This document specifies a concept of application of phased-array guided-wave testing for various types of inaccessible structures, including buried pipelines.

Materials considered are carbon steel and stainless steel. This document does not include principles and criteria for underground facilities and the phased-array ultrasonic guided-wave testing scheme.

Furthermore, this document consists of an optimized process to draw reliable test results on inaccessible pipe cases. This document provides guidance on the use of phased-array guided-wave testing for various types of inaccessible structures, including buried pipelines made of carbon steel and stainless steel. The methodology outlined in this document includes an optimized process for achieving reliable test results on inaccessible pipe cases, with adjustments made to the beam pattern of the GW's focus location based on the defect type, location, and frequency. The process also takes into consideration the distribution diagram of the guided waves and the characteristics of the selected mode, with optimal focusing and steering achieved by adjusting the excitation time delay for each transducer based on the number of circumferential arrangement intervals of a given array probe.