Nuclear steam turbine longitudinal tree type blade lacing wire boss in-situ flaw detection method

Abstract

The invention particularly relates to an in-situ flaw detection method for a lacing wire boss of a fir-tree-shaped blade of a nuclear turbine. The in-situ flaw detection method comprises the following steps: step 1, selecting an ultrasonic phased array as flaw detection equipment; 2, designing a reference test block; step 3, designing an ultrasonic scanning mode; and 4, performing ultrasonic flaw detection. The ultrasonic phased array technology is adopted, and effective in-situ flaw detection of the lacing wire boss of the steam turbine blade is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of nondestructive testing, in particular to an in-situ flaw detection method for a nuclear power steam turbine fir-tree blade tie rod boss. Background Art

[0002] Steam turbine blades are key equipment in power plant turbines. They rotate at high speeds in extremely harsh environments and are subjected to great stress. The fir-tree-shaped blades of a nuclear power plant's steam turbine are divided into seven levels in total. In order to prevent damage caused by blade resonance, a tie-rib boss is designed and processed on the blade body of the next-to-last stage, and the blades are assembled against each other. According to the results of the penetrant inspection of the nuclear power plant's last two overhauls, linear displays were found on the wear surfaces of the tie-rib bosses of multiple next-to-last stage blades. Penetrant inspection requires the blades to be disassembled, which is time-consuming and labor-intensive, and the blades are easily damaged during the disassembly process. At present, there is no reference to the in-situ flaw detection technology for blade tie-rib bosses in China. Based on this, it is necessary to design a flaw detection inspection process to achieve effective in-situ flaw detection of steam turbine blade tie-rib bosses. Summary of the invention

[0003] The object of the present invention is to provide an on-site flaw detection method for a nuclear power steam turbine fir-tree blade tie rod boss, which adopts ultrasonic phased array technology to achieve effective on-site flaw detection of the turbine blade tie rod boss.

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] A method for in-situ flaw detection of a nuclear power steam turbine fir-tree blade tie rod boss, comprising the following steps:

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

[0007] Step 2: Design reference test blocks;

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

[0009] Step 4: Ultrasonic flaw detection.

[0010] In the present invention, in step 1, the ultrasonic detector selects an ultrasonic phased array instrument; the ultrasonic phased array instrument applies up to 1024 focusing laws simultaneously; the vertical line error of the ultrasonic phased array is within 5%, the horizontal linear error is within 1%, and the minimum gain step is 0.1dB.

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

[0012] In the present invention, in step 2, the reference test block is manufactured using blades from the same furnace and batch as the inspected workpiece, and its acoustic performance and external dimensions are consistent with those of the inspected workpiece; the wear surfaces of the blade outer arc side tie rod boss and the blade inner arc side tie rod boss of the reference test block are both engraved with rectangular grooves; the groove dimensions are 5 mm long and 0.5 mm deep, and are used for setting the benchmark sensitivity.

[0013] In the present invention, in step 3, three scanning methods are designed; the first scanning method is: placing the first wedge block of the probe on the reinforcement boss on the outer arc side of the blade, and aiming the sound beam at the wear surface of the reinforcement boss on the outer arc side of the blade; the second scanning method is: placing the second wedge block of the probe on the reinforcement boss on the inner arc side of the blade, and aiming the sound beam at the wear surface of the reinforcement boss on the outer arc side of the blade; the third scanning method is: placing the third wedge block of the probe on the reinforcement boss on the outer arc side of the blade, and aiming the sound beam at the wear surface of the reinforcement boss on the inner arc side of the blade.

[0014] In the present invention, step 4, ultrasonic flaw detection, comprises the following steps:

[0015] Step 4.1. According to different scanning modes and corresponding probe wedge combinations, set the focal law and sound velocity on the ultrasonic phased array instrument to complete the calibration of the baseline sensitivity of the three scanning modes:

[0016] Step 4.2: Before scanning the workpiece, ensure that there are no scratches on the surface of the workpiece and no dirt that may affect the movement of the probe, and ensure that the surface roughness of the workpiece is Ra≤6.3μm;

[0017] Step 4.3: When scanning the inspected workpiece, first increase the base sensitivity by 12 dB for scanning, and then scan in the first to third scanning methods in sequence; during the scanning process, the scanning speed is less than 75 mm / s, and the probe fits well with the corresponding scanning position to obtain the best scanning direction and cover the entire blade tie rod boss wear surface;

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

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

[0020] In the present invention, in step 4.1, the calibration of the reference sensitivity of the three scanning modes is completed, including the following steps:

[0021] Place the first wedge of the probe on the reinforcement boss on the outer arc side of the reference test block blade, aim the sound beam at the groove on the wear surface of the reinforcement boss on the outer arc side 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 reinforcement boss on the inner arc side of the reference test block blade, aim the sound beam at the groove on the wear surface of the reinforcement boss on the outer arc side 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 reinforcement boss on the outer arc side of the reference test block blade, aim the sound beam at the groove on the wear surface of the reinforcement boss on the inner arc side 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 benchmark sensitivity of the third scanning method.

[0024] In the present invention, in step 4.2, the dirt that affects the movement of the probe includes oxide scale, paint and other dirt.

[0025] Beneficial technical effects of the present invention:

[0026] The in-situ flaw detection inspection method for the fir-tree type blade tie-rib boss of a nuclear power steam turbine of the present invention realizes the ultrasonic phased array detection of the full range of the wear surface of the fir-tree type blade tie-rib boss of the steam turbine without removing the blade; combined with the advantages of phased array ultrasonic inspection and detection, the defect signal is particularly easy to identify, and the signal-to-noise ratio exceeds 6dB, ensuring the inspection quality; the operation is simple and convenient, the practicability is strong, the equipment is easy to carry, and the work efficiency is improved, which is particularly important for shortening the overhaul period of nuclear power plants. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is the front view of the fir-tree blade of the steam turbine;

[0028] Figure 2 This is the front view of the tie rod boss of the fir-tree blade of the steam turbine;

[0029] Figure 3 This is a schematic diagram of the first ultrasonic scanning method;

[0030] Figure 4 This is a schematic diagram of the second ultrasonic scanning method;

[0031] Figure 5 Schematic diagram of the third ultrasonic scanning method.

[0032] In the figure, 1. the blade tie rod boss; 2. the blade outer arc side tie rod boss; 3. the blade inner arc side tie rod boss; 4. the blade tie rod boss wear surface. DETAILED DESCRIPTION

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used in the specification of the application are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0034] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0035] The technical solution of the present invention is clearly and completely described below in conjunction with the accompanying drawings and specific embodiments.

[0036] See also Figure 1-5 The in-situ flaw detection method of the nuclear power steam turbine fir-tree type blade tie rod boss of the present invention is used to perform in-situ flaw detection of the fir-tree type blade tie rod boss of the inspected workpiece steam turbine, comprising the following steps:

[0037] Step 1. Select ultrasonic detector and probe;

[0038] Step 2: Design reference test blocks;

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

[0040] Step 4: Ultrasonic flaw detection.

[0041] In this embodiment, the key area of ​​the flaw detection inspection of the inspected workpiece is the wear surface of the blade reinforcement boss; the inspectors are level II and level III personnel specified in HAF602.

[0042] In this embodiment, in step 1, the ultrasonic detector selects the TOPAZ64 portable ultrasonic phased array instrument produced by Zetec; the ultrasonic phased array instrument can apply up to 1024 focusing laws at the same time, and can better play the advantages of the planar phased array technology; the ultrasonic phased array instrument uses multiple two-dimensional ultrasonic images to obtain three-dimensional imaging in an overlapping manner, thereby facilitating the inspection personnel to judge the signal; the vertical line error of the ultrasonic phased array instrument is within 5%, the horizontal linear error is within 1%, the minimum gain step is 0.1dB, it has a wide bandwidth and high sensitivity, and has complete DAC and TCG functions.

[0043] In this embodiment, in step 1, the probe of the ultrasonic phased array instrument selects a planar array probe. Compared with a one-dimensional linear phased array probe, a two-dimensional planar array probe has array elements in the horizontal and vertical directions. By controlling the time delay of the excitation pulses of each array element in the planar array probe, the deflection and focusing of the ultrasonic beam in three-dimensional space can be achieved, thereby obtaining three-dimensional spatial data; one probe is equipped with three wedges, namely 5M8x4-0.6x1-N50S, 5M8x4-0.6x1-N60S-1 and 5M8x 4-0.6x1-N60S-2; In order to better fit the scanning area, the contact surface of the probe wedge is a contoured structure, and the curvature is consistent with the scanning position of the probe; the material of the wedge is low-attenuation polystyrene; in order to overcome the limitation of the narrow position of the blade in place, the height of the probe and wedge combination is limited to within 15mm; the coupling agent of the probe is CG-08 coupling agent produced by Wujiang Hongda Flaw Detection Equipment Co., Ltd., which is a paste with good sound transmission performance and easy to remove. The total content of chlorine and fluorine in the coupling agent is not more than 250ppm.

[0044] In this embodiment, in step 2, the reference test block is manufactured using blades from the same furnace and batch as the inspected workpiece, and its acoustic performance and external dimensions are consistent with those of the inspected workpiece; the wear surfaces of the blade outer arc side tie rod boss 2 and the blade inner arc side tie rod boss 3 of the reference test block are both engraved with rectangular grooves; the groove dimensions are 5 mm long and 0.5 mm deep, and are used for setting the benchmark sensitivity.

[0045] In this embodiment, in step 3, three scanning methods are designed; the first scanning method is: placing the wedge block 5M8x4-0.6x1-N50S of the probe on the reinforcement boss 2 on the outer arc side of the blade, and aiming the sound beam at the wear surface of the reinforcement boss 2 on the outer arc side of the blade; the second scanning method is: placing the wedge block 5M8x4-0.6x1-N60S-1 of the probe on the reinforcement boss 3 on the inner arc side of the blade, and aiming the sound beam at the wear surface of the reinforcement boss 2 on the outer arc side of the blade; the third scanning method is: placing the wedge block 5M8x4-0.6x1-N60S-2 of the probe on the reinforcement boss 2 on the outer arc side of the blade, and aiming the sound beam at the wear surface of the reinforcement boss 3 on the inner arc side of the blade.

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

[0047] Step 4.1. According to different scanning modes and corresponding probe wedge combinations, set the focusing law and sound velocity on the ultrasonic phased array instrument to complete the calibration of the benchmark sensitivity of the three scanning modes:

[0048] Step 4.2: Before scanning the workpiece, ensure that there are no scratches on the surface of the workpiece and no dirt that may affect the movement of the probe, and ensure that the surface roughness of the workpiece is Ra≤6.3μm;

[0049] Step 4.3, when scanning the inspected workpiece, first increase the reference sensitivity by 12 dB for scanning, and then perform the scanning in sequence according to the first to third scanning methods; during the scanning process, the scanning speed is less than 75 mm / s, and the probe fits well 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 that exceed 25% of the benchmark sensitivity wave height. When the defect amplitude exceeds the benchmark sensitivity, it is recommended to perform relevant processing.

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

[0052] In this embodiment, in step 4.1, the calibration of the baseline sensitivity of the three scanning modes is completed, including the following steps:

[0053] Place the probe wedge 5M8x4-0.6x1-N50S on the outer arc side reinforcement boss 2 of the reference test block blade, aim the sound beam at the groove on the wear surface of the outer arc side reinforcement 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 instrument gain value 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 reinforcement boss 3 of the reference test block blade, aim the sound beam at the groove on the wear surface of the outer arc side reinforcement 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 instrument gain value at this time as the reference sensitivity of the second scanning method;

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

[0056] In this embodiment, in step 4.2, the dirt that affects the movement of the probe includes oxide scale, paint and other dirt.

[0057] In this embodiment, the method further includes: after the ultrasonic flaw detection is completed, removing the coupling agent on the inspected workpiece.

[0058] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for in-situ flaw detection of a truss boss of a nuclear power steam turbine fir-tree blade, characterized in that: The steps include: Step 1: Select ultrasonic phased array as the flaw detection equipment; Step 2: Design reference test blocks; Step 3: Design the ultrasonic scanning method; Step 4: Ultrasonic flaw detection.

2. The in-situ flaw detection method for the rib boss of a nuclear power steam turbine fir-tree blade according to claim 1 is characterized in that: In step 1, the probe of the ultrasonic phased array instrument selects a planar array probe, and one probe is equipped with three wedges, namely the first wedge, the second wedge and the third wedge; the contact surface of the probe wedge is a contoured structure, and the curvature is consistent with the scanning position of the probe; the material of the wedge is polystyrene; the height of the combination of the probe and the wedge is limited to within 15 mm.

3. The in-situ flaw detection method for the rib boss of a nuclear power steam turbine fir-tree blade according to claim 2 is characterized in that: In step 3, three scanning methods are designed; the first scanning method is: placing the first wedge block of the probe on the reinforcement boss (2) on the outer arc side of the blade, and aiming the sound beam at the wear surface of the reinforcement boss (2) on the outer arc side of the blade; the second scanning method is: placing the second wedge block of the probe on the reinforcement boss (3) on the inner arc side of the blade, and aiming the sound beam at the wear surface of the reinforcement boss (2) on the outer arc side of the blade; the third scanning method is: placing the third wedge block of the probe on the reinforcement boss (2) on the outer arc side of the blade, and aiming the sound beam at the wear surface of the reinforcement boss (3) on the inner arc side of the blade.

4. The in-situ flaw detection method for the rib boss of a nuclear power steam turbine fir-tree blade according to claim 3 is characterized in that: Step 4, ultrasonic flaw detection, includes the following steps: Step 4.

1. According to different scanning modes and corresponding probe wedge combinations, set the focal law and sound velocity on the ultrasonic phased array instrument to complete the calibration of the baseline sensitivity of the three scanning modes: Step 4.2: Before scanning the workpiece, ensure that there are no scratches on the surface of the workpiece and no dirt that may affect the movement of the probe, and ensure that the surface roughness of the workpiece is Ra≤6.3μm; Step 4.3, when scanning the inspected workpiece, first increase the base sensitivity by 12 dB for scanning, and then perform the scanning in sequence according to the first to third scanning methods; during the scanning process, the scanning speed is less than 75 mm / s, and the probe is well fitted 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 exceeding 25% of the reference sensitivity wave height.

5. The in-situ flaw detection method for the rib boss of a nuclear power steam turbine fir-tree blade according to claim 4 is characterized in that: In step 4.1, the focusing rule includes the focusing depth and the fan scanning angle range. The fan scanning angle in the main axis direction is set to (35°~72°), the fan scanning angle in the secondary axis direction is set to (-20°~20°), and the focusing depth is 15mm.

6. The in-situ flaw detection method for the rib boss of a nuclear power steam turbine fir-tree blade according to claim 4, characterized in that: In step 4.1, the calibration of the baseline sensitivity of the three scanning methods is completed, including the following steps: The first wedge of the probe is placed on the reinforcement boss (2) on the outer arc side of the blade of the reference test block, the sound beam is aimed at the groove on the wear surface of the reinforcement boss (2) on the outer arc side of the blade of the reference test block, the echo height in the groove signal is adjusted to 80% of the full screen scale, and the gain value of the instrument at this time is recorded as the reference sensitivity of the first scanning mode; The second wedge of the probe is placed on the inner arc side reinforcement boss (3) of the reference test block blade, the sound beam is aimed at the groove on the wear surface of the outer arc side reinforcement boss (2) of the reference test block blade, the echo height in the groove signal is adjusted to 80% of the full screen scale, and the gain value of the instrument at this time is recorded as the reference sensitivity of the second scanning method; The third wedge of the probe is placed on the reinforcement boss (2) on the outer arc side of the reference test block blade, the sound beam is aimed at the groove on the wear surface of the reinforcement boss (3) on the inner arc side of the reference test block blade, the echo height in the groove signal is adjusted to 80% of the full screen scale, and the gain value of the instrument at this time is recorded as the reference sensitivity of the third scanning method.

7. The in-situ flaw detection method for the rib boss of a nuclear power steam turbine fir-tree blade according to claim 4 is characterized in that: In step 4.2, contaminants that affect the movement of the probe include scale, paint, and other contaminants.

8. The in-situ flaw detection method for the rib boss of a nuclear power steam turbine fir-tree blade according to claim 1 is characterized in that: In step 1, the ultrasonic detector selects an ultrasonic phased array instrument; the ultrasonic phased array instrument applies up to 1024 focusing laws simultaneously; the vertical line error of the ultrasonic phased array is within 5%, the horizontal linear error is within 1%, and the minimum gain step is 0.1dB.

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

10. The in-situ flaw detection method for the rib boss of a nuclear power steam turbine fir-tree blade according to claim 9, characterized in that: The groove dimensions are 5 mm long and 0.5 mm deep.

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