Microwave Holographic Imaging of Nonmetallic Concentric Pipes

Abstract

Recently, nonmetallic materials, which are resilient to corrosion, low cost, and lightweight, have been exploited in many industrial sectors such as oil and gas field. A common application of them is in the form of pipes. Despite the advantages, these pipes can be damaged by delamination, defects, holes, and erosion, which may lead to major production failures or even environmental catastrophes. To prevent these issues, nondestructive testing (NDT) of these pipes is required to replace these components in a timely manner. Due to the fact that the traditional NDT methods are mostly effective for metallic pipes, microwave holographic imaging is proposed for inspection of multiple concentric nonmetallic pipes. Besides, standardized minimum norm (SMN) is used to mitigate the depth biasing problem in the proposed imaging technique. To reduce the complexity of the imaging system, we aim at using the narrowest possible frequency band using an array of receiver antennas. The performance of the proposed NDT method is validated through simulation and experimental data in two scenarios including the antennas placed outside the pipes and inside the pipes.