First Robotic Device To Inspect Unpiggable Gas Transmission Pipeline

Full deployment and inspection of unpiggable pipelines has been achieved with Explorer II. Explorer II is an untethered, modular, remotely controllable, self-powered inspection robot for the visual and non-destructive inspection of 6- and 8-inch natural gas tranmission and distribution system pipelines.

The heart of this system is a Remote Field Eddy Current (RFEC) sensor able to measure the pipeline’s wall thickness. In addition, two fisheye cameras at each end of the robot provide high-quality visual inspection capabilities for locating joints, tee-offs, and other pipeline configuration. The robot is launched, operated, and retrieved under live conditions and can negotiate diameter changes, bends and tees up to 90 degrees as well as inclined and vertical pieces of the pipeline network. In its first full deployment of the system, more than 2,000 feet of a pipeline were successfully inspected.

Explorer II is the result of collaboration between industry and government in the wake of the enactment of the 2002 PHMSA/DOT ruling regarding the inspection of natural gas transmission pipelines. In order to address the need to inspect pipelines not inspectable (unpiggable) using conventional technologies, NYSEARCH, the R&D organization within the Northeast Gas Association, the National Energy Technologies Laboratory (NETL) of the U.S. Department of Energy, and the PHMSA division of the U.S. Department of Transportation invested in the development of a state-of-the art system for the inspection of pipelines in the 6- to 8-inch range.

Following a competitive review of proposals from various organizations, this funding consortium selected the National Robotics Institute at Carnegie Mellon University in Pittsburgh to develop a robotic platform able to carry into a pipeline a RFEC sensor which was developed by the Southwest Research Institute in San Antonio. Following the development and extensive testing of the prototype system in the laboratory and in the field, Explorer II was deployed for its first full pre-commercial inspection of a live unpiggable transmission pipeline by Invodane Engineering, of Toronto, Ontario, Canada.
The safeguarding of the integrity of the pipeline network in the United States is primarily driven by the pipeline integrity management rule for gas transmission pipelines issued by the Office of Pipeline Safety (OPS) of the U.S. Department of Transportation (DOT) on Dec. 12, 2003. Gas transmission pipelines in High Consequence Areas (HCA), i.e. areas with substantial population in the vicinity of pipelines, need to be assessed by their operators on a periodic basis. A variety of tools may be used to carry out this assessment including inline inspection tools (pigs), hydrotesting, and direct assessment. Other technologies are allowed on the condition that they provide equivalent to the above methods’ assessment of the pipe's condition.

The most important issue facing the industry in fulfilling its obligations under this rule is the inability of or lack of technologies able to provide inline inspection of pipelines that cannot be inspected using conventional smart pigs. The most prominent reasons that render a pipeline unpiggable are flow rates that are lower than needed to propel a pig or the presence of obstacles (such as valves, mitered bends, back-to-back in and out of plane bends) that may make the use of a pig impossible.