For successful ultrasonic inspections, which factor is crucial before starting the examination?

Performing calibration checks is essential before starting ultrasonic inspections for several reasons. Calibration ensures that the ultrasonic testing equipment is measuring accurately and providing reliable data. This involves checking the equipment against known standards or calibration blocks that have defined thicknesses and reflectors.

Through calibration, inspectors can confirm that the system is functioning correctly and can detect flaws accurately. This step is crucial since even minor inaccuracies in the equipment's response can lead to misinterpretations of the data, potentially resulting in missed defects or false positives. Proper calibration helps maintain a high level of confidence in the inspection results, which is vital for ensuring the safety and integrity of the components being tested.

The other factors, while they may contribute to the overall inspection process, do not have the foundational impact that calibration does. For example, while cleaning the surface is important for optimal contact and signal transmission, it does not replace the necessity of ensuring that the equipment is calibrated. Similarly, lighting conditions and the frequency of ultrasonic waves, while relevant, are secondary to the necessity of accurate measurements provided by a calibrated system.