Non-invasive inspection method for unpiggable pipeline sections
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New pipeline integrity rules require that operators directly assess pipeline sections that previously could not be inspected by conventional on-line inspection processes, such as smart pigs. The new rules require direct assessment of these lines or sections of lines. Hydrostatic testing may be an option in these cases, but can be very costly. Clearly, other technologies would be desirable if they produced inspection results that give the operator assurance the line in questions will meet operational conditions. One of the emerging technologies to address this need is long-range ultrasonic inspection. Long-range ultrasonic testing or guided-wave ultrasonic testing was commercially introduced in early 1998 for in-service monitoring of pipes and pipelines. The oil, gas, and chemical process industries now use it for detection of corrosion and other metal-loss defects, and it is gaining acceptance as a valid means of assessing the condition of pipes and pipelines where inspection preparation or access is difficult or expensive. The rise of the technology is especially significant in view of the recent United States government emphasis on pipeline condition assessment and the lack of a proven technique to inspect the pipelines that cannot be evaluated with 'smart pig' technology. The technique (as represented by the Teletest system) has now been extensively used in the field for evaluating the condition of pipes in the range of 2-48in diameter, and has performed well in identifying corrosion in pipes in a variety of situations. As with any new technology, a crucial stage in gaining acceptance by industry as a proven inspection and monitoring tool is the performance achieved in real field situations. This paper describes process now being used by PetroChem Inspection Services to inspect buried and above-ground pipeline sections.