Welding sealing device and method suitable for low-alloy steel pump shell

Abstract

The invention provides a welding sealing device and method suitable for a low-alloy steel pump case, the sealing device comprises a surfacing isolation layer, a heat shield side welding base and a sealing ring, and the surfacing isolation layer is located on the main flange face of the pump case; the heat shield side welding base is welded to the side, close to the surfacing isolation layer, of the heat shield. Two ends of the sealing ring are respectively connected with the surfacing isolation layer and the heat shield side welding base; an installation gap is formed between the pump shell main flange and the heat shield, and the sealing ring is located on the outer side of the installation gap and used for sealing the installation gap. According to the welding sealing device for the low-alloy steel pump shell, the surfacing isolation layer is welded to the main flange face of the pump shell, the heat shield side welding base is arranged on the heat shield, and meanwhile the surfacing isolation layer and the heat shield side welding base are used for being connected with the sealing ring, so that welding preheating and postweld heat treatment can be omitted, and structural deformation caused by heat treatment is avoided; the assembly of the main pump core bag and the pump shell is influenced.

Description

Technical Field

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

[0002] The main pump of a passive nuclear power plant uses a double-pass wound gasket seal. The pump casing is made of low-alloy steel and the heat shield is made of martensitic stainless steel. Under operating conditions such as cold shutdown transients, there is a large difference in deformation between the pump casing and the heat shield, which may cause primary coolant leakage.

[0003] When the leakage rate exceeds the requirements of the operation and maintenance strategy, there is a risk of unplanned shutdown to repair the main pump.

[0004] Based on this, the inventor of the present application proposes a welding sealing device and method suitable for a low alloy steel pump casing, 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 deformation difference between the pump casing and the heat shield may cause leakage of the primary circuit coolant, and to provide a welding sealing device and method suitable for a low alloy steel pump casing.

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

[0007] The present invention provides a welding sealing device suitable for a low alloy steel pump casing, which is characterized by comprising:

[0008] The cladding isolation layer is located on the main flange surface of the pump casing;

[0009] A heat shield side welding base, welded to a side of the heat shield close to the cladding isolation layer;

[0010] The sealing ring has two ends connected to the cladding isolation layer and the heat shield side welding base respectively; wherein,

[0011] An installation gap is formed between the main flange of the pump casing and the heat shield, and the sealing ring is located outside the installation gap and is used to seal the installation gap.

[0012] According to an embodiment of the present invention, the sealing ring is C-shaped, and the opening side faces away from the heat shield.

[0013] According to one embodiment of the present invention, the sealing ring has a first connecting end and a second connecting end, the first connecting end is welded to the cladding isolation layer, and the welding position is located inside the main bolt on the main flange of the pump casing;

[0014] The second connection end is located at an end of the heat shield side welding base facing away from the heat shield.

[0015] According to an embodiment of the present invention, the sealing ring is connected to the build-up isolation layer and the heat shield side welding base through fillet welds.

[0016] According to one embodiment of the present invention, the surfacing isolation layer at least covers the installation area of ​​the main bolts on the main flange of the pump casing.

[0017] According to an embodiment of the present invention, the heat shield side welding base is connected to the heat shield via a fillet weld.

[0018] According to an embodiment of the present invention, the material of the heat shield side welding base is nickel-based material.

[0019] According to an embodiment of the present invention, the surfacing isolation layer is made of stainless steel or nickel-based material.

[0020] The present invention also provides a welding sealing method applicable to a low alloy steel pump casing, using the welding sealing device applicable to a low alloy steel pump casing as described above, the method comprising:

[0021] Step 1, welding a cladding isolation layer on the main flange surface base of the pump casing and welding a heat shield side welding base on the heat shield toward one side of the cladding isolation layer;

[0022] Step 2: welding a sealing ring between the cladding isolation layer and the heat shield side welding base.

[0023] The positive and progressive effects of the present invention are:

[0024] The present invention is suitable for a welding sealing device of a low alloy steel pump casing. A cladding isolation layer is welded on the main flange surface of the pump casing, and a heat shield side welding base is arranged on the heat shield. At the same time, the cladding isolation layer and the heat shield side welding base are used to connect the sealing ring, thereby eliminating welding preheating and post-weld heat treatment, avoiding structural deformation caused by heat treatment, and affecting the assembly of the main pump core package and the pump casing. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] 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:

[0026] Figure 1 It is a structural schematic diagram of a welding sealing device applicable to a low alloy steel pump casing of the present invention;

[0027] Figure 2 It is a structural schematic diagram of a surfacing isolation layer on the main flange of a pump casing of the present invention;

[0028] Figure 3 It is a structural schematic diagram of a heat shield side welding base on the heat shield of the present invention;

[0029] Figure 4 It is a schematic diagram of the connection between the heat shield side welding base and the sealing ring on the heat shield of the present invention;

[0030] Figure 5 The present invention is a flow chart of the welding sealing method for a low alloy steel pump casing.

[0031] 1. Surfacing isolation layer;

[0032] 2. Pump casing main flange;

[0033] 3. Welding base on the heat shield side;

[0034] 4. Heat shield; 41. Installation clearance;

[0035] 5. Sealing ring; 51. First connecting end; 52. Second connecting end;

[0036] 6. Main bolt. DETAILED DESCRIPTION

[0037] 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.

[0038] 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.

[0039] As shown in this application and claims, unless the context clearly indicates an exception, the words "a", "an", "an" and / or "the" do not refer to the singular and may also include the plural. Generally speaking, the terms "include" and "comprise" only indicate the inclusion of the steps and elements that have been clearly identified, and these steps and elements do not constitute an exclusive list. The method or device may also include other steps or elements.

[0040] Please refer to Figures 1 to 4The present invention proposes a welding sealing device suitable for low alloy steel pump casing, comprising a cladding isolation layer 1, a heat shield side welding base 3 and a sealing ring 5, wherein the cladding isolation layer 1 is located on the main flange 2 of the pump casing; the heat shield side welding base 3 is welded to the side of the heat shield 4 close to the cladding isolation layer 1; and the two ends of the sealing ring 5 are respectively connected to the cladding isolation layer 1 and the heat shield side welding base 3. Among them, an installation gap 41 is formed between the main flange 2 of the pump casing and the heat shield 4, and the sealing ring 5 is located outside the installation gap 41 and is used to seal the installation gap 41.

[0041] It can be seen that the design of the welding sealing device must first consider the material selection. The material selection mainly considers the mechanical properties, welding properties, forging properties, machining properties, etc. of the material. The material selection should consider the matching of the welding base material with the sealing ring 5, the heat shield 4, and the pump casing main flange 2. The structural design needs to consider the optimization of the structural mechanical properties. Under the space constraints of the pump casing main flange 2, the heat shield 4 and the main bolt 6, its structural strength must not only withstand the pressure boundary design pressure, but also ensure that the fatigue stress of the welding seal under complex thermal transients meets the requirements. Finally, the welding seal structure design should not change the original pump casing and heat shield 4 functions.

[0042] The welding method for the welding seal of the main pump of a passive nuclear power plant must first ensure the feasibility of on-site welding, and consider that there is no preheating or post-weld heat treatment condition on site. Secondly, the welding method should avoid the deformation of the pump casing or heat shield 4 caused by the welding heat input, which will lead to the problem that the main pump core package and the pump casing cannot be assembled.

[0043] It should be noted that the pump casing of the main pump of a passive nuclear power plant is made of low-alloy steel forgings, and the heat shield 4 is a martensitic forging. Traditionally, preheating and post-weld heat treatment are required during sealing ring welding. It is difficult to implement local uniform heating and insulation 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.

[0044] In the present invention, before the pump casing main flange 2 is connected to the heat shield 4, the pump casing can be turned over, and then the cladding isolation layer 1 is welded forward, so that the welding process is safer and more conducive to welding operation.

[0045] During the pump casing forging processing stage, an isolation layer 1 is welded on the entire surface of the pump casing main flange 2. The isolation layer can be made of stainless steel or nickel-based material.

[0046] During the forging process of the heat shield 4, the heat shield side welding base 3 is welded to the heat shield 4 by using fillet welds. The material of the heat shield side welding base 3 is a nickel-based material.

[0047] Before the main pump core package leaves the factory, the sealing ring 5 is welded to the welding base 3 on the heat shield side.

[0048] That is, after forming the cladding isolation layer 1 on the pump casing main flange 2 and forming the heat shield side welding base 3 on the heat shield 4, the heat shield 4 is installed with the pump casing main flange 2, and then the sealing ring 5 is welded.

[0049] The bottom of the pump casing main flange 2 is connected to the main pump core package through 24 main bolts 6. The specific installation process is as follows:

[0050] 1. Before welding, align the main pump core package (heat shield 4 is part of the core package structure) with the pump casing;

[0051] 2. Divide the 24 main bolts into 4 groups, staggered and evenly distributed;

[0052] 3. Install the first and third sets of main bolts, a total of 12;

[0053] 4. Stretch the 1st and 3rd groups of main bolts;

[0054] 5. Install the sealing ring 5 on one side of the main bolts of groups 1 and 3;

[0055] 6. Install 2 and 4 sets of main bolts;

[0056] 7. Stretch the main bolts of groups 2 and 4;

[0057] 8. Remove the main bolts of groups 1 and 3;

[0058] 9. Install the sealing ring 5 on one side of the main bolts of groups 2 and 4;

[0059] 10. Install 1 and 3 sets of main bolts;

[0060] 11. Stretch the main bolts of groups 1 and 3;

[0061] 12. Stretch all main bolts evenly again.

[0062] Please refer to Figure 1 and Figure 4 The shape of the sealing ring 5 can be C-shaped, and the opening side of the C-shaped sealing ring 5 is away from the heat shield 4.

[0063] The installation gap 41 between the conventional pump casing main flange 2 and the heat shield 4 is sealed by a double-pass wound gasket. Under such conditions, such as cold shutdown transient, the pump casing and the heat shield 4 have different thermal deformations, which may lead to the gasket seal failure.

[0064] Specifically, the sealing ring 5 has a first connecting end 51 and a second connecting end 52. The first connecting end 51 is welded to the surfacing isolation layer 1, and the welding position is located on the inner side of the main bolt 6 on the main flange 2 of the pump casing; the second connecting end 52 is located at the end of the welding base 3 on the heat shield side away from the heat shield 4.

[0065] That is, the sealing ring 5 is arranged outside the installation gap 41 between the pump casing main flange 2 and the heat shield 4, and is located on the inner side of the main bolt 6, thereby satisfying the connection between the pump casing main flange 2 and the heat shield 4 without interfering with the installation of the main bolt 6.

[0066] Specifically, the sealing ring 5 is connected to the built-up isolation layer 1 and the heat shield side welding base 3 through fillet welds.

[0067] It can be seen that the installation strength and structural stability of the sealing ring 5 can be improved by connecting the opposite ends of the sealing ring 5 to the cladding isolation layer 1 and the heat shield side welding base 3 through fillet welds respectively.

[0068] In one embodiment, the build-up welding insulation layer 1 covers at least the installation area of ​​the main bolts 6 on the main flange 2 of the pump casing.

[0069] Preferably, the surface of the main flange 2 of the pump casing is completely covered with the cladding isolation layer 1, thereby improving the welding quality of the edge of the cladding layer.

[0070] The opposite sides of the heat shield side welding base 3 are connected to the heat shield 4 via fillet welds, which can improve the connection strength between the heat shield side welding base 3 and the heat shield 4.

[0071] In summary, the present invention is suitable for a welding sealing device of a low alloy steel pump casing. A cladding isolation layer 1 is welded on the surface of the main flange 2 of the pump casing, and a heat shield side welding base 3 is arranged on the heat shield 4. At the same time, the cladding isolation layer 1 and the heat shield side welding base 3 are used to connect the sealing ring 5, thereby eliminating welding preheating and post-weld heat treatment, avoiding structural deformation caused by heat treatment, and affecting the assembly of the main pump core package and the pump casing.

[0072] The present invention completes the processing of the cladding isolation layer 1 and the heat shield side welding base 3 of the pump casing before leaving the factory. The power station site only needs to weld a weld seam between the sealing ring 5 and the cladding layer of the main flange 2 of the pump casing. The on-site overhead welding construction amount is small, which can solve the problem that the site does not have the conditions for heat treatment.

[0073] The sealing device of the present invention realizes the welding connection between the sealing ring 5 and the main flange 2 of the pump casing through the built-up welding isolation layer 1 of the pump casing, without changing the structural dimensions of the original pump casing and without destroying the pressure bearing capacity of the original pump casing.

[0074] The heat shield side welding base 3 of the sealing device of the present invention is welded outside the heat shield 4, which does not affect the pressure bearing capacity and heat insulation function of the heat shield 4.

[0075] Please refer to Figure 5 The present invention also proposes a welding sealing method suitable for a low alloy steel pump casing, using the above welding sealing device suitable for a low alloy steel pump casing, the method comprises:

[0076] Step 1, welding a cladding isolation layer on the main flange surface base of the pump casing and welding a heat shield side welding base on the heat shield toward the cladding isolation layer side;

[0077] Step 2: Weld a sealing ring between the cladding isolation layer and the welding base on the heat shield side.

[0078] Because a cladding isolation layer is welded on the main flange surface of the pump casing, and a heat shield side welding base is welded on the heat shield, it is convenient to implement a C-type seal with a better stress state.

[0079] In addition, the sealing device of the present invention realizes the welding connection between the sealing ring and the pump casing through the cladding isolation layer of the pump casing, which does not change the original pump casing structure size and does not damage the original pump casing pressure bearing capacity. The welding base on the heat shield side of the sealing device of the present invention is welded on the outside of the heat shield, which does not affect the heat shield pressure bearing capacity and thermal insulation function.

[0080] It can be seen that the sealing device and method of the present invention are implemented for the low-alloy steel pump casing of a passive nuclear power plant under construction. During the construction stage of the pump casing and heat shield forgings, the pump casing and heat shield welding base are processed to avoid uncontrollable deformation caused by the welding base processing process.

[0081] At the power station site, only one weld needs to be welded at the cladding isolation layer between the sealing ring and the main flange surface of the pump casing. The on-site welding construction workload is small, which can solve the problem of lack of heat treatment conditions on site.

[0082] 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.

[0083] 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.

[0084] 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 suitable for low alloy steel pump casing, characterized in that: include: The cladding isolation layer is located on the main flange surface of the pump casing; A heat shield side welding base, welded to a side of the heat shield close to the cladding isolation layer; The sealing ring has two ends connected to the cladding isolation layer and the heat shield side welding base respectively; wherein, An installation gap is formed between the main flange of the pump casing and the heat shield, and the sealing ring is located outside the installation gap and is used to seal the installation gap.

2. The welding sealing device suitable for low alloy steel pump casing according to claim 1 is characterized in that: The sealing ring is C-shaped, and the opening side faces away from the heat shield.

3. The welding sealing device suitable for low alloy steel pump casing according to claim 1 is characterized in that: The sealing ring has a first connecting end and a second connecting end, the first connecting end is welded to the surfacing isolation layer, and the welding position is located inside the main bolt on the main flange of the pump casing; The second connection end is located at an end of the heat shield side welding base facing away from the heat shield.

4. The welding sealing device suitable for low alloy steel pump casing according to claim 3 is characterized in that: The sealing ring is connected to the surfacing isolation layer and the heat shield side welding base through fillet welds.

5. The welding sealing device suitable for low alloy steel pump casing according to claim 1 is characterized in that: The cladding isolation layer at least covers the installation area of ​​the main bolts on the main flange of the pump casing.

6. The welding sealing device suitable for low alloy steel pump casing according to claim 1, characterized in that: The heat shield side welding base is connected to the heat shield via a fillet weld.

7. The welding sealing device suitable for low alloy steel pump casing according to claim 1, characterized in that: The material of the heat shield side welding base is nickel-based material.

8. The welding sealing device suitable for low alloy steel pump casing according to claim 1, characterized in that: The material of the surfacing isolation layer is stainless steel or nickel-based material.

9. A welding sealing method suitable for low alloy steel pump casing, characterized in that: Using the welding sealing device applicable to a low alloy steel pump casing as described in any one of claims 1 to 8, the method comprises: Step 1, welding a cladding isolation layer on the main flange surface base of the pump casing and welding a heat shield side welding base on the heat shield toward one side of the cladding isolation layer; Step 2: welding a sealing ring between the cladding isolation layer and the heat shield side welding base.

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