Microwave Measurement and Quantitative Evaluation of Wall Thinning in Metal Pipes

In this paper, wall thinning having values of 3 to 80% pipe thickness were detected significantly. In the experiment, a microwave network analyzer was employed to generate microwave signals propagating in the pipe where the frequency was swept from 47.38 to 47.47 GHz. By building up a resonance model for the microwave signals propagating in the pipe, and by analyzing the resonance results of the microwaves at the receiving port, we derived a nondestructive method that can determine the degree of the wall thinning in the pipe remotely. By comparing the experimental results with those derived by the theoretical analysis, it is shown that the errors of the evaluated results are less than± 0.5% of the pipe diameter. It indicates that high precision for quantitative evaluation can be achieved by using this nondestructive method.