The objective of this project is to develop, construct, integrate, and test/demonstrate an accurate and dependable in-line pipeline inspection tool for natural gas transmission and distribution pipelines (four to eight inches in diameter). The inspection tool will consist of an advanced sensor, based on eddy current technology, capable of detecting pipeline defects and a semi-autonomous robotic platform (for locomotion). The inspection tool will be capable of operating in variable pipe diameters and maneuvering through bends, tees, and pipeline valves.
Gas Technology Institute
Pipeline Research Council International, Inc.
Operations Technology Development, Inc.
Des Plaines, Illinois 60018
Regulations put in place in late 2003 have encouraged the development of technologies for inspecting unpiggable pipelines. In addition to the development of sensing technologies, robots for moving sensors through unpiggable pipelines are also under development. Among possible sensor technologies for unpiggable pipelines, the Remote Field Eddy Current technique stands out as a very good candidate. Its chief advantage is that its components can be much smaller than the diameter of the pipeline. The Gas Technology Institute (GTI) for example has used a 2” exciter coil for 6” pipe and a 4” exciter coil for 12” pipe.
At low frequencies, tens to hundreds of hertz, electromagnetic waves will not propagate down the bore of the pipe because these frequencies are well below the cutoff for propagation, which is at several gigahertz. About two pipe diameters down the pipe, this direct signal has all but disappeared. However, low frequency electromagnetic fields can travel out of the pipe and then re-enter the pipe at this point. Because attenuation for this path is much less at two pipe diameters, these indirect or remote fields swamp the direct field. However, this is exactly what is needed. Any defect near the sensing coils will alter the propagation of the waves back into the pipe and hence generate a signal that differs from the defect-free signal by a calculable amount related to the defect severity. It is anticipated that the method will have accuracy comparable to MFL. Its chief disadvantages are high power consumption and slow inspection speeds ( ½ mph or less).
This inspection tool will provide a means of non-destructive pipeline examination (quantitative evaluation of pipe wall loss) and provide a technique for inspecting a large portion of the pipeline infrastructure that cannot be inspected with existing equipment.
This project has been completed. The final report is available under "Additional Information" below.
Final Project Report [PDF-3.31MB] - October, 2006
Phase 1 Topical Report [PDF-3959KB] - October, 2005 - Gas Technology Institute
Project design review report [PDF-231KB] - July, 2005 - Gas Technology Institute
Status Assessment [PDF-378KB] - November, 2004 - Gas Technology Institute
“Remote Field Eddy Current Inspection for Unpiggable Pipelines”, Stephen F. Takach, Ph.D., Albert Teitsma, Ph.D., Julie Maupin, Paul Seger, Paul Shuttleworth, Proceedings of “Natural Gas Technologies 2005”, Orlando, FL, January 30 – February 2, 2005.