GB/T 31932-2015Method for electromagnetic automatic ultrasonic testing for thicker steel plates (English PDF)

7.2 Testing rate

During electromagnetic ultrasonic defect testing, the testing rate shall not exceed 2m/s.

7.3 Testing sensitivity

7.3.1 The testing sensitivity of electromagnetic automatic ultrasonic defect testing equipment can be calibrated by electronic technology, OR otherwise by comparative sample.

7.3.2 When using electronic technology for calibration, the sensitivity of the testing system shall be set by the first bottom wave of the testing steel plate's flawless location based on the probe's large flat probe DGS curve, probe 5mm flat bottom hole DGS curve, OR diameter 5mm flat bottom hole DAC curve;

AND meanwhile the diameter 5mm flat bottom hole DGS curve or DAC curve is set as alarm threshold. The probe's DGS curve can be provided by the probe manufacturer, whilst the DAC curve shall be subject to actual measurement by the comparative samples having different depth and diameter 5mm flat bottom holes.

7.3.3 When using the comparative sample for calibration, one method is at the comparative sample's flawless location, ADJUST the first reflected wave height to 50% of the full scale, then INCREASE the dB difference (actual measurement) between the comparative sample's first reflected wave and the diameter 5mm flat bottom hole wave, which is used as the testing sensitivity; the other method is at the comparative sample, ADJUST the 3mm flat groove reflected wave height to 50% of full scale, then DECREASE the dB difference (actual measurement) between the 3mm flat bottom groove and the diameter 5mm flat bottom hole wave, which is used as the testing sensitivity.

7.4 Calibration

7.4.1 The electromagnetic automatic ultrasonic defect testing equipment shall be regularly calibrated.

7.4.2 During the continuous operation of equipment, at least every 8h, USE the comparative sample to calibrate the testing sensitivity. As compared with the standard result, if the variance of the testing result is not less than 10%, it shall adjust the testing system, so as to make its performance reach to the specified requirements; it shall also re-conduct the defect testing for the tested steel plate after the previous calibration. […]