Welding sealing device and method for in-service nuclear power plant low alloy steel pump shell

Abstract

The invention provides a welding sealing device and method for an in-service nuclear power plant low alloy steel pump case, the sealing device comprises a pump case side welding base, a heat shield side welding base and a sealing ring, the pump case side welding base comprises a first mounting part and a second mounting part which are arranged at an included angle; the first mounting part penetrates through a mounting gap between the pump shell main flange and the heat shield, and the second mounting part extends to the outer side of the mounting gap; the heat shield side welding base is arranged on one side, facing the second mounting part, of the heat shield; the two ends of the sealing ring are connected with the second installation part and the heat shield side welding base correspondingly so as to seal the installation gap. According to the low-alloy steel pump shell welding sealing device for the in-service nuclear power plant, one end of the shell side welding base and the pump shell main flange are in angle welding, the welding heat input amount is small, and the situation that the assembly of a main pump core bag and the pump shell is affected due to structural deformation caused by too large heat input in the welding process can be avoided.

Description

Technical Field

[0001] The invention relates to the technical field of nuclear power plant main pump sealing, and in particular to a low alloy steel pump casing welding sealing device and method for an in-service nuclear power plant. Background Art

[0002] The main pump of a passive nuclear power plant adopts a double-pass spiral wound gasket seal. Its pump casing is made of low alloy steel and the heat shield is made of martensitic stainless steel. Under conditions such as cold shutdown transient, there is a large deformation difference between the pump casing and the heat shield, which may cause primary coolant leakage. When the leakage rate exceeds the requirements of the operation and maintenance strategy, there will be a risk of unplanned shutdown of the main pump for maintenance.

[0003] In-service power plants, due to limitations in on-site construction conditions, there are usually no conditions for welding preheating or post-weld heat treatment at the main pump main seal, which poses a challenge to modifying the main pump main flange seal to a welded seal in in-service power plants.

[0004] Based on this, the inventor of the present application proposes a welding sealing device and method for low alloy steel pump casings in operating nuclear power plants, in order to solve the above technical problems. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the defect in the prior art that the main flange of the main pump cannot be subjected to welding preheating or post-weld heat treatment due to limitations of on-site construction conditions, and to provide a welding sealing device and method for a low alloy steel pump casing in an in-service nuclear power plant.

[0006] The present invention solves the above technical problems through the following technical solutions:

[0007] The present invention provides a low alloy steel pump casing welding sealing device for an in-service nuclear power plant, which is characterized by comprising:

[0008] The welding base on the pump casing side includes a first mounting portion and a second mounting portion arranged at an angle, wherein the first mounting portion is arranged through the mounting gap between the main flange of the pump casing and the heat shield, and the second mounting portion extends to the outside of the mounting gap;

[0009] A heat shield side welding base, disposed on a side of the heat shield facing the second mounting portion;

[0010] A sealing ring, with two ends respectively connected to the second mounting portion and the heat shield side welding base to seal the mounting gap.

[0011] According to an embodiment of the present invention, the first mounting portion and the second mounting portion are integrally provided.

[0012] According to an embodiment of the present invention, the first mounting portion and the second mounting portion are vertically arranged.

[0013] According to an embodiment of the present invention, one end of the first mounting portion is attached to the side wall of the main flange of the pump casing, and one end of the second mounting portion is attached to the main flange surface of the pump casing.

[0014] According to an embodiment of the present invention, the sealing ring is a C-shaped ring, and the opening faces the side away from the heat shield.

[0015] According to an embodiment of the present invention, two ends of the sealing ring are respectively connected to the second mounting portion and the heat shield side welding base through fillet welds.

[0016] According to one embodiment of the present invention, the material of the welding base on the pump casing side is stainless steel or nickel-based alloy;

[0017] The material of the heat shield side welding base is nickel-based alloy.

[0018] According to an embodiment of the present invention, the sealing ring and the second mounting portion are both located on the inner side of the main bolts on the main flange of the pump casing.

[0019] The present invention also provides a method for welding and sealing a low alloy steel pump casing in an in-service nuclear power plant, using the welding and sealing device for a low alloy steel pump casing in an in-service nuclear power plant as described above, the sealing method comprising:

[0020] Step 1, cutting off the corrosion-resistant cladding layer on the inner wall of the original pump casing, and processing a bevel at the root of the corrosion-resistant cladding layer;

[0021] Step 2, connecting the first mounting portion of the welding base on the pump casing side to the root fillet weld of the corrosion-resistant cladding layer, and making one end surface of the second mounting portion attached to the main flange surface of the original pump casing;

[0022] Step 3, welding a heat shield side welding base on the heat shield, and welding one end of the sealing ring to the heat shield side welding base;

[0023] Step 4: Install the heat shield to the original pump housing, and weld the other end of the sealing ring to the second mounting portion.

[0024] According to one embodiment of the present invention, before step 4, the method further includes:

[0025] The main bolts connecting the original pump casing and the heat shield are disassembled and assembled in groups to ensure that the main bolts can provide pre-support for the original pump casing and the heat shield.

[0026] The positive and progressive effects of the present invention are:

[0027] The present invention is used for welding and sealing devices of low alloy steel pump casings in nuclear power plants in service. A fillet welding is performed between one end of a welding base on the pump casing side and a main flange of the pump casing. The welding heat input is small, and structural deformation caused by excessive heat input during the welding process can be avoided, which affects the assembly of the main pump core package and the pump casing.

[0028] There are fillet welds between the sealing ring and the welding base on the pump casing side and the welding base on the heat shield side. There is no surfacing layer and the overhead welding is carried out. The construction process is simple and the welding quality can be guaranteed.

[0029] The welded base on the pump casing side is close to the inner wall of the pump casing, and can rely on the pump casing to bear radial force without destroying the pressure-bearing capacity of the original pump casing.

[0030] The welding base on the heat shield side is welded on the outside of the heat shield, which does not affect the pressure bearing capacity and thermal insulation function of the heat shield. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The above and other features, properties and advantages of the present invention will become more apparent through the following description in conjunction with the accompanying drawings and embodiments, in which:

[0032] Figure 1 It is a schematic diagram of the structure of the welding sealing device of the low alloy steel pump casing used in the nuclear power plant in service according to the present invention;

[0033] Figure 2 This is a structural diagram of installing the pump casing side welding base on the pump casing main flange;

[0034] Figure 3 It is a schematic diagram of the structure of the heat shield side welding base installed on the heat shield;

[0035] Figure 4 It is a schematic diagram of the structure of the welding sealing ring on the heat shield;

[0036] Figure 5 The present invention is a flow chart of the welding sealing method for low alloy steel pump casings in an in-service nuclear power plant.

[0037] 1. Welding base on pump casing side; 11. First mounting part; 12. Second mounting part;

[0038] 2. Pump casing main flange;

[0039] 3. Heat screen;

[0040] 4. Installation clearance;

[0041] 5. Welding base on the heat shield side;

[0042] 6. Sealing ring;

[0043] 7. Main bolt. DETAILED DESCRIPTION

[0044] The present invention is further described below in conjunction with specific embodiments and drawings. More details are elaborated in the following description to facilitate a full understanding of the present invention. However, the present invention can obviously be implemented in a variety of other ways different from the description herein. Those skilled in the art can make similar generalizations and deductions based on actual application situations without violating the connotation of the present invention. Therefore, the protection scope of the present invention should not be limited by the content of this specific embodiment.

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0046] Please refer to Figures 1 to 4 The present invention proposes a low alloy steel pump casing welding sealing device for an in-service nuclear power plant, comprising a pump casing side welding base 1, a heat shield side welding base 5 and a sealing ring 6. The pump casing side welding base 1 comprises a first mounting portion 11 and a second mounting portion 12 arranged at an angle, the first mounting portion 11 is penetrated through the mounting gap 4 between the pump casing main flange 2 and the heat shield 3, and the second mounting portion 12 extends to the outside of the mounting gap 4; the heat shield side welding base 5 is arranged on the side of the heat shield 3 facing the second mounting portion 12; the two ends of the sealing ring 6 are respectively connected to the second mounting portion 12 and the heat shield side welding base 5 to seal the mounting gap 4.

[0047] Since the pump casing of the main pump of the in-service passive nuclear power plant has been welded to the lower part of the evaporator, overhead welding is difficult and the quality of the weld is difficult to ensure.

[0048] The main pump casing flange is a low alloy steel forging, and the heat shield 3 is a martensitic forging. Both require preheating and post-weld heat treatment during welding. It is difficult to implement local uniform heating and insulation operations at the weld on site, and it will cause material deformation, which will have an adverse effect on the installation and subsequent maintenance of the main pump.

[0049] In the traditional solution, an installation gap 4 is formed between the pump casing main flange 2 and the heat shield 3, and a double-pass wound gasket is arranged in the installation gap 4 to seal between the pump casing main flange 2 and the heat shield 3 to prevent leakage of the primary circuit coolant.

[0050] In the present invention, since the pump casing has been welded to the outside of the evaporator, a portion of the corrosion-resistant cladding layer on the inner wall of the pump casing is firstly cut off, and a bevel is processed at the root, which is connected to one side of the flange surface of the pump casing.

[0051] Then, the pump casing side welding base 1 is welded on the pump casing main flange 2 side and at the corresponding bevel position, and the pump casing side welding base 1 is connected to the pump casing main flange 2 through a fillet weld. At this time, the welding method is performed in a horizontal direction, the welding is simple, and the welding quality can be guaranteed.

[0052] Specifically during welding, the second mounting portion 12 of the pump casing side welding base 1 can be placed close to the surface of the pump casing main flange 2, and the pump casing side welding base 1 can be fixed with tooling to prevent the pump casing side welding base 1 from falling off, and then the first mounting portion 11 can be welded to the pump casing main flange 2.

[0053] It can be seen that the material of the pump casing side welding base 1 is stainless steel or nickel-based alloy.

[0054] After the construction of the pump casing side welding base 1 is completed, the heat shield side welding base 5 is welded to the heat shield 3 side, and the opposite ends of the heat shield side welding base 5 are connected to the heat shield 3 through fillet welds.

[0055] It can be seen that the material of the heat shield side welding base 5 is nickel-based material.

[0056] After the welding of the heat shield side welding base 5 is completed, one end of the sealing ring 6 is welded to the heat shield side welding base 5 through a fillet weld.

[0057] Thereafter, the heat shield 3 is mounted on the main flange 2 of the pump casing, and the other end of the sealing ring 6 is welded to the welding base 1 on the heat pump side.

[0058] When the heat shield 3 and the main flange 2 of the pump casing are connected, some of the main bolts 7 may be installed first to pre-support the heat shield 3, and then the sealing devices may be alternately arranged.

[0059] It should be noted that the design of the welded sealing structure must first consider the material selection. The material selection mainly considers the material's mechanical properties, welding properties, forging properties, machining properties, etc. The material selection must also consider the matching of the welding base material with the sealing ring 6, heat shield 3, and pump casing main flange 2 surface materials.

[0060] The structural design needs to consider the optimization of the structural mechanical properties. Under the space constraints of the pump casing flange surface, the heat shield 3 and the main bolts 7, its structural strength must not only withstand the design pressure of the pressure boundary, but also ensure that the fatigue stress of the welded seal under complex thermal transients meets the requirements. Finally, the welded seal structure design should not change the original pump casing and heat shield 3 functions.

[0061] The welding method must first ensure the feasibility of on-site welding, and must take into account the absence of preheating or post-weld heat treatment conditions on site. Secondly, the welding method should avoid deformation of the pump casing or heat shield 3 caused by welding heat input, which may lead to the problem that the main pump core package and the pump casing cannot be assembled.

[0062] In the present invention, transition materials are selected to connect the pump casing main flange 2, the sealing ring 6 and the heat shield 3, so that welding preheating or post-weld heat treatment can be avoided, and structural deformation caused by heat treatment can be avoided, which affects the assembly of the main pump core package and the pump casing.

[0063] In one embodiment, the first mounting portion 11 and the second mounting portion 12 of the pump casing side welding base 1 are integrally arranged and perpendicular to each other.

[0064] In this way, the overall structure of the welding base 1 on the pump casing side is stronger, and when the second mounting portion 12 is in contact with the surface of the pump casing main flange 2, the first mounting portion 11 can be welded to the pump casing side wall under the support of the tooling, and the welding method is horizontal welding, which is more convenient.

[0065] Optionally, the sealing ring 6 is a C-shaped ring, and the opening faces the side away from the heat shield 3 .

[0066] The sealing ring 6 is a C-shaped ring with its opening facing the side away from the heat shield 3, so that the sealing ring 6 can be connected to the heat shield side welding base 5 and the second mounting portion 12 arranged in parallel by fillet welding.

[0067] Furthermore, the sealing ring 6 and the second mounting portion 12 are both located on the inner side of the main bolts 7 on the main flange 2 of the pump casing.

[0068] Therefore, when actually installing the sealing device, the steps are as follows:

[0069] The first step is to cut off the corrosion-resistant cladding layer on the inner wall of the original pump casing and process a bevel at the root to facilitate welding of the first mounting portion 11 of the welding base 1 on the pump casing side with the cladding layer.

[0070] Step 2: Weld the welding base 1 on the pump casing side. First install the welding base 1 on the pump casing side so that the second mounting portion 12 is close to the main flange 2 of the pump casing, and use tooling to fix the welding base 1 on the pump casing side to prevent it from falling, and then weld the first mounting portion 11 and the groove of the cladding layer.

[0071] Step 3: Weld the heat shield side welding base 5, and weld the heat shield side welding base 5 to the heat shield 3 using fillet welds. During welding, the main bolts 7 are in a removed state.

[0072] Step 4: Weld the sealing ring 6 to the heat shield side welding base 5. Use fillet weld to weld one end of the sealing ring 6 to the heat shield side welding base 5. The main bolt 7 is in a removed state.

[0073] Step 5: Weld the sealing ring 6 to the welding base 1 on the pump casing side.

[0074] Among them, the pump casing main flange 2 and the main pump core package are connected by 24 main bolts 7. When welding, the main core package (the heat shield 3 is a part of the core package structure) is first aligned with the pump casing, and then the main bolts 7 are divided into 4 groups, which are staggered and evenly distributed.

[0075] First install the 1st and 3rd groups of main bolts 7 (12 pieces), stretch the 1st and 3rd groups of main bolts 7, and start welding the sealing ring 6 to the welding base 1 on the pump casing side (at the position of the 2nd and 4th groups of main bolts 7).

[0076] After welding is completed, the second and fourth groups of main bolts 7 are installed and stretched, and the first and third groups of main bolts 7 are removed at the same time. Thereafter, the sealing ring 6 and the welding base 1 on the pump casing side are welded at the positions of the first and third groups of main bolts 7.

[0077] Then install the 1st and 3rd groups of main bolts 7 and after stretching the 1st and 3rd groups of main bolts 7, stretch all the main bolts 7 evenly.

[0078] In summary, the present invention is used for the welding and sealing device of the low-alloy steel pump casing in the nuclear power plant in service. The corner welding between one end of the welding base 1 on the pump casing side and the main flange 2 of the pump casing has a small welding heat input, which can avoid excessive heat input during the welding process causing structural deformation and affecting the assembly of the main pump core package and the pump casing.

[0079] The sealing ring 6 and the welding base 1 on the pump casing side and the welding base 5 on the heat shield side are all fillet welds, and overhead welding construction without a surfacing layer is performed. The construction process is simple and the welding quality can be guaranteed.

[0080] The welding base 1 on the pump casing side is close to the inner wall of the pump casing, and can rely on the pump casing to bear radial force without destroying the pressure bearing capacity of the original pump casing.

[0081] The heat shield side welding base 5 is welded on the outside of the heat shield 3, which does not affect the pressure bearing capacity and heat insulation function of the heat shield 3.

[0082] Please refer to Figure 5 The present invention also proposes a welding sealing method for a low alloy steel pump casing in an in-service nuclear power plant, using the above welding sealing device for a low alloy steel pump casing in an in-service nuclear power plant, the sealing method comprises:

[0083] S1. Remove the corrosion-resistant cladding layer on the inner wall of the original pump casing and process a bevel at the root of the corrosion-resistant cladding layer;

[0084] S2, connecting the first mounting portion of the welding base on the pump casing side to the root fillet weld of the corrosion-resistant cladding layer, and making one end surface of the second mounting portion attached to the main flange surface of the original pump casing;

[0085] S3, welding a heat shield side welding base on the heat shield, and welding one end of the sealing ring to the heat shield side welding base;

[0086] S4. Install the heat shield to the original pump casing, and weld the other end of the sealing ring to the second installation part.

[0087] It can be seen that before step 4, it also includes: respectively disassembling and assembling the main bolts connecting the original pump casing and the heat shield to ensure that the main bolts can pre-support the original pump casing and the heat shield. In this way, the main bolts will not interfere with the construction of the sealing device.

[0088] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "install", "connect", "connect", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can also be a mechanical connection. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0089] The present application uses specific words to describe the embodiments of the present application. For example, "one embodiment", "an embodiment", and / or "some embodiments" refer to a certain feature, structure or characteristic related to at least one embodiment of the present application. Therefore, it should be emphasized and noted that "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or multiple times in different positions in this specification does not necessarily refer to the same embodiment. In addition, some features, structures or characteristics in one or more embodiments of the present application can be appropriately combined.

[0090] Although the present invention is disclosed as above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, any modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope defined by the claims of the present invention.

Claims

1. A welding sealing device for low alloy steel pump casings in an in-service nuclear power plant, characterized in that: include: The welding base on the pump casing side includes a first mounting portion and a second mounting portion arranged at an angle, wherein the first mounting portion is arranged through the mounting gap between the main flange of the pump casing and the heat shield, and the second mounting portion extends to the outside of the mounting gap; A heat shield side welding base, disposed on a side of the heat shield facing the second mounting portion; A sealing ring, with two ends respectively connected to the second mounting portion and the heat shield side welding base to seal the mounting gap.

2. The welding sealing device for low alloy steel pump casings of in-service nuclear power plants according to claim 1 is characterized in that: The first mounting portion and the second mounting portion are integrally arranged.

3. The welding sealing device for low alloy steel pump casings of in-service nuclear power plants according to claim 1 is characterized in that: The first mounting portion and the second mounting portion are vertically arranged.

4. The welding sealing device for low alloy steel pump casings of in-service nuclear power plants according to claim 1 is characterized in that: One end of the first mounting portion is attached to the side wall of the main flange of the pump casing, and one end of the second mounting portion is attached to the main flange surface of the pump casing.

5. The welding sealing device for low alloy steel pump casings of in-service nuclear power plants according to claim 1 is characterized in that: The sealing ring is a C-shaped ring, and the opening faces the side away from the heat shield.

6. The welding sealing device for low alloy steel pump casings of in-service nuclear power plants according to claim 5 is characterized in that: Two ends of the sealing ring are respectively connected to the second mounting portion and the heat shield side welding base through fillet welds.

7. The welding sealing device for low alloy steel pump casings of in-service nuclear power plants according to claim 1 is characterized in that: The material of the welding base on the pump casing side is stainless steel or nickel-based alloy; The material of the heat shield side welding base is nickel-based alloy.

8. The welding sealing device for low alloy steel pump casings of in-service nuclear power plants according to claim 1 is characterized in that: The sealing ring and the second mounting portion are both located on the inner side of the main bolts on the main flange of the pump casing.

9. A welding and sealing method for low alloy steel pump casings in an in-service nuclear power plant, characterized in that: The welding sealing device for low alloy steel pump casing of an in-service nuclear power plant as claimed in any one of claims 1 to 7 is used, and the sealing method comprises: Step 1, cutting off the corrosion-resistant cladding layer on the inner wall of the original pump casing, and processing a bevel at the root of the corrosion-resistant cladding layer; Step 2, connecting the first mounting portion of the welding base on the pump casing side to the root fillet weld of the corrosion-resistant cladding layer, and making one end surface of the second mounting portion attached to the main flange surface of the original pump casing; Step 3, welding a heat shield side welding base on the heat shield, and welding one end of the sealing ring to the heat shield side welding base; Step 4: Install the heat shield to the original pump housing, and weld the other end of the sealing ring to the second mounting portion.

10. The welding and sealing method for low alloy steel pump casings in an in-service nuclear power plant according to claim 9, characterized in that: Before step 4, the method further includes: The main bolts connecting the original pump casing and the heat shield are disassembled and assembled in groups to ensure that the main bolts can provide pre-support for the original pump casing and the heat shield.

Images