Innovative Electromagnetic Sensors for Pipeline Crawlers
Internal inspection of pipelines is an important tool for ensuring safe and reliable delivery of fossil energy products. Current inspection systems that are propelled through the pipeline by the product flow cannot be used to inspect all pipelines because of the various physical barriers they encounter. Recent development efforts include a new generation of powered inspection platforms that crawl slowly inside a pipeline and are able to maneuver past the physical barriers that can limit inspection. At Battelle, innovative electromagnetic sensors are being designed and tested for these new pipeline crawlers. The various sensor types can be used to assess a wide range of pipeline anomalies including corrosion, mechanical damage, and cracks. Battelle is in the final year on a projected three-year development effort. In the first year, two innovative electromagnetic inspection technologies were designed and tested. Both were based on moving high-strength permanent magnets to generate inspection energy. One system involved translating permanent magnets towards the pipe. A pulse of electric current would be induced in the pipe to oppose the magnetization according to Lenz's Law. The decay of this pulse would indicate the presence of defects in the pipe wall. This inspection method is similar to pulsed eddy current inspection methods, with the fundamental difference being the manner in which the current is generated. Details of this development effort were reported in the first semiannual report on this project. The second inspection methodology is based on rotating permanent magnets. The rotating exciter unit produces strong eddy currents in the pipe wall. At distances of a pipe diameter or more from the rotating exciter, the currents flow circumferentially. These circumferential currents are deflected by pipeline defects such as corrosion and axially aligned cracks. Simple sensors are used to detect the change in current densities in the pipe wall. The second semiannual report on this project reported on experimental and modeling results. The results showed that the rotating system was more adaptable to pipeline inspection and therefore only this system will be carried into the second year of the sensor development. In the third reporting period, the rotating system inspection was further developed. Since this is a new inspection modality without published fundamentals to build upon, basic analytical and experimental investigations were performed. A closed form equation for designing rotating exciters and positioning sensors was derived from fundamental principles. Also signal processing methods were investigated for detection and assessment of pipeline anomalies. A lock in amplifier approach was chosen as the method for detecting the signals. Finally, mechanical implementations for passing tight restrictions such as plug valves were investigated. This inspection concept is new and unique; a United States patent application has been submitted. In this reporting period, a general design of the rotating permanent magnet inspection system is presented. The rotating permanent magnet inspection system is feasible for pipes ranging in diameter from 8 to 18 inches using a two pole configuration. Experimental results and theoretical calculations provide the basis for selection of the critical design parameters. The parameters include a significant magnet to pipe separation that will facilitate the passage of pipeline features. With the basic values of critical components established, the next step is a detailed mechanical design of a pipeline ready inspection system.
- Research Organization:
- Battelle Memorial Institute, Columbus, OH (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- FC26-03NT41881
- OSTI ID:
- 882458
- Country of Publication:
- United States
- Language:
- English
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