Universal pump casing for nuclear power main pump

Abstract

A universal pump casing (1) for a nuclear power main pump, the universal pump casing comprising: a spherical housing (11); a discharge section (12), which is arranged on one side of the spherical housing (11) and configured to connect to a cold-end pipeline of a system; a suction section (14), which is arranged at an axial upper end of the spherical housing (11) and configured to connect to a steam generator (2) and a suction guide pipe (3) of a main pump; and an annular end cover (15), which is located at an axial lower end of the spherical housing (11) and configured to connect to a main pump cartridge (6), wherein the annular end cover (15) is provided with a plurality of main bolt holes (151), which are spaced apart; and one side of each main bolt hole (151) is provided with a positioning spigot (152), and the other side thereof is provided with a positioning end face (153).

Description

A universal pump casing for nuclear power main pump

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application 202310945737.X filed on July 28, 2023, entitled “A universal pump casing for a nuclear power main pump,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention belongs to the technical field of nuclear power, and in particular relates to a universal pump casing for a nuclear power main pump. Background Art

[0004] In AP1000 / CAP1400 passive nuclear power plants, the main pump is a critical component of the primary coolant system. Currently, there are two main types of main pumps: canned main pumps and wet-wound main pumps. These two types of main pumps are manufactured by different manufacturers and utilize completely different technical approaches. Main pump installation generally involves two steps. First, the main pump casing is welded to the steam generator to form the steam generator assembly. Once the steam generator assembly is installed on-site at the power plant, the main pump core is assembled onto the main pump casing. This welding of the main pump casing to the steam generator is a prerequisite for the steam generator to ship from the factory and a critical step in the nuclear power plant's critical path.

[0005] Because the pump casings of shielded main pumps and wet-wound main pumps differ in design and are not interchangeable, the main pump type must be decided before the pump casing is welded to the steam generator. Once welded, it cannot be adjusted. Furthermore, the main pump casing welded to the steam generator cannot be replaced during the life of the power plant, forcing the use of the fixed main pump type, which lacks operational flexibility.

[0006] Summary of the Invention

[0007] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a universal pump casing for nuclear power main pumps, which can solve the problem that shielded main pumps and wet-winding main pumps cannot be interchanged. The appropriate main pump type can be selected according to actual needs, and the main pump type can also be replaced midway, with strong applicability.

[0008] The present invention provides a universal pump casing for a nuclear power main pump, comprising:

[0009] spherical shell;

[0010] The discharge section is provided on one side of the spherical shell and is used to connect to the cold end pipe of the system;

[0011] A suction section, provided at the axial upper end portion of the spherical shell, for connecting the steam generator and the suction duct of the main pump;

[0012] An annular end cover, located at the axial lower end of the spherical shell, for connecting to the main pump core package;

[0013] in,

[0014] The annular end cover is provided with a plurality of main bolt holes at intervals.

[0015] One side of the main bolt hole is provided with a positioning stop, and the other side is provided with a positioning end surface.

[0016] Furthermore, an inlet nozzle is provided at the upper end of the suction section, and the inlet nozzle is connected to the primary side outlet nozzle of the lower head of the steam generator;

[0017] A first nickel-based isolation cladding layer is provided on the inlet nozzle.

[0018] Furthermore, the lower end of the suction section is connected to the suction duct of the main pump, and the suction section is connected to the suction duct of the main pump through a suction duct fixing ring.

[0019] Furthermore, the suction section is connected to the suction duct fixing ring via a thread.

[0020] Furthermore, a suction section flow channel is provided inside the suction section, and the suction section flow channel adopts a cylindrical structure.

[0021] A first stainless steel surfacing layer is welded on the inner wall of the suction section.

[0022] Furthermore, a transition section is provided at the end of the discharge section, and the discharge section is connected to the cold end pipe of the system through the transition section;

[0023] The discharge section includes a tapered tube section and a safety end, one end of the tapered tube section is connected to the spherical shell, and the other end is connected to one end of the safety end;

[0024] The other end of the safety end is connected to the transition section;

[0025] The cone tube section adopts a cone-shaped structure, and the safety end adopts a cylindrical structure.

[0026] Furthermore, a second nickel-based isolation cladding layer is provided on the conical tube section, and the second nickel-based isolation cladding layer is welded to the safety end;

[0027] A second stainless steel surfacing layer is welded on the inner wall of the cone tube section.

[0028] Furthermore, a discharge section flow channel is provided inside the discharge section, and the discharge section flow channel adopts a conical structure.

[0029] Furthermore, a lifting platform is provided at the connection between the spherical shell and the suction section, and lifting holes are evenly distributed on the lifting platform, and the lifting holes are used to lift the universal pump shell.

[0030] Furthermore, an annular water pressure chamber is provided inside the spherical shell.

[0031] Compared with the prior art, the present invention has the following advantages and positive effects:

[0032] 1. The present invention provides a universal pump casing for a nuclear power main pump, comprising a spherical casing, a discharge section, a suction section, and an annular end cover. The casing is manufactured in the form of forgings, thereby improving the quality of the universal pump casing forging blank and shortening the delivery cycle. The properties of the pump casing are changed from a proprietary part of the pump to a mature universal part, thereby realizing the socialized and specialized manufacturing of the pump casing and ultimately achieving the best quality of the pump casing.

[0033] 2. The present invention provides an annular end cover, and the positioning stop and positioning end face on the annular end cover are positioned with the stop and end face on the motor end cover, and are connected by main bolts. At the same time, the positioning end face is also the main sealing surface, which plays the main sealing function. By unifying the dimensions of the positioning stop, positioning end face, and main bolt hole on the annular end cover, the annular end cover meets both the installation requirements of the shielded main pump and the installation requirements of the wet-winding main pump. The universal pump casing can be applied to both the shielded main pump and the wet-winding main pump, solving the problem that the shielded main pump and the wet-winding main pump cannot be interchanged. Whether in the early stage of the project or during the operation of the power plant, the appropriate main pump type can be selected according to actual needs, and the main pump type can even be replaced midway.

[0034] 3. The present invention sets the suction section to adopt a cylindrical structure, and the head of the cylindrical suction section flow channel is higher. If the impeller diameter is inconsistent with the inner diameter of the suction pipeline, the suction duct of the main pump at the rear end of the suction section can be reduced in diameter to form a fluid domain with uniform area variation in the entire suction section flow channel, reducing the impact on the impeller inlet and having strong applicability. A suction duct fixing ring is provided at the end of the suction section. The form of the suction duct fixing ring is different in different pump factories. By unifying the form and size of the suction duct fixing ring, it can meet the installation requirements of the suction ducts of the two main pumps.

[0035] 4. The present invention is provided with a discharge section, and the discharge section flow channel can adopt a conical discharge section flow channel. The taper is generally controlled within the range of 7° to 13° to prevent the area from changing too much and causing increased energy loss. The conical structure has less impact on hydraulic performance and is more conducive to energy conversion of the fluid in the pump casing.

[0036] 5. The present invention employs a spherical shell, which not only bears the primary pressure but also performs important hydraulic functions. While meeting ASME specifications and pump hydraulic performance requirements, and based on the practical needs of the forging process, the internal and external dimensions of the spherical shell are simplified and uniformed. This also satisfies functional requirements such as hoisting and vibration sensor installation. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments of the present application.

[0038] FIG1 is a schematic diagram of the installation of a universal pump casing for a nuclear power main pump according to an embodiment of the present invention;

[0039] FIG2 is a structural diagram of a general pump casing for a nuclear power main pump according to an embodiment of the present invention;

[0040] FIG3 is a structural diagram of an annular end cover according to an embodiment of the present invention;

[0041] FIG4 is a cross-sectional view of an annular end cover according to an embodiment of the present invention;

[0042] 5 is a flow chart of calculating the principal stress on the surface of the annular end cover and the strength of the main bolts in an embodiment of the present invention;

[0043] FIG6 is a structural diagram of the suction section in an embodiment of the present invention;

[0044] FIG7 is an enlarged view of point A in FIG6 (with the bolt removed) in an embodiment of the present invention;

[0045] FIG8 is a structural diagram of the suction section of a cylindrical suction section flow channel according to an embodiment of the present invention;

[0046] 9 is a structural diagram of the suction section of the conical suction section flow channel according to an embodiment of the present invention;

[0047] FIG10 is a comparison diagram of the effects of different flow rates on the lift of a cylindrical suction section flow channel and a conical suction section flow channel in an embodiment of the present invention;

[0048] FIG11 is a structural diagram of the discharge section (conical discharge section flow channel) in an embodiment of the present invention;

[0049] FIG12 is an enlarged view of point A in FIG11 according to an embodiment of the present invention;

[0050] FIG13 is a structural diagram of the discharge section (cylindrical discharge section flow channel) in an embodiment of the present invention;

[0051] FIG14 is a structural diagram of a spherical shell in an embodiment of the present invention.

[0052] Reference numerals:

[0053] 1-Universal pump housing;

[0054] 11- spherical shell;

[0055] 111-annular pressure water chamber;

[0056] 112-third stainless steel surfacing layer;

[0057] 12-discharging section;

[0058] 121-Security terminal;

[0059] 122-cone tube section;

[0060] 1221-second nickel-based isolation cladding layer;

[0061] 1222-second stainless steel surfacing layer;

[0062] 123-discharge section flow channel;

[0063] 1231-Cylindrical discharge section flow channel;

[0064] 1232-conical discharge section flow channel;

[0065] 124-full penetration weld;

[0066] 13- Transition section;

[0067] 14-inhalation segment;

[0068] 141-inlet nozzle;

[0069] 1411-first nickel-based isolation cladding layer;

[0070] 142-first stainless steel surfacing layer;

[0071] 143-suction section flow channel;

[0072] 1431-Cylindrical suction section flow channel;

[0073] 1432-conical suction section flow channel;

[0074] 15- annular end cap;

[0075] 151-main bolt hole;

[0076] 152-positioning stop;

[0077] 153-positioning end face;

[0078] 16- Hoisting platform;

[0079] 161-Lifting hole;

[0080] 2-Steam generator;

[0081] 21- steam generator lower head;

[0082] 211-primary side outlet nozzle;

[0083] 3- Suction duct of the main pump;

[0084] 31-first threaded hole;

[0085] 32-bolts;

[0086] 4-Suction catheter fixing ring;

[0087] 41- second threaded hole;

[0088] 5- System cold section piping;

[0089] 6- Main pump core package;

[0090] 61-motor end cover;

[0091] 62-main bolt;

[0092] a-Trend curve of the influence of different flow rates on the head of the conical suction section flow channel;

[0093] b-Trend curve of the influence of different flow rates on the head of the cylindrical suction section flow channel. DETAILED DESCRIPTION

[0094] In order to better understand the technical solution of the present application, the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0095] 1 is a schematic diagram of the installation of a universal pump casing 1 for a nuclear power main pump according to an embodiment of the present invention. The universal pump casing 1 is connected to a steam generator 2, a system cold section pipeline 5 and a main pump core package 6 respectively.

[0096] As shown in Figure 1, the suction section 14 of the universal pump casing 1 is welded to the steam generator lower head 21 of the steam generator 2 and suspended at the steam generator lower head 21. Specifically, the suction section 14 is welded to the primary side outlet nozzle 211 of the steam generator lower head 21; the discharge section 12 of the universal pump casing 1 is welded to the system condensation duct 5 through the transition section 13; the annular end cover 15 of the universal pump casing 1 is connected to the main pump core package 6. Specifically, the motor end cover 61 of the main pump core package 6 is penetrated by a main bolt 62 and connected to the annular end cover 15, thereby realizing the connection between the universal pump casing 1 and the main pump core package 6.

[0097] Figure 2 is a structural diagram of a universal pump casing 1 for a nuclear power main pump according to an embodiment of the present invention. The universal pump casing 1 is made of forgings. The universal pump casing 1 is decomposed into four parts: a spherical shell 11, a discharge section 12, a suction section 14 and an annular end cover 15.

[0098] As shown in Figures 1 and 2, the universal pump casing 1 comprises a spherical shell 11, with a discharge section 12 disposed on one side. Along the axial direction of the spherical shell 11, a suction section 14 is disposed at the upper end, and an annular end cap 15 is disposed at the lower end. A transition section 13 is disposed above the discharge section 12. Specifically, the discharge section 12 extends radially out of the spherical shell 11, passes through the transition section 13, and ultimately connects to the system cold-end pipe 5. The transition section 13 is made of the same grade of austenitic stainless steel as the system cold-end pipe 5 and is butt-welded to the system cold-end pipe 5.

[0099] The Universal Pump Casing 1 is a forged component, improving the quality of the forging stock and shortening delivery cycles. This transforms the pump casing's properties from a proprietary pump component to a mature, universal component, enabling the commercialization and professionalization of pump casing manufacturing, ultimately ensuring the selection of the best pump casings. The Universal Pump Casing 1 is primarily made of SA-508Gr.3Cl.2 low-alloy steel, which offers moderate strength, good ductility, and low neutron sensitivity, perfectly meeting the forging process and performance requirements of the pump casing.

[0100] FIG3 is a structural diagram of the annular end cover 15 according to an embodiment of the present invention, FIG4 is a cross-sectional view of the annular end cover 15 according to an embodiment of the present invention, and FIG5 is a flow chart of calculating the principal stress on the surface of the annular end cover 15 and the strength of the main bolt 62 according to an embodiment of the present invention.

[0101] The annular end cover 15 is both the pressure-bearing boundary of the universal pump casing 1 and an important functional module of the universal pump casing 1. As shown in Figures 2 to 4, a plurality of main bolt holes 151 are evenly spaced on the annular end cover 15. Figure 3 shows an embodiment using 24 main bolt holes 151. A positioning stop 152 is provided on one side of the main bolt hole 151, and a positioning end face 153 is provided on the other side. The main pumps of the two pump types will be positioned by the positioning stop 152 and the positioning end face 153 of the annular end cover 15. As shown in Figure 1, the main bolt 62 is passed through the motor end cover 61 on the main pump core package 6 and enters the main bolt hole 151 to realize the connection between the annular end cover 15 and the main pump core package 6, thereby forming a complete pump unit. The motor end cover 61 and the annular end cover 15 have the same design and will not be repeated here. The positioning stop 152 and positioning end face 153 on the annular end cover 15 are positioned with the stop and end face on the motor end cover 61 and connected via main bolts 62 , wherein the positioning end face 153 serves as the main sealing surface and performs a sealing function.

[0102] The annular end cover 15 serves as a pressure-bearing boundary, and the principal stress on the surface of the annular end cover 15 and the strength of the main bolt 62 are calculated according to the Roark stress-strain formula.

[0103] As shown in Figure 5, the calculation is performed in three steps:

[0104] S1: Transfer the design pressure into the annular end cover 15.

[0105] S2: Calculate radial, annular and shear stresses, and calculate the equal distributed load acting on the plane of the annular end cover 15 (the outer side is a fixed load and the inner side is a free load).

[0106] S3: Substitute the results calculated by the Roark stress-strain formula into the maximum shear stress assessment criterion for biaxial stress comparison. The characteristic equation is used to solve for the first principal stress σ1, the second principal stress σ2, and the third principal stress σ3, where the third principal stress σ3 is the effective pressure. The strength of main bolt 62 is the difference between the maximum and minimum principal stresses, |σ3 - σ1|.

[0107] The following describes each step in detail.

[0108] S1: Transfer the design pressure into the annular end cover 15.

[0109] In the above steps, in order to calculate the stress intensity of the annular end cover 15, it is necessary to transfer the design pressure q1 acting on the universal pump casing 1 to the area of ​​the annular end cover 15 to obtain the equivalent pressure q2.

[0110] S2: Calculate radial, annular and shear stresses, and calculate the equal distributed load acting on the plane of the annular end cover 15 (the outer side is a fixed load and the inner side is a free load).

[0111] Specifically, in the above steps, the radial stress is calculated:

[0112] Among them, σ r is the radial stress, Mr is the unit radial bending moment, and t is the wall thickness of the annular end cover.

[0113] Calculate hoop stress:

[0114] Among them, σ t is the hoop stress, M t is the tangential bending moment, t is the wall thickness of the annular end cap, θ is the radial slope of the plate, D is the plate constant, r is the location of the load, v is the Poisson's ratio of the annular end cap material, M r Unit radial bending moment.

[0115] Calculate shear stress:

[0116] Where τ is the shear stress, Q a is the unit shear force, q is the design pressure, a is the outer radius of the annular end cover, r0 is the radius of load distribution, and t is the wall thickness of the annular end cover.

[0117] S3: Substitute the results calculated by the Roark stress-strain formula into the maximum shear stress assessment criterion for biaxial stress comparison. The characteristic equation is used to solve for the first principal stress σ1, the second principal stress σ2, and the third principal stress σ3, where the third principal stress σ3 is the effective pressure. The strength of main bolt 62 is the difference between the maximum and minimum principal stresses, |σ3 - σ1|.

[0118] Specifically, in the above steps, the calculation is as follows:

[0119] σ3=σ i

[0120] σ i =q2

[0121] Among them, σ1 is the first principal stress, σ2 is the second principal stress, σ3 is the third principal stress (effective pressure), σ i is the longitudinal stress and q2 is the equivalent pressure.

[0122] The stress assessment criteria are:

[0123] σ mid <1.0×S×C

[0124] σ max <1.5×S×C

[0125] σ mid =2τ

[0126] σ max It is the largest among |σ1-σ2|, |σ2-σ3|, and |σ3-σ1|.

[0127] Among them, σ mid is the central plane stress intensity, σ max is the maximum surface principal stress intensity, S is the allowable stress at design temperature, and C is the casting coefficient.

[0128] The annular end cover 15 is an important functional unit and must be compatible with the main pump core package 6 of both pump types. The positioning stop 152 and positioning end face 153 on the annular end cover 15 are two benchmarks for installing the main pump core package 6. By standardizing the dimensions of the positioning stop 152, positioning end face 153, and main bolt hole 151 on the annular end cover 15, the dimensional tolerance and form and position tolerance meet the installation requirements of both the shielded main pump core package and the wet-winding main pump core package. This enables the universal pump casing 1 to be applicable to both shielded main pumps and wet-winding main pumps, solving the problem of the inability to interchange shielded main pumps and wet-winding main pumps. Whether in the early stages of a project or during power plant operation, the appropriate main pump type can be selected according to actual needs, and the main pump type can even be replaced midway.

[0129] Figure 6 is a structural diagram of the suction section 14 of an embodiment of the present invention, Figure 7 is an enlarged view of point A in Figure 6 of an embodiment of the present invention, Figure 8 is a structural diagram of the suction section 14 of the cylindrical suction section flow channel 1431 of an embodiment of the present invention, Figure 9 is a structural diagram of the suction section 14 of the conical suction section flow channel 1432 of an embodiment of the present invention, and Figure 10 is a comparison diagram of the effects of different flow rates on the lift of the cylindrical suction section flow channel 1431 and the conical suction section flow channel 1432 of an embodiment of the present invention.

[0130] As shown in Figure 6, an inlet nozzle 141 is provided at the upper end of the suction section 14 and is connected to the primary side outlet nozzle 211 of the lower head 21 of the steam generator. A first nickel-based isolation cladding layer 1411 is provided on the inlet nozzle 141. A first stainless steel cladding layer 142 is welded on the inner wall of the suction section 14 and the low-alloy steel surface in contact with the inner wall of the suction section 14. The lower end of the suction section 14 is connected to the suction duct 3 of the main pump through the suction duct fixing ring 4, thereby realizing the connection between the suction section 14 and the main pump.

[0131] Specifically, the inlet nozzle 141 and the primary outlet nozzle 211 are connected by butt welding. Since the inlet nozzle 141 is made of low-alloy steel and the primary outlet nozzle 211 is made of stainless steel, the two materials are different and cannot be directly welded. Therefore, a first nickel-based isolation weld overlay 1411 is applied to the end of the inlet nozzle 141 and machined into a flat groove to achieve the connection between the inlet nozzle 141 and the primary outlet nozzle 211.

[0132] The lower end of the suction section 14 is connected to the suction duct fixing ring 4 by a thread (the thread is not drawn in Figure 6). The lower end of the suction section 14 is provided with an internal thread, and the suction duct fixing ring 4 is provided with an external thread. The internal thread and the external thread cooperate with each other to realize the connection between the suction section 14 and the suction duct fixing ring 4.

[0133] As shown in Figure 7, the main pump's suction duct 3 is penetrated by a first threaded hole 31, and the suction duct retaining ring 4 is penetrated by a second threaded hole 41. Bolts 32 pass through the first threaded hole 31 and into the second threaded hole 41, connecting the main pump's suction duct 3 and the suction duct retaining ring 4. This also serves to position the connection between the main pump's suction duct 3 and the suction duct retaining ring 4. The suction duct retaining ring 4 features a standardized stopper, mounting surface, and threaded hole, meeting the installation requirements of the suction duct retaining ring 4 for both main pump types. Made of austenitic stainless steel, it can be directly positioned with the main pump's suction duct 3 via the stopper and connected via bolts 32 (stainless steel screws) without any isolation measures. The second threaded hole 41 in the suction duct retaining ring 4 features a deep countersunk hole, accommodating the installation of both main pump suction ducts 3. The design of the suction duct retaining ring 4 varies from pump manufacturer to pump manufacturer. By standardizing the design and dimensions of the suction duct retaining ring 4, it meets the installation requirements of both main pump suction ducts 3.

[0134] The size design of the suction section flow channel 143 is determined by the pump equipment manufacturer based on the size of the suction duct 3 nozzle of the main pump and the size of the impeller inlet. As shown in Figures 8 and 9, the existing suction section flow channel 143 has two types: a cylindrical suction section flow channel 1431 and a conical suction section flow channel 1432.

[0135] As shown in Figure 10, after performing computational fluid dynamics (CFD) analysis on the effects of the two forms of suction section flow channels 143 on the lift, we obtained trend curve a of the effect of the conical suction section flow channel 1432 on the lift at different flow rates and trend curve b of the effect of the cylindrical suction section flow channel 1431 on the lift at different flow rates. By comparison, the two structural forms of the suction section flow channel 143 have little effect on the lift of the main pump. The lift of the cylindrical suction section flow channel 1431 is slightly higher than that of the conical suction section flow channel 1432 overall. Except for the 0.9Q flow point, the lift difference between the two is about 0.3-0.5m. To make the expression clearer, the flow rate and lift in Figure 10 are both normalized flow rate and normalized lift.

[0136] The cylindrical structure of suction section flow channel 143 ensures high head while meeting manufacturing process accessibility, minimizing impact on the main pump's hydraulic performance. Therefore, the cylindrical structure is adopted for suction section 14 of the universal pump casing 1. If the impeller diameter and the pipeline inner diameter are inconsistent, the main pump's suction conduit 3 can be tapered to create a uniformly varied fluid domain throughout suction section flow channel 143, reducing impact on the impeller inlet and enhancing applicability.

[0137] Figure 11 is a structural diagram of the discharge section 12 (conical discharge section flow channel 1232) of an embodiment of the present invention, Figure 12 is an enlarged view of point A in Figure 11 of an embodiment of the present invention, and Figure 13 is a structural diagram of the discharge section (cylindrical discharge section flow channel 1231) of an embodiment of the present invention.

[0138] As shown in Figure 11, the discharge section 12 includes a tapered tube section 122 and a safety end 121. One end of the tapered tube section 122 is connected to the spherical housing 11, and the other end is connected to the safety end 121. The tapered tube section 122 is conical in structure, while the safety end 121 is cylindrical. A discharge section flow channel 123 is provided within the discharge section 12. A second stainless steel overlay layer 1222 is welded to the inner wall of the tapered tube section 122 and to the low-alloy steel surface in contact with the inner wall of the tapered tube section 122.

[0139] As shown in Figure 12, the end face of the conical tube section 122 is provided with a second nickel-based isolation overlay layer 1221, and the end face of the conical tube section 122 is welded to the safety end 121 through the second nickel-based isolation overlay layer 1221. This is because the conical tube section 122 is led out from the spherical shell 11 of the universal pump housing 1. The part led out from the spherical shell 11 is the conical tube section 122 forged integrally with the spherical shell 11. The material of the conical tube section 122 is the same as that of the spherical shell 11, which is low-alloy steel. The safety end 121 is made of F316LN austenitic stainless steel pipe forgings and can be directly welded to the system cold section pipeline 5. However, the material of the conical tube section 122 is different from that of the safety end 121 and cannot be directly welded. Therefore, a nickel-based isolation overlay layer 1221 is provided on the end face of the conical tube section 122 to weld the conical tube section 122 to the safety end 121.

[0140] Specifically, a full penetration weld 124 is used between the second nickel-based isolation overlay layer 1221 and the safety end 121 to facilitate the required radiographic inspection and meet the pump casing inspectability design requirements.

[0141] As shown in Figures 11 and 13, the discharge section flow channel 123 can adopt a conical discharge section flow channel 1232 or a cylindrical discharge section flow channel 1231. From the perspective of hydraulic performance, the taper should not be too large to prevent excessive changes in area and increased energy loss. The taper is generally controlled within the range of 7° to 13°. From a hydraulic perspective, the conical structure has less impact on hydraulic performance and is more conducive to energy conversion of the fluid within the pump casing. However, from a manufacturing process perspective, the cylindrical structure is easier to implement. Therefore, considering the importance of hydraulic performance to the overall performance of the main pump, and provided that the manufacturing process is feasible, the universal pump casing 1 adopts a conical discharge section flow channel 1232.

[0142] FIG14 is a structural diagram of the spherical shell 11 according to an embodiment of the present invention.

[0143] The spherical shell 11 not only bears the main pressure-bearing function but also bears important hydraulic functions in the universal pump casing 1. As shown in Figure 14, the inner arc of the spherical shell 11 is composed of the inner diameter of the spherical shell 11 and two rounded corners. The design of the inner arc of the spherical shell 11 meets the relevant requirements of the ASME specifications, the hydraulic performance of the pump, and the forging process. The outer diameter of the spherical shell 11 is mainly determined by the thickness of the spherical shell 11. Taking into account the accessibility of the forging process, the inner diameter and the outer diameter of the spherical shell 11 adopt a concentric circle structure, and the outer profile of the spherical shell 11 is simplified to consist only of the outer diameter and a straight line tangent to it. The thickness of the spherical shell 11 fully considers the pressure load, transient working load, thermal load, pipe load, seismic load and other load combinations that the universal pump casing 1 bears, and meets the stress assessment criteria requirements of the ASME specifications, simplifying the internal and external dimensions of the spherical shell 11 as much as possible, and making the dimensions of the spherical shell 11 tend to be unified.

[0144] .

[0145] Specifically, the inner cavity of the spherical shell 11 is an annular pressurized water chamber 111, which is the core of the main pump casing flow channel and a critical pressure-bearing unit. The flow channel design of the annular pressurized water chamber 111 requires a joint design from both hydraulic and pressure-bearing perspectives, with iterative calculations performed. From a hydraulic perspective, the annular pressurized water chamber 111 further converts the energy of the fluid at the guide vane outlet, converting velocity energy into pressure energy. From a pressure-bearing perspective, due to its larger pressure-bearing surface, the flow channel shape is designed to better withstand high pressures. The design of the annular pressurized water chamber 111 follows the ASME standard for head design requirements, with a preliminary design of its cross-sectional shape and dimensions. Based on this cross-sectional shape and dimensions, a reverse calculation is performed to verify whether the hydraulic design meets the requirements. If not, the axial dimensions are readjusted, and the cross-sectional shape and dimensions of the annular pressurized water chamber 111 are redefined according to the ASME standard. This iterative calculation and iteration process ultimately determines the flow channel dimensions of the annular pressurized water chamber 111.

[0146] The inner wall of the spherical shell 11 and the low alloy steel surface in contact with the inner wall of the spherical shell 11 are both welded with a third stainless steel overlay layer 112 .

[0147] A lifting platform 16 is provided at the connection between the spherical shell 11 and the suction section 14 , and lifting holes 161 are evenly provided on the lifting platform 16 . The lifting holes 161 are used for lifting the universal pump shell 1 , meeting functional requirements such as lifting and vibration sensor installation.

[0148] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A universal pump casing for a nuclear power main pump, characterized in that: include: Spherical shell; The discharge section is arranged on one side of the spherical shell and is used to connect the cold end pipeline of the system; A suction section, arranged at the axial upper end of the spherical shell, for connecting the steam generator and the suction conduit of the main pump; An annular end cover, located at the axial lower end of the spherical housing, and used for connecting the main pump core package; in, The annular end cover is provided with a plurality of main bolt holes at intervals. A positioning stop is provided on one side of the main bolt hole, and a positioning end surface is provided on the other side.

2. The universal pump casing for a nuclear power main pump according to claim 1, characterized in that: An inlet nozzle is provided at the upper end of the suction section, and the inlet nozzle is connected to the primary outlet nozzle of the lower head of the steam generator; The inlet nozzle is provided with a first nickel-based isolation cladding layer.

3. The universal pump casing for a nuclear power main pump according to claim 1, characterized in that: The lower end of the suction section is connected to the suction conduit of the main pump, and the suction section is connected to the suction conduit of the main pump through a suction conduit fixing ring.

4. The universal pump casing for a nuclear power main pump according to claim 3, characterized in that: The suction section is connected to the suction conduit fixing ring via threads.

5. The universal pump casing for a nuclear power main pump according to claim 1, characterized in that: The suction section is provided with a suction section flow channel inside, and the suction section flow channel adopts a cylindrical structure. A first stainless steel cladding layer is welded on the inner wall of the suction section.

6. The universal pump casing for a nuclear power main pump according to claim 1, characterized in that: A transition section is provided at the end of the discharge section, and the discharge section is connected to the cold end pipeline of the system through the transition section; The discharging section comprises a conical tube section and a safety end, one end of the conical tube section is connected to the spherical shell, and the other end is connected to one end of the safety end; The other end of the safety end is connected to the transition section; The cone tube section adopts a cone-shaped structure, and the safety end adopts a cylindrical structure.

7. The universal pump casing for a nuclear power main pump according to claim 6, characterized in that: A second nickel-based isolation cladding layer is provided on the conical tube section, and the second nickel-based isolation cladding layer is welded to the safety end; A second stainless steel cladding layer is welded on the inner wall of the cone tube section.

8. The universal pump casing for a nuclear power main pump according to claim 1, characterized in that: A discharge section flow channel is provided inside the discharge section, and the discharge section flow channel adopts a conical structure.

9. The universal pump casing for a nuclear power main pump according to claim 1, characterized in that: A hoisting platform is provided at the connection between the spherical shell and the suction section, and hoisting holes are evenly distributed on the hoisting platform. The hoisting holes are used to hoist a universal pump shell.

10. The universal pump casing for a nuclear power main pump according to claim 1, characterized in that: An annular water pressure chamber is arranged inside the spherical shell.

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