New Sensor Accurately Maps Natural Gas Pipeline Corrosion

A prototype sensor that can quickly and inexpensively measure pitting and deterioration of natural gas pipelines has passed a critical test on its path to commercialization, the U.S. Department of Energy announced.

Known as the "conformable array," the sensor provided accurate, automated measurements of corrosion on the exterior of pipes during a recent field test at Southwest Research Institute (SwRI) in San Antonio. The sensor is being developed by SwRI, in cooperation with Houston's Clock Spring Company and the Department of Energy's National Energy Technology Laboratory (NETL).

The next-generation sensor leapfrogs over current methods for measuring external pipeline corrosion, according to Richard Baker, who manages the project for NETL. "Traditional technologies use manual measurements, while the new sensor is computerized and automated," Baker said. "This jump in technology means faster, more accurate, and less expensive corrosion measurements."

Integrity of the 1.2 million miles of natural gas distribution and transmission pipelines that crisscross the United States is essential to maintaining the Nation's natural gas supplies. Modernizing our national infrastructure, including the natural gas transmission and distribution system, is one of five specific national goals outlined in President' Bush's National Energy Policy. The Office of Fossil Energy is implementing a comprehensive pipeline infrastructure reliability program to help meet this important goal and enhance system reliability.

"The quantity of natural gas pipelines within the United States is staggering," Baker said. "If you laid the transmission and distribution pipelines end to end, they would reach to the moon and back twice, and with enough left over to circle the globe ten times - and this doesn't even count the individual service lines that run into homes and businesses. The operational integrity of every foot of these pipes is crucial to ensure continuing service."

Pipeline corrosion results from water, condensation, scratches, or other actions that can damage a pipe's protective coating and sensitive joints. Like rust on a car, pipeline corrosion can extend far down into the metal, well beyond the visual signs on the surface. Detecting and measuring corrosion are essential to determine the strength and life expectancy of the pipe.

The traditional method for detecting pipeline corrosion requires excavation to expose a pitted section of pipe, sandblasting to remove all dirt and debris, then manual measurements by a technician using a hand-held gauge and bridging bar. Time-consuming and expensive, this method is also subject to the technician's interpretation. The new sensor also requires that a pipeline be exposed, but it does not require sandblasting. This improvement substantially reduces costs and the time involved in the investigation. Because the method is automated, it eliminates individual interpretation and improves accuracy.

The flexible sensor is about 6 inches square, and designed to conform to the contours of the pipe. Two rigid circuit boards, each about 3 inches by 6 inches, attach to the sensor at opposite ends, making a rectangular unit about 6 inches by 12 inches. Rugged enough for field use, the unit is applied to a pipeline's exterior, and the sensor takes an image of the overlaid area. The unit is then moved, and new images taken, until a picture has been produced of the pipe's circumference.

The data is transmitted to a computer in real time through a cable attached to one of the circuit boards. The computer forms a composite image of corrosion from the individual snapshots, and analyzes the extent of the damage. The analysis is used to assess the strength and integrity of the pipeline, and the pipe can be repaired, replaced, or monitored as needed.

The conformable array was developed as part of DOE's Office of Fossil Energy's Delivery Reliability program, which develops technologies to enhance the reliability of natural gas delivery and meet future demand for clean-burning natural gas.