Method for detecting internal defects of non-radiative steel wire rope core conveying belt

Abstract

The invention discloses a method for detecting internal defects of a non-radiative steel wire rope core transmission band, which belongs to the field of industrial non-destructive testing, and adopts a low-energy electromagnetic wave transmission transmission band, selects proper working frequency band and power, and utilizes different electromagnetic wave absorption of a steel wire core in the transmission band to detect the internal defects of the steel wire rope core transmission band. And the fracture condition of the steel wire rope core in the transmission belt can be judged. The X-ray conveying belt can replace internal defects of an existing X-ray conveying belt with radiation, does not radiate operators, and is safe and environment-friendly.

Description

Technical Field

[0001] The invention belongs to the field of industrial nondestructive testing, and in particular relates to a method for detecting internal defects of a non-radiative steel wire rope core transmission belt. Background Art

[0002] Belt conveyor is a continuous transportation equipment in modern production. It has the advantages of large transportation capacity, long distance, low energy consumption, stable operation, convenient loading and unloading, and suitable for bulk material transportation. It is widely used in mining, coal, electricity, chemical industry, metallurgy, construction and other fields. Together with cars and trains, it has become the three main transportation tools. Belt conveyor is mainly composed of transmission belt, frame, roller, drum, tensioning device, transmission device, etc. Among them, the transmission belt is the key component of belt conveyor traction and transportation, accounting for 40%-60% of the total belt conveyor cost.

[0003] Conveyor belts are the second largest rubber industrial product after tires and are important components for traction and transportation of belt conveyors. In order to strengthen the support of the conveyor belt and increase the wear resistance and service life of the conveyor surface, a belt core is added to the conveyor belt. Currently, the belt core is mainly a steel wire rope core.

[0004] During the operation of belt conveyor equipment, the conveyor belt may fail due to aging, increased load, scratches by obstacles, etc. In particular, the joints of the conveyor belt may twitch, stretch, or even break due to excessive force. The internal steel wire rope core may rust and break due to water erosion caused by rubber damage, or fall off due to decreased adhesion between it and the rubber. Once a failure occurs, it will cause major safety accidents such as belt breakage or longitudinal tearing, leading to production suspension, loss of transported materials, damage to equipment, huge economic losses, and even casualties, seriously affecting production safety. Therefore, it is necessary to inspect the conveyor belt in a timely manner during operation.

[0005] In order to avoid the occurrence of failures, there are many means of conveyor belt inspection, such as online real-time inspection, regular inspection and internal defect inspection. In particular, internal defect inspection is of great significance in avoiding potential failures by discovering internal defects. At present, the internal defect inspection of steel wire rope core conveyor belts mainly relies on X-ray inspection equipment, which uses high-energy X-ray particles to pass through the conveyor belt and directly image the internal information of the conveyor belt (including defects). Since the conveyor belt cannot move in a confined space, the X-ray ionizing radiation during non-destructive testing will affect the health of nearby operators, so a new radiation-free detection method is needed.

[0006] A non-radiative electromagnetic wave source is used to detect defects in the steel wire core transmission belt. In the art, the steel in the steel wire has shielding properties against electromagnetic waves, and the carbon in the transmission belt also has strong absorption of electromagnetic waves. The detection of steel wire and carbon by electromagnetic waves is a difficult problem in the industry. The present invention uses a new method to detect steel wire defects in a carbon-containing transmission belt. Summary of the invention

[0007] In order to solve the problem of no radiation in the internal defect detection of the moving conveyor belt in a non-confined space, the present invention adopts a non-radiative electromagnetic wave source as the emission source, replacing the radiative X-ray source. When the electromagnetic wave passes through the conveyor belt, the rubber structure and the steel wire rope core inside the conveyor belt absorb the electromagnetic wave differently, and the intensity displayed at the receiving end is different. By selecting an electromagnetic wave source with a specific frequency band and power, the receiving end can directly display the internal defect information of the conveyor belt. It has the characteristics of safety and no radiation.

[0008] The present invention adopts a non-radiative electromagnetic wave source as the emission source instead of a radiative X-ray source. When the electromagnetic wave passes through the transmission belt, the internal structure of the transmission belt and the steel wire rope core have different absorption of the electromagnetic wave, resulting in different intensities displayed at the receiving end. By selecting an electromagnetic wave source with a specific frequency band and power, the receiving end can directly display the internal defect information of the transmission belt in an image, thereby providing a non-radiative steel wire rope transmission belt internal defect detection method.

[0009] The technical solution adopted by the present invention to solve its technical problem is: a method for detecting internal defects of a non-radiative steel wire rope core transmission belt, by selecting the working frequency of an electromagnetic wave source and the power of the electromagnetic wave source, imaging the steel wire rope core transmission belt, identifying internal defects, and realizing imaging of steel wire rope core defects.

[0010] Furthermore, an electromagnetic wave source with appropriate frequency and power is selected. Electromagnetic waves can pass through the transmission belt containing the steel wire rope core. The power of the wave source determines the thickness of the transmission belt and the imaging clarity, and the frequency and moving speed of the wave source determine the imaging resolution of the steel wire rope core. First, the frequency of the wave source is selected according to the layout of the steel wire rope core, and then the power of the wave source is selected according to the thickness of the transmission belt and the diameter of the steel wire rope core. Electromagnetic waves are emitted by the wave source and received on the other side through the transmission belt. The cross section of the transmission belt can be imaged by a line scan, and then the transmission belt is moved longitudinally to form a planar image of the steel wire rope core defect. Since the power energy of the wave source is relatively small and the emission is perpendicular to the transmission belt direction, it is almost harmless to the surrounding environment and personnel. It is a radiation-free detection method.

[0011] The beneficial effects of the present invention are: It can replace the internal defects of the current X-ray transmission belt with radiation, has no radiation to the operator, is safe and environmentally friendly. It does not require high-voltage reduction and explosion-proof measures, and is particularly suitable for mine environments.

[0012] Due to the strong shielding property of electromagnetic waves on metals and the strong absorption property on carbon, it is difficult to detect defects in metals and carbon using electromagnetic waves. The key point of the method proposed in the present invention is to select an electromagnetic wave source with a certain power and frequency band to detect defects in the wire rope. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of the electromagnetic wave detection transmission belt; Figure 2 It is a schematic diagram of the signal after the electromagnetic wave source is detected; Figure 3 It is a signal diagram of the defect after detection; Figure 4 It is a schematic diagram of defect detection imaging.

[0014] in, Figure 1 The reference numerals in the drawings are: electromagnetic wave source 1, transmission belt 2, electromagnetic wave receiving device 3. DETAILED DESCRIPTION

[0015] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in each embodiment of the present invention described below can be combined with each other as long as they do not conflict with each other. To achieve the above-mentioned purpose, the present invention adopts the following technical scheme.

[0016] The present invention provides a method for detecting internal defects of a non-radiative steel wire rope core transmission belt, which is mainly divided into four steps: the first step is to select the working frequency of the electromagnetic wave source; the second step is to select the power size of the electromagnetic wave source; the third step is to image the transmission belt of the steel wire rope core; and the fourth step is to identify the internal defects.

[0017] The selection of the electromagnetic wave source working frequency includes: The selection of the electromagnetic wave source frequency is mainly related to the arrangement spacing of the steel wire cores in the transmission belt. The center distance of the steel wire core is d. In order to identify the internal defect of one of the steel wire cores being broken, the resolution must be at least d / 3 to ensure that it can be identified. The wave source resolution is determined by half the wavelength (λ / 2), that is, λ / 2 is less than d / 3 to identify an internal defect. λ / 2 ≤d / 3, then λ≤2d / 3. The relationship between frequency and wavelength λ=C / f, C is the speed of light, f≥3C / 2d. The frequency of the electromagnetic wave source must be greater than the minimum calculated frequency.

[0018] Taking the center distance d as 15mm as an example, in order to identify the internal defect of a broken steel rope core, the resolution of this wave source must reach at least d / 3, that is, 15 / 3=5mm, to ensure that one of the steel rope cores can be identified. The wave source λ≤2d / 3=10mm, that is, the wave source with a wavelength less than 10mm can be used. The wave source frequency f≥3C / 2d is a wave source of 30GHz, and the wave source frequency should be greater than 30GHz.

[0019] The selection of the power of the electromagnetic wave source is as follows: Since the transmission belt requires wear resistance, the thickness of the rubber layer is different according to the specific specifications. It is generally divided into three parts: the upper covering rubber, the middle reinforcing layer containing the core rubber, and the lower covering rubber. Wear-resistant carbon is added to the rubber of each part. At the same time, the reinforcing layer of the transmission belt is a multi-strand structure of the steel wire core. Carbon and steel materials have a certain uniform absorption of electromagnetic waves, resulting in the need to increase the power when the wave source penetrates the transmission belt. When the thickness of the transmission belt is less than 20mm and the diameter of the steel wire rope core is within 8mm, the wave source power can be selected within 1 watt, which can penetrate the transmission belt for internal imaging. When the thickness of the transmission belt is more than 20mm and the diameter of the steel wire rope core is more than 8mm, the wave source power must be increased to 2 watts or even higher to penetrate the transmission belt for internal imaging.

[0020] Imaging of steel cord conveyor belts is as follows: Figure 1 As shown in the electromagnetic wave detection schematic diagram, the electromagnetic wave source 1 is located on one side of the steel wire core transmission belt 2, emitting electromagnetic waves of a certain power. The electromagnetic waves pass through the steel wire core transmission belt 2, and the electromagnetic wave receiving device 3 on the other side receives the remaining electromagnetic waves. The electromagnetic waves emitted and received by the electromagnetic wave source 1 and the electromagnetic wave receiving device 3 are the accumulated values ​​of multiple electromagnetic waves, such as Figure 1 The electromagnetic wave transmitted by the dotted line is shown. The electromagnetic wave received by the signal passing through the transmission belt 2 is processed by calculation. Here, the amplitude of the electromagnetic wave is mainly extracted for calculation. A detector is connected to the electromagnetic wave receiving end to extract the amplitude of the electromagnetic wave, and the specific value of the signal amplitude at each point can be obtained.

[0021] Combined with a row of multi-point scanning or a row of multi-wave sources, a cross-section signal of the transmission belt is imaged. Since the steel wire core absorbs electromagnetic waves, the amplitude is reduced. The electromagnetic waves at the position without the steel wire core are large, and the electromagnetic waves at the position with the steel wire core are small. The signal curve of a row of the electromagnetic wave receiving device is as follows: Figure 2 Combined with the longitudinal movement of the conveyor belt, a flat image of the interior of the steel wire rope core can be formed.

[0022] The identification of internal defects specifically includes: the internal defects of the wire rope core conveyor belt are mainly wire rope breakage, dislocation, etc., which will be reflected in the loss of a row of originally evenly distributed wire rope cores during signal processing, such as Figure 3 As shown in the figure, the signal value changes. After multiple scans, an image will be obtained. Figure 4As shown, the normal steel wire rope is displayed as continuous, and when one of the steel wire ropes is broken, the image shows that there is no missing part. The internal imaging diagram will display the defect information, and the internal defect information can be directly identified. The non-radiative steel wire rope core transmission belt internal defect detection method of the present invention uses a low-power non-high-voltage electromagnetic wave source for imaging, which causes almost no harm to the surrounding environment and personnel, and can replace the current X-ray transmission belt internal defect with radiation, which is non-radiative to the operator, safe and environmentally friendly. There is no high-voltage reduction explosion-proof measures, which is particularly suitable for mine environments.

Claims

1. A method for detecting internal defects of a non-radiative steel cord core transmission belt, characterized in that: By selecting the working frequency and power of the electromagnetic wave source, the steel wire rope core transmission belt is imaged, and internal defects are identified to achieve imaging of the steel wire rope core defects.

2. A method for detecting internal defects of a non-radiative steel cord transmission belt according to claim 1, characterized in that: The selection of the electromagnetic wave source frequency is related to the arrangement spacing of the steel wire cores in the transmission belt, where the center distance of the steel wire rope cores is d, C is the speed of light, the wave source frequency is ≥3C / 2d, and the frequency of the selected electromagnetic wave source is greater than the calculated minimum frequency.

3. The method for detecting internal defects of a non-radiative steel cord transmission belt according to claim 1, characterized in that: The power of the electromagnetic wave source is selected according to the thickness and diameter of the transmission belt, including: when the thickness of the transmission belt is less than 20mm and the diameter of the steel wire rope core is within 8mm, the wave source power is selected to be within 1 watt, penetrating the transmission belt for internal imaging; when the thickness of the transmission belt is more than 20mm and the diameter of the steel wire rope core is more than 8mm, the wave source power is selected to be more than 2 watts.

4. A method for detecting internal defects of a non-radiative steel cord transmission belt according to claim 1, characterized in that: Electromagnetic waves are emitted through an electromagnetic wave source and received on the other side through a transmission belt to image the cross section of the transmission belt. The amplitude of the electromagnetic wave is extracted when the electromagnetic wave signal passes through the transmission belt. Combined with a row of multi-point scanning or a row of multi-wave sources, the amplitude signal of the electromagnetic wave is obtained for a cross section of the transmission belt for imaging. Combined with the longitudinal movement of the transmission belt, a flat image of the interior of the steel wire rope core is formed.

5. The method for detecting internal defects of a non-radiative steel cord core transmission belt according to claim 1, characterized in that: To identify internal defects, during signal processing, if a row of originally evenly distributed steel wire rope cores is missing, the signal value will change and the internal imaging will show the defect information.

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