The goal of this project is to develop electromagnetic sensors (based on eddy current technology) that can be integrated with a robotic platform (crawler) to conduct internal natural gas pipeline inspections. Combinations of sensor types will be used to assess a wide range of pipeline conditions, including corrosion (pitting, localized, and extended), mechanical damage, cracking, and seam weld defects. Small physical size and weight, as well as low electrical power consumption, are the primary design constraints for the crawler systems.
Battelle Columbus Laboratories – research products and project management
Columbus, Ohio 43201
Internal inspection of pipelines is an important capability for ensuring safe and reliable delivery of fossil energy products. However, not all pipelines can be inspected with current systems that move inside the pipeline propelled by the product flow. Inspection platforms that crawl slowly inside a pipeline are being developed to maneuver past the physical barriers that limit inspection. Small physical size and weight, as well as low electrical power consumption, are the primary design targets for crawler sensor systems. Pipeline inspection equipment in commercial use today has not been designed to meet these goals, rather, most equipment focuses on high-speed, long distance inspection.
For this project, Battelle will develop innovative electromagnetic sensors for pipeline crawlers. The electromagnetic techniques will incorporate moving permanent magnets, either rotating (for the case of sinusoidal eddy currents) or translational (for pulsed eddy currents). Such magnets reduce power consumption and improve energy coupling into the pipe wall. The successful development of this concept will augment other eddy current technologies currently available or being developed.
Battelle will develop sensor prototypes for bench scale testing on a representative defect by evaluating defect detection characterization potential, as well as implementation considerations including power, size, and mass. Development will include four subtasks: (1) establish resolution requirements for the sensor systems by combining historical incident defect data assessment criteria, (2) review general physical constraints and obstructions that challenge current internal inspection methods and review current pipeline crawler platforms to assess preliminary specifications for the sensor systems, (3) design and develop sensors that efficiently induce strong electromagnetic signals in the pipe using high-strength permanent moving magnets, and (4) perform bench scale tests to assess the performance of the electromagnetic sensor systems and ensure that they can detect all significant defect types and magnitudes.
Battelle will then identify and select sensors to be hardened and mounted on test bed inspection equipment. Detection and characterization capability will be quantified on a full range of defects under unpressurized conditions, using the inspection vehicles, pull rigs, and defect sets available at Battelle’s Pipeline Safety and Reliability Center. Sensor systems will be optimized to achieve desired performance levels.
Finally, if a suitable crawler platform is available at a reasonable level of development, the sensors with the greatest potential for pipeline inspection will be combined with the crawler system and tested. Final testing will be performed at the pipeline test facility or, if available, on an operating pipeline.
The image on the left shows the logarithm of the magnitude of the currents at the inside pipe wall. The current is strongest at the magnetizer poles, but becomes uniform at a distance of about half a pipe diameter away. The image on the right shows the current flow in the pipe, the direction as indicated by the arrows. While the current flow is complex near the rotating magnet poles, the current at a pipe diameter or more away from the magnetizer is uniform and sinusoidal.
This combined inspection tool will provide a means of non-destructive natural gas pipeline examination and provide a technique for inspecting a large portion of the pipeline infrastructure that cannot be inspected with existing equipment (unpiggable pipelines).
Battelle is developing a rotating permanent magnet inspection system where pairs of permanent magnets are rotated around the central axis. This alternative to the more common concentric coil method can be used to induce high current densities in the pipe. Along the pipe away from the magnets in either direction, the currents flow in the circumferential direction. Anomalies and wall thickness variations are detected with an array of sensors that measure local changes in the magnetic field produced by the current flowing in the pipe. The inspection methodology can be configured to pass tight restrictions and narrow openings such as plug valves. The separation between the magnets and the pipe wall is on the order of an inch (2.5cm). The strength of circumferential current produces signals on the order of a few gauss, which can be detected by hall effect sensors positioned between 8 and 40 inches (10 and 100 cm) away from the rotating magnets.
Accomplishments to date include:
All work under this effort has been successfully completed demonstrating the feasibility of the use of a rotating permanent magnet system for inspection of unpiggable natural gas pipelines. The details of the project and its results can be found in the project final report. A link to the report is included in the "Additional Information" section below.
Final Project Report [PDF-4.46MB]
April, 2006: Pipeline Inspection Technologies Demonstration Report [PDF-7.29MB]
Project Report 2006: Rotating Permanent Magnet Exciter for Pipeline Inspections [PDF-3.14MB]
Status Assessment [PDF-397KB]
Pipeline Inspection Technologies – Demonstration Report [PDF-7327KB] – participant in the sensor tests.
Topical Report - April 2004: "Gas Pipeline Pigability" [PDF-54KB]
Presentation and Proceedings Publication – “Rotating Permanent Magnet Exciter for Pipeline Inspection” – Natural Gas Technologies 2005, Orlando, Florida, February 2005.