Pressurizing double-layer corrugated pipe assembly structure of parking seal for nuclear main pump

Abstract

The invention discloses a pressurizing double-layer corrugated pipe assembly structure of a parking seal for a nuclear main pump. The pressurizing double-layer corrugated pipe assembly structure comprises a soft ring seat, an inner corrugated pipe, an outer corrugated pipe and a base which are coaxially arranged. Two first open half-wave ends of the inner corrugated pipe are respectively welded on the inner convex rings on the soft ring seat and the base in a sealing manner; two second open half-wave ends of the outer corrugated pipe are respectively welded on the outer convex rings on the soft ring seat and the base in a sealing manner; a soft ring installation part is arranged on the side, away from the base, of the soft ring base, and the soft ring installation part and the soft ring base are coaxially arranged. The inner convex ring and the outer convex ring are used for converting a welding seam structure among the inner corrugated pipe, the outer corrugated pipe, the soft ring seat and the base into a butt welding seam from a fillet welding seam, through welding and detection are easy, and the quality and the sealing performance of the welding seam are guaranteed. The inner convex ring and the outer convex ring are used for solving the centering problem of the inner corrugated pipe, the outer corrugated pipe, the soft ring seat and the base in the welding process, the connecting position precision is guaranteed, and meanwhile the coaxiality of the inner corrugated pipe and the outer corrugated pipe is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of sealing, and in particular relates to a pressurized double-layer bellows component structure of a parking seal for a nuclear main pump. Background Art

[0002] The nuclear main pump located in the core and steam generator loop (main loop) is the "heart" of the nuclear power plant. It circulates coolant to absorb the fission reaction heat in the core and then releases the heat in the steam generator. The shutdown seal is the last barrier of the nuclear main pump. On the one hand, it is used to ensure the sealing after shutdown caused by the failure of the main shaft seal of the main pump to prevent the coolant in the pump from leaking out; on the other hand, it is used to ensure the sealing of the main shaft of the main pump during the main shaft seal maintenance stage.

[0003] At present, the more advanced nuclear main pump parking seal adopts two rings for sealing on the plane. The two rings are a hard ring and a soft ring respectively. The hard ring is sealingly connected to the main shaft, and the soft ring is installed on the soft ring seat. The soft ring seat is fixed on one end of the double-layer bellows, and the other end of the double-layer bellows is installed on the pump casing through the base.

[0004] When the main shaft seal of the nuclear main pump fails or is under maintenance, the nuclear main pump stops running and pressurizes the double-layer bellows to stretch the double-layer bellows, pushing the soft ring and the hard ring to fit together to form a sealed contact. After the main shaft sealing performance is restored, the pressure in the double-layer bellows is released to shrink the double-layer bellows, driving the soft ring to move away from the hard ring, so that the soft ring and the hard ring are disengaged, and the nuclear main pump can operate.

[0005] The connections between the bellows and the soft ring seat and the base of the existing parking seal are all fillet welded. This welding form with a large difference in wall thickness is very likely to cause welding stress and welding defects. During the alternation between the working and non-working periods of the parking seal, the fillet welds will also cause fatigue damage, making it difficult to meet the requirements of the parking seal's service life of 50-70 years and no replacement or maintenance during service. Summary of the invention

[0006] In order to at least partially solve the problems of connection quality, welding stress and fatigue life of the connection between the double-layer bellows and the soft ring seat and the base of the existing parking seal, the present application proposes a pressurized double-layer bellows assembly structure for the parking seal of a nuclear main pump, which includes a soft ring seat, an inner bellows, an outer bellows and a base. The soft ring seat, the inner bellows, the outer bellows and the base are coaxially arranged, the inner bellows and the outer bellows both 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;

[0007] Corresponding to the two first open half-wave ends of the inner bellows, an inner convex ring is provided on the side of the soft ring seat opposite to the base, and each first open half-wave end is sealed and welded to the corresponding inner convex ring;

[0008] Corresponding to the two second open half-wave ends of the outer bellows, an outer convex ring is provided on the side of the soft ring seat opposite to the base, and each second open half-wave end is sealed and welded to the corresponding outer convex ring;

[0009] A soft ring mounting portion is arranged on a side of the soft ring seat away from the base, and the soft ring mounting portion is arranged coaxially with the soft ring seat.

[0010] After the inner and outer convex rings are set, the weld structure between the inner and outer bellows and the soft ring seat and the base is changed from a fillet weld to a butt weld, which is easy to penetrate and detect, ensuring the quality of the weld and the welding seal between the inner and outer bellows and the soft ring seat and the base. The use of the inner and outer convex rings solves the problem of centering the inner and outer bellows and the soft ring seat and the base during welding, ensuring the position accuracy of the connection, and at the same time improving the coaxiality of the inner and outer bellows. If the inner and outer bellows are not concentric, the axial forces acting on the soft ring seat and the base will be inconsistent due to the different areas acted by the medium pressure in the pressure chamber. After the inner and outer bellows are eccentric, the axial force generated on the large area side of the soft ring seat or the base acted by the pressure medium is large, and the axial force generated on the small area side is small, resulting in different contact pressures in the contact area between the soft ring and the hard ring. 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 with small contact pressure between the soft ring and the hard ring is also less than 0.3116, which increases the risk of fatigue damage at the welding points between the inner and outer bellows and the soft ring seat and the base.

[0011] Furthermore, the inner convex ring, the outer convex ring, the soft ring seat and the base are coaxially arranged. This design enables the inner and outer bellows to extend after the pressure fluid is added therebetween, so that the soft ring end face on the soft ring seat can be stably translated along the first axis direction, 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 part. Otherwise, if the coaxiality of the inner and outer bellows is poor or the inner convex ring, the outer convex ring, the soft ring seat and the base are not coaxial, when the soft ring is pressed against the hard ring, the contact pressure between the soft ring and the hard ring is uneven, and it is difficult to achieve an ideal parking sealing effect.

[0012] Further, a first stress release groove is provided on both sides of the inner and outer sides of each inner convex ring, and the first stress release groove is annular, and a second stress release groove is provided on both sides of the inner and outer convex ring, and the second stress release groove is annular. Preferably, the end faces of the inner and outer convex rings are coplanar with the end faces of the soft ring seat or base where they are located.

[0013] By utilizing the first stress release groove and the second stress release groove, an inner convex ring and an outer convex ring can be formed to reduce the difference in stiffness at the connection between the inner and outer bellows and the soft ring seat and the base, which is beneficial for causing the soft ring seat and the base to have thermal expansion or contraction deformation similar to that of the inner and outer bellows during welding, thereby reducing the welding stress at the weld.

[0014] Specifically, the inner circumference of each inner convex ring is defined by the outer circumference of the first stress release groove located on the inner side thereof, and the outer circumference of each inner convex ring is defined by the inner circumference of the first stress release groove located on the outer side thereof;

[0015] The inner circumference of each outer convex ring is defined by the outer circumference of the second stress release groove located on the inner side thereof, and the outer circumference of each outer convex ring is defined by the inner circumference of the second stress release groove located on the outer side thereof.

[0016] Specifically, the inner convex ring and the outer convex ring on the soft ring seat are integrally formed on the soft ring seat; the inner convex ring and the outer convex ring on the base are integrally formed on the base. This design can effectively avoid the stress generated when the inner convex ring and the outer convex ring are installed by welding.

[0017] Specifically, the depths of the first stress release groove and the second stress release groove on the soft ring seat are both 0.57 times the calculated thickness of the soft ring seat; the depths of the first stress release groove and the second stress release groove on the base are both 0.57 times the calculated thickness of the base. The limitation of the depths of the first stress release groove and the second stress release groove, on the one hand, can effectively reduce the rigidity of the inner and outer convex rings on the soft ring seat and the base, ensure their deformation capacity, and reduce the welding stress at the welding point between the bellows and the inner and outer convex rings; on the other hand, it avoids the weld between the bellows and the inner and outer convex rings being in the edge stress zone, improving the stress state at the weld. After the first stress release groove and the second stress release groove are provided, the areas of the soft ring seat and the base corresponding to the first stress release groove and the second stress release groove are formed into thin-walled areas. When the inner and outer bellows are welded, the stress generated on the soft ring seat and the base will be released in the thin-walled areas. When the depth of the first stress release groove and the second 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, thereby improving the safety of the structure.

[0018] Furthermore, the tangent lines of the first open half-wave end and the second open half-wave end both extend along the first axis. This design enables the thrust or pull generated by the inner and outer bellows to be transmitted to the soft ring seat along the first axis, and then to the soft ring, so that the soft ring and the corresponding hard ring complete the seal.

[0019] Specifically, 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 end face of the first open half-wave end overlaps with the projection of the end face of the connected inner convex ring; 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 end face of the second open half-wave end overlaps with the projection of the end face of the connected outer convex ring.

[0020] Under the above-mentioned limitations, the connecting parts of the inner and outer bellows and the corresponding inner and outer convex rings can be completely overlapped to form a true butt weld. On the one hand, it is easy to ensure the welding quality; on the other hand, when the parking seal is working, the weld is only subjected to axial force but not tangential force, which improves the stress state of the weld and increases the fatigue life of the parking seal.

[0021] Specifically, in order to facilitate the adjustment of the extension and retraction of the inner bellows and the outer bellows, the space enclosed by the inner bellows, the outer bellows, the soft ring seat and the base is formed into a pressure chamber, and a fluid loading hole connecting the inside and outside of the pressure chamber is provided on the base. The fluid loading hole is used for an external fluid pressure charging device, and the fluid is introduced into the pressure chamber through the fluid loading hole by means of the fluid pressure charging device, so that the inner bellows and the outer bellows are extended, so that the soft ring installed on the soft ring seat can contact with the hard ring to form a seal. When the fluid in the pressure chamber flows outward, the inner bellows and the outer bellows can retract, so that the soft ring is released from contact with the hard ring. The fluid can specifically be a liquid such as water and hydraulic oil, or a gas such as air and nitrogen.

[0022] Specifically, in order to ensure welding accuracy and reduce deformation caused by welding, the first open half-wave end is welded to the inner convex ring by laser welding; the second open half-wave end is welded to the outer convex ring by laser welding.

[0023] Generally, the design life of a nuclear main pump is 50-70 years, and the main shaft seal is regularly repaired or replaced once every 6 years. In this way, the shutdown seal needs to work up to 12 times in the life cycle of the nuclear main pump. With abnormal maintenance and safety factors, it 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 sealing; butt welding of the convex ring and the bellows can effectively improve the welding quality and reduce welding stress, thereby improving the fatigue life of the pressurized double-layer bellows assembly structure of the soft ring and the hard ring under large contact load conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1It is a structural schematic diagram of an embodiment of a pressurized double-layer bellows assembly structure.

[0025] Figure 2 yes Figure 1 Enlarged view of part A.

[0026] Figure 3 yes Figure 1 Enlarged view of part B.

[0027] Figure 4 It is a schematic diagram of the structure of the outer bellows.

[0028] Figure 5 This is a schematic diagram of the second structure of the soft ring seat.

[0029] Figure 6 This is a schematic diagram of the third structure of the soft ring seat.

[0030] Figure 7 It is a schematic diagram of welding of a bellows and a soft ring seat in the prior art.

[0031] Figure 8 It is a schematic diagram of the structure of a nuclear main pump equipped with a parking seal having a pressurized double-layer bellows assembly structure. DETAILED DESCRIPTION

[0032] First, the welding structure of the bellows and the soft ring seat A81 or the base A in the prior art is described below. Figure 7 At present, the connection between the inner bellows A83, the outer bellows A82 and the soft ring seat A81 is directly welded. During welding, fillet welding is used to weld the inner and outer sides of the inner bellows A83 and the outer bellows A82 to form a fillet 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, thereby affecting the service life of the soft ring seat A and the base A.

[0033] The following is a further detailed description of the pressurized double-layer bellows assembly structure 10 for the nuclear main pump parking seal. Figure 1-Figure 3 In the accompanying drawings, the direction of arrow Y indicates the direction of the first axis.

[0034] In this embodiment, the pressurized double-layer bellows assembly structure 10 specifically includes a soft ring seat 11, an inner bellows 15, an outer bellows 14 and a base 17. The inner bellows 15 and the outer bellows 14 both extend along the first axial direction, and the outer bellows 14 is coaxially sleeved on the outer side of the inner bellows 15, and there is a distance between the inner bellows 15 and the outer bellows 14. The soft ring seat 11, the inner bellows 15, the outer bellows 14 and the base 17 are coaxially arranged.

[0035] For ease of description, the structures of the inner bellows 15 and the outer bellows 14 are first described below. In this embodiment, the structures of the inner bellows and the outer bellows are the same. The structures of the inner bellows and the outer bellows are described below using the outer bellows 14 as an example. Figure 4 The outer bellows includes a plurality of full-wave bands 140 connected in sequence and two half-wave bands at both ends. Figure 3 In the figure, three full-bands 140 are shown by way of example, the range enclosed by the first double-dotted line ellipse D roughly includes one full-band 140, the range enclosed by the second double-dotted line E roughly includes one half-band, and the end of each half-band away from the other half-band is called an open half-wave end. There is no specific requirement for the number of full-bands in the inner bellows and the outer bellows.

[0036] For the convenience of description, the two half-wave segments of the inner bellows are both referred to as the first half-wave segment 151, and the open half-wave end of the first half-wave segment is referred to as the first open half-wave end 152. The two half-wave segments of the outer bellows are both referred to as the second half-wave segment 141, and the open half-wave end of the second half-wave segment is referred to as the second open half-wave end 142. The tangent lines of the first open half-wave end 152 extend along the first axis, and the tangent line 145 of the second open half-wave end 142 extends along the first axis.

[0037] The soft ring seat 11 is in the shape of a circular ring, and has a first center hole 113 in the center thereof, which extends along the first axis and is in the shape of a through hole. The base 17 is in the shape of a circular ring, and has a second center hole 173 in the center thereof, which extends along the first axis and is in the shape of a through hole. The first center hole 113 and the second center hole 173 are used to be sleeved on the main shaft 48 of the nuclear main pump, and the detailed installation method is described below. A soft ring mounting portion 13 is provided on the side of the soft ring seat 11 away from the base, and the soft ring mounting portion 13 is coaxially arranged with the soft ring seat 11. Specifically in this embodiment, the soft ring mounting portion 13 is specifically an annular groove.

[0038] Corresponding to the two first open half-wave ends 152 of the inner bellows 15, an inner convex ring is provided on the side of the soft ring seat 11 opposite to the base 17. For ease of description, the inner convex ring on the soft ring seat 11 is referred to as the first inner convex ring 117, and the inner convex ring on the base 17 is referred to as the second inner convex ring 177. Each first open half-wave end is sealedly welded to the corresponding inner convex ring by laser welding.

[0039] Corresponding to the two second open half-wave ends 142 of the outer bellows 14, an outer convex ring is provided on the side of the soft ring seat 11 opposite to the base 17. For ease of description, the outer convex ring on the soft ring seat 11 is referred to as a first outer convex ring 116, and the outer convex ring on the base 17 is referred to as a second outer convex ring 176. Each second open half-wave end is sealedly welded to the corresponding outer convex ring by laser welding.

[0040] In the direction of the first axis, 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 is coaxially arranged with the outer convex ring.

[0041] In this embodiment, a first stress release groove A112 is provided on both the inner and outer sides of the first inner convex ring 117, and a first stress release groove B172 is provided on both 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 both annular. That is, an annular first stress release groove is provided on both the inner and outer sides of each inner convex ring.

[0042] The inner circumference of the first inner convex ring 117 is defined by the outer circumference of the first stress release groove A112 located on the inner side thereof, and the outer circumference of the first inner convex ring 117 is defined by the inner circumference of the first stress release groove A112 located on the outer side thereof. The inner circumference of the second inner convex ring 177 is defined by the outer circumference of the first stress release groove B172 located on the inner side thereof, and the outer circumference of the second inner convex ring 177 is defined by the inner circumference of the first stress release groove B172 located on the outer side thereof.

[0043] That is, the inner circumference of each inner convex ring is defined by the outer circumference of the first stress release groove located on the inner side thereof, and the outer circumference of each inner convex ring is defined by the inner circumference of the first stress release groove located on the outer side thereof.

[0044] A second stress release groove A111 is provided on both the inner and outer sides of the first outer convex ring 116, and a second stress release groove B171 is provided on both 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 both annular. That is, an annular second stress release groove is provided on both the inner and outer sides of each outer convex ring.

[0045] The inner circumference of the first outer convex ring 116 is defined by the outer circumference of the second stress release groove A111 located inside the first outer convex ring 116, and the outer circumference of the first outer convex ring 116 is defined by the inner circumference of the second stress release groove A111 located outside the first outer convex ring 116. The inner circumference of the second outer convex ring 176 is defined by the outer circumference of the second stress release groove B171 located inside the first outer convex ring 176, and the outer circumference of the second outer convex ring 176 is defined by the inner circumference of the second stress release groove B171 located inside the first outer convex ring 176.

[0046] That is, the inner circumference of each outer convex ring is defined by the outer circumference of the second stress release groove located on the inner side thereof, and the outer circumference of each outer convex ring is defined by the inner circumference of the second stress release groove located on the outer side thereof. The first inner convex ring 117 and the first outer convex ring 116 are both formed integrally on the soft ring seat, and the second inner convex ring 177 and the second outer convex ring 176 are both formed integrally on the base.

[0047] The end faces of the first inner convex ring 117 and the first outer convex ring 116 facing the base 17 are coplanar with the end face of the soft ring seat 11 facing the base 17, and the end faces of the second inner convex ring 177 and the second outer convex ring 176 facing the soft ring seat 11 are coplanar with the end face of the base 17 facing the soft ring seat 11. That is, the end faces of the inner and outer convex rings are coplanar with the end faces of the soft ring seat 11 or the base 17 where they are located.

[0048] The inner convex ring, the outer convex ring, the soft ring seat and the base are coaxially arranged.

[0049] Specifically, in this embodiment, the soft ring seat and the base are both made of steel plates, and the first inner convex ring 117, the first outer convex ring 116, and the corresponding first stress release groove A112 and the second stress release groove A111 are processed on the soft ring seat by a machine tool. The second inner convex ring 177, the second outer convex ring 176, and the corresponding first stress release groove B172 and the second stress release groove B171 are processed on the base by a machine tool.

[0050] In this embodiment, the depth of the first stress release groove A112 and the second stress release groove A111 are the same, which is 0.57 times the calculated thickness of the soft ring seat 11. The calculated thickness refers to the thickness required to ensure the strength and rigidity of the soft ring seat 11 and the base 17 under all load conditions such as the medium pressure in the pressure chamber and the contact pressure between the soft ring and the hard ring, which can be calculated according to the pressure vessel design specifications. Figure 2 In FIG. 1 , the mark H1 indicates the depth of the first stress release groove A112 or the second stress release groove A111, and H2 indicates the thickness of the soft ring seat 11. The depth of the first stress release groove B172 and the second stress release groove B171 is the same, which is 0.57 times the calculated thickness of the base 17.

[0051] 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 projection of the end face of the first open half-wave end overlaps with the end face of the connected inner convex ring.

[0052] 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 direction of the first axis, the projection of the end face of the second open half-wave end overlaps with the end face of the connected outer convex ring.

[0053] In this embodiment, the axial cross-sections of the inner convex ring and the outer convex ring are both rectangular, and the first stress release groove and the second stress release groove are also rectangular. Figure 5 and Figure 6 It can be understood that in other embodiments, the axial cross-sections of the inner convex ring and the outer convex ring can also be isosceles trapezoidal. Figure 5 In the structure shown, the axial cross-sections of the first stress release groove and the second stress release groove are both isosceles trapezoidal. Figure 6 In the structure shown, the first stress release groove and the second stress release groove are both in the shape of a right-angle trapezoid.

[0054] The space enclosed by the inner bellows 15, the outer bellows 14, the soft ring seat 11 and the base 17 forms a pressure chamber 19, and a fluid loading hole 18 communicating with the inside and outside of the pressure chamber is provided on the base.

[0055] The following is a description of the specific installation method of the pressurized double-layer bellows assembly structure in the nuclear main pump in this embodiment. Figure 8 The nuclear main pump includes a pump casing 41 and a sealing box 20 installed together along the first axis direction. An impeller 43 is rotatably installed in the pump casing 41. A pump inlet 42 is provided at one end of the pump casing 41 away from the sealing box, and a pump outlet 44 is provided on one side of the pump casing 41 in the radial direction. One end of the main shaft 48 extends into the pump casing and is fixedly connected to the impeller 43, and the other end of the main shaft 48 extends outward from the sealing box 20. In this embodiment, the sealing box 20 includes a cylinder 21 extending along the first axis direction and a base 17 of a pressurized double-layer bellows assembly structure. The base 17 is arranged at one end of the cylinder facing the impeller direction. The cylinder 21 and the base 17 are sealed and welded together. The base 17 is sealed and fixed to the pump casing with bolts, so that the sealing box 20 is sealed and installed on the pump casing.

[0056] The pressurized double-layer bellows assembly structure and the sealing pair together constitute the parking seal, which is located between the main seal 30 and the impeller 43 of the nuclear main pump. The main seal includes a static ring 32 fixedly set on the inner wall of the cylinder and a dynamic ring 31 sealingly 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 provided between the static ring and the cylinder, and the end cover 25 is fixed to the side of the cylinder away from the base by bolts to keep the main seal in the sealing box 20. In order to simplify the drawings, in the drawings, the structure of the main seal 30 only shows some components, not all of its components. The detailed structure and installation method of the main seal are existing mature technologies and will not be repeated.

[0057] The inner bellows 15 and the outer bellows 14 are located on the side of the base 17 away from the impeller 43 , so that the soft ring seat 11 is located on the side of the inner bellows 15 and the outer bellows 14 away from the base.

[0058] The sealing pair comprises a planar upper ring 56 sleeved on the main shaft and a soft ring 52, wherein the planar upper ring 56 is sealedly fixed on the main shaft, and the soft ring is located on the side of the planar upper ring facing the impeller. The planar upper ring 56 is the hard ring mentioned above.

[0059] In this embodiment, the planar upper ring is fixed on the main shaft 48 by an upper petal ring 561 and a lower petal ring 562. An upper ring groove 481 and a lower ring groove 482 are provided on the outer peripheral surface of the main shaft 48. The upper ring groove 481 and the lower ring groove 482 both extend around the outer peripheral surface of the main shaft. The upper petal ring 561 is tightly clamped in the upper ring groove, and the lower petal ring 562 is tightly clamped in the lower ring groove. The upper petal ring 561 and the lower petal ring 562 are respectively tightly pressed on both sides of the planar upper ring to fix the planar upper ring on the main shaft. The upper petal ring 561 and the lower petal ring 562 each have two ring petals. It can be understood that in other embodiments, the number of ring petals of the upper petal ring 561 and the lower petal ring 562 can be set according to specific needs. The planar upper ring 56 is made of 304 stainless steel.

[0060] The soft ring 52 is made of M106F graphite material, and is fixed in the annular groove as the soft ring mounting portion. The soft ring 52 is bonded to the soft ring seat 11 by using silicone modified epoxy resin.

[0061] To facilitate connection to an external fluid pressure device 60 , the fluid loading hole 18 is roughly L-shaped and penetrates the outer peripheral surface of the base outwardly. The outer end of the fluid loading hole 18 has an internal thread, and a short pipe 181 is screwed on the fluid loading hole 18 .

[0062] The fluid charging device 60 includes a pressurizer 62 and a storage tank 61. The inlet of the pressurizer 62 is connected to the storage tank 61, and the outlet of the pressurizer is connected to the short pipe 181 via the delivery pipe 63. A regulating valve 64 is installed at the outlet of the pressurizer. The pressurizer 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 between the pressure detection unit and the delivery pipe is located between the regulating valve and the short pipe 181, and the connection point between the vent pipe 65 and the delivery pipe is also located between the regulating valve and the short pipe 181. A vent valve 66 is installed on the vent pipe 65. Specifically in this embodiment, the storage tank 61 is used to store nitrogen, and the pressurizer 62 specifically adopts a gas compressor.

[0063] When the inflator fills the pressure chamber with fluid, the inner bellows and the outer bellows can be extended at the same time, pushing the soft ring 52 to move toward the plane ring 56 and sealingly pressing against the plane ring 56. When the pressure in the pressure chamber reaches the set pressure value, the fluid is stopped from being filled into the pressure chamber, and a non-percolation contact interface is formed between the plane ring 56 and the soft ring 52. When the fluid in the pressure chamber is discharged, the bellows assembly can move away from the plane ring 56 and return to its original state. When the pressure in the pressure chamber reaches the set pressure value, the porosity of the contact interface between the plane ring 56 and the soft ring 52 is less than 0.3116.

[0064] Generally, the design life of a nuclear main pump is 50-70 years, and the main shaft seal is regularly repaired or replaced once every 6 years. In this way, the shutdown seal needs to work up to 12 times in the life cycle of the nuclear main pump. With abnormal maintenance and safety factors, it 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 sealing; butt welding of the convex ring and the bellows can effectively improve the welding quality and reduce welding stress, thereby improving the fatigue life of the pressurized double-layer bellows assembly structure of the soft ring and the hard ring under large contact load conditions.

Claims

1. A pressurized double-layer bellows assembly structure for a nuclear main pump parking seal, characterized in that: It includes a soft ring seat, an inner bellows, an outer bellows and a base, wherein the soft ring seat, the inner bellows, the outer bellows and the base are coaxially arranged, the inner bellows and the outer bellows both extend along the first axis direction, and the outer bellows is coaxially sleeved on the outer side of the inner bellows, and there is a distance between the inner bellows and the outer bellows; Corresponding to the two first open half-wave ends of the inner bellows, an inner convex ring is provided on the side of the soft ring seat opposite to the base, and each first open half-wave end is sealed and welded to the corresponding inner convex ring; Corresponding to the two second open half-wave ends of the outer bellows, an outer convex ring is provided on the side of the soft ring seat opposite to the base, and each second open half-wave end is sealed and welded to the corresponding outer convex ring; A soft ring mounting portion is arranged on a side of the soft ring seat away from the base, and the soft ring mounting portion is arranged coaxially with the soft ring seat.

2. The pressurized double-layer bellows assembly structure according to claim 1 is characterized in that: The inner convex ring, the outer convex ring, the soft ring seat and the base are coaxially arranged.

3. The pressurized double-layer bellows assembly structure according to claim 1 is characterized in that: A first stress relief groove is provided on both the inner and outer sides of each inner convex ring. The first stress relief groove is annular. A second stress release groove is arranged on both inner and outer sides of each outer convex ring, and the second stress release groove is annular.

4. The pressurized double-layer bellows assembly structure according to claim 3 is characterized in that: The inner circumference of each inner convex ring is defined by the outer circumference of the first stress release groove located on the inner side thereof, and the outer circumference of each inner convex ring is defined by the inner circumference of the first stress release groove located on the outer side thereof; The inner circumference of each outer convex ring is defined by the outer circumference of the second stress release groove located on the inner side thereof, and the outer circumference of each outer convex ring is defined by the inner circumference of the second stress release groove located on the outer side thereof.

5. The pressurized double-layer bellows assembly structure according to claim 3 is characterized in that: The inner convex ring and the outer convex ring located on the soft ring seat are integrally formed on the soft ring seat; The inner convex ring and the outer convex ring located on the base are integrally formed on the base.

6. The pressurized double-layer bellows assembly structure according to claim 1 is characterized in that: The depths of the first stress release groove and the second stress release groove on the soft ring seat are both 0.57 times the calculated thickness of the soft ring seat; the depths of the first stress release groove and the second stress release groove on the base are both 0.57 times the calculated thickness of the base.

7. The pressurized double-layer bellows assembly structure according to claim 1 is characterized in that: Tangent lines of the first open half-wave end and the second open half-wave end both extend along the first axis direction.

8. The pressurized double-layer bellows assembly structure according to claim 1 is characterized in that: 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 projection of the end face of the first open half-wave end overlaps with the projection of the end face of the connected inner convex ring; 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 direction of the first axis, the projection of the end face of the second open half-wave end overlaps with the end face of the connected outer convex ring.

9. The pressurized double-layer bellows assembly structure according to claim 1 is characterized in that: The space enclosed by the inner bellows, the outer bellows, the soft ring seat and the base forms a pressure chamber, and a fluid loading hole communicating with the inside and outside of the pressure chamber is arranged on the base.

10. The pressurized double-layer bellows assembly structure according to claim 1, characterized in that: The first open half-wave end is welded to the inner convex ring by laser welding; the second open half-wave end is welded to the outer convex ring by laser welding.

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