Ultrasonic Guided Wave for Pipeline and Storage Tank Corrosion Defect Inspection

Pipeline and storage tank corrosion defect inspection is one of the most important concerns for integrity management of oil & gas storage and transportation industry. Besides the internal inspection for pipeline, tri-axis high-resolution magnetic leakage inspection technique which is applied for trunk line inspection, long range ultrasonic guided wave technique based on Lamb wave is adopted for inaccessible part inspection in technique package for pipeline inspection in PetroChina. Corrosion in the tank floor and wall is a serious threat for environmental and economic safety. Owing to the capabilities of ultrasonic guided wave which are long-range, in-plane propagation, in-service storage tank floor/wall inspection becomes possible by employing an array of SH wave transducers mounting on the edge of the outer storage tank floor. At this point, ultrasonic guided wave shows its capability for pipeline and storage tank corrosion defect inspection. With the advancement of high-performance transducer, its capability will be boosted for even longer and remoter detection. Currently, ultrasonic guided wave system for pipeline could detect defect 200 m away in ideal case while 3∼6 m for storage tank floor in practical case. The complexity of the application of ultrasonic guided wave in tank floor inspection lies in the object containing multiple lap joint welds along the large diameter of the tank (up to 100 m) and the complicated reconstruction of the two-dimensional defect distribution information. The prototype of ultrasonic guided wave system for storage tank is able to detect defects along the edge of storage tank floor. Once the propagation mechanism at overlap joint welds is broken through, the system capability is believed to be greatly improved. The main scope of the paper is to introduce the ultrasonic guided wave principles and the system design of the inspection systems for pipeline and storage tank, respectively, including the system electrical module, hardware program and the module of data acquisition, analysis and processing. Besides, the field application study cases are included to show the capability of both systems and their potential for integrity management in oil & gas storage and transportation field.