provided with a pin hole position A and a pin hole position B. The center of pin hole position A is located on the extension line of the line connecting the center of the stepped hole 17 and the outer center of the guide body 7. The line connecting the center of pin hole position B and the outer center of the guide body 7 forms an angle 18 with the line connecting pin hole position A and the outer center of the guide body 7. Angle 18 is 40-50 degrees; in this embodiment, angle 18 is preferably 45 degrees. The guide body 7 is provided with a short pin hole 15 and a long pin hole 16. The long pin hole 16 axially extends through the guide body 7 and includes a large hole section 1601 and a small hole section 1602 that are coaxially connected. The short pin hole 15 is a countersunk hole and opens on the same side as the large hole section 1601. The short pin holes 15 and long pin holes 16 on two adjacent guide bodies 7 are alternately formed at pin hole position A and pin hole position B, respectively. According to the above structure provided in this embodiment, on the one hand, by providing the short pin hole 15 and the long pin hole 16, it is convenient to determine the phase of the step hole 17 in the circumferential direction of the guide body 7 and the relative position of the through hole 21 (described later) during processing, thereby forming a reliable assembly reference. By cooperating with the positioning pin 14, the short pin hole 15 and the long pin hole 16, and the convex ring 704 and the annular groove 703, it is possible to ensure that the phase consistency of the step holes 17 on each guide body 7, the first-stage middle section 10 and the final-stage middle section 11 in the circumferential direction of the guide body 7 after assembly; on the other hand, by designing the short pin holes 15 and the long pin holes 16 on two adjacent guide bodies 7 to be alternately formed at the pin hole position A and the pin hole position B, each guide body 7 only needs to process one short pin hole 15 and one long pin hole 16, thereby realizing the guide body 7. Sequential assembly; specifically, for example, when the short pin hole 15 on the guide body 7 corresponding to an impeller 6 is formed at the pin hole position A, the long pin hole 16 is formed at the pin hole position B, then the long pin hole 16 on the guide body 7 corresponding to the impeller 6 of the next stage after the current impeller 6 is formed at the pin hole position A on the guide body 7, and the short pin hole 15 is formed at the pin hole position B. It can be understood that the short pin hole 15 and / or the long pin hole 16 are also determined to correspond to the pin hole position A and the pin hole position B of the guide body 7 on the first-stage middle section 10 and the last-stage middle section 11, that is, the first-stage middle section 10, the guide body 7, and the last-stage middle section 11 can be accurately positioned and connected by cooperating with the locating pin 14, the short pin hole 15 and the long pin hole 16, and the annular groove 703 and the convex ring 704.

[0031] In another embodiment of this application, please refer to Figures 1 to 6The high-reliability multi-stage centrifugal pump also includes a locating pin 14, which is used to pass through the large hole section 1601 and be connected to the small hole section 1602 and the short pin hole 15, so that all the step holes 17 are located on the same side relative to the outer circle center of the guide body 7. In this way, due to the thickness of the guide body 7, by setting the long pin hole 16 to have a large hole section 1601 that does not cooperate with the locating pin 14 and a small hole section 1602 that cooperates with the locating pin 14, on the one hand, it is beneficial to reduce the length of the high-precision hole, thereby saving machining hours and thus saving costs; on the other hand, making the small hole section 1602 for cooperation have a suitable length, which is beneficial to reducing the difficulty during assembly and improving positioning accuracy; further, a tapered section is provided at the connection between the large hole section 1601 and the small hole section 1602 and at the opening of the short pin hole 15 for guiding the locating pin 14, which further reduces the difficulty of assembly.

[0032] In another embodiment of this application, please refer to Figures 1 to 6 , a number of through holes 21 are evenly distributed on the guide body 7 and the final middle section 11, the axes of the through holes 21 are parallel to the outer circle axis of the guide body 7, and a number of threaded holes 23 are provided on the first-stage middle section 10 corresponding to the through holes 21; it also includes a tightening stud 20 that is penetrated through the through hole 21 and has external thread sections at both ends, the external thread section at one end of the tightening stud 20 is screwed into the threaded hole 23, and the external thread section at the other end is exposed from the final middle section 11 and is screwed with a nut 24, the tightening stud 20 and the nut 24 are used to connect the first-stage middle section 10, the guide body 7 and the final middle section 11 into a whole, so that the first-stage middle section 10, the guide body 7 and the final middle section 11 constitute a stable component, which is convenient for installation on the outer cylinder 4. It can be understood that the installation connection between the component and the outer cylinder 4 can adopt the existing technology.

[0033] It should be noted that, in this article, the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements that are inherent to such process, method, article or apparatus.

[0034] In the description of this application, it should be understood that the terms "upper", "lower", "one end", "the other end", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application.

[0035] At the same time, the contents not described in detail in this specification belong to the existing technology well known to those skilled in the art.

[0036] Although the embodiments of the present application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A high-reliability multistage centrifugal pump, comprising an outer cylinder (4), a main shaft (1), a first-stage middle section (10) coaxially mounted in the outer cylinder (4), a guide body (7), and a final-stage middle section (11), wherein the guide body (7) has a plurality of impellers (6) arranged between the first-stage middle section (10) and the final-stage middle section (11), the main shaft (1) is matched with the first-stage middle section (10), the guide body (7), and the final-stage middle section (11) and further comprising a pump cover (5) and a suction side stuffing box (19) respectively arranged at both ends of the outer cylinder (4), the pump The cover (5) and the suction side stuffing box body (19) are both provided with a bearing body (2), the bearing body (2) is provided with a bearing (3) for slewing support of the main shaft (1), the first-stage middle section (10), the guide body (7), and the final-stage middle section (11) are all provided with a stepped hole (17) for installing a casing sealing ring (8), the impeller (6) is provided with an impeller sealing ring (9) at both ends, the impeller sealing ring (9) and the casing sealing ring (8) are rotatably matched, and also includes a balancing drum (22) installed on the main shaft (1) and located at the pump cover (5), characterized in that: The axis of the stepped hole (17) has a downward eccentricity e in the direction of the plumb line relative to the outer axis of the corresponding first-stage middle section (10), the guide body (7), and the final-stage middle section (11). i , the eccentricity e i =y i -y p ;y i is the eccentricity of the impeller (6) at the position on the main shaft (1) corresponding to the first-stage middle section (10), the guide body (7), and the final-stage middle section (11), y p is the eccentricity of the balance drum (22) on the main shaft (1); wherein, , where G i For the load at the position of the impeller (6); a i is the axial distance from the impeller (6) to one of the bearings (3) close to the balance drum (22); L is the distance between the two bearing (3) fulcrums; E is the elastic modulus of the material of the main shaft (1); J i is the average moment of inertia of the impeller (6); , where d i is the shaft diameter of the main shaft (1) at the position of the impeller (6); , where G p A is the load at the position of the balance drum (22); p is the axial distance from the balance drum (22) to the adjacent bearing (3); L is the distance between the two bearing (3) fulcrums; E is the elastic modulus of the material of the main shaft (1); J p is the average moment of inertia at the balance drum (22); , where d p is the shaft diameter of the main shaft (1) at the balance drum (22).

2. The high reliability multistage centrifugal pump according to claim 1, characterized in that: The guide body (7) comprises a radial guide vane (701) and a guide body middle section (702) of an integral structure; an annular groove (703) is provided on the guide body (7) at one end surface of the radial guide vane (701); an axially protruding convex ring (704) is provided on one side of the guide body middle section (702); the annular groove (703) and the convex ring (704) are coaxial with the outer circle of the guide body (7); and an interference of 0.005 to 0.03 mm is provided between the outer circles of the convex rings (704) of two adjacent guide bodies (7) and the corresponding inner walls of the annular groove (703).

3. The high reliability multistage centrifugal pump according to claim 2, characterized in that: The step holes (17) on each guide body (7) have two holes located respectively on the guide body middle section (702) and the radial guide vane (701); the inner diameter of the step holes (17) located on the guide body middle section (702) is greater than the inner diameter of the step holes (17) located on the radial guide vane (701).

4. The high reliability multistage centrifugal pump according to claim 2, characterized in that: The guide body (7) is also provided with a pin hole position A and a pin hole position B, and the center of the pin hole position A is located on the extension line of the line connecting the center of the step hole (17) and the center of the outer circle of the guide body (7), and the line connecting the center of the pin hole position B and the center of the outer circle of the guide body (7) and the line connecting the pin hole position A and the center of the outer circle of the guide body (7) form an angle (18), and the angle (18) is 40-50 degrees; the guide body (7) is provided with a short pin hole (15) and a long pin hole (16), the long pin hole (16) axially penetrates the guide body (7) and comprises a large hole section (1601) and a small hole section (1602) that are coaxially connected, the short pin hole (15) is a countersunk hole and opens on the same side as the large hole section (1601), wherein the short pin holes (15) and the long pin holes (16) on two adjacent guide bodies (7) are alternately formed at the pin hole position A and the pin hole position B, respectively.

5. The high reliability multistage centrifugal pump according to claim 4, characterized in that: It also includes a positioning pin (14), which is used to pass through the large hole section (1601) and be sleeved into the small hole section (1602) and the short pin hole (15), so that all the step holes (17) are located on the same side relative to the outer circle center of the guide body (7).

6. The high reliability multistage centrifugal pump according to claim 4, characterized in that: The guide body (7) and the final middle section (11) are also provided with a plurality of through holes (21) evenly distributed around the circumference, the axes of the through holes (21) being parallel to the outer axis of the guide body (7), and the first middle section (10) is provided with a plurality of threaded holes (23) corresponding to the through holes (21); and further comprising a tensioning stud (20) penetrating the through holes (21) and having external threaded sections formed at both ends, the external threaded section at one end of the tensioning stud (20) being screwed into the threaded hole (23), and the external threaded section at the other end being exposed from the final middle section (11) and being screwed with a nut (24), the tensioning stud (20) and the nut (24) being used to connect the first middle section (10), the guide body (7) and the final middle section (11) into a whole.

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