WASHINGTON, DC — The Department of Energy's National Energy Technology Laboratory is developing the first technology that can detect flaws in plastic natural gas pipelines without disrupting pipeline operations. It potentially is applicable to almost one-quarter of the Nation's natural gas pipeline system.
Safe and inexpensive, the new technology deploys a tiny robot inside plastic pipelines. The robot carries a sensor controlled by a microcomputer which can identify cracks, dents, pinholes, and other anomalies by measuring variations in electric fields on the outside of pipe walls. The technology allows inspection of plastic pipelines from the inside without interrupting the flow of gas, taking them out of service, or digging them up. It can detect potential gas pipeline failures well in advance of a rupture.
More than 500,000 miles of buried polyethylene (plastic) natural gas pipelines have been installed over the past 40 years in the United States. They are part of a transmission and distribution system which encompasses more than 2.1 million miles of pipelines that serves 175 million industrial, commercial, and residential users in the United States.
Even as America's demand for natural gas continues to grow, ratcheting up the need for new pipeline capacity, its existing gas pipeline infrastructure is aging. Congress passed, and President Bush signed into law, the Pipeline Safety Improvement Act (PSIA) in 2002. This law requires enhanced maintenance programs and continuing integrity-management inspection of all pipelines where a failure could threaten public safety, property, or the environment. The Interstate Natural Gas Association estimates that implementing PSIA the first 10 years will cost industry more than $2 billion.
Pipeline operations are overseen by the Pipeline & Hazardous Materials Safety Administration (PHMSA), which is part of the Department of Transportation.
Traditionally, pipeline operators have sent pipeline inspection gauges called "pigs" through pipelines to clean and inspect them. "Smart" pigs use technologies such as ultrasonics or magnetic flux leakage to gauge the condition of pipe walls.
But "smart pigs" can't be used on many pipelines requiring inspection because of diameter restrictions, low pressure differentials/flows, pipe bends, or obstructing valves. This has created an urgent need to develop a prototype remote in-line pipe inspection system that can traverse all pipes while providing continuous, real-time detection of pipe anomalies or defects.
The new technology is part of a joint effort by PHMSA and NETL to develop inspection technologies which can detect mechanical damage, corrosion, and other threats to pipeline integrity. The regulatory agency declared it a success following demonstrations of it and other pipeline technologies conducted by the Batelle Memorial Institute.
The NETL sensor measures capacitance?the amount of electrical charge stored for a given electric potential?when an electric field is projected through the pipe wall by the probe's head. An absence of material?such as an abnormality in the pipe wall?within the electric field manifests itself as a decrease in capacitance.
The $575,000 project was developed exclusively in-house by NETL, the only national laboratory devoted mainly to fossil fuel energy. The next step is to continue testing and modeling work to produce several candidate versions of a plastic pipe defect detector. The immediate goals are to: enhance the sensor element's electrical field projection; increase the sensitivity of the sensor/probe design; improve sensor precision; and, continue ongoing improvements in hardware and sensing techniques.
The ultimate goal is to develop a capacitance imaging sensor to the point of viable commercial licensing to the private sector. Commercialization of this DOE-developed technology will benefit the Nation by making it possible to inspect almost one-quarter of its gas pipeline infrastructure without disrupting service. It is a new and cost-effective way to ensure the safety and reliability of a delivery system that transports one of the most vital components of America's energy supply.