What factors affect the accuracy and resolution of oil casing wall thickness detection

API standards stipulate that the inner and outer surfaces of inlet and outlet oil casings must be free of folds, separations, cracks, and scratches. These defects must be thoroughly removed to a depth not less than 12.5% of the nominal oil casing wall thickness. Oil casings must undergo full-coverage automated wall thickness detection. Currently, there is an indirect method for measuring oil casing wall thickness based on the principle of magnetic leakage. It does not directly measure the oil casing wall thickness but rather indirectly measures it by measuring the magnetic field changes caused by variations in the oil casing wall thickness.

Therefore, magnetic field strength has a significant impact on the accuracy and resolution of oil casing wall thickness detection, making it unsuitable for online automated detection. Magnetic ultrasonic testing does not require coupling agents, but it is difficult to excite ultrasonic waves in pipes with uneven surfaces. Industrial ultrasonic phased array probes are expensive to manufacture and have complex systems. Currently, such equipment is rarely seen in my country.

Based on the principle of ultrasonic measurement of oil casing wall thickness, oil casing manufacturers analyzed focusing probes suitable for automatic oil casing inspection. By selecting probes with appropriate focal lengths and crystal sizes, a full-coverage automatic oil casing wall thickness inspection system was constructed, resulting in significant improvements within the full coverage range. The design and selection of the probe are crucial to the thickness of the oil casing. Generally, the acoustic beam emitted by the circular crystal of the probe has a certain diameter, which expands with increasing distance. Selecting a probe that uses an acoustic lens to focus the acoustic beam locally increases energy.

After the oil casing inspection is completed, a thickness detector is installed to fully cover the area. The ultrasonic thickness inspection system is generally installed after the testing equipment is installed. Under the specified parameters, the probe angle is adjusted, and the rotation speed of the rotary motor and the scanning speed of the oil casing are determined.