Subsea Corrosion/Erosion Monitoring

Abstract

Young Technology Showcase Detection and monitoring are important prognostic means in preserving material integrity and reducing the life cycle cost of industrial infrastructure, ships, aircraft, ground vehicles, pipelines, oil installations, etc. Having better control of your infrastructure’s condition will enable you to optimize profitability and lower maintenance cost. Hence, monitoring an oil and gas pipeline will not only work as a precaution, but can also give information on when replacement or repair is necessary, thereby maximizing uptime. There is a huge need for reliable monitoring of pipe wall thickness, both topside and subsea. Even in topside applications, the conditions of operation may be hostile and problems such as large temperature variations, lack of space, fluid loading issues, and a host of other factors make development of such a tool a challenging task. Going subsea makes it even more demanding when you have to take into account factors such as high pressure and limited access. Over the past years, ClampOn has offered a corrosion/erosion monitor (CEM) for topside installations. Major advantages of this technology are its noninvasiveness, high repeatability, lack of any transducer movement, and high coverage. The measurement principle is based on dispersion of ultrasonic-guided wave modes, and by using electromagnetism, these waves are transmitted along the pipe wall without the sensor being in direct contact with the metallic surface. This makes it an excellent candidate for subsea use. It is installed on the outer pipe wall to produce real-time wall thickness information, not as a spot measurement, but as a unique average path wall thickness. With several successful installations topside, the ClampOn CEM has also found applications subsea, with the first unit installed at 2300 m in the Gulf of Mexico in February and another 10 units to follow in the future. Corrosion and erosion in subsea installations is detected by several methods. In topside applications, the alternatives are both more reliable and many. In subsea applications, the more hostile environment makes the detection of corrosion and erosion a more challenging task. Piggable pipelines are normally inspected at regular intervals and tracking of pipeline integrity is in general not problematic. Some unpiggable pipelines can be inspected using cable-operated tools, but such inspections are expensive and may require a shutdown of production. Subsea production templates, flow jumpers, manifolds, and flow lines can today only be inspected by preinstallation of corrosion/erosion sensors or by use of sensors controlled by remotely operated vehicles (ROVs).