The Department of Energy’s (DOE) National Energy Technology Laboratory (NETL) said last week it has spent $575,000 to develop a new robotics system that will be capable of detecting flaws in polyethylene natural gas pipelines without disrupting operations. These plastic distribution pipes makes up almost one-quarter of the nation’s natural gas pipeline system.
The Pipeline Safety Improvement Act (PSIA) in 2002 required 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 of America estimated that implementing PSIA would cost industry more than $2 billion in the first 10 years.
In addition to the high cost, there also are inspection challenges. More than 500,000 miles of buried plastic natural gas pipelines have been installed over the past 40 years in the United States. But much of it can’t be inspected and cleaned using traditional pipeline inspection gauges called “pigs.”
“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.
DOE said the new NETL sensor technology currently under development will be a safe and inexpensive solution. It involves a robot that will be deployed carrying a sensor controlled by a microcomputer that can identify cracks, dents, pinholes and other anomalies by measuring variations in electric fields on the outside of pipe walls. The 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.
This new technology will allow inspection of plastic pipelines from the inside without interrupting the flow of gas, taking them out of service or digging them up. It also will be able to detect potential gas pipeline failures well in advance of a rupture, DOE said.
The Pipeline & Hazardous Materials Safety Administration declared the new technology a success following demonstrations of it and other pipeline technologies conducted by the Batelle Memorial Institute.
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.
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