Double-layer corrugated pipe pressurizing assembly for shutdown seal of nuclear main pump
By designing the butt welds between the inner and outer corrugated pipes and the soft ring seat and base, and by using the convex ring and stress relief groove, the problems of welding stress and fatigue damage were solved, extending the service life of the nuclear main pump shutdown seal.
Patent Information
- Application Number
- CN202520242910.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-16
- Publication Date
- 2026-01-02
- Estimated Expiration
- 2035-02-16
AI Technical Summary
The existing double-layer bellows connection between the main nuclear pump shutdown seal and the soft ring seat and base has welding stress and fatigue damage problems, which makes it difficult to meet the requirements of 50-70 years of service life and irregular maintenance.
The design incorporates butt welds between inner and outer corrugated pipes, soft ring seats, and bases, combined with convex rings and stress relief grooves to improve welding quality and stress conditions, reduce welding stress, and ensure coaxiality and sealing.
It improves welding quality, reduces welding stress, extends the fatigue life of shutdown seals, and meets the long-term service requirements of nuclear main pumps.
Smart Images
Figure CN223754628U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of sealing, and particularly relates to a double-layer bellows pressurization assembly for parking sealing of a nuclear main pump. BACKGROUND
[0002] The nuclear main pump located on the reactor core and the steam generator loop (main loop) is the "heart" of the nuclear power plant, which circulates and transports the coolant to absorb the heat of the fission reaction at the reactor core and then releases the heat in the steam generator. The parking sealing, as the last barrier of the nuclear main pump, is used to ensure the sealing after the main shaft sealing of the main pump fails to cause shutdown, preventing the leakage of the coolant in the pump; and is also used to ensure the sealing of the main shaft of the main pump during the maintenance of the main shaft sealing.
[0003] At present, the parking sealing of the more advanced nuclear main pump adopts two rings for sealing, namely a hard ring and a soft ring. The hard ring is sealingly connected to the main shaft, and the soft ring is installed on a soft ring seat which is fixed to one end of a double-layer bellows. The other end of the double-layer bellows is installed on the pump shell through a base.
[0004] When the main shaft sealing of the nuclear main pump fails or is maintained, the nuclear main pump stops running, the double-layer bellows is pressurized, the double-layer bellows is elongated, the soft ring is pushed to abut against the hard ring, and a sealing contact is formed. After the performance of the main shaft sealing is restored, the pressure in the double-layer bellows is released, the double-layer bellows is retracted, the soft ring is moved away from the hard ring, the soft ring is separated from the hard ring, and the nuclear main pump can run.
[0005] The connection of the bellows of the existing parking sealing with the soft ring seat and the base is an angular joint welding. This welding form with a large difference in wall thickness is prone to welding stress and welding defects. During the replacement of the parking sealing during work and non-work, the angular joint welding position will also cause fatigue damage, which is difficult to meet the requirements of 50-70 years of service life of the parking sealing and no replacement and maintenance during the service period. CONTENT OF THE UTILITY MODEL
[0006] In order to at least partially solve the problems of the connection quality, welding stress and fatigue life of the connection position of the double-layer bellows of the existing parking sealing with the soft ring seat and the base, the application provides a double-layer bellows pressurization assembly for parking sealing of a nuclear main pump, which comprises a bellows assembly, a soft ring seat and a base. The bellows assembly comprises two bellows which are sleeved together, the two bellows are an inner bellows and an outer bellows, the inner bellows and the outer bellows both extend along a first axis direction, the outer bellows is coaxially sleeved outside the inner bellows, and the inner bellows and the outer bellows have a distance therebetween; the soft ring seat, the inner bellows, the outer bellows and the base are coaxially arranged;
[0007] On the side of the soft ring seat opposite to the base, a convex ring is arranged, and each open half-wave end is sealingly welded on the corresponding convex ring; the end face of the convex ring on the soft ring seat is coplanar with the end face of the soft ring seat, and the end face of the convex ring on the base is coplanar with the end face of the base;
[0008] A soft ring mounting portion is arranged on the side of the soft ring seat away from the base, and the soft ring mounting portion is coaxially arranged with the soft ring seat.
[0009] After the convex ring is arranged, the welding seam structure between the inner and outer bellows and the soft ring seat and the base is changed from fillet welding to butt welding, which is easy to weld and detect, and ensures the quality of the welding seam and the welding sealing of the inner and outer bellows and the soft ring seat and the base. By using the convex ring, the centering problem of the inner and outer bellows and the soft ring seat and the base during welding is solved, the position accuracy of the connection is ensured, and the coaxiality of the inner and outer bellows is improved.
[0010] If the inner and outer bellows are not coaxial, the axial forces acting on the soft ring seat and the base will be inconsistent due to the different areas of the medium pressure in the pressure cavity. After the inner and outer bellows are eccentric, the axial force acting on the large area side of the soft ring seat or the base is large, and the axial force acting on the small area side is small, so that the contact pressure of the contact area between the soft ring and the hard ring is not uniform; if the percolation channel in the contact area between the soft ring and the hard ring is to be eliminated, the porosity of each part of the contact area should be less than 0.3116, that is, the contact pressure of the overall contact surface needs to be increased to ensure that the porosity of the area where the contact pressure between the soft ring and the hard ring is small is also less than 0.3116, which increases the risk of fatigue damage at the welding position of the inner and outer bellows and the soft ring seat and the base.
[0011] Further, the convex ring, the soft ring seat and the base are coaxially arranged. This design can make the soft ring end face on the soft ring seat stably translate along the first axis direction when the inner and outer bellows are elongated after being filled with pressure fluid, effectively avoiding the uneven distribution of the axial thrust of the inner and outer bellows along the circumferential direction of the axis of the soft ring mounting portion. Otherwise, if the coaxiality of the inner and outer bellows or the coaxiality of the convex ring and the soft ring seat and the base is poor, the contact pressure between the soft ring and the hard ring will not be uniform when the soft ring is pressed against the hard ring, and it is difficult to achieve the ideal parking sealing effect.
[0012] Further, a stress release groove is arranged on the inner and outer sides of each convex ring, and the stress release groove is annular.
[0013] By using the stress release groove, the convex ring with poor rigidity difference at the connection position of the inner and outer bellows and the soft ring seat and the base can be formed, which is conducive to making the soft ring seat and the base have similar thermal expansion or contraction deformation as the inner and outer bellows during welding, and reducing the welding stress at the welding seam.
[0014] Specifically, the inner circumferential surface of each convex ring is defined by the outer circumferential surface of the stress release groove located at the inner side of the convex ring, and the outer circumferential surface of each convex ring is defined by the inner circumferential surface of the stress release groove located at the outer side of the convex ring.
[0015] Specifically, the convex rings located on the soft ring seat are integrally formed on the soft ring seat, and the convex rings located on the base are integrally formed on the base. This design can effectively avoid the stress generated when the convex rings are installed by welding.
[0016] Specifically, the depth of the stress release groove located on the soft ring seat is 0.57 times the calculated thickness of the soft ring seat, and the depth of the stress release groove located on the base is 0.57 times the calculated thickness of the base. The above-mentioned stress release groove depth limitation, on the one hand, can effectively reduce the stiffness of the convex rings on the soft ring seat and the base, ensure the deformation ability, and reduce the welding stress at the welding position of the bellows and the convex ring; on the other hand, it avoids the welding seam of the bellows and the convex ring being in the edge stress zone, and improves the stress state at the welding seam. After setting the stress release groove, the area corresponding to the stress release groove of the soft ring seat and the base forms a thin-walled area. When welding the bellows, the stress generated on the soft ring seat and the base will be released at the thin-walled area. When the depth of the stress release groove reaches 0.57 times the calculated thickness of the soft ring seat or the base, the stress generated by welding can be completely released, and the safety of the structure is improved.
[0017] Further, the tangent lines of the open half-wave end extend along the first axis direction. This design can make the thrust or tension generated by the bellows transmitted to the soft ring seat along the first axis direction, and then transmitted to the soft ring, so that the soft ring and the corresponding hard ring complete sealing.
[0018] Specifically, the inner diameter of the end face of the open half-wave end is the same as the inner diameter of the end face of the connected convex ring, and the outer diameter of the end face of the open half-wave end is the same as the outer diameter of the end face of the connected convex ring; in the first axis direction, the projection of the end face of the open half-wave end overlaps the projection of the end face of the connected convex ring.
[0019] Under the above-mentioned limitation, the connection part of the inner and outer bellows and the corresponding convex ring can completely coincide, forming a truly butt joint, on the one hand, which can easily ensure the welding quality; on the other hand, during the parking sealing work, the welding seam is only subjected to axial force and is not subjected to tangential force, which improves the stress state of the welding seam and improves the fatigue life of the parking sealing.
[0020] Specifically, to facilitate the adjustment of the elongation and retraction of the inner and outer corrugated pipes, the space between the soft ring seat, the base, the inner corrugated pipe and the outer corrugated pipe is formed into a pressure chamber, and a fluid loading hole is arranged on the base to communicate the inside and outside of the pressure chamber. The fluid loading hole is used to connect a fluid pressure charging device, and the fluid pressure charging device is used to pass fluid into the pressure chamber through the fluid loading hole, so that the inner and outer corrugated pipes are elongated, and the soft ring mounted on the soft ring seat can be in contact with the hard ring to form a seal. When the fluid in the pressure chamber flows outwards, the inner and outer corrugated pipes can be retracted, so that the soft ring is out of contact with the hard ring. The fluid can be water, hydraulic oil or other liquids, or air, nitrogen or other gases.
[0021] Specifically, to ensure welding precision and reduce deformation caused by welding, the half-wave end is welded on the corresponding convex ring by laser welding.
[0022] The design life of a general nuclear main pump is 50-70 years, and the main shaft seal is maintained or replaced once every 6 years, so that the parking seal needs to work 12 times in the life cycle of the nuclear main pump, plus abnormal maintenance and safety factor, and needs to work more than 20 times in total. If the contact load between the soft ring and the hard ring is large, low-cycle fatigue will be caused. Therefore, maintaining the coaxiality between the components can reduce the contact pressure between the soft ring and the hard ring when the seal is achieved; the butt welding of the convex ring and the corrugated pipe can effectively improve the welding quality and reduce the welding stress, thereby improving the fatigue life of the double-layer corrugated pipe pressure assembly of the soft ring and the hard ring under the condition of large contact load. BRIEF DESCRIPTION OF DRAWINGS
[0023] Figure 1 is a structural schematic diagram of an embodiment of a double-layer corrugated pipe pressure assembly.
[0024] Figure 2 is a structural schematic diagram of an embodiment of a double-layer corrugated pipe pressure assembly. Figure 1
[0025] Figure 3 is an enlarged view of part A in Figure 1
[0026] Figure 4 is a structural schematic diagram of an outer corrugated pipe.
[0027] Figure 5 is a second structural schematic diagram of a soft ring seat.
[0028] Figure 6 is a third structural schematic diagram of a soft ring seat.
[0029] Figure 7 is a welding schematic diagram of a corrugated pipe and a soft ring seat in the prior art.
[0030] Figure 8 It is a structural schematic diagram of a nuclear main pump installed with a parking seal of a double-layer bellows pressurization assembly. DETAILED DESCRIPTION
[0031] Firstly, the welding structure of the bellows and the soft ring seat A81 or the base A in the prior art is described below, please refer to Figure 7 At present, the connection between the inner bellows A83 and the outer bellows A82 and the soft ring seat A81 adopts a direct welding mode. During welding, the welding mode is used to weld the inner and outer sides of the inner bellows A83 and the outer bellows A82 to form an angle weld 84. During the welding process, the internal stress generated in the soft ring seat A or the base A cannot be eliminated and remains in the soft ring seat A and the base A. These internal stresses will be transmitted in the soft ring seat A or the base A over time, affecting the safety of the internal structure of the soft ring seat A and the base A, and thus affecting the service life of the soft ring seat A and the base A.
[0032] The double-layer bellows pressurization assembly 10 of the parking seal of the nuclear main pump is further described below, please refer to Figures 1-3 In the drawings, the direction of the arrow Y represents the first axis direction.
[0033] In this embodiment, the double-layer bellows pressurization assembly 10 specifically includes a bellows assembly, a soft ring seat 11 and a base 17. The bellows assembly includes two bellows that are sleeved together, which are an inner bellows 15 and an outer bellows 14. Both the inner bellows and the outer bellows extend along the first axis direction, and the outer bellows is coaxially sleeved on the outside of the inner bellows, and there is a distance between the inner bellows and the outer bellows. The soft ring seat 11, the inner bellows 15, the outer bellows 14 and the base 17 are coaxially arranged.
[0034] For ease of description, the structure of the inner bellows 15 and the outer bellows 14 is described first below. In this embodiment, the structures of the two bellows are the same, and the structure of the outer bellows 14 is described below as an example, please refer to Figure 4 The outer bellows includes a plurality of full-wave bands 140 that are sequentially connected and two half-wave bands at both ends. Figure 3 In the drawings, three full-wave bands 140 are exemplarily shown. The range enclosed by the first double-dot line ellipse D generally includes one full-wave band 140, and the range enclosed by the second double-dot line E generally includes one half-wave band. The end of each half-wave band away from the other half-wave band is called an open half-wave end. The number of full-wave bands in the inner bellows and the outer bellows is not specifically required.
[0035] For the convenience of description, the two half-wave segments of the inner bellows are both referred to as first half-wave segments 151, and the open half-wave end of the first half-wave segment is referred to as a first open half-wave end 152. The two half-wave segments of the outer bellows are both referred to as second half-wave segments 141, and the open half-wave end of the second half-wave segment is referred to as a second open half-wave end 142. The tangent of the first open half-wave end 152 extends along the first axial direction, and the tangent 145 of the second open half-wave end 142 extends along the first axial direction.
[0036] The soft ring seat 11 is annular, and has a first central hole 113 in the center thereof, which extends along the first axial direction and is in the form of a through hole. The base 17 is annular, and has a second central hole 173 in the center thereof, which extends along the first axial direction and is in the form of a through hole. The first central hole 113 and the second central hole 173 are used to be sleeved on the main shaft 48 of the core pump, and the detailed mounting manner will be described below. The soft ring mounting portion 13 is arranged on the side of the soft ring seat 11 away from the base, and in this embodiment, the soft ring mounting portion is specifically an annular groove.
[0037] Corresponding to the two first open half-wave ends 152 of the inner bellows 15, an inner convex ring is arranged on the side of the soft ring seat 11 opposite to the base 17, and for the convenience of description, the inner convex ring located on the soft ring seat 11 is referred to as a first inner convex ring 117, and the inner convex ring located on the base 17 is referred to as a second inner convex ring 177. Each first open half-wave end is sealingly welded on the corresponding inner convex ring by laser welding.
[0038] Corresponding to the two second open half-wave ends 142 of the outer bellows 14, an outer convex ring is arranged on the side of the soft ring seat 11 opposite to the base 17, and for the convenience of description, the outer convex ring located on the soft ring seat 11 is referred to as a first outer convex ring 116, and the outer convex ring located on the base 17 is referred to as a second outer convex ring 176. Each second open half-wave end is sealingly welded on the corresponding outer convex ring by laser welding. The inner convex ring and the outer convex ring are collectively referred to as a convex ring.
[0039] In the first axial direction, the projections of the two inner convex rings completely overlap, the projections of the two outer convex rings completely overlap, and the inner convex ring and the outer convex ring located on the soft ring seat are coaxially arranged, and the inner convex ring and the outer convex ring located on the base are coaxially arranged.
[0040] In this embodiment, a first stress release groove A112 is arranged on the inner and outer sides of the first inner convex ring 117, and a first stress release groove B172 is arranged on the inner and outer sides of the second inner convex ring 177. The two first stress release grooves A112 and the two first stress release grooves B172 are annular. That is, an annular first stress release groove is arranged on the inner and outer sides of each inner convex ring.
[0041] The inner circumferential surface of the first inner convex ring 117 is defined by the outer circumferential surface of the first stress release groove A112 located at the inner side of the first inner convex ring 117, and the outer circumferential surface of the first inner convex ring 117 is defined by the inner circumferential surface of the first stress release groove A112 located at the outer side of the first inner convex ring 117. The inner circumferential surface of the second inner convex ring 177 is defined by the outer circumferential surface of the first stress release groove B172 located at the inner side of the second inner convex ring 177, and the outer circumferential surface of the second inner convex ring 177 is defined by the inner circumferential surface of the first stress release groove B172 located at the outer side of the second inner convex ring 177.
[0042] That is, the inner circumferential surface of each inner convex ring is defined by the outer circumferential surface of the first stress release groove located at the inner side of the inner convex ring, and the outer circumferential surface of each inner convex ring is defined by the inner circumferential surface of the first stress release groove located at the outer side of the inner convex ring.
[0043] A second stress release groove A111 is arranged at the inner and outer sides of the first outer convex ring 116, and a second stress release groove B171 is arranged at the inner and outer sides of the second outer convex ring 176. The two second stress release grooves A111 and the two second stress release grooves B171 are annular. That is, an annular second stress release groove is arranged at the inner and outer sides of each outer convex ring.
[0044] The inner circumferential surface of the first outer convex ring 116 is defined by the outer circumferential surface of the second stress release groove A111 located at the inner side of the first outer convex ring 116, and the outer circumferential surface of the first outer convex ring 116 is defined by the inner circumferential surface of the second stress release groove A111 located at the outer side of the first outer convex ring 116. The inner circumferential surface of the second outer convex ring 176 is defined by the outer circumferential surface of the second stress release groove B171 located at the inner side of the second outer convex ring 176, and the outer circumferential surface of the second outer convex ring 176 is defined by the inner circumferential surface of the second stress release groove B171 located at the inner side of the second outer convex ring 176.
[0045] That is, the inner circumferential surface of each outer convex ring is defined by the outer circumferential surface of the second stress release groove located at the inner side of the outer convex ring, and the outer circumferential surface of each outer convex ring is defined by the inner circumferential surface of the second stress release groove located at the outer side of the outer convex ring. The first inner convex ring 117 and the first outer convex ring 116 are integrally formed on the soft ring seat, and the second inner convex ring 177 and the second outer convex ring 176 are integrally formed on the base.
[0046] The end surface of the first inner convex ring 117 and the first outer convex ring 116 facing the base is coplanar with the end surface of the soft ring seat facing the base, and the end surface of the second inner convex ring 177 and the second outer convex ring 176 facing the soft ring seat is coplanar with the end surface of the base facing the soft ring seat. That is, the end surface of the inner and outer convex rings is coplanar with the end surface of the soft ring seat or the base where the inner and outer convex rings are located.
[0047] The inner convex ring, the outer convex ring, the soft ring seat and the base are coaxially arranged.
[0048] Specifically, in this embodiment, both the soft ring seat and the base are made of steel plate. A first inner convex ring 117, a first outer convex ring 116, and corresponding first stress relief grooves A112 and second stress relief grooves A111 are formed on the soft ring seat in one step. Similarly, a second inner convex ring 177, a second outer convex ring 176, and corresponding first stress relief grooves B172 and second stress relief grooves B171 are formed on the base in one step.
[0049] In this embodiment, the first stress relief groove A112 and the second stress relief groove A111 have the same depth, both being 0.57 times the calculated thickness of the soft ring seat. The calculated thickness refers to the thickness necessary to ensure the strength and stiffness of the soft ring seat and base under all load conditions, including the pressure of the medium within the pressure chamber and the contact pressure between the soft ring and the hard ring. This thickness can be calculated according to pressure vessel design specifications. Figure 2 In the diagram, H1 indicates the depth of the first stress relief groove A112 or the second stress relief groove A111, and H2 indicates the thickness of the soft ring seat. The first stress relief groove B172 and the second stress relief groove B171 have the same depth, which is 0.57 times the calculated thickness of the base.
[0050] The inner diameter of the end face of the first open half-wave end is the same as the inner diameter of the end face of the connected inner convex ring, and the outer diameter of the end face of the first open half-wave end is the same as the outer diameter of the end face of the connected inner convex ring; in the first axial direction, the projections of the end face of the first open half-wave end and the end face of the connected inner convex ring overlap.
[0051] The inner diameter of the end face of the second open half-wave end is the same as the inner diameter of the end face of the connected outer convex ring, and the outer diameter of the end face of the second open half-wave end is the same as the outer diameter of the end face of the connected outer convex ring; in the first axial direction, the projections of the end face of the second open half-wave end and the end face of the connected outer convex ring overlap.
[0052] In this embodiment, the axial cross-sections of both the inner and outer convex rings are rectangular, and both the first and second stress relief grooves are also rectangular. Please refer to [link to relevant documentation]. Figure 5 and Figure 6 It is understood that in other embodiments, the axial cross-sections of the inner and outer convex rings can also be isosceles trapezoids. Figure 5 In the structure shown, the axial sections of both the first stress relief groove and the second stress relief groove are isosceles trapezoids. Figure 6 In the structure shown, both the first stress relief groove and the second stress relief groove are right-angled trapezoids.
[0053] The space enclosed by the inner bellows, outer bellows, soft ring seat and base forms a pressure chamber 19, and a fluid loading hole 18 connecting the inside and outside of the pressure chamber is provided on the base.
[0054] The following describes the installation of the double-layer bellows pressurizing assembly in the nuclear main pump according to the present embodiment. Please refer to Figure 8 The nuclear main pump comprises a pump shell 41 and a seal case 20 installed together along a first axial direction, an impeller 43 rotatably installed in the pump shell 41, a pump inlet 42 formed at an end of the pump shell 41 away from the seal case 20, and a pump outlet 44 formed at a side of the pump shell 41 in a radial direction. An end of a main shaft 48 extends into the pump shell 41 and is fixedly connected to the impeller 43, and the other end of the main shaft 48 extends out of the seal case 20. In the present embodiment, the seal case 20 comprises a cylinder 21 extending along the first axial direction and a base 17 of the double-layer bellows pressurizing assembly, the base 17 is arranged at an end of the cylinder 21 facing the impeller 43, the cylinder 21 and the base 17 are sealingly welded together, and the base is sealingly fixed to the pump shell by bolts, so that the seal case is sealingly installed on the pump shell.
[0055] The double-layer bellows pressurizing assembly and the seal pair jointly form a parking seal, which is located between a main seal 30 of the nuclear main pump and the impeller 43. The main seal comprises a static ring 32 fixedly arranged on an inner wall of the cylinder 21 and a dynamic ring 31 sealingly and fixedly installed on the main shaft 48, and the dynamic ring and the static ring form a mechanical seal pair. A sealing ring 33 is arranged between the static ring and the cylinder 21, and an end cover 25 is fixedly arranged on a side of the cylinder 21 away from the base 17, so as to keep the main seal in the seal case. In the drawings, only part of the structure of the main seal 30 is shown, and the whole structure of the main seal is not shown, for the sake of simplifying the drawings. The detailed structure and installation mode of the main seal are both mature technologies, and will not be described herein.
[0056] The inner bellows 15 and the outer bellows 14 are located at a side of the base 17 away from the impeller 43, so that the soft ring seat 11 is located at a side of the inner bellows 15 and the outer bellows 14 away from the base 17.
[0057] The seal pair comprises a flat upper ring 56 and a soft ring 52, wherein the flat upper ring 56 is sealingly fixed on the main shaft 48, and the soft ring is located at a side of the flat upper ring 56 facing the impeller 43. The flat upper ring 56 is the hard ring as described above.
[0058] In the embodiment, the planar upper ring is fixed on the main shaft 48 by the upper split ring 561 and the lower split ring 562, and the upper ring groove 481 and the lower ring groove 482 are arranged on the outer circumferential surface of the main shaft 48, and the upper ring groove 481 and the lower ring groove 482 are arranged along the outer circumferential surface of the main shaft 48. The upper split ring 561 is tightly clamped in the upper ring groove, and the lower split ring 562 is tightly clamped in the lower ring groove, and the upper split ring 561 and the lower split ring 562 are tightly pressed on both sides of the planar upper ring, so as to fix the planar upper ring on the main shaft. The upper split ring 561 and the lower split ring 562 each have two ring petals. It can be understood that in other embodiments, the number of ring petals of the upper split ring 561 and the lower split ring 562 can be arranged according to specific needs. The planar upper ring 56 is made of 304 stainless steel.
[0059] The soft ring 52 is made of M106F graphite material, and the soft ring 52 is fixed in the annular groove as a soft ring mounting portion. The soft ring 52 is bonded to the soft ring seat 11 by using silicone modified epoxy resin.
[0060] In order to facilitate the connection of the external fluid pressure charging device 60, the fluid loading hole 18 is substantially L-shaped and penetrates the outer circumferential surface of the base outwardly, and the outer end of the fluid loading hole 18 has an internal thread, and a short connecting pipe 181 is screwed on the fluid loading hole 18.
[0061] The fluid pressure charging device 60 includes a pressure charger 62 and a storage tank 61, the inlet of the pressure charger 62 is communicated with the storage tank 61, the outlet of the pressure charger is communicated with the short connecting pipe 181 through a delivery pipe 63, and an adjusting valve 64 is installed at the outlet of the pressure charger, and the pressure charger is used to charge the fluid in the storage tank into the pressure chamber. A pressure detection unit 72 and a vent pipe 65 are installed on the delivery pipe, the connection point of the pressure detection unit with the delivery pipe is located between the adjusting valve and the short connecting pipe 181, and the connection point of the vent pipe 65 with the delivery pipe is also located between the adjusting valve and the short connecting pipe 181, and a vent valve 66 is installed on the vent pipe 65. Specifically, in the embodiment, the storage tank 61 is used to store nitrogen, and the pressure charger 62 is specifically a gas compressor.
[0062] When the pressure charger charges the fluid into the pressure chamber, the inner bellows and the outer bellows can be elongated at the same time, the soft ring 52 is pushed to move towards the planar upper ring and tightly abuts against the planar upper ring, when the pressure in the pressure chamber reaches the set pressure value, the charging of the fluid into the pressure chamber is stopped, and the planar upper ring and the soft ring form a non-extrusion contact interface; when the fluid in the pressure chamber is discharged, the bellows assembly can move away from the planar upper ring and restore to the original state. When the pressure in the pressure chamber reaches the set pressure value, the porosity of the contact interface between the planar upper ring and the soft ring is less than 0.3116.
[0063] The design life of the general nuclear main pump is 50-70 years, and the main shaft seal is serviced or replaced once every 6 years, so the parking seal needs to work 12 times in the life cycle of the nuclear main pump, plus abnormal maintenance and safety factor, the cumulative work needs more than 20 times. If the contact load between the soft ring and the hard ring is large, it will cause low cycle fatigue. Therefore, maintaining the coaxiality between the parts can reduce the contact pressure between the soft ring and the hard ring when sealing; the butt welding of the convex ring and the bellows can effectively improve the welding quality and reduce the welding stress, thereby improving the fatigue life of the double-layer bellows pressure assembly of the soft ring and the hard ring under the condition of large contact load.
Claims
1. Double bellows pressurization assembly for parking seal of a nuclear primary pump, characterized in that, The double-layer bellows pressurization assembly comprises a bellows assembly, a soft ring seat and a base, the bellows assembly comprises two bellows which are sleeved together, the two bellows are an inner bellows and an outer bellows respectively, the inner bellows and the outer bellows extend along a first axis direction, the outer bellows is coaxially sleeved outside the inner bellows, and the inner bellows and the outer bellows have a distance therebetween; the soft ring seat, the inner bellows, the outer bellows and the base are coaxially arranged; Corresponding to the two open half-wave ends of each bellows, a convex ring is arranged on the side of the soft ring seat opposite to the base, each open half-wave end is sealingly welded on the corresponding convex ring, the end face of the convex ring on the soft ring seat is coplanar with the end face of the soft ring seat, and the end face of the convex ring on the base is coplanar with the end face of the base; A soft ring mounting portion is arranged on the side of the soft ring seat away from the base, and the soft ring mounting portion is coaxially arranged with the soft ring seat.
2. The double-layer bellows pressurization assembly according to claim 1, wherein The convex ring, the soft ring seat and the base are coaxially arranged.
3. The double-layer bellows pressurization assembly according to claim 1, wherein A stress release groove is arranged on the inner and outer sides of each convex ring, and the stress release groove is annular.
4. The double-layer bellows pressurization assembly according to claim 3, wherein The inner circumferential surface of each convex ring is defined by the outer circumferential surface of the stress release groove on the inner side thereof, and the outer circumferential surface of each convex ring is defined by the inner circumferential surface of the stress release groove on the outer side thereof.
5. The double-layer bellows pressurization assembly according to claim 3, wherein The convex rings on the soft ring seat are integrally formed on the soft ring seat, and the convex rings on the base are integrally formed on the base.
6. The double-layer bellows pressurization assembly according to claim 1, wherein The depth of the stress release groove on the soft ring seat is 0.57 times the calculated thickness of the soft ring seat, and the depth of the stress release groove on the base is 0.57 times the calculated thickness of the base.
7. The double-layer bellows pressurization assembly according to claim 1, wherein The tangent of the open half-wave end extends along the first axis direction.
8. The double-layer bellows pressurization assembly according to claim 1, wherein The inner diameter of the end face of the open half-wave end is the same as the inner diameter of the end face of the connected convex ring, and the outer diameter of the end face of the open half-wave end is the same as the outer diameter of the end face of the connected convex ring; in the first axis direction, the projection of the end face of the open half-wave end overlaps the projection of the end face of the connected convex ring.
9. The double-layer bellows pressurization assembly according to claim 1, wherein The space between the soft ring seat, the base, the inner bellows and the outer bellows forms a pressure cavity, and a fluid loading hole is arranged on the base to communicate the inside and outside of the pressure cavity.
10. The double-layer bellows pressurization assembly according to claim 1, wherein The open half-wave end is welded on the corresponding convex ring by laser welding.