Robots Probe Underground Pipes3 Sep, 2007 By: Andrew G. Roe,P.E.
Municipalities and industries such as oil and gas are employing robots to gather new data on old pipelines.
For years, engineers and owners of pressurized pipelines have been seeking better ways to monitor the condition of buried pipes. In lieu of exposing pipes for inspection, pipeline owners have used various types of remotely controlled probes, cameras, and other devices to obtain information about underground pipes. The oil and gas industries have largely led the charge, driven by regulations and risks associated with catastrophic failures and explosions.
Recent developments indicate that petroleum industry techniques can be tailored for municipal applications, such as water distribution pipelines. Robotic systems are offering new capabilities in obtaining real-time data, capturing the attention of budget-conscious owners of aging infrastructure systems. The July explosion of a steam pipeline in New York City provided a wake-up call that buried utility pipes cannot be considered out of sight, out of mind.
The oil and gas industries began exploring ways to remotely clean and inspect pipelines in the 1960s. Devices known as “pigs” were inserted into pressurized pipelines and driven through pipes by product flow to remove deposits and other obstructions. Conventional pigs are still used today and have been supplemented by “smart pigs” that gather data on pipe diameter, wall thickness, corrosion symptoms, and other characteristics. Pigs have also been used by municipalities to clean water lines, but they have not gained widespread adoption in water systems, due to the numerous pipe size changes, valve restrictions, and other quirks common to water networks. Most existing water systems were also designed without the proper fittings needed to launch and retrieve pigs.
While sanitary sewers and other gravity pipelines have relied largely on conventional inspection methods and occasional video-based inspection to identify leaks and infiltration sources, water, steam, and other pressurized pipelines have lacked dependable inspection techniques. Motorized robotic devices originally developed for petroleum markets appear to be changing that situation. One technique for water systems uses a robotic crawler equipped with an electromagnetic system that sends a signal through the pipe wall to assess pipe conditions. Mississauga, Ontario-based Pressure Pipe Inspection Company (PPIC) has used its Remote Field Transformer Coupling (RFTC) technology to inspect more than 2,500 miles of water line around the world. The system is particularly useful in identifying breaks in the steel prestressing windings of prestressed concrete cylinder pipe, said Xiangjie Kong, PPIC’s technology manager.
Remotely operated vehicles are used to advance inspection equipment through pipelines. (Image courtesy of PPIC.)
PPIC’s system was used to inspect more than 100 miles of water pipelines for the City of Dallas Water Utilities (DWU). The RFTC technology helped DWU avoid hefty costs of replacing long lengths of pipe by identifying specific distressed pipe segments that have since been repaired.
Kong sees a growing need for robotic inspection of water systems. The water industry is “a bit behind” the petroleum industry in inspection technology due to perceived lower risks involved with water line failures, Kong said. But the gap may narrow as “people are paying more attention to underground infrastructure,” he said. Incorporating data into a GIS database can also facilitate pipe data analysis on a joint-by-joint basis.
PPIC also offers a leak-detection system that finds water line leaks as small as 0.25 gallons per hour. The system, known as Sahara , uses a sensor head tethered to a cable inserted into a live, pressurized pipeline. The sensor determines the exact location of a leak by identifying unique acoustic signals and estimates the magnitude of the leak. The system also can map pipes of unknown location. A third system, a stationary acoustic monitoring system, can help identify active deterioration in the prestressing wires of prestressed concrete. Another system under development is geared to adapt the RFTC system for use in live pipelines.
Other public and private entities are exploring robotic devices for multiple applications. Anil Agrawal, professor of civil engineering at the City College of New York, has been researching the use of ultrasonic and laser technologies to scan internal surfaces of steam heat, water and gas pipelines. His team has been testing ultrasonic crawlers in partnership with European agencies since 2004. To further enhance the intelligence of robotic systems, he foresees incorporating radio frequency identification (RFID) tags and GPS tracking to accurately locate pipe features. New developments in sensor technologies will also allow merging data from multiple sources, such as ultrasonic, laser, and ground penetrating radar. With numerous utilities located in congested areas, internal inspection using robotic crawlers is "the only viable option” in many cases, he said.
A robotic crawler is prepared for use in a heat pipe in Rotterdam, The Netherlands. (Image courtesy of City College of New York.)
Sarver, Pennsylvania-based Geospatial Corporation recently introduced an articulated Smart Probe that reportedly can be adapted to map and inspect numerous types of pipelines, ranging from small-diameter industrial and telecommunications conduits to large-diameter water, sewer, and petroleum transmission lines. The system uses multiple gyroscopic inertial measurements to measure angular and linear velocity changes in the x, y, and z axes as the unit moves through the pipeline.
At nearby Carnegie Mellon University in Pittsburgh , researchers have developed a remote-controlled, wireless crawling robot that captures near-real-time images of a pipe's interior in addition to other data. The team’s Explorer robot is segmented like a link sausage with front- and rear-fisheye cameras and lights. It can interact with a remote operator who controls and views it from a street-side control van at the excavation site. Consolidated Edison of New York recently supported the first deployment of the robot in Yonkers , where it inspected hundreds of feet of 8" diameter, live, cast-iron gas main sections originally installed in 1890.
As research and development progresses, still other applications are likely for pressurized and gravity pipelines. The aging infrastructure in the United States and other countries will likely place additional pressure on owners to maintain existing systems beyond their original design lives, and only reconstruct when necessary. With additional inspection and monitoring tools, owners can target their limited funds more wisely.