A method for in-situ flaw detection of the bracing boss on the fir tree-shaped blade of a nuclear power turbine.

Abstract

This invention specifically relates to an in-situ flaw detection method for the bracing protrusions of fir tree-shaped blades in nuclear power turbines, comprising the following steps: Step 1, selecting an ultrasonic phased array as the flaw detection equipment; Step 2, designing a reference test block; Step 3, designing an ultrasonic scanning method; Step 4, ultrasonic flaw detection. This invention utilizes ultrasonic phased array technology to achieve effective in-situ flaw detection of bracing protrusions on turbine blades.

Description

Technical Field

[0001] This invention relates to the field of nondestructive testing technology, and in particular to an in-situ flaw detection method for the bracing boss of a fir tree-shaped blade in a nuclear power turbine. Background Technology

[0002] Steam turbine blades are critical components of power plant steam turbines, rotating at high speeds in extremely harsh environments while enduring immense stress. A nuclear power plant's steam turbine has seven stages of fir-tree-shaped blades. To prevent damage caused by blade resonance, tie rods are machined onto the blades of the second and final stages, with the blades tightly fitted together. Based on penetrant testing results from the plant's two recent major overhauls, linear wear patterns were found on the wear surfaces of the tie rods on multiple second and final stage blades. Penetrant testing requires disassembling the blades, which is time-consuming, labor-intensive, and highly susceptible to damage during disassembly. Currently, there are no readily available in-situ flaw detection techniques for blade tie rods in China. Therefore, it is necessary to design a flaw detection process to achieve effective in-situ flaw detection of steam turbine blade tie rods. Summary of the Invention

[0003] The purpose of this invention is to provide an in-situ flaw detection method for the bracing bosses of fir tree-shaped blades in nuclear power turbines, which uses ultrasonic phased array technology to achieve effective in-situ flaw detection of the bracing bosses of turbine blades.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] A method for in-situ flaw detection of the bracing boss on the fir tree-shaped blade of a nuclear power turbine includes the following steps:

[0006] Step 1: Select an ultrasonic phased array as the flaw detection equipment;

[0007] Step 2: Design a reference test block;

[0008] Step 3: Design the ultrasonic scanning method;

[0009] Step 4: Ultrasonic flaw detection.

[0010] In this invention, in step 1, the ultrasonic testing instrument is an ultrasonic phased array instrument; the ultrasonic phased array instrument can simultaneously apply up to 1024 focusing rules; the vertical line error of the ultrasonic phased array is within 5%, the horizontal linearity error is within 1%, and the minimum gain step is 0.1dB.

[0011] In this invention, in step 1, the ultrasonic phased array instrument uses a planar array probe, with one probe equipped with three wedges, namely the first wedge, the second wedge, and the third wedge; the contact surface of the probe wedge has a contoured structure, and the curvature is consistent with the scanning position of the probe; the wedge is made of polystyrene; the height of the probe and wedge combination is limited to within 15mm.

[0012] In this invention, in step 2, the reference test block is made from blades manufactured in the same furnace and batch as the workpiece under test, and its acoustic performance and external dimensions are consistent with those of the workpiece under test; rectangular grooves are engraved on the wear surfaces of the outer arc side tie rod boss and the inner arc side tie rod boss of the blade of the reference test block; the groove dimensions are 5mm in length and 0.5mm in depth, and are used to set the reference sensitivity.

[0013] In this invention, step 3 involves three scanning methods: the first method involves placing the first wedge of the probe on the outer arc side of the blade's tie rod protrusion, with the sound beam aligned with the wear surface of the tie rod protrusion on the outer arc side of the blade; the second method involves placing the second wedge of the probe on the inner arc side of the blade's tie rod protrusion, with the sound beam aligned with the wear surface of the tie rod protrusion on the outer arc side of the blade; and the third method involves placing the third wedge of the probe on the outer arc side of the blade's tie rod protrusion, with the sound beam aligned with the wear surface of the tie rod protrusion on the inner arc side of the blade.

[0014] In this invention, step 4, ultrasonic flaw detection, includes the following steps:

[0015] Step 4.1: Based on different scanning methods and corresponding probe wedge combinations, set the focusing law and sound velocity on the ultrasonic phased array instrument to complete the calibration of the reference sensitivity for the three scanning methods:

[0016] Step 4.2 Before scanning the workpiece, ensure that the inspection surface of the workpiece is free of scratches and dirt that may affect the movement of the probe, and ensure that the surface roughness Ra of the inspection workpiece is ≤ 6.3 μm;

[0017] Step 4.3: When scanning the workpiece under inspection, first increase the reference sensitivity by 12dB and then scan according to the first to third scanning methods in sequence. During the scanning process, the scanning speed is less than 75mm / s, and the probe is in good contact with the corresponding scanning position to obtain the best scanning direction and cover the entire wear surface of the blade tie rod boss.

[0018] Step 4.4: Record defect signals that exceed 25% of the reference sensitivity wave height.

[0019] In this invention, in step 4.1, the focusing rule includes the focusing depth and the range of the fan sweep angle. The fan sweep angle in the main axis direction is set to (35°~72°), the fan sweep angle in the secondary axis direction is set to (-20°~20°), and the focusing depth is 15mm.

[0020] In this invention, step 4.1 involves calibrating the reference sensitivity of the three scanning methods, including the following steps:

[0021] Place the first wedge of the probe on the outer arc side tie rod protrusion of the reference test block blade, align the sound beam with the groove on the wear surface of the outer arc side tie rod protrusion of the reference test block blade, adjust the echo height in the groove signal to 80% of the full screen scale, and record the gain value of the instrument at this time as the reference sensitivity of the first scanning method.

[0022] Place the second wedge of the probe on the inner arc side tie rod protrusion of the reference test block blade, align the sound beam with the groove on the wear surface of the outer arc side tie rod protrusion of the reference test block blade, adjust the echo height in the groove signal to 80% of the full screen scale, and record the gain value of the instrument at this time as the reference sensitivity of the second scanning method.

[0023] Place the third wedge of the probe on the outer arc side tie rod protrusion of the reference test block blade, align the sound beam with the groove on the wear surface of the inner arc side tie rod protrusion of the reference test block blade, adjust the echo height in the groove signal to 80% of the full screen scale, and record the gain value of the instrument at this time as the reference sensitivity of the third scanning method.

[0024] In this invention, in step 4.2, the contaminants affecting probe movement include oxide scale, paint, and other contaminants.

[0025] Beneficial technical effects of the present invention:

[0026] The present invention provides an in-situ flaw detection method for the bracing bosses of fir-tree type nuclear power turbine blades. This method enables ultrasonic phased array testing of the entire wear surface of the bracing bosses on the longitudinal tree-type blades of turbines without removing the blades. Combining the advantages of phased array ultrasonic testing, defect signals are particularly easy to identify, and the signal-to-noise ratio exceeds 6dB, ensuring inspection quality. The method is simple and convenient to operate, highly practical, and easy to carry, improving work efficiency. It is especially important for shortening the overhaul period of nuclear power plants. Attached Figure Description

[0027] Figure 1 This is a front view of a fir-tree type blade for a steam turbine.

[0028] Figure 2 This is a front view of the bracing boss on the fir-tree shaped blade of a steam turbine.

[0029] Figure 3 This is a schematic diagram of the first scanning method using ultrasound.

[0030] Figure 4 This is a schematic diagram of the second scanning method of ultrasound.

[0031] Figure 5 This is a schematic diagram of the third scanning method of ultrasound.

[0032] In the figure, 1 is the blade tie rod boss; 2 is the blade outer arc side tie rod boss; 3 is the blade inner arc side tie rod boss; and 4 is the blade tie rod boss wear surface. Detailed Implementation

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein in the specification is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “equivalent to”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0034] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0035] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments.

[0036] See Figure 1-5 The in-situ flaw detection method for the tie rod boss of the fir tree-shaped blade of a nuclear power turbine, as described in this invention, includes the following steps:

[0037] Step 1: Select the ultrasonic testing instrument and probe;

[0038] Step 2: Design a reference test block;

[0039] Step 3: Design the ultrasonic scanning method;

[0040] Step 4: Ultrasonic flaw detection.

[0041] In this embodiment, the key area for flaw detection of the workpiece is the wear surface of the blade tie rod boss; the inspection personnel are Level II and Level III personnel as specified in HAF602.

[0042] In this embodiment, in step 1, the ultrasonic testing instrument selected is the Zetec TOPAZ64 portable ultrasonic phased array instrument. This ultrasonic phased array instrument can simultaneously apply up to 1024 focusing rules, which can better leverage the advantages of area phased array technology. This ultrasonic phased array instrument uses multiple two-dimensional ultrasonic images to obtain three-dimensional imaging by superposition, thereby facilitating the inspection personnel's judgment of the signal. The ultrasonic phased array instrument has a vertical line error of less than 5%, a horizontal line error of less than 1%, a minimum gain step of 0.1dB, wide bandwidth and high sensitivity, and complete DAC and TCG functions.

[0043] In this embodiment, in step 1, the ultrasonic phased array probe is selected as a planar array probe. Compared with a one-dimensional linear phased array probe, a two-dimensional planar array probe has array elements in both the horizontal and vertical directions. By controlling the time delay of the excitation pulse of each array element in the planar array probe, the ultrasonic beam can be deflected and focused in three-dimensional space, thereby acquiring three-dimensional spatial data. Each probe is equipped with three wedges, namely 5M8x4-0.6x1-N50S, 5M8x4-0.6x1-N60S-1, and 5M8x 4-0.6x1-N60S-2; To better fit the scanning area, the contact surface of the probe wedge has a contoured structure with a curvature consistent with the probe's scanning position; The wedge is made of low-attenuation polystyrene; To overcome the limitations of the narrow space of the in-situ blade, the height of the probe and wedge assembly is limited to within 15mm; The couplant for the probe is CG-08 type couplant produced by Wujiang Hongda Flaw Detection Equipment Co., Ltd., which is a paste with good sound transmission performance and easy removal, and the total chlorine and fluorine content in the couplant is no more than 250ppm.

[0044] In this embodiment, in step 2, the reference test block is made from blades manufactured in the same furnace and batch as the workpiece under test, and its acoustic performance and external dimensions are consistent with those of the workpiece under test; rectangular grooves are engraved on the wear surfaces of the outer arc side tie rod boss 2 and the inner arc side tie rod boss 3 of the blade of the reference test block; the groove dimensions are 5mm in length and 0.5mm in depth, which are used to set the reference sensitivity.

[0045] In this embodiment, three scanning methods are designed in step 3. The first scanning method is to place the probe wedge 5M8x4-0.6x1-N50S on the outer arc side tie rod protrusion 2 of the blade, and align the sound beam with the wear surface of the outer arc side tie rod protrusion 2. The second scanning method is to place the probe wedge 5M8x4-0.6x1-N60S-1 on the inner arc side tie rod protrusion 3 of the blade, and align the sound beam with the wear surface of the outer arc side tie rod protrusion 2. The third scanning method is to place the probe wedge 5M8x4-0.6x1-N60S-2 on the outer arc side tie rod protrusion 2 of the blade, and align the sound beam with the wear surface of the inner arc side tie rod protrusion 3.

[0046] In this embodiment, step 4, ultrasonic flaw detection, includes the following steps:

[0047] Step 4.1: Based on different scanning methods and corresponding probe wedge combinations, set the focusing law and sound velocity on the ultrasonic phased array instrument to complete the calibration of the reference sensitivity for the three scanning methods:

[0048] Step 4.2 Before scanning the workpiece, ensure that the inspection surface of the workpiece is free of scratches and dirt that may affect the movement of the probe, and ensure that the surface roughness Ra of the inspection workpiece is ≤ 6.3 μm;

[0049] Step 4.3: When scanning the workpiece under inspection, first increase the reference sensitivity by 12dB and then scan according to the first to third scanning methods in sequence. During the scanning process, the scanning speed is less than 75mm / s, and the probe is in good contact with the corresponding scanning position to obtain the best scanning direction and cover the entire blade tie rod boss wear surface 4.

[0050] Step 4.4: Record defect signals with a waveform height exceeding 25% of the reference sensitivity. When the defect amplitude exceeds the reference sensitivity, it is recommended to perform relevant processing.

[0051] In this embodiment, in step 4.1, the focusing rule includes the focusing depth and the fan sweep angle range. The fan sweep angle in the main axis direction is set to (35°~72°), the fan sweep angle in the secondary axis direction is set to (-20°~20°), and the focusing depth is 15mm.

[0052] In this embodiment, step 4.1 involves calibrating the baseline sensitivity of the three scanning methods, including the following steps:

[0053] Place the probe wedge 5M8x4-0.6x1-N50S on the outer arc side tie rod boss 2 of the reference test block blade, align the sound beam with the groove on the wear surface of the outer arc side tie rod boss 2 of the reference test block blade, adjust the echo height in the groove signal to 80% of the full screen scale, and record the gain value of the instrument at this time as the reference sensitivity of the first scanning method.

[0054] Place the probe wedge 5M8x4-0.6x1-N60S-1 on the inner arc side tie rod boss 3 of the reference test block blade, align the sound beam with the groove on the wear surface of the outer arc side tie rod boss 2 of the reference test block blade, adjust the echo height in the groove signal to 80% of the full screen scale, and record the gain value of the instrument at this time as the reference sensitivity of the second scanning method.

[0055] Place the probe wedge 5M8x4-0.6x1-N60S-2 on the outer arc side tie rod boss 2 of the reference test block blade, align the sound beam with the groove on the wear surface of the inner arc side tie rod boss 3 of the reference test block blade, adjust the echo height in the groove signal to 80% of the full screen scale, and record the gain value of the instrument at this time as the reference sensitivity of the third scanning method.

[0056] In this embodiment, in step 4.2, the contaminants affecting probe movement include oxide scale, paint, and other contaminants.

[0057] In this embodiment, the following is also included: after the ultrasonic flaw detection is completed, the coupling agent on the inspected workpiece is removed.

[0058] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for in-situ flaw detection of the bracing boss on the fir-tree shaped blade of a nuclear power turbine, characterized in that, Includes the following steps: Step 1: Select an ultrasonic phased array as the flaw detection equipment; Step 2: Design a reference test block; Step 3: Design the ultrasonic scanning method; Step 4: Ultrasonic flaw detection inspection; In step 1, the ultrasonic phased array probe is selected as a planar array probe, with one probe equipped with three wedges, namely the first wedge, the second wedge, and the third wedge. In order to better fit the scanning area, the contact surface of the probe wedge is a contoured structure with the curvature consistent with the scanning position of the probe. The wedge is made of polystyrene. The height of the probe and wedge combination is limited to within 15mm. In step 3, three scanning methods are designed. The first scanning method is to place the first wedge of the probe on the outer arc side tie rod protrusion (2) of the blade and align the sound beam with the wear surface of the outer arc side tie rod protrusion (2). The second scanning method is to place the second wedge of the probe on the inner arc side tie rod protrusion (3) of the blade and align the sound beam with the wear surface of the outer arc side tie rod protrusion (2). The third scanning method is to place the third wedge of the probe on the outer arc side tie rod protrusion (2) of the blade and align the sound beam with the wear surface of the inner arc side tie rod protrusion (3). In step 4, the workpiece being inspected is scanned in sequence according to the first to the third scanning methods.

2. The in-situ flaw detection method for the bracing boss of the fir tree-shaped blade of a nuclear power turbine according to claim 1, characterized in that, Step 4, ultrasonic flaw detection, includes the following steps: Step 4.1: Based on different scanning methods and corresponding probe wedge combinations, set the focusing law and sound velocity on the ultrasonic phased array instrument to complete the calibration of the reference sensitivity for the three scanning methods: Step 4.2 Before scanning the workpiece, ensure that the inspection surface of the workpiece is free of scratches and dirt that may affect the movement of the probe, and ensure that the surface roughness Ra of the inspection workpiece is ≤ 6.3 μm; Step 4.3: When scanning the workpiece, first increase the reference sensitivity by 12dB and then scan in sequence according to the first to third scanning methods; during the scanning process, the scanning speed is less than 75mm / s, and the probe is in good contact with the corresponding scanning position to obtain the best scanning direction and cover the entire blade tie rod boss wear surface (4). Step 4.4: Record defect signals that exceed 25% of the reference sensitivity wave height.

3. The in-situ flaw detection method for the bracing boss of the fir-tree type blade of a nuclear power turbine according to claim 2, characterized in that, In step 4.1, the focusing rule includes the focusing depth and the range of the fan sweep angle. The fan sweep angle in the main axis direction is set to 35° to 72°, the fan sweep angle in the secondary axis direction is set to -20° to 20°, and the focusing depth is 15mm.

4. The in-situ flaw detection method for the bracing boss of the fir tree-shaped blade of a nuclear power turbine according to claim 2, characterized in that, Step 4.1 involves calibrating the baseline sensitivity for the three scanning methods, including the following steps: Place the first wedge of the probe on the outer arc side tie rod protrusion (2) of the reference test block blade, align the sound beam with the groove on the wear surface of the outer arc side tie rod protrusion (2) of the reference test block blade, adjust the echo height in the groove signal to 80% of the full screen scale, and record the gain value of the instrument at this time as the reference sensitivity of the first scanning method. Place the second wedge of the probe on the inner arc side tie rod protrusion (3) of the reference test block blade, align the sound beam with the groove on the wear surface of the outer arc side tie rod protrusion (2) of the reference test block blade, adjust the echo height in the groove signal to 80% of the full screen scale, and record the gain value of the instrument at this time as the reference sensitivity of the second scanning method. Place the third wedge of the probe on the outer arc side tie rod protrusion (2) of the reference test block blade, align the sound beam with the groove on the wear surface of the inner arc side tie rod protrusion (3) of the reference test block blade, adjust the echo height in the groove signal to 80% of the full screen scale, and record the gain value of the instrument at this time as the reference sensitivity of the third scanning method.

5. The in-situ flaw detection method for the bracing boss of the fir tree-shaped blade of a nuclear power turbine according to claim 2, characterized in that, In step 4.2, contaminants that affect probe movement include scale, paint, and other dirt.

6. The in-situ flaw detection method for the bracing boss of the fir tree-shaped blade of a nuclear power turbine according to claim 1, characterized in that, In step 1, the ultrasonic testing instrument selected is an ultrasonic phased array instrument; the ultrasonic phased array instrument can apply up to 1024 focusing rules at the same time; the vertical line error of the ultrasonic phased array is within 5%, the horizontal linearity error is within 1%, and the minimum gain step is 0.1dB.

7. The in-situ flaw detection method for the bracing boss of the fir tree-shaped blade of a nuclear power turbine according to claim 1, characterized in that, In step 2, the reference test block is made from blades manufactured in the same furnace and batch as the workpiece under test, and its acoustic performance and external dimensions are consistent with those of the workpiece under test; rectangular grooves are engraved on the wear surfaces of the outer arc side tie rod boss (2) and the inner arc side tie rod boss (3) of the blade of the reference test block.

8. The method for in-situ flaw detection of the bracing boss on the fir-tree type blade of a nuclear power turbine according to claim 7, characterized in that, The groove dimensions are 5mm in length and 0.5mm in depth.

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