Search

The principle of operation of the VD-20NF eddy current flaw detector The principle of operation of the VD-20NF flaw detector is based on the generation of eddy currents on the surface of the controlled part and subsequent analysis of the signal at the output of the converter, which correlates with the characteristics of the active secondary field. The device consists of two main blocks: electronic one and electromechanical one, in which an eddy current converter of transformer type is installed. The controlled products (bearing rollers) enter through the input tray into the electromechanical unit of the flaw detector, where they move sequentially and fall under the pressure rollers of the overhead converter holder. The clamping mechanism is adjusted to each size of the rollers, so as to ensure tight contact with the curved surface and fix the tip of the transducer at the required distance from it. The detection of defects occurs due to the imbalance of the converter when it is located above the surface of the controlled product, caused by the interaction of the primary electromagnetic field generated by the converter with the secondary electromagnetic field of eddy currents induced in the controlled product by the primary field. When cracks are detected, the electronic unit of the flaw detector gives sound and light warning signals, and also triggers the electromagnet of the sorter, which directs the controlled roller into the tray for defective products. In the absence of defects, the controlled roller is directed towards the output tray of the flaw detector. Design features and advantages The VD-20NF eddy current flaw detector is equipped with removable input and output trays, power-on switches and a drive for feeding controlled products to the converter, as well as handrails for convenient transportation of the unit. The mechanisms of the electromechanical unit are protected by a frame made of steel plates. The electronic unit of the flaw detector is portable and can be installed both on the top panel of the electromechanical unit and on the surface of the desktop. Controls and indications of defect detection are located on the front panel of the electronic unit. The delivery package also includes a power adapter for the electronic unit and a tuning sample. The advantages of the VD-20NF flaw detector include: high reliability (the service life of the flaw detector is more than 10 years); it is easy to set up and operate; it has several types of defect detection alarms; the high probability of detecting defective products (at least 99.9%); low number of false positives (less than 5%). Scope of application According to the current standards of safety and product quality control during repair work in locomotive depots and repair plants, bearing rollers that have passed visual inspection and are recognized as suitable for further operation according to the criteria of geometry and condition of the working surface are subject to mandatory additional control using eddy current flaw detection to detect fatigue cracks invisible during visual inspection on the rolling surface of the rollers. The VD-20NF eddy current flaw detector allows for quality control and automatic disassembly of bearing rollers of various shapes and sizes both in laboratory and factory conditions in full compliance with the requirements of the regulatory documents of Rosstandart and the methods of performing control measurements used in JSC "Russian Railways".

It is especially effective for use in products made of composite materials (including with honeycomb filler). Distinctive features: The AD-42 IP is a compact acoustic system sensitive to changes in mechanical impedance caused by product defects. The indication of the device indicates that there are voids, non-adhesives, delaminations or changes in the structure of composite materials (including with honeycomb filler and laminated plastics) under the sensor. The device is used to monitor various materials and their combinations. The energy consumption of the unit is low because the converter is switched on when the sensor is placed on the monitored product. Being light enough, the device allows you to perform monitoring in hard-to-reach places or in confined spaces. The results of the control can be stored in the built-in non-volatile memory and transferred to a PC. Converters Options: - 3 types of converters for various tasks Emitters: - 1 or 2 on each converter Switching-on: - The converters are switched on when they are placed on a controlled object. Technical characteristics: Weight, kg: 0.73 Dimensions, mm: 210x150x70 Power supply: 4 AA batteries Work without recharging the battery, h: 8 Battery discharge visual indication The defect alarm is visual on the converter and audible on the instrument panel (or) in headphones.

KOIDZ-VD kits consist of samples of artificial defects (SAD) and samples of gaps (SG). Samples of artificial defects are made in the form of flat and curved plates and cylinders, on the working surfaces of which defects are made in the form of continuity violations like slits of various depths, opening widths and lengths. The working surfaces of flat SADs are two opposite surfaces on which longitudinal slits are cut by an electroerosion method The working surfaces of the SAD, reproducing a positive curved surface, are samples with a cylindrical surface. The working surface of the SAD reproducing negative curvature is the inner surface of the curved plate — the place of inflection. The KOIDZ-VD kit contains an SAD for determining the influence of various quantities. To determine the effect of the roughness of the working surfaces, the kit contains SADs with different roughness, on which defects of the same depth are made. To determine the effect of positive curvature and surface roughness, the kit contains cylindrical samples with different roughness of working surfaces on which defects of the same depth are made. To determine the simultaneous effect of negative curvature and surface roughness, the kit contains curved plates on which two defects of the same depth are cut, one of which is located on the flat, the other on the curved parts of the sample. To determine the effect of the chemical composition of the material of the controlled products, the kit contains samples of steel 10, steel 20 and steel 45. The same defects are made on each sample. To account for the influence of specific electrical conductivity, the kit contains samples from non-magnetic structural materials: aluminum alloy D16T and titanium alloy VT-23. The same defects are made on each sample. Gap samples are flat and curved plates of different thicknesses made of dielectric material. Technical specifications The range of nominal values of the depth of defects, mm: from 0.1 to 10. The limits of permissible error of the value of the depth of defects, mm: from ± 0.02 to ± 0.25. The range of nominal values of the width of the opening of defects, mm: from 0.03 to 0.15. The limits of the permissible error of the width of the opening of defects, mm: from ± 0.01 to ± 0.05. The range of nominal values of the length of defects, mm: from 6 to 100. The limits of permissible error of the value of the length of defects, mm: from ± 0.5 to ± 1. The range of nominal values of the thickness of the dielectric gap samples, mm: from 0.2 to 10. The limits of the permissible error of the thickness of the samples, mm: from ± 0.02 to ± 0.5. The range of nominal values of the radius of curvature of curved surfaces with defects, mm: - convex: from 13 to 510; - concave: 10.