Inner cavity detection device and method for tubular structure in nuclear power steam generator

Abstract

The invention discloses an inner cavity detection device and method for a tubular structure in a nuclear power steam generator, and solves the technical problems that the mode of manually observing and detecting the inner wall surface of the tubular structure needs a large amount of manpower, the detection process is tedious, the detection result is greatly influenced by artificial experience, the detection precision is low, and the speed is low. The inner cavity detection device for the tubular structure in the nuclear power steam generator comprises an end guide head, a transparent annular connecting piece, an endoscope assembly and a capacitance sensor assembly, the capacitance sensor assembly measures a capacitance value, and based on the capacitance distance measurement principle, the data value of the inner diameter of a to-be-detected pipe can be accurately obtained; quantitative data are provided for judging whether damage, cracks and the like exist in the inner cavity of the to-be-detected pipe or not, quality abnormal points of the inner wall of the to-be-detected pipe are rapidly determined, the inner wall image of the to-be-detected pipe fed back by the endoscope assembly is assisted, manual observation is carried out, and abnormal reasons are determined. And mechanical and manual detection is carried out together, so that the detection efficiency and accuracy are improved.

Description

Technical Field

[0001] This invention relates to a device and method for detecting the internal cavity of tubular structures, and more specifically to a device and method for detecting the internal cavity of tubular structures in nuclear power steam generators. Background Technology

[0002] Nuclear power steam generator equipment contains some tubular structures. Before equipment assembly and during use, these tubular structures need to be inspected for scratches, corrosion, and processing defects on their inner walls to ensure that the quality of the inner walls meets the installation and operation requirements.

[0003] Because the aforementioned tubular structures are generally deep circular holes with small diameters, the measuring instruments have limited room to maneuver, and adjustments remain constant. The smaller the inner diameter and the longer the length of the tubular structure, the greater the difficulty of its inspection.

[0004] Currently, the main inspection method is manual observation. Operators insert cameras into the tubular structure to capture images of the inner wall, and then manually inspect them to determine if there are scratches, corrosion, or other quality problems. This method not only requires a large amount of manpower and is cumbersome, but the results are also heavily influenced by human experience, resulting in low accuracy, slow speed, and a lack of data management tools. It is difficult to achieve high-efficiency, high-precision, and digital inspection, which severely restricts the efficiency of assembly and routine maintenance of nuclear power steam generator equipment. Summary of the Invention

[0005] The purpose of this invention is to address the technical problems of existing methods for observing and inspecting the inner wall of tubular structures, which require a large amount of manpower, involve a cumbersome inspection process, and are greatly affected by human experience, resulting in low inspection accuracy and slow speed. The invention provides a device and method for inspecting the inner cavity of tubular structures in nuclear power steam generators.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A cavity detection device for a tubular structure in a nuclear power steam generator is characterized by comprising an end guide head, a transparent annular connector, an endoscope assembly, and a capacitive sensor assembly.

[0008] The endoscope assembly includes a cylindrical endoscope mount, an endoscope, and a light source located at the top of the endoscope, with the endoscope located inside the endoscope mount.

[0009] The top of the endoscope mounting base is connected to the end guide head through the transparent annular connector, and a conical reflector is provided at one end face of the end guide head inside the transparent annular connector.

[0010] The capacitive sensor assembly includes a hollow capacitive sensor mounting base and a capacitive sensor sleeved on the outer wall of the capacitive sensor mounting base. One end of the capacitive sensor mounting base is connected to the bottom end of the endoscope mounting base.

[0011] Both the endoscope and the capacitance sensor are electrically connected to an external control terminal via cables, enabling the transmission of the internal wall image and the capacitance value detected by the capacitance sensor to the external control terminal.

[0012] Furthermore, let α be the angle between the mirror surface of the conical reflector and the axis of the conical reflector, L1 be the distance between the tip of the conical reflector and the top end face of the endoscope, L2 be the distance between the tip of the conical reflector and the top end face of the endoscope mounting base, and R1 be the outer diameter of the transparent annular connector. Then, 45° < α ≤ 60°, 0.8R1 ≤ L1 ≤ 1.2R1, and 0 ≤ L2 ≤ L1.

[0013] Furthermore, the transparent annular connector, endoscope mounting base, and capacitive sensor mounting base have the same outer diameter, and the guide end of the end guide head is spherical with an outer diameter larger than that of the transparent annular connector.

[0014] Furthermore, the outer peripheral wall of the endoscope mounting base is provided with a plurality of mounting holes and screw holes for mounting locking screws. The locking screws pass through the screw holes and abut against the outer wall of the endoscope, so as to fix the endoscope inside the endoscope mounting base.

[0015] Each mounting hole is equipped with a spring ball assembly. The maximum circumferential outer envelope diameter formed by multiple spring ball assemblies after compression is greater than the outer diameter of the endoscope mounting base, which is used to protect the outer wall of the endoscope mounting base.

[0016] The spring ball assembly includes a spring and a ball that abuts against the outer end of the spring, and the diameter of the outer port of the mounting hole is smaller than the diameter of the ball, so that both the ball and the spring can be confined within the mounting hole.

[0017] Furthermore, the mounting hole is a through hole, and a sleeve is fitted on the outer peripheral wall of the endoscope. The position of the sleeve corresponds to the position of the mounting hole, and the inner end of the spring abuts against the outer wall of the sleeve.

[0018] Furthermore, the capacitive sensor mounting base has protective spring clip mounting positions at both ends, and the area between the two protective spring clip mounting positions is the capacitive sensor mounting position;

[0019] The protective spring mounting position is used to install a protective spring. One end of the protective spring is a circular ring end, and the other end is a circular annular comb tooth end. The maximum outer envelope diameter of the circular annular comb tooth end is greater than the outer diameter of the capacitive sensor mounting base.

[0020] Furthermore, a plurality of glue injection holes are provided on the circumferential sidewall of the ring end. Glue is injected into the glue injection holes to fix the protective spring to the capacitive sensor mounting base.

[0021] The annular end is provided with a through groove along its axial direction.

[0022] A measuring electrode is fitted at the center of the mounting position of the capacitance sensor. Two annular insulating layers are respectively provided on both sides of the measuring electrode, and an equipotential ring is provided between the two annular insulating layers on the same side. The measuring electrode, the annular insulating layers, and the equipotential ring together constitute the capacitance sensor.

[0023] Furthermore, the transparent annular connector is a transparent glass annular connector.

[0024] Meanwhile, the present invention also provides a method for detecting the internal cavity of a tubular structure in a nuclear power plant steam generator, which is characterized by including the following steps:

[0025] Step 1: Prepare an internal cavity detection device for a tubular structure in a nuclear power steam generator as described in claim 1;

[0026] Step 2: Obtain N standard tubes with different inner diameters. Place the cavity detection device for the tubular structure in the nuclear power steam generator prepared in Step 1 into the N standard tubes in sequence to obtain n first capacitance values. Then, calibrate the inner diameters of the N standard tubes corresponding to the n first capacitance values ​​one by one to obtain a database of the correspondence between the first capacitance values ​​and the inner diameters; where N≥3, n=N;

[0027] Step 3: Obtain the tube to be tested. Insert the inner cavity detection device for the tubular structure in the nuclear power steam generator prepared in Step 1 into the tube to be tested, obtain the second capacitance value at different locations inside the tube and the inner wall image of the tube to be tested, and output it to the external control terminal.

[0028] Step 4: The external control terminal compares the second capacitance values ​​at different locations inside the tube under test obtained in Step 3 with the n first capacitance values ​​in the database obtained in Step 2, and determines the inner diameter at different locations inside the tube under test according to the following principles:

[0029] If the second capacitance value at a certain location is equal to one of the n first capacitance values, then the inner diameter corresponding to that first capacitance value is determined to be the inner diameter of that location in the tube to be tested.

[0030] If the second capacitance value at a certain location is not equal to any of the n first capacitance values, and lies between two adjacent first capacitance values, then the inner diameter of that location in the tube under test is determined as follows:

[0031] Define the second capacitance value at this location inside the tube under test as C, and its corresponding inner diameter as d. The two adjacent first capacitance values ​​are C1, C2, and C3, and C4, and C5, and C6, and C7, and C8, and C9, and C10, and C11, and C12, and C13, and C14, and C15, and C16, and C17, and C18, and C19, and C10, and C11, and C12, and C13, and C14, and C15, respectively. i and C i+1 And C i The corresponding inner diameter is d i C i+1 The corresponding inner diameter is d i+1 ,but Where C i <C<C i+1 ,

[0032] Step 5: Generate an inner diameter variation diagram from the inner diameters at different locations inside the tube to be tested obtained in Step 4. Compare the generated inner diameter variation diagram with the designed inner diameter variation diagram of the tube to be tested. If the inner diameter of a certain location in the generated inner diameter variation diagram is D2 and the inner diameter of the corresponding location in the designed inner diameter variation diagram is D3, then the inner diameter variation value ΔD at that location is D2-D3. If |ΔD| is greater than the preset value, then mark that location as an abnormal point.

[0033] Step 6: Based on the image of the inner wall of the tube to be tested obtained in Step 3, observe the abnormal points marked in Step 5, determine the cause of the abnormality, and complete the testing of the tube to be tested.

[0034] Furthermore, the inner diameters of the N standard tubes obtained in step 2 satisfy the following condition with respect to the design inner diameter of the tube to be tested:

[0035] Define the inner diameter of N standard tubes as D1, and the minimum design inner diameter of the tube to be tested as D. min The maximum inner diameter is D max Therefore, the range for selecting the inner diameter D1 of the N standard pipes is: 0.9D min ≤D1≤3D max .

[0036] Compared with the prior art, the present invention has the following beneficial technical effects:

[0037] 1. This invention relates to an internal cavity inspection device for tubular structures in nuclear power steam generators. By incorporating an endoscope assembly and a capacitance sensor assembly, the capacitance sensor measures the capacitance value. Based on the principle of capacitance ranging, it accurately obtains the data value of the inner diameter of the tube under test, providing quantitative data for determining whether there is damage, cracks, or other defects in the inner cavity of the tube. An external control terminal compares and analyzes the output of the inner diameter change diagram of the tube under test. By comparing and analyzing the inner diameter change diagram with the designed inner diameter, abnormal points on the inner wall of the tube under test can be quickly identified. This is supplemented by images of the inner wall of the tube fed back by the endoscope assembly, allowing for manual observation to determine the cause of the abnormality. The combined mechanical and manual inspection improves inspection efficiency and accuracy, better assisting inspectors in assessing the safety and reliability of the internal structure of the tube under test.

[0038] 2. This invention relates to an internal cavity detection device for tubular structures in nuclear power steam generators. The guide end of the end guide head is designed as a spherical structure to guide the entire device into the tube to be tested. At the same time, the diameter of the guide head is designed to be larger than the diameter of the rear transparent annular connector, endoscope mounting base, and capacitive sensor mounting base. When the internal cavity detection device for tubular structures in nuclear power steam generators enters the tube to be tested, it can protect the rear-end components or parts if there are large obstacles or foreign objects inside the tube.

[0039] 3. The present invention is used for the internal cavity detection device of the tubular structure in the nuclear power steam generator. The transparent ring connector is designed as a transparent glass ring connector, which has good light transmission effect, enabling the light emitted by the light source to illuminate the inside of the tube under test, and the light reflected back from the inner wall of the tube under test is successfully received by the conical reflector, resulting in better imaging effect.

[0040] 4. The present invention is used for the internal cavity detection device of tubular structures in nuclear power steam generators. By designing 45°<α≤60°, 0.8R1≤L1≤1.2R1, and 0≤L2≤L1, it can ensure that all the conical mirror surfaces can fully receive the reflected light from the inner wall of the tube under test, resulting in more sufficient reception of reflected light. In addition, the design of the angle and the distance between the tip of the conical mirror and the top end face of the endoscope makes the imaging effect better and can more clearly show the inner wall structure of the tube under test.

[0041] 5. The present invention provides an internal cavity detection device for tubular structures in nuclear power steam generators. A screw hole is provided on the side wall of the endoscope mounting base for installing a locking screw. The locking screw presses against the inner wall of the endoscope mounting base to position and install the endoscope. This installation method facilitates the replacement of the endoscope and is convenient and quick to install.

[0042] 6. The present invention provides an internal cavity detection device for tubular structures in nuclear power steam generators. By setting a spring ball assembly and compressing it to form a maximum circumferential outer envelope diameter larger than the outer diameter of the endoscope mounting base, the endoscope mounting base can be better protected. When encountering an obstacle, the ball expands and contracts under the action of the spring, which can maintain the stability of the internal cavity detection device for tubular structures in nuclear power steam generators without affecting its normal use.

[0043] 7. This invention relates to an internal cavity detection device for tubular structures in nuclear power steam generators. The comb-tooth end of the protective spring weakens its rigidity, giving it a certain degree of flexibility. This effectively protects the capacitive sensor without affecting the normal operation of the internal cavity detection device for tubular structures in nuclear power steam generators. Furthermore, a through groove is provided at the annular end of the protective spring for easy installation. Additionally, a glue injection hole is provided at the annular end of the protective spring to strengthen the connection between the protective spring and the capacitive sensor mounting base. The maximum outer envelope diameter of the annular comb-tooth end of the protective spring is designed to be larger than the outer diameter of the capacitive sensor mounting base. When the internal cavity detection device for tubular structures in nuclear power steam generators travels inside the tube under test, if it encounters burrs or other foreign objects on the tube wall, the spring can protect the capacitive sensor.

[0044] 8. This invention provides a method for detecting the inner cavity of tubular structures in nuclear power steam generators. By establishing a database of the correspondence between standard first capacitance values ​​and inner diameters, when testing the tube under test, the detected value is directly compared with the standard value one by one, and the actual detected inner diameter of the tube under test is output, generating an inner diameter change diagram. The generated inner diameter change diagram is compared with the designed inner diameter change diagram of the tube under test to identify anomalies. At the same time, combined with the image of the inner wall of the tube under test obtained by endoscopy, the anomalies are analyzed to complete the tube test. This method combines mechanical and manual methods, with automatic mechanical marking and manual key inspection, improving detection efficiency and accuracy. Attached Figure Description

[0045] Figure 1 This is a three-dimensional structural schematic diagram of an embodiment of the internal cavity detection device for a tubular structure in a nuclear power steam generator according to the present invention;

[0046] Figure 2 This is a front view of an embodiment of the internal cavity detection device for a tubular structure in a nuclear power steam generator according to the present invention;

[0047] Figure 3 This is a cross-sectional view of an embodiment of the internal cavity detection device for a tubular structure in a nuclear power steam generator according to the present invention;

[0048] Figure 4 for Figure 3 Enlarged view of part A;

[0049] Figure 5 This is a schematic diagram of the detection state structure of an embodiment of the internal cavity detection device for a tubular structure in a nuclear power steam generator according to the present invention;

[0050] Figure 6 This is a schematic diagram of the end guide head structure of an embodiment of the internal cavity detection device for a tubular structure in a nuclear power steam generator according to the present invention;

[0051] Figure 7This is a schematic diagram of the transparent annular connector in an embodiment of the internal cavity detection device for a tubular structure in a nuclear power steam generator according to the present invention;

[0052] Figure 8 This is a schematic diagram of the conical reflector in an embodiment of the internal cavity detection device for a tubular structure in a nuclear power steam generator according to the present invention;

[0053] Figure 9 This is a schematic diagram of the endoscope mounting base structure of an embodiment of the internal cavity detection device for tubular structures in nuclear power steam generators according to the present invention;

[0054] Figure 10 This is a front view of the endoscope mounting base of an embodiment of the internal cavity detection device for tubular structures in nuclear power steam generators according to the present invention;

[0055] Figure 11 This is a schematic diagram of the endoscope structure of an embodiment of the internal cavity detection device for tubular structures in nuclear power steam generators according to the present invention;

[0056] Figure 12 This is a schematic diagram of the capacitive sensor mounting base structure of an embodiment of the internal cavity detection device for a tubular structure in a nuclear power steam generator according to the present invention;

[0057] Figure 13 This is a schematic diagram of the capacitive sensor assembly structure of an embodiment of the internal cavity detection device for a tubular structure in a nuclear power steam generator according to the present invention;

[0058] Figure 14 This is a schematic diagram of the protective spring structure of an embodiment of the internal cavity detection device for a tubular structure in a nuclear power steam generator according to the present invention.

[0059] The annotations in the attached figures are explained as follows:

[0060] 1. End guide head; 2. Transparent annular connector; 3. Endoscope mounting base; 31. Mounting hole; 32. Screw hole; 4. Endoscope; 5. Light source; 6. Conical reflector; 7. Capacitive sensor mounting base; 8. Capacitive sensor; 81. Insulating layer; 82. Equipotential ring; 83. Measuring electrode; 9. Spring ball assembly; 91. Spring; 92. Ball; 10. Protective spring; 11. Support tube; 12. Test tube; 13. External control terminal. Detailed Implementation

[0061] To make the objectives, advantages, and features of the present invention clearer, the following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a method and apparatus for detecting the internal cavity of a tubular structure in a nuclear power plant steam generator. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0062] like Figure 1-14 As shown, an internal cavity detection device for a tubular structure in a nuclear power steam generator includes an end guide head 1, a transparent annular glass connector (i.e., a transparent annular connector 2), an endoscope assembly, and a capacitive sensor assembly.

[0063] The endoscope assembly includes a cylindrical endoscope mounting base 3, an endoscope 4, and an LED light (i.e., light source 5) located at the top of the endoscope 4. The endoscope 4 is located inside the endoscope mounting base 3. The top of the endoscope mounting base 3 is connected to the end guide head 1 by adhesive through a transparent annular glass connector. A conical reflector 6 is provided at one end face of the end guide head 1 inside the transparent annular glass connector. One end of the conical reflector 6 is conical, and the other end is cylindrical. The cylindrical end is placed into a preset groove in the end guide head 1 and is then glued together.

[0064] The outer peripheral wall of the endoscope mounting base 3 has multiple mounting holes 31 and screw holes 32 for installing locking screws. The locking screws pass through the screw holes 32 and abut against the outer wall of the endoscope 4 to fix the endoscope 4 inside the endoscope mounting base 3. Screw holes 32 are provided on the side wall of the endoscope mounting base 3 for installing locking screws. The locking screws hold the endoscope 4 against the inner wall of the endoscope mounting base 3, thus positioning and installing the endoscope 4. This installation method facilitates the replacement of the endoscope 4 and is convenient and quick to install.

[0065] Each mounting hole 31 is equipped with a spring-ball assembly 9. The maximum circumferential outer diameter formed by the compression of multiple spring-ball assemblies 9 is greater than the outer diameter of the endoscope mounting base 3, which is used to protect the outer wall of the endoscope mounting base 3. The use of a maximum circumferential outer diameter formed by the compression of the spring-ball assemblies 9 being greater than the outer diameter of the endoscope mounting base 3 provides better protection for the endoscope mounting base 3. The spring-ball assembly 9 includes a spring 91 and a ball 92 abutting against the outer end of the spring 91. The diameter of the outer port of the mounting hole 31 is smaller than the diameter of the ball 92, so that both the ball 92 and the spring 91 are confined within the mounting hole. When the mounting hole 31 is a countersunk hole, a mounting cap smaller than the diameter of the mounting hole 31 can be used to install the mounting cap onto the mounting hole 31, thereby confining both the ball 92 and the spring 91 within the mounting hole. When the mounting hole 31 is a through hole, a sleeve is fitted onto the outer peripheral wall of the endoscope 4. The sleeve is positioned corresponding to the mounting hole 31. The spring 91 passes through the mounting hole 31 and abuts against the outer wall of the sleeve to limit its axial movement. When an obstacle is encountered, the ball bearing 92 extends and retracts under the action of the spring 91, which maintains the stability of the internal cavity detection device for tubular structures in nuclear power steam generators without affecting its normal use.

[0066] The capacitive sensor assembly includes a hollow capacitive sensor mounting base 7 and a capacitive sensor 8 sleeved on the outer wall of the capacitive sensor mounting base 7. One end of the capacitive sensor mounting base 7 is connected to the bottom end of the endoscope mounting base 3. The capacitive sensor mounting base 7 has a square hole for the passage of the capacitive sensor cable. A support tube 11 is threadedly connected to the end of the capacitive sensor mounting base 7 away from the endoscope 4, facilitating the insertion of the testing device into the tube to be tested by the operator.

[0067] The capacitive sensor mounting base 7 has protective spring mounting positions at both ends, with the capacitive sensor mounting position located between the two protective spring mounting positions. The protective spring mounting positions are used to mount the protective spring 10. One end of the protective spring 10 is a circular ring end, and the other end is a circular annular comb-tooth end. The maximum outer diameter of the circular annular comb-tooth end is larger than the outer diameter of the capacitive sensor mounting base 7. Multiple glue injection holes are provided on the circumferential sidewall of the circular ring end. Glue is injected into these holes to fix the protective spring 10 to the capacitive sensor mounting base 7.

[0068] A through groove is provided at the annular end along its axial direction. The through groove at the annular end of the protective spring 10 enables the annular end to be elastic, which facilitates the installation of the protective spring 10.

[0069] A measuring electrode 83 is fitted at the center of the capacitive sensor mounting position. Two annular insulating layers 81 are respectively provided on both sides of the measuring electrode 83, and an equipotential ring 82 is provided between the two annular insulating layers 81 on the same side. The measuring electrode 83, the annular insulating layers 81, and the equipotential ring 82 together constitute the capacitive sensor 8.

[0070] The transparent annular connector 2, endoscope mounting base 3, and capacitive sensor mounting base 7 have the same outer diameter, and the gap between the three and the inner wall of the tube to be tested 12 is 1-4mm. The guide end of the end guide head 1 is spherical, and its outer diameter is larger than that of the transparent annular connector 2. The maximum diameter of the end guide head 1 is 0.1-0.2mm smaller than the inner diameter of the tube to be tested. In this way, the end guide head 1 is almost in contact with the inner wall of the tube to be tested 12, thereby ensuring accurate positioning of the system during operation.

[0071] The light emitted by the LED lamp generates multiple reflected light on the inner wall of the tube under test 12. The multiple reflected light passes through the transparent ring connector 2 and enters the conical reflector 6. The conical reflector 6 converges the multiple reflected light and then enters the endoscope 4, so that the endoscope 4 can generate an image of the inner wall.

[0072] Both the endoscope 4 and the capacitance sensor 8 are electrically connected to the computer terminal system (i.e., the external control terminal 13) via cables, so that the image of the inner wall and the capacitance value detected by the capacitance sensor 8 can be transmitted to the computer terminal system.

[0073] Define the angle between the mirror surface of the conical reflector 6 and its axis as α, the distance between the tip of the conical reflector 6 and the top end face of the endoscope 4 as L1, the distance between the tip of the conical reflector 6 and the top end face of the endoscope mounting base 3 as L2, and the outer diameter of the transparent annular connector 2 as R1. Then, 45° < α ≤ 60°, 0.8R1 ≤ L1 ≤ 1.2R1, and 0 ≤ L2 ≤ L1. This design allows all the mirror surfaces of the conical reflector 6 to fully receive the reflected light from the inner wall of the tube under test, resulting in more complete light reception. Combined with the angle and the distance between the tip of the conical reflector 6 and the top end face of the endoscope 4, this design improves the imaging effect and clearly reveals the inner wall structure of the tube 12 under test.

[0074] Meanwhile, the present invention also provides a method for detecting the internal cavity of a tubular structure in a nuclear power plant steam generator, comprising the following steps:

[0075] Step 1: Prepare an internal cavity detection device for a tubular structure in a nuclear power steam generator as described in claim 1;

[0076] Step 2: Obtain N standard tubes with different inner diameters. Place the internal cavity detection device for the tubular structure in the nuclear power steam generator, prepared in Step 1, into the N standard tubes sequentially to obtain n first capacitance values. Then, calibrate the inner diameters of the N standard tubes corresponding to the n first capacitance values ​​to obtain a database of the correspondence between the first capacitance values ​​and the inner diameters; where N≥3, n=N; and the inner diameters of the N standard tubes and the designed inner diameter of the tube 12 to be tested satisfy the following conditions:

[0077] Define the inner diameter of N standard pipes as D1, and the minimum design inner diameter of the pipe to be tested, 12, as D. min The maximum inner diameter is D max Therefore, the range for selecting the inner diameter D1 of the N standard pipes is: 0.9D min ≤D1≤3D max .

[0078] Step 3: Obtain the tube to be tested 12. Insert the internal cavity detection device for the tubular structure in the nuclear power steam generator prepared in Step 1 into the tube to be tested 12 to obtain the second capacitance value at different locations inside the tube to be tested 12 and the inner wall image of the tube to be tested 12, and output it to the external control terminal 13. The inner wall image is formed by imaging the inner wall area of ​​the tube to be tested 12 into a circular plane image, and then outputting the circular plane image to the computer terminal. Finally, it is displayed in the computer terminal system as a rectangular plane image expanded from the circular plane image.

[0079] Step 4: The external control terminal 13 compares the second capacitance values ​​at different locations within the tube 12 under test obtained in Step 3 with the n first capacitance values ​​in the database obtained in Step 2, and determines the inner diameter at different locations within the tube 12 under test according to the following principles:

[0080] If the second capacitance value at a certain location is equal to one of the n first capacitance values, then the inner diameter corresponding to that first capacitance value is determined to be the inner diameter of that location inside the tube 12 to be tested.

[0081] If the second capacitance value at a certain location is not equal to any of the n first capacitance values, and is located between two adjacent first capacitance values, then the inner diameter of that location in the tube 12 under test is determined as follows:

[0082] Define the second capacitance value at this location inside the tube 12 under test as C, and its corresponding inner diameter as d. The two adjacent first capacitance values ​​are C1, C2, and C3, C4, and C5, respectively. i and C i+1 And C i The corresponding inner diameter is d i C i+1 The corresponding inner diameter is d i+1 ,but Where C i <C<C i+1 ,

[0083] Step 5: Generate an inner diameter variation diagram from the inner diameters at different locations within the tube to be tested obtained in Step 4. Compare the generated inner diameter variation diagram with the designed inner diameter variation diagram for the tube to be tested 12. If the inner diameter at a certain location in the generated inner diameter variation diagram is D2, and the inner diameter at the corresponding location in the designed inner diameter variation diagram is D3, then the inner diameter variation value at that location is ΔD = D2 - D3. If |ΔD| is greater than a preset value, then mark that location as an abnormal point; the preset value is the minimum allowable error value.

[0084] Step 6: Based on the inner wall image of the tube 12 to be tested obtained in Step 3, observe the abnormal points marked in Step 5, determine the cause of the abnormality, and complete the testing of the tube 12 to be tested.

[0085] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0086] In the description of this invention, it should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present invention.

Claims

1. A device for detecting the cavity of a tubular structure in a nuclear power plant steam generator, characterized in that: Includes an end guide head (1), a transparent annular connector (2), an endoscope assembly, and a capacitive sensor assembly; The endoscope assembly includes a cylindrical endoscope mounting base (3), an endoscope (4), and a light source (5) located at the top of the endoscope (4), with the endoscope (4) located inside the endoscope mounting base (3); The top end of the endoscope mounting base (3) is connected to the end guide head (1) through the transparent annular connector (2), and a conical reflector (6) is provided at one end face of the end guide head (1) inside the transparent annular connector (2); The capacitive sensor assembly includes a hollow capacitive sensor mounting base (7) and a capacitive sensor (8) sleeved on the outer wall of the capacitive sensor mounting base (7). One end of the capacitive sensor mounting base (7) is connected to the bottom end of the endoscope mounting base (3). Both the endoscope (4) and the capacitance sensor (8) are electrically connected to the external control terminal (13) via cables, so that the image of the inner wall and the capacitance value detected by the capacitance sensor (8) can be transmitted to the external control terminal (13).

2. The internal cavity detection device for a tubular structure in a nuclear power steam generator according to claim 1, characterized in that: Define the angle between the mirror surface of the conical mirror (6) and the axis of the conical mirror (6) as α, the distance between the tip of the conical mirror (6) and the top end face of the endoscope (4) as L1, the distance between the tip of the conical mirror (6) and the top end face of the endoscope mounting base (3) as L2, and the outer diameter of the transparent annular connector (2) as R1. Then 45°<α≤60°, 0.8R1≤L1≤1.2R1, and 0≤L2≤L1.

3. The internal cavity detection device for a tubular structure in a nuclear power steam generator according to claim 1, characterized in that: The transparent annular connector (2), endoscope mounting base (3) and capacitive sensor mounting base (7) have the same outer diameter, and the guide end of the end guide head (1) is spherical with an outer diameter larger than that of the transparent annular connector (2).

4. The internal cavity detection device for a tubular structure in a nuclear power steam generator according to claim 1, characterized in that: The outer peripheral wall of the endoscope mounting base (3) is provided with a plurality of mounting holes (31) and screw holes (32) for mounting locking screws. The locking screws pass through the screw holes (32) and abut against the outer wall of the endoscope (4) so ​​as to fix the endoscope (4) inside the endoscope mounting base (3). Each mounting hole (31) is provided with a spring ball assembly (9). The maximum circumferential outer envelope diameter formed by multiple spring ball assemblies (9) after compression is greater than the outer diameter of the endoscope mounting base (3), which is used to protect the outer wall of the endoscope mounting base (3). The spring ball assembly (9) includes a spring (91) and a ball (92) that abuts against the outer end of the spring (91), and the diameter of the outer port of the mounting hole (31) is smaller than the diameter of the ball (92) so that both the ball (92) and the spring (91) can be confined within the mounting hole.

5. The internal cavity detection device for a tubular structure in a nuclear power steam generator according to claim 4, characterized in that: The mounting hole (31) is a through hole. A sleeve is fitted on the outer peripheral wall of the endoscope (4). The position of the sleeve corresponds to the position of the mounting hole (31). The inner end of the spring (91) abuts against the outer wall of the sleeve.

6. The internal cavity detection device for a tubular structure in a nuclear power steam generator according to claim 1, characterized in that: The capacitive sensor mounting base (7) has protective spring clip mounting positions at both ends, and the capacitive sensor mounting position is located between the two protective spring clip mounting positions. The protective spring mounting position is used to install the protective spring (10). One end of the protective spring (10) is a circular ring end, and the other end is a circular annular comb tooth end. The maximum outer envelope diameter of the circular annular comb tooth end is greater than the outer diameter of the capacitive sensor mounting base (7).

7. The internal cavity detection device for a tubular structure in a nuclear power steam generator according to claim 6, characterized in that: Multiple glue injection holes are provided on the circumferential sidewall of the ring end. By injecting glue into the glue injection holes, the protective spring (10) is fixedly connected to the capacitive sensor mounting base (7). The annular end is provided with a through groove along its axial direction. A measuring electrode (83) is sleeved at the middle position of the capacitor sensor mounting position. Two annular insulating layers (81) are respectively provided on both sides of the measuring electrode (83), and an equipotential ring (82) is provided between the two annular insulating layers (81) on the same side. The measuring electrode (83), the annular insulating layer (81), and the equipotential ring (82) together constitute the capacitor sensor (8).

8. The internal cavity detection device for a tubular structure in a nuclear power steam generator according to claim 1, characterized in that: The transparent annular connector (2) is a transparent glass annular connector.

9. A method for detecting the internal cavity of a tubular structure in a nuclear power plant steam generator, characterized in that, Includes the following steps: Step 1: Prepare an internal cavity detection device for a tubular structure in a nuclear power steam generator as described in claim 1; Step 2: Obtain N standard tubes with different inner diameters. Place the cavity detection device for the tubular structure in the nuclear power steam generator prepared in Step 1 into the N standard tubes in sequence to obtain n first capacitance values. Then, calibrate the inner diameters of the N standard tubes corresponding to the n first capacitance values ​​one by one to obtain a database of the correspondence between the first capacitance values ​​and the inner diameters; where N≥3, n=N; Step 3: Obtain the tube to be tested (12). Insert the inner cavity detection device for the tubular structure in the nuclear power steam generator prepared in Step 1 into the tube to be tested (12) to obtain the second capacitance value at different locations inside the tube to be tested (12) and the inner wall image of the tube to be tested (12), and output it to the external control terminal (13). Step 4: The external control terminal (13) compares the second capacitance values ​​at different locations inside the tube under test (12) obtained in Step 3 with the n first capacitance values ​​in the database obtained in Step 2, and determines the inner diameter at different locations inside the tube under test (12) according to the following principles: If the second capacitance value at a certain location is equal to one of the n first capacitance values, then the inner diameter corresponding to that first capacitance value is determined to be the inner diameter of that location in the tube to be tested (12). If the second capacitance value at a certain location is not equal to any of the n first capacitance values, and is located between two adjacent first capacitance values, then the inner diameter of that location in the tube to be tested (12) is determined according to the following method: Define the second capacitance value at this location inside the tube to be tested (12) as C, and its corresponding inner diameter as d. The two adjacent first capacitance values ​​are C1, C2, and C3, C4, and C5, C6, and C7, respectively. i and C i+1 And C i The corresponding inner diameter is d i C i+1 The corresponding inner diameter is d i+1 ,but Where C i <C<C i+1 , Step 5: Generate an inner diameter change diagram from the inner diameters at different locations within the tube (12) to be tested obtained in Step 4. Compare the generated inner diameter change diagram with the designed inner diameter change diagram of the tube (12) to be tested. If the inner diameter of a certain location in the generated inner diameter change diagram is D2 and the inner diameter of the corresponding location in the designed inner diameter change diagram is D3, then the inner diameter change value ΔD = D2 - D3 at that location. If the absolute value of ΔD is greater than the preset value, then mark that location as an abnormal point. Step 6: Based on the inner wall image of the tube to be tested (12) obtained in Step 3, observe the abnormal points marked in Step 5, determine the cause of the abnormality, and complete the detection of the tube to be tested (12).

10. The method for detecting the inner cavity of a tubular structure in a nuclear power steam generator according to claim 9, characterized in that, The inner diameters of the N standard tubes obtained in step 2 satisfy the following condition with the design inner diameter of the tube to be tested (12): Define the inner diameter of N standard tubes as D1, and the minimum design inner diameter of the tube to be tested (12) as D. min The maximum inner diameter is D max Therefore, the range for selecting the inner diameter D1 of the N standard pipes is: 0.9D min ≤D1≤3D max .

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