Application of ultrasonic guided wave for structural health monitoring of pipeline

Abstract

Corrosion and erosion in pipes are a major concern for the chemical industries specifically during the transportation of corrosive chemicals in steel pipes.Such problems can lead to potential unscheduled plant down time and economic losses which can be in the order of USD500K per day. Conventional ultrasonic thickness (UT) measurement is routinely used to quantify remaining wall thickness of pipes. In most practical transportation pipeline situations, the test surface is so large that apoint by point inspection of the entire surface is not feasible. As a result, industries seek a more efficient method to detect defects on their pipelines. In this work, the application of guided wave technology to address this serious industrial problem was quantitatively assessed in terms of technical capabilities, economic feasibility and suitability to be incorporated as part of the industry risk based inspection programmes. The technical capabilities are qualitatively and quantitatively assessed through nine performance objectives, which were formulated to determine if it can be adopted in the industry. Through laboratory study and field work at a paint pigment chemical manufacturing plant, it was shown that guided wave successfully met all nine performance objectives. It was demonstrated to be suitable for the detection of common defects such as pit and patch corrosion in a 12 inch nominal pipe size (NPS) Schedule 60 sulphuric acid pipeline.Key performance achievements found from this field study included a maximum inspection range of 260m from a single test location and the capability of detecting and monitoring growth of defect of up to 2% cross-sectional area loss. Through the use of the Inspection Value Method, it was shown in the case of the 2.75km acid pipeline the use of guided wave with follow-up UT inspection can value their system at a net present value (NPV) of RM0.9 million at the 25th year; in comparison to NPV of - RM0.1 million (negative) as a result of using conventional manual UT on its own.A new inspection procedure which incorporates the use of guided wave along with other conventional NDT methods was proposed which complied with API 579-1 Fitness for Service requirements.