An Experimental Study on Phased Array Ultrasonic Testing for Internal Inspection of Gas Storage Wells

A reduction in wall thickness, caused by corrosion, of the inner and outer surfaces of underground compressed natural gas storage wells is one of the main causes of failure. Therefore, taking wall thickness measurements is an important task during periodic inspection. This study proposes a corrosion detection technique based on the well’s shape using cylindrical convex ultrasonic phased array and develops a cylindrical convex phased array probe with 512 elements. Using an example well of ∅177 × 10.36 mm, the influences of process parameters such as active aperture, focal length, gain, and gate threshold are studied. In addition, an experiment is conducted on a sample well with artificial defects for parameters optimization. Next, experimental tests are carried out on the well at the test platform according to the optimized parameters. The results show that the proposed technique is of high sensitivity and efficiency for the detection of corrosion defects and is able to detect pitting corrosion of more than ∅2 mm and line corrosion of 1 mm width.