Production process of C-shaped sealing ring of reactor pressure vessel

Abstract

The invention discloses a production process of a C-shaped sealing ring of a reactor pressure vessel, which comprises the following steps: preparing a silver plate and a nickel-based alloy plate for cutting off, cleaning the cut-off plate for use, finely cutting off the plate again after the plate is cleaned, re-welding the cut-off plate, and finishing a welding seam of the re-welded plate. After finishing is completed, all the plates are subjected to integrity inspection and prefabricated forming, after plate treatment is completed, a spring is wound and subjected to heat treatment, the spring is cut, a notch is finished, and the finished spring is welded; according to the invention, the line tightness and the sealing width are increased, a high-temperature test bench is developed, comprehensive performance test under 35 MPa and 600 DEG C can be completed, technological equipment required by production of the large-diameter sealing ring is developed, the sealing ring does not have any leakage and abnormal phenomena in the experiment process of the sealing ring, and after the test, the sealing ring is not damaged. And the sealing silver layer has no crack, folding, shedding and peeling phenomena.

Description

Technical Field

[0001] The present invention relates to the technical field of seal ring production, and in particular to a production process of a C-shaped seal ring for a reactor pressure vessel. Background Art

[0002] The reactor pressure vessel (RPV) of a nuclear power plant is an important device for the main coolant pressure boundary barrier. It has the characteristics of high temperature, high pressure, and strong radioactivity. The sealing between the top cover and the vessel flange of the RPV is one of the key technologies in its design and manufacture, and it plays an important role in the long-term safe operation of the nuclear power unit. This seal adopts a double-channel metal seal ring structure. The seal rings mainly include two types: a hollow grooved metal O-ring and a spring-energized metal C-ring. The former is plated with silver on the outer side of the metal O-ring, and several radial small holes are drilled on the inner side of the ring. After pressurization, the medium can freely flow into the inner cavity of the ring to form an axial self-tightening seal. The C-ring utilizes the combined action of the sealing layer and the spiral spring to improve the resilience and sealing performance. Since the C-ring is superior to the metal O-ring in terms of service performance and reliability, it has been widely used. For a long time, due to the inability to manufacture independently in China, the seal rings for the RPV top cover flange of operating and under-construction nuclear power plants all rely on foreign imports.

[0003] In Chinese Patent No. 201921464660.X, only the preservation and transportation of the seal ring can be carried out, and the research and development and testing cannot be carried out. The key technologies in the research and development process are the winding, welding, and heat treatment of the spring, the welding process and inspection of the coating layer and the sealing layer, the combination, forming, and cleaning of the C-ring, etc. Therefore, the present invention proposes a production process of a C-shaped seal ring for a reactor pressure vessel to solve the problems existing in the prior art. Summary of the Invention

[0004] In view of the above problems, the purpose of the present invention is to propose a production process of a C-shaped seal ring for a reactor pressure vessel. This production process of the C-shaped seal ring for a reactor pressure vessel increases the linear tightness and the sealing width, develops a high-temperature test bench, and can complete the comprehensive performance test at 35 MPa and 600 °C. It also develops process equipment that can meet the production requirements of large-diameter seal rings. During the experiment on the seal ring, no leakage and abnormal phenomena occur to the seal ring. After the test, there are no cracks, folds, peeling, and flaking phenomena on the sealed silver layer.

[0005] To achieve the purpose of the present invention, the present invention is realized through the following technical solutions: A production process of a C-shaped seal ring for a reactor pressure vessel, comprising the following steps:

[0006] Step 1: Prepare a silver plate and a nickel-based alloy plate for cutting, and clean the cut plates for use;

[0007] Step 2: After the sheet metal is cleaned, cut the sheet metal finely again, and then weld the cut sheet metal;

[0008] Step 3: Trim the welds of the welded sheet metal. After trimming, inspect the integrity of all sheet metal and preform it;

[0009] Step 4: After the sheet metal is processed, wind and heat-treat the spring, cut the spring, and then trim the cut;

[0010] Step 5: Weld the trimmed spring. After welding, trim the weld. After trimming, inspect and clean all springs;

[0011] Step 6: Combine the formed sheet metal with the spring, polish and grind the surface, and finally inspect and clean to complete the production of the C-shaped sealing ring.

[0012] Further improvement lies in: In the said Step 1, prepare silver plate and nickel-based alloy plate materials, and make size markings. Place the silver plate and nickel-based alloy plate on the cutting machine, fix the materials with clamps to ensure that they will not move during the cutting process. According to the pre-marked size, adjust the position of the blade of the cutting machine, slowly push the blade, and cut the silver plate and nickel-based alloy plate along the marked line. Wipe the surface of the cut sheet metal with alcohol and a soft cloth to remove grease, fingerprints and other non-metallic impurities.

[0013] Further improvement lies in: In the said Step 2, place the sheet metal on the fine cutting machine, fix it with clamps, cut the sheet metal again, and then place the cut sheet metal on the welding platform. Select appropriate welding parameters according to the material and thickness of the sheet metal, and perform welding processing on the sheet metal.

[0014] Further improvement lies in: In the said Step 3, use a grinding tool to polish the weld, remove welding slag and uneven parts, trim the weld to ensure the height and width of the weld. Use tools such as calipers and micrometers to accurately measure the dimensions of the sheet metal, perform non-destructive testing on the sheet metal to ensure that there are no defects inside the weld. Place the sheet metal into the mold, use a hydraulic press to press the sheet metal to form the preliminary shape of the C-shaped sealing ring. Take out the pressed sheet metal and cool it to set the shape to ensure its shape stability, and trim the preformed C-shaped sealing ring to remove excess burrs to complete the forming work.

[0015] A further improvement lies in: in the fourth step, the material is fed into a winding machine and wound according to the set parameters to form a preliminary shape of the spring. The wound spring is placed in an annealing furnace for annealing treatment to eliminate the stress generated during winding and restore the toughness of the material. The spring is heated to a certain temperature and then rapidly cooled for quenching treatment to improve the hardness and strength of the spring. A cutting machine is used to cut the spring to form the required length, and finally the cut is trimmed.

[0016] A further improvement lies in: in the fifth step, the spring is processed. Welding and weld trimming are carried out on the spring. Non-destructive testing is performed on the spring. The spring is thoroughly rinsed with distilled water to remove the remaining cleaning agent and dissolved metal ions.

[0017] A further improvement lies in: in the sixth step, the spring is placed at a predetermined position on the plate and fixed with a fixture. The spring is precisely aligned with the plate. The spring is welded and fixed to the plate using a welding device. Then, the surface of the combined C-shaped seal ring is preliminarily polished with a grinding wheel. Ultrasonic flaw detection is performed on the seal ring. The C-shaped seal ring is dried with a blower to ensure it is completely dry, preventing water stains and corrosion. Finally, a final inspection is carried out on the cleaned C-shaped seal ring to ensure its surface is clean, without residues and water stains.

[0018] A further improvement lies in: the C-shaped seal ring is subjected to cold and heat tests through a test device. The room temperature performance test device consists of a 5000kN compression testing machine, a helium mass spectrometer leak detector, and a computer control and data processing system, realizing the functions of automatically testing, recording, and outputting various performance data of the C-shaped ring. The test device for simulating the primary circuit of a nuclear power plant is a hot state test loop.

[0019] A further improvement lies in: the reactor pressure vessel subjects the C-shaped seal ring to cold and heat tests. By boosting the pressure to 15.5 MPa, heating to 310 °C, maintaining the pressure and temperature for 30 min, and cooling to less than 100 °C. The heating rate is not greater than 56 °C / h, and the cooling rate is not less than 56 °C / h. The above cycle is repeated 6 times. Before the cold and hot state alternating test, a hydrostatic test is carried out. The test pressure is 22.8 MPa, and the pressure holding time is ≥30 min. During the whole process of the hydrostatic test and the cold and hot state alternating test, visual inspection shows no leakage.

[0020] A further improvement lies in: the C-shaped seal ring consists of three parts. The outer seal layer and the middle cladding layer form a shell, and a spiral cylindrical spring is wrapped inside the shell.

[0021] The beneficial effects of the present invention are as follows: The present invention increases the tightness and sealing width of the C-shaped sealing ring, develops a high-temperature test bench, which can complete the comprehensive performance test at 35 MPa and 600 °C, develops the process equipment required to meet the production of large-diameter sealing rings. During the experiment on the sealing ring, no leakage or abnormal phenomenon occurs to the sealing ring. After the test, there are no cracks, folds, peeling, or flaking on the sealing silver layer, and the sealing ring is not damaged at all. By using high-performance alloy materials and surface treatment technologies, the C-shaped sealing ring has excellent corrosion resistance and can work stably for a long time in the harsh environment of the nuclear reactor. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0023] Figure 1 Schematic diagram of the production process flow of the C-shaped ring of the present invention;

[0024] Figure 2 Schematic diagram of the test sample ring of the C-shaped ring of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0026] In the description of the present invention, it should be noted that unless otherwise clearly defined and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the internal communication of two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0027] In Document 201921464660.X, by coaxially arranging two annular grooves in each layer and placing C-shaped sealing rings in the annular grooves, the transportation and storage of two sets of C-shaped sealing rings can be achieved, which can improve the safety during the transportation and storage of C-shaped sealing rings and enhance the transportation efficiency. However, this document only conducts transportation work on the sealing rings and cannot conduct experiments on the sealing rings. In this application, through precise manufacturing processes and strict dimensional control, the C-shaped sealing rings can provide reliable sealing effects, preventing the leakage of high-pressure and high-temperature media inside the reactor. Moreover, the design and material selection of the C-shaped sealing rings enable them to withstand the high-temperature and high-pressure conditions during the operation of nuclear reactors, ensuring the structural integrity and functional stability of the sealing rings.

[0028] According to Figure 1 、 Figure 2 shown, this embodiment provides a production process for C-shaped sealing rings of a reactor pressure vessel, including the following steps:

[0029] Step 1: Prepare silver plates and nickel-based alloy plates for cutting, and clean the cut plates for use.

[0030] Step 2: After the plates are cleaned, cut them finely again, and then weld the cut plates.

[0031] Step 3: Trim the welds of the welded plates. After trimming, inspect the integrity of all plates and preform them.

[0032] Step 4: After the plates are processed, wind and heat-treat the springs, cut the springs, and trim the cut ends.

[0033] Step 5: Weld the trimmed springs. After welding, trim the welds. After trimming, inspect and clean all springs.

[0034] Step 6: Combine the formed plates and springs, polish and grind the surface, and finally inspect and clean them. Finally, package and store them to complete the production of C-shaped sealing rings.

[0035] In the said Step 1, prepare silver plates and nickel-based alloy plate materials, and mark the dimensions. Place the silver plates and nickel-based alloy plates on the cutting machine, fix the materials with clamps to ensure that they do not move during the cutting process. According to the pre-marked dimensions, adjust the position of the cutting machine's blade, slowly push the blade, and cut the silver plates and nickel-based alloy plates along the marked lines. Then, wipe the surfaces of the cut plates with alcohol and a soft cloth to remove grease, fingerprints, and other non-metallic impurities.

[0036] In Step 2, place the sheet on a precision cutting machine, fix it with a fixture, cut the sheet again, then place the cut sheet on a welding platform, select appropriate welding parameters according to the material and thickness of the sheet, and perform welding processing on the sheet.

[0037] In Step 3, use a grinder to polish the weld seam, remove welding slag and uneven parts, trim the weld seam to ensure the height and width of the weld seam, use tools such as calipers and micrometers to accurately measure the dimensions of the sheet, perform non-destructive testing on the sheet to ensure there are no defects inside the weld seam, place the sheet into a mold, use a hydraulic press to press the sheet to form a preliminary shape of a C-shaped sealing ring, take out the pressed sheet, cool and shape it to ensure its shape is stable, and trim the pre-formed C-shaped sealing ring to remove excess burrs to complete the forming work.

[0038] In Step 4, feed the material into a winding machine and wind it according to the set parameters to form a preliminary shape of a spring. Place the wound spring into an annealing furnace for annealing treatment to eliminate the stress generated during the winding process and restore the toughness of the material. Heat the spring to a certain temperature and then quickly cool it for quenching treatment to improve the hardness and strength of the spring. Use a cutting machine to cut the spring to form the required length, and finally trim the cut.

[0039] In Step 5, process the spring, perform welding and weld seam trimming on the spring, perform non-destructive testing on the spring, and thoroughly rinse the spring with distilled water to remove residual cleaning agents and dissolved metal ions.

[0040] In Step 6, place the spring at the predetermined position on the sheet, fix it with a fixture, accurately align the spring with the sheet, use a welding device to weld and fix the spring to the sheet, then preliminarily polish the surface of the combined C-shaped sealing ring with a grinding wheel, perform ultrasonic flaw detection on the sealing ring, dry the C-shaped sealing ring with a blower to ensure it is completely dry, prevent water spots and corrosion, and finally perform a final inspection on the cleaned C-shaped sealing ring to ensure its surface is clean, free of residues and water stains, and finally perform packaging and warehousing to complete the production of the C-shaped sealing ring.

[0041] The C-shaped sealing ring undergoes thermal and cold tests through a test device. The room temperature performance test device consists of a 5000 kN compression testing machine, a helium mass spectrometer leak detector, and a computer control and data processing system, realizing the functions of automatically testing, recording, and outputting various performance data of the C-shaped ring. The test device for simulating the primary circuit of a nuclear power plant is a hot test loop.

[0042] The reactor pressure vessel conducts cold and hot tests on the C-type sealing ring. By boosting the pressure to 15.5 MPa, raising the temperature to 310 °C, maintaining the pressure and temperature for 30 min, and cooling to less than 100 °C. The heating rate is not greater than 56 °C / h, and the cooling rate is not less than 56 °C / h. Repeat the above cycle 6 times. Before the cold and hot alternating tests, a hydrostatic test is carried out. The test pressure is 22.8 MPa (gauge pressure), and the pressure holding time is ≥30 min. During the whole process of the hydrostatic test and the cold and hot alternating tests, visual inspection shows no leakage at all.

[0043] The C-type sealing ring consists of three parts. The outer sealing layer and the intermediate coating layer form the outer shell, and a helical cylindrical spring is wrapped inside the outer shell.

[0044] When the C-type sealing ring of this reactor pressure vessel is in use, when the sealing ring is compressed, each turn of the helical spring generates an additional reaction force on the metal outer shell, causing plastic deformation of the outer sealing layer and filling the microscopic roughness and local apparent defects on the flange sealing surface. This combination of elasticity and plasticity and the sealing design of metal-to-metal contact endow the sealing ring with good sealing performance, as well as the ability to compensate for flange deformation and sealing load relaxation caused by temperature and pressure fluctuations. The leakage rate can reach below 10-9 Pa·m3 / s (helium, ΔP = 1 bar). The dimensions are strictly controlled within the allowable tolerances and are uniform and stable along the circumference. Its welding uses microbeam plasma arc melting welding. Each sealing ring is only allowed to have one welding joint. The outer diameter of the spring wire after grinding is within the range of ±0.02 mm of the initial outer diameter. The welding of the alloy coating uses tungsten inert gas welding without filler metal, and the silver plate welding of the sealing layer uses helium shielded welding. The weld is flush with the base metal, and there are no cracks and welding defects. For the welding joint process assessment requirements, a tensile test of the weld is carried out. Its tensile strength Rm, yield strength Rp0.2, and elongation A% (5d) are between 90% and 110% of the measured values of the base metal. Through the compression and rebound test, the effective rebound amount and the total rebound amount, sealing characteristic parameters, Y0, Y1, and Y2 loads and the corresponding helium leakage rates are measured. For the hydrostatic test, the hydrostatic test pressure is 30 MPa, the test temperature is ≤65 °C, and the pressure holding time is ≥30 min. The developed C-shaped sealing ring successfully passes the room temperature performance and cold and hot alternating tests.

[0045] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A production process for a reactor pressure vessel C-type sealing ring, characterized in that: The following steps are involved: Step 1: Prepare the silver plate and the nickel-based alloy plate for cutting, and then clean the cut plates for use; Step 2: After the plate is cleaned, the plate is finely cut again, and then the cut plate is welded; Step 3: Perform weld trimming on the welded plates. After the trimming is completed, perform integrity inspection on all plates and preform them; Step 4: After the plate processing is completed, the spring is wound and heat treated, the spring is cut and the cut is trimmed; Step 5: Weld the trimmed springs, trim the welds after welding, and inspect and clean all springs after trimming; Step 6: Combine the formed sheet with the spring, polish the surface, and finally inspect and clean it to complete the production of the C-type sealing ring.

2. The production process of a reactor pressure vessel C-type sealing ring according to claim 1, characterized in that: In step one, the silver plate and the nickel-based alloy plate are placed on a cutting machine, the plates are fixed with a clamp, the cutting machine blade is driven to move according to the pre-marked size, the silver plate and the nickel-based alloy plate are cut along the marked line, and the surface of the cut plate is cleaned with alcohol and a soft cloth.

3. The production process of a reactor pressure vessel C-type sealing ring according to claim 1, characterized in that: In the step 2, the plate is placed on a fine cutting machine to be cut again, and then the cut plate is placed on a welding platform to be welded.

4. The production process of a reactor pressure vessel C-type sealing ring according to claim 1, characterized in that: In the step three, a grinder is used to grind the weld and trim the weld to ensure the height and width of the weld. The size of the plate is accurately measured, and after the measurement is completed, the plate is subjected to non-destructive testing. The plate is placed in a mold and pressed using a hydraulic press. The pressed plate is taken out and cooled and formed. Finally, the preformed C-shaped sealing ring is trimmed to remove excess burrs to complete the plate forming work.

5. The production process of a reactor pressure vessel C-type sealing ring according to claim 1, characterized in that: In the step 4, the spring material is fed into a winding machine and wound according to set parameters to form a preliminary shape of the spring. The wound spring is placed in an annealing furnace for annealing. The spring is heated to a certain temperature and then rapidly cooled for quenching. The spring is then cut with a cutting machine to form the required length, and the incision is finally trimmed.

6. The production process of a reactor pressure vessel C-type sealing ring according to claim 1, characterized in that: In step five, the spring is processed, welded and welded, and then non-destructively tested. The spring is thoroughly rinsed with distilled water to remove residual cleaning agent and dissolved metal ions.

7. The production process of a reactor pressure vessel C-type sealing ring according to claim 1, characterized in that: In step six, the spring is placed at a predetermined position on the plate and fixed with a clamp. The spring and the plate are precisely aligned. The surface of the assembled C-type sealing ring is then polished with a grinding wheel. The sealing ring is ultrasonically inspected. The C-type sealing ring is dried with a fan to ensure that it is completely dry to prevent water spots and corrosion. Finally, the cleaned C-type sealing ring is inspected.

8. The production process of a reactor pressure vessel C-type sealing ring according to claim 1, characterized in that: The C-shaped sealing ring is subjected to performance testing through a room temperature performance testing device, which is composed of a 5000kN compression testing machine, a helium mass spectrometer leak detector, and a computer control and data processing system, and realizes the functions of automatically testing, recording, and outputting various performance data of the C-shaped ring. The test device simulating the main circuit of a nuclear power plant is a hot test circuit.

9. The production process of a reactor pressure vessel C-type sealing ring according to claim 8, characterized in that: The C-type sealing ring is subjected to a hot and cold test by a test device, by increasing the pressure to 15.5MPa, increasing the temperature to 310°C, maintaining the pressure and temperature for 30min, cooling to less than 100°C, with a heating rate of no more than 56°C / h and a cooling rate of no less than 56°C / h. The above cycle is repeated 6 times. Before conducting the cold and hot alternating test, a water pressure test is carried out, the test pressure is 22.8MPa, and the pressure holding time is ≥30min.

10. The production process of a reactor pressure vessel C-type sealing ring according to claim 1, characterized in that: The C-shaped sealing ring is composed of three parts, an outer sealing layer and an intermediate coating layer form an outer shell, and a spiral cylindrical spring is wrapped in the outer shell.

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