Long-range visual inspection of mains using a tetherless robot

Improving preventive maintenance and emergency response while reducing associated costs

Gregory Penza, President, ULC Robotics, Inc., Deer Park, New York; Dr. George Vradis, Consultant, NYSEARCH, New York, New York; and T. Mark Andraka, Senior Engineer, PECO Energy Company, Philadelphia, Pennsylvania, and member, APWA UPROW Committee

The nation's pipeline infrastructure is aging, especially the gas distribution network, and this makes tools that inspect natural gas mains more valuable to utility companies than ever. The traditional approach to locating leaks and defects in pipelines relies heavily on multiple excavations, lots of guesswork and substantial manpower. This process is costly and often disruptive to the public.

For companies that manage underground infrastructures, the implications and potential for savings in the areas of preventive maintenance, inspection and emergency response cannot easily be overstated. The natural gas industry in the U.S. alone maintains more than a million miles of pipeline. A long-range untethered robot for inspection of underground pipelines has numerous advantages and now that technology is available.

Take the gas industry as an example. Gas companies in the U.S. spend more than 650 million dollars each year to assess and repair leaks. Although it is difficult to estimate specific dollars and cents, the fact that these repairs are done with either little prior assessment or very costly external inspection via excavation is certainly a significant contributor to this expense. Many companies make decisions as to whether to spot or section repair, reline or replace a leaking main based on evidentiary data such as maps, historical repairs, leak surveys and corrosion data—rather than on detailed knowledge of a pipe's actual condition. One can safely say that enabling companies to make more informed decisions on repairs could save the industry tens of millions of dollars annually.

Remote control robot enables cost-effective inspection
A long-range and easily deployable tool will greatly enhance the diagnostic and maintenance capabilities of gas operators. Inspection provides gas utilities with valuable information so they can determine whether to rehabilitate or replace certain pieces of pipe, and the best method of doing so. Such a tool can also be used for emergency maintenance by assisting in the location of: water infiltration into low pressure gas mains (eliminating or shortening costly main outages); cracked cast-iron gas mains; damaged steel mains; and obstructions from foreign material.

The Explorer robot (perched on top of a test pipe) features an articulated body that can travel great distances to generate high-resolution images of a pipe's interior.

The Explorer Robot is a remote-controlled and completely untethered, crawling robot developed by the Robotics Institute at Carnegie Mellon University with funding from NYSEARCH (the research, development and demonstration organization within the Northeast Gas Association) and co-funding from the U.S. Department of Energy through the National Energy Technology Laboratory. Pipeline inspection services using Explorer are available from ULC Robotics in Deer Park, New York.

Explorer's main advantage is its ability to travel up to one mile from its launching point and negotiate pipeline features such as offsets and bends, as well as travel through inclined and vertical pipe segments. Its innovative modular design resembles a series of sausage links strung together. Each of the system's seven modules (or links) houses components that enable it to function properly. Specially designed articulated and pitch-roll joints connect each module to the next, giving the six-foot robot the flexibility it needs to twist and turn (including sharp, 90-degree turns) as it travels through pipelines 6 to 8 inches in diameter.

Explorer is launched either vertically or at an angle using specially designed pressurized launching chambers and off-the-shelf fittings. Detailed procedures have been developed in order to allow safe launching into live gas mains. Once inside, Explorer can move about (forwards and backwards) for hours, feeding live images of the pipe's interior to the operator. Its fish-eye cameras at both ends, with their 180-degree field of view, take high-resolution images of pipe interiors that are wirelessly relayed back to an operator. The operator retains remote control of the lightweight, battery-operated robot throughout the entire inspection process.

The locomotor module houses dual-drive actuators that deploy and retract a set of three legs, equipped with custom-molded driving wheels. It can sustain speeds up to four inches per second, although speeds attained during inspection are typically lower to ensure proper image processing. The image management system allows the operator to observe either of the two views (or both simultaneously) and images could be dewarped and mosaiqued for better image analysis and storage.

Operational experience
The Explorer has been deployed and field-tested several times over the last few years and every time has met and exceeded expectations.

Explorer traveled over 2,500 feet within a low-pressure cast iron main in a field test with Con Ed.

One such deployment was with Con Edison in a residential neighborhood in Yonkers, New York. Explorer launched in the middle of an 800-foot segment in a live, eight-inch, low-pressure cast iron main bounded by a 90-degree tee on one end and a replacement plastic section at the other. The robot was launched and retrieved four times over two days—traveling more than 2,500 feet of pipe (with some debris) and making six turns through the 90-degree tee. The robot operated flawlessly and met all safety standards the utility imposed.

Additional companies, including Rochester Gas & Electric, have supported Explorer field deployments. A live, 1979-vintage high-pressure main at the State University of New York at Brockport campus was also inspected. The eight-inch main ran straight westward from the point where the launcher was installed for more than a half mile; about 75 feet in the other directions were two back-to-back elbows (one 90 degrees and one 70 degrees) followed by a long, straight segment. The field trial lasted four days, during which four launching and four retrieval procedures were performed and in excess of 6,000 feet of pipe was covered. During its travel in the pipe, Explorer performed eight successful elbow turns and traveled more than one-half mile in one direction from a single hole in one run, leaving ample battery-power. A number of mapped and unmapped features were verified.

Broad implications
While the Explorer has proven its value in pressurized gas environments, there are also plans to enhance its capabilities so it can operate in other environments, such as sewer and water infrastructure, and to provide additional inspection capabilities. Currently underway are (1) a Remote Field Eddy Current Sensor to incorporate non-destructive evaluation (NDE) capabilities and (2) a feasibility study to establish the use of a fiber-optic tether to enable operation inside plastic pipes as well as metallic water and sewerage force mains. Although the introduction of the tether will limit the range of the robot, it will allow it to operate in environments where it cannot be used today due to the inherent limitations of the wireless technology. Waterproofing is also being considered to enhance the robot's abilities to operate in pipes with significant water infiltration.

Gregory Penza can be reached at (631) 491-7473 or gpenza@ulcrobotics.com; Dr. George Vradis can be reached at (212) 354-4790 or Gvradis@aol.com; and T. Mark Andraka can be reached at (215) 841-6485 or mark.andraka@peco-energy.com.

Benefits of Wireless Robotic Approach

  • Minimizes required excavation—reducing manpower needs and downtime while improving worker and public safety
  • Better insight into condition of mains enables effective preventive maintenance and better decisions on whether to replace or rehabilitate—best method
  • Helps gas companies perform recently federally mandated inspections
  • Versatile technology has applications in industries beyond gas—including sewer and water