A high-efficiency nondestructive method for remote detection and quantitative evaluation of pipe wall thinning using microwaves

We report an efficient nondestructive evaluation (NDE) method to measure the pipe wall thinning (PWT) remotely using microwaves. A microwave vector network analyzer (VNA) and a self-designed transmitting and receiving (T&R) coaxial-line sensor were employed in the experiment to generate microwave signals propagating in the pipe where the frequency was swept from 14.00 to 14.20 GHz. A brass pipe with inner diameter of 17.03 mm, 1.0 mm wall thickness, 2.0 m length, and connected, respectively, with 6 joints having the length of 17.0 mm and PWT from 0% to 60% of wall thickness was measured. By taking the pipe as a circular waveguide of microwave, after building up a resonance condition and then solving the resonance equations, the evaluation of PWT was realized. By comparing the evaluated results obtained using our suggested method with the nominal inner diameters of the joints, the maximum evaluation error is found to be less than 0.05 mm, which is less than 0.294% of the inner diameter of the pipe, which indicates that a high precision evaluation method is established.