preliminary preparation

Equipment and consumables inspection: After turning on, confirm that the display screen, buttons, and power supply are normal, and ensure that battery powered devices have sufficient power. Select probes based on the workpiece, with straight probes suitable for detecting internal defects and angled probes suitable for weld seam detection. At the same time, check the probe chip for cracks and the cable for damage. Prepare specialized coupling agents and other consumables to ensure that the coupling agents are free of impurities to ensure sound wave transmission.

Workpiece and environment preparation: Clean the inspection area of the workpiece with sandpaper, alcohol, etc., remove oil stains, rust, etc., polish to a smooth surface, and avoid affecting the coupling effect. Mark the detection range, such as covering the weld seam and both sides of the heat affected zone for weld seam detection. The testing environment should be dry and ventilated, avoiding direct sunlight and strong electromagnetic interference, and the temperature should be controlled within the instrument's suitable range (generally -10 ℃ -50 ℃).

instrument calibration

Basic parameter preset: Enter the parameter interface and input parameters such as probe frequency and chip size. The angle probe also needs to be supplemented with refractive angle and leading edge distance; Further input the thickness of the workpiece and the sound velocity of the material. For example, if the sound velocity of steel is about 5900m/s, the corresponding material can also be directly selected from the instrument's preset library.

Zero point calibration: Apply coupling agent to the probe and adhere it to the flat surface of standard test blocks such as CSK-IA. Adjust the range knob to display the start and bottom waves in the effective area of the screen. Align the probe with the known thickness position of the test block, adjust the zero knob to align the bottom wave peak with the corresponding scale, repeat 2-3 times to ensure zero stability and eliminate the influence of probe delay on positioning.

Sensitivity calibration: select the artificial defect position of the standard test block matching the workpiece, find the defect reflection wave, adjust the gain knob to make the wave reach 80% of the full scale of the screen, record the gain value at this time as the reference sensitivity, and ensure that the specified size of defects can be detected.

Formal testing

Scanning operation: Apply a thin layer of coupling agent evenly in the detection area, and use a handheld probe to scan steadily at a speed not exceeding 100mm/s. Welding seams and other areas can be scanned using serrated or cross scanning methods, and the overlap rate between adjacent scans should be ≥ 10% to avoid missed inspections. During scanning, the probe maintains uniform pressure to prevent false signals caused by jumping.

Signal observation and recording: When there are no defects, the screen mainly displays the initial wave and the bottom wave. If additional abnormal waves occur, the probe needs to be fine tuned to confirm whether the signal is stable. A stable abnormal wave is most likely a defect signal, and its position, wave height, depth, and other information can be recorded. A marker pen can also be used to mark the defect position on the workpiece. In addition, the defect type can be preliminarily determined by waveform characteristics, such as cracks corresponding to sharp and high amplitude echoes, and gas pore echoes with rounded and blunt peaks.

wrapping up

Data processing: Store the detection data and defect waveforms in instruments or external USB drives, and have qualified personnel analyze the data to determine whether the defects meet the standards. If necessary, other non-destructive testing methods can be used for verification. Afterwards, write a report indicating the workpiece information, testing parameters, defect details, and other related content.

Equipment maintenance: Wipe the instrument and probe with a soft cloth, remove residual coupling agent, and be careful not to touch the probe chip. Store instruments, probes, etc. in a dry and ventilated place, avoiding direct sunlight and collisions.

In addition, there may be differences in the operation details of different brands and models of flaw detectors. Before operation, it is necessary to refine the steps according to the corresponding instrument manual.