Method for remotely detecting welding seam of heating surface

Abstract

The invention discloses a method for remotely detecting a weld joint of a heating surface. Relates to the technical field of ultrasonic thickness measurement detection, in particular to the technical field of ultrasonic welding seam remote detection. According to the method for remotely detecting the welding seam of the heated surface, the welding seam of the heated surface is detected by adopting a self-designed single crystal probe, the self-designed single crystal probe comprises a probe part and a wedge block, the probe part is detachably mounted on the wedge block, the thickness of the wedge block is designed to be 6 mm, 10 mm and 15 mm, and during detection, the single crystal probe is detachably mounted on the wedge block. Wedge blocks with different thicknesses are selected for detection according to actual requirements. The self-designed single crystal probe can carry a long-distance detection mechanism to realize long-distance detection of the low-reheating surface pipe, and by combining the self-designed detection method matched with the single crystal probe, the technical problems of difficulty in long-distance detection of the defects of the low-reheating surface pipe and low accuracy in the prior art can be effectively solved, the detection time is saved, and the detection efficiency is improved. The detection precision is improved.

Description

Technical Field

[0001] The invention relates to the technical field of ultrasonic thickness measurement detection, and in particular to the technical field of ultrasonic weld long-distance detection. Background Art

[0002] In recent years, the role and positioning of traditional thermal power units have changed, transforming towards basic security and system regulation power supply, which has put forward higher requirements for the reliability of thermal power units. As an important monitored component of thermal power units, the "four-tube boiler" must also be the top priority. The explosion and leakage of the "four-tube boiler" seriously threatens the safe and stable operation of power generation companies. The No. 1 power station boiler of a power generation company in the service area was designed and manufactured by Dongfang Boiler Co., Ltd. The boiler is a high-efficiency ultra-supercritical parameter transformer operation DC furnace, a single reheat, a single furnace, and a front and rear wall hedge combustion full suspension structure П-type boiler, with a maximum continuous evaporation capacity of 2127.40t / h, a rated evaporation capacity of 2065t / h, a rated superheated steam temperature of 605℃, and a reheated steam temperature of 623℃.

[0003] During the hydraulic test of the boiler secondary system on a certain day, it was found that the low-temperature reheater tube screen was leaking. As of this failure, the boiler had been running for about 13,000 hours. The low-temperature reheater tube that leaked this time was made of 12Cr1MoVG, with a specification of Φ57.0×4.0mm. The support block welded at the leaking tube was made of 12Cr18Ni9 with a thickness of 6mm. The support block and the low-temperature reheater tube were welded by manual arc welding, and the welding material was A302. The low-temperature reheater horizontal tube was installed in a stacked manner with special-shaped support blocks, and the distance between the tube screens was 56mm.

[0004] The cracking position of the low-temperature reheater tube on site is located at the welding seam between the support block and the low-temperature reheater tube, extending from the outer wall to the inner wall. Figure 1 (a) is shown. The location and structure of the on-site support block are shown in Figure 1 As shown in (b), the black rectangular part in the figure is the special-shaped support block. There are two manhole doors above and below the low horizontal section transistor group. The inspection personnel can enter the manhole door to conduct close-up inspection of the upper support block, but the rest of the parts are out of reach due to the long distance. Traditional ultrasonic, X-ray, magnetic powder and other inspection methods cannot effectively detect defects in this position. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a method for long-distance detection of heated surface welds. The method adopts a independently designed single crystal probe to detect the heated surface welds. The independently designed single crystal probe includes a probe part and a wedge. The probe part is detachably mounted on the wedge. The thickness of the wedge is designed to be 6 mm, 10 mm and 15 mm. During detection, wedges of different thicknesses are selected for detection according to actual needs.

[0006] Furthermore, the probe part includes a signal line interface and a single chip, the signal line interface is used to transmit a signal to the single chip, the signal is a feedback signal received after the probe emits an ultrasonic wave, and the single chip is used to transmit and receive ultrasonic pulses.

[0007] Furthermore, the wedge block is installed and disassembled by screwing.

[0008] Furthermore, during detection, the independently designed single crystal probe is mounted on a remote detection mechanism for detection.

[0009] Furthermore, during the test, a wedge block with a thickness of 15 mm is first selected to screen the product to be tested. The screening standard is that the measured value L≥L2+L1 is a qualified product, otherwise it is a product to be tested, where L represents the thickness measurement result, L1 represents the thickness of the support block, and L2 represents the thickness of the pipe wall;

[0010] A wedge with a thickness of 6 mm is used to screen the first expected test product. The screening standard is that if the measured value L>L1, it is a qualified product, otherwise it is a second expected test product;

[0011] A wedge with a thickness of 10 mm is used to screen the two products to be inspected. For the same two products to be inspected, if the absolute value of the error between the measurement value obtained by using a wedge with a thickness of 10 mm and the measurement value obtained by using a wedge with a thickness of 6 mm is ≤0.5 mm, the two products to be inspected are considered to be defective products.

[0012] The beneficial effects of the method described in the present invention are as follows: in order to realize the long-distance detection of low reheating surface tube defects, the method described in the present invention independently designs a special probe specially used for the long-distance detection of low reheating surface tube defects. The probe can be equipped with a long-distance detection mechanism to realize the long-distance detection of low reheating surface tubes. Combined with the detection method independently designed in the present invention with a single crystal probe, it can effectively overcome the technical problems of the difficulty and low accuracy of long-distance detection of low reheating surface tube defects in the prior art, save detection time, and improve detection accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 (a) is a schematic diagram of the cracking position of the low-temperature reheater tube. Figure 1 (b) is a schematic diagram of the support block position;

[0014] Figure 2 Schematic diagram of the detection technology for defect identification through ultrasonic thickness testing;

[0015] Figure 3 This is a diagram showing the effect of the detection process when a crack occurs in the support block and the crack is parallel to the support block;

[0016] Figure 4 The effect diagram of the detection process when a crack occurs in the support block and the crack forms a certain angle with the support block;

[0017] Figure 5 This is the detection principle diagram of the dual crystal detection probe;

[0018] Figure 6 The defect signal schematic diagram cannot be identified when using dual crystal ultrasonic wave to identify defects;

[0019] Figure 7 This is a structural diagram of the single crystal probe independently designed in the present invention;

[0020] Figure 8 This is a structural diagram of the wedge block in the single crystal probe independently designed in this invention. DETAILED DESCRIPTION

[0021] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the protection scope of the present invention.

[0022] In the method described in the present invention, in order to realize the remote detection of low reheating surface tube defects, a special probe for remote detection of low reheating surface tube defects is independently designed. The probe can be equipped with a remote detection mechanism to realize the remote detection of low reheating surface tubes.

[0023] The detection technology principle involved in the method described in the present invention is to apply single crystal ultrasonic thickness measurement detection technology, by adding a delay wedge block method, combined with specific detection measures, to achieve detection and identification of crack defects in the support block of the heating surface tube.

[0024] Detection principle introduction:

[0025] The principle of the detection technology for defect identification through ultrasonic thickness measurement is as follows Figure 2 As shown in the figure, assuming that the thickness of the support block is L1 and the thickness of the pipe wall is L2, the crack direction of the support block on site is parallel to the support block or at an acute angle, so the on-site detection effect can be divided into the following three situations:

[0026] Case 1: When the support block has no cracks, the detection process is as follows Figure 2 As shown, θ is the angle between the vertical line and the tangent line of the tube wall. According to the geometric relationship, the thickness measurement result at this time is L=L2+L1 / COSθ. Since 0°≤θ≤90°, 0≤COSθ≤1, L≥L2+L1.

[0027] Case 2: When the support block has cracks and the cracks are parallel to the support block, the detection process is as follows Figure 3 As shown, according to the geometric relationship, the thickness measurement result at this time is L=L1.

[0028] Case 3: When a crack occurs on the support block and the crack forms a certain angle with the support block, the detection process is as follows Figure 4 As shown, at this time θ is the angle between the vertical line and the straight line where the pipe wall crack is located. According to the geometric relationship, it can be seen that at this time L<L1.

[0029] In summary, the ultrasonic thickness measurement method can be used to determine whether there is cracking in the weld of the heated surface support block. That is, when the measured thickness value L≥LI+L2, the support block at this position has not cracked; when the measured thickness value L≤L1, the weld of the support block at this position has cracked and failed.

[0030] Improvement of testing equipment:

[0031] The most common thickness measurement equipment is the dual crystal detection probe, which consists of two independent crystals separated by sound insulation material inside the probe. The two crystals are angled, so when one crystal emits an ultrasonic pulse, the pulse path will produce a "V" shape, enter the material through the ultrasonic coupling agent, and be detected by the other crystal. Figure 5 The instrument then uses the speed of the pulse and the time it takes to travel from one wafer to the other (from when the pulse is emitted to when it is received) to calculate the thickness of the material.

[0032] Dual crystal ultrasonic waves were used on site to identify defects. However, it was found that the defect signal could not be identified and the instrument could not even measure the thickness value. Figure 6 It can be seen that the inner wall of the test sample is a curved surface. Since the pulse signal is scattered on the curved surface during the detection process, the receiving chip cannot receive the echo signal.

[0033] On this basis, a self-designed single crystal probe detection solution is proposed. The single crystal probe is composed of a chip, which can both transmit and receive ultrasonic pulses, so it can avoid the disadvantage that the test sample is arc-shaped and cannot receive the test signal. The measurement range (thickness) of single crystal is limited, and it is mostly used to measure thinner workpieces. The on-site measurement needs exceed the range of single crystal detection probes available on the market. On this basis, a single crystal probe dedicated to low reheating surface tube defect detection is designed, such as Figure 7 As shown, the single crystal probe consists of two parts, including a probe part 1 and a wedge 2. The probe part 1 and the wedge 2 are detachably mounted. The probe part 1 includes a signal line interface 11 and a single crystal 12. Figure 8As shown, the wedge block 2 is designed to be detachable, and is installed and disassembled by threaded screwing, which makes it convenient to replace the wedge block 2 on site according to different situations. The thickness of the wedge block 2 is designed to be 6mm, 10mm, and 15mm. With the assistance of the three thicknesses of the wedge blocks 2, full coverage of on-site detection needs can be achieved.

[0034] During detection, the independently designed single crystal probe is mounted on a remote detection mechanism for detection. For example, the detection device in the Chinese utility model patent application "A weld detection device for special-shaped support blocks of heated surface tubes" (application number: 202420618646.5) can be selected, and the independently designed single crystal probe is mounted on the telescopic mechanism in the detection device to achieve remote detection in different situations.

[0035] Assume that, at the inspection site, L1+L2=10mm, when the thickness of the selected wedge 2 is 6mm, the detectable range is adjusted to (0.5~6.5mm) through the cooperation of the instrument and wedge 2, which is suitable for defect screening (case 2, case 3); when the thickness of the selected wedge 2 is 10mm, the detectable range is adjusted to (0.5~10.5mm) through the cooperation of the instrument and the wedge, which is exactly the same as the value of L1+L2; when the thickness of the selected wedge 3 is 15mm, the detectable range is adjusted to (0.5~15.5mm) through the cooperation of the instrument and the wedge. At this time, the measurement range can realize defect measurement under the condition of L≥L2+L1 (case 1).

[0036] To ensure the safety of on-site equipment, first use a 15mm wedge 2 to match the instrument to conduct a preliminary screening of the parts to be tested. The screening standard is that the measured value L≥L2+L1 is qualified; after screening out suspicious products, use the measuring equipment with a 6mm wedge 2 to screen the test parts. When the measurement result L≤L1, it is a defective sample. The 10mm wedge 2 is used as a backup device. When there is doubt about the test result of the 6mm wedge 2, the test equipment of the 10mm wedge 2 can be used to measure the sample. When the error of the two measurement results is ≤0.5mm, the result of the 6mm wedge 2 measurement is defined as accurate. When the error of the two measurement results is >0.5mm, use a conventional thickness test block to correct the instrument, and then use it on-site after correction.

[0037] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes to the technical scheme and utility model / inventive concept of the present invention within the technical scope disclosed in the present invention, and they should be covered by the protection scope of the present invention.

Claims

1. A method for long-distance detection of heated surface welds, characterized in that: The method uses a self-designed single crystal probe to detect the weld of the heated surface. The self-designed single crystal probe comprises a probe part (1) and a wedge (2). The probe part (1) is detachably mounted on the wedge (2). The thickness of the wedge (2) is designed to be 6 mm, 10 mm and 15 mm. During detection, wedges (2) of different thicknesses are selected for detection according to actual needs.

2. The method for long-distance detection of heated surface welds according to claim 1, characterized in that: The probe part (1) comprises a signal line interface (11) and a single crystal chip (12). The signal line interface (11) is used to transmit a signal to the single crystal chip (12), wherein the signal is a feedback signal received after the probe emits an ultrasonic wave. The single crystal chip (12) is used to transmit and receive ultrasonic wave pulses.

3. The method for long-distance detection of heated surface welds according to claim 2, characterized in that: The wedge block (2) is installed and disassembled by screwing with a thread.

4. The method for long-distance detection of heated surface welds according to claim 3, characterized in that: During detection, the independently designed single crystal probe is mounted on a remote detection mechanism for detection.

5. The method for long-distance detection of heated surface welds according to claim 4, characterized in that: During the test, a wedge block (2) with a thickness of 15 mm is first selected to screen the product to be tested. The screening standard is that the measured value L ≥ L2 + L1 is a qualified product, otherwise it is a product to be tested, where L represents the thickness measurement result, L1 represents the thickness of the support block, and L2 represents the thickness of the pipe wall; A wedge block (2) with a thickness of 6 mm is used to screen a first expected test product, and the screening standard is that if the measured value L>L1, it is a qualified product, otherwise it is a second expected test product; A wedge block (2) with a thickness of 10 mm is used to screen the two products to be tested. For the same two products to be tested, when the absolute value of the error between the measurement value obtained by using the wedge block (2) with a thickness of 10 mm and the measurement value obtained by using the wedge block (2) with a thickness of 6 mm is ≤0.5 mm, the two products to be tested are considered to be defective products.

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