Methods for the verification and calibration of non-destructive magnetic particle inspection equipment

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A magnetic particle flaw detector is a specialized device used to detect cracks and defects on the surface or near the surface of ferromagnetic materials. Its working principle involves generating a magnetic field with the aid of this device in order to magnetize the workpiece under inspection; magnetic particles are then applied evenly over its surface, and the distribution of these particles is observed in order to identify any cracks or other defects on the workpiece’s surface. The structural types of magnetic particle flaw detectors generally fall into fixed and portable categories. The current calibration specification for magnetic particle flaw detectors is JG(Machinery) 100-92 \"Calibration Specification for Magnetic Particle Flaw Detectors.\" This specification applies to the calibration of magnetic particle flaw detectors that operate with alternating current, direct current, half-wave rectification, or full-wave rectification (including fluorescent magnetic particle flaw detectors). The items for the calibration of magnetic particle flaw detectors include: the relative error of the indicated value at each setting, the output of the current regulation device, the time required for the indicator to show the correct value, the magnetic field strength on the surface of the test piece, the allowable temperature and the permitted temperature rise, as well as the operating functionality and insulation performance. According to the calibration items for magnetic particle flaw detectors, the calibration instruments and test pieces include: a DC megohmmeter, a voltage testing transformer, AC and DC voltmeters and ammeters, DC current transformers, DC shunts, semiconductor temperature sensors, timing devices, remanent magnetism testers, T2 copper bars measuring 25mm x 460mm in size, as well as steel bars measuring 30mm x 300mm in size; these steel bars are of type 86C (water-quenched), 480C (fire-quenched), 38–RC type, and 45# grade. The specific calibration methods are described in detail in the relevant calibration regulations, so they will not be covered here. Magnetic particle flaw detectors that meet the requirements are issued with a certification of conformity, while those that do not meet the requirements are given a notice of inspection results, indicating the specific defects. The inspection cycle for magnetic particle flaw detectors is generally one year. The main technical specifications and inspection methods for radiographic flaw detectors: Radiographic flaw detectors refer to X-ray devices used for non-destructive testing of industrial product components. It generates X-rays by bombarding an anode target with high-speed electrons, uses these X-rays to penetrate the component being inspected, and produces an image of the component’s internal structure on film or other imaging devices, thereby determining whether there are any defects in the component. X-ray flaw detectors can be divided into fixed and mobile types, as well as portable directional and circumferential X-ray flaw detectors. The current calibration specification for X-ray flaw detectors in demagnetizers is G40-2001 \"Calibration Specification for Linear Flaw Detectors\", which is applicable to the initial and subsequent calibrations of X-ray flaw detectors with a rated tube voltage of 400 KV. The calibration parameters, namely the requirements for metrological performance, include: air kerma rate, penetration power, repeatability, radiation angle, timer error, and air kerma rate of the transmitted X-rays. The equipment used for testing X-ray flaw detectors mainly includes: dosimeters, counters, standard test blocks, densitometers or microphotometers, X-ray protection meters, X-ray film, and film viewing lamps. Its main testing equipment, the dosimeter, consists of an amplifier, a switch-mode power supply, a changeover switch, and a liquid crystal digital display. A certain polarization voltage is applied to the chamber; when X-rays irradiate the ionization chamber, the magnetic particle flaw detector causes the air to ionize, and the resulting ions are collected by the central electrode to form an ionization current. The radiation dose is proportional to this value; the weak ionization current is amplified by an amplifier and displayed on a liquid crystal display. The specific methods for calibration are described in detail in the calibration regulations, so they will not be repeated here. Fluorescent magnetic particle flaw detectors that pass the inspection are issued with a certificate confirming their compliance, and X-ray flaw detectors that also meet the requirements are given a similar certificate; a notice of the inspection results is issued as well for all qualifying items. The calibration cycle is generally one year. In conclusion, China’s current laws and regulations on metrology set clear requirements for measuring instruments, while calibration represents a regulatory requirement specific to China for the management of such instruments. With China’s accession to the WTO, further shifts in functions will inevitably bring about changes in management as well. Apart from the measuring instruments required by laws and regulations, most testing equipment has its technical specifications determined based on usage requirements, in order to ensure the stability and reliability of those testing instruments. Portable flaw detectors serve as a guarantee for inspectors to make accurate assessments of material properties, ensuring that they continue to meet the requirements for product testing.