Back to Top
Skip to main content
Design, Construction, and Field Demonstration of EXPLORER: A Long-Range, Untethered Live Gas Pipeline Inspection Robot System
Project Number

The goal of this project is to enhance the reliability and integrity of the nation's natural gas infrastructure system. Work conducted under this project will finalize the design, construct a prototype unit, and field demonstrate EXPLORER – a modular, remotely controlled, self-powered, long range, untethered robot system for the inspection of live gas distribution mains. 

EXPLORER - Pipeline Inspection System
EXPLORER - Pipeline Inspection System



Carnegie Mellon University Robotics Institute (CMU) – EXPLORER development
Northeast Gas Association (NGA) – project management

New York, NY 10036


With an aging gas pipeline infrastructure, utilities face ever-increasing needs for more frequent inspections of the distribution network. At present, in the case of a leaking pipeline, the operator has to make a safe and cost-effective decision as to whether to spot- or section- repair a line, reline it, or replace it, based on in-situ evidentiary data (i.e. maps, historical repairs, leak surveys, corrosion data, etc). Internal visual pipe inspection holds promise to become the most effective method to assess internal pipe conditions, and for this reason, the industry has concentrated resources in developing internal pipe inspection robots.

In order to explore the possibility of developing an advanced long-range untethered gas main inspection system for in-situ assessment and pipe-network cataloging, Carnegie Mellon University (CMU) undertook a study of possible configurations and technologies that could be integrated into such a robotic system. The result of this effort is EXPLORER, a real-time, remotely controlled, modular, visual inspection robot system for the in-situ inspection and imaging of live six- and eight-inch diameter distribution gas mains. EXPLORER is designed to travel through straight pipe and pipe diameter reductions, as well as negotiate elbows, sharp bends, and tees, using scripted routines and a combination of its on-board driving arms and steering joints. The system is sealed and purged, thus providing safe operation in natural gas environments, and is capable of negotiating wet and partially filled (i.e. water, mud) pipes.

The robot's architecture is symmetric. A seven-element articulated body design houses a mirror image arrangement of locomotor/camera modules, battery carrying modules, and locomotor support modules, with a computing and electronics module in the middle. The robot's computer and electronics are protected in purged and pressurized housings. Articulated joints connect each module to the next. The locomotor modules are connected to their neighbors with pitch-roll joints, while the others are connected via pitch-only joints. These specially designed joints allow orientation of the robot within the pipe, in any direction needed.

The locomotor module houses a mini fish-eye camera, along with its lens and lighting elements. The camera has a 190-degree field of view and provides high resolution color images of the pipe's interior. The locomotor module also houses dual drive actuators designed to allow for the deployment/retraction of three legs equipped with custom molded driving wheels. The robot can sustain speeds of up to four inches per second. However, inspection speeds are typically lower than that in order for the operator to obtain an image that can be processed. Given that each locomotor has its own camera, the system provides views at either end thus allowing observation during travel in both directions. The image management system allows for the operator to observe either of the two views or both of them simultaneously on his/her screen.

The EXPLORER's batteries, which can be of several types depending on cost and recharge limitations, have been sized for a “typical” eight-hour mission. The support modules are primarily to help center the robot in the pipe for launching and imaging purposes. The computer module at the center of the robot contains the custom-packaged 32-bit low power processor. It also includes any needed support hardware for robot control and communication between robot and operator.

Two different systems are used for robot launching into a live pipe. In the case of low pressure applications, the system employed is an off-the-shelf, to which has been attached a specially designed launcher tube. Specialized fittings are needed for the six-inch and eight-inch versions. In the case of high pressure, a specially designed vertical launch chamber attached to an off-the-self Mueller C1-36 tapping fitting is used.


A large portion of the natural gas pipelines in the United States cannot be inspected by standard in-line inspection tools. Upcoming regulations will require inspection and assessment of all distribution and transmission pipelines in the United States. However, inspection methods to meet this requirement are limited, and in the case of six to eight inch distribution pipelines, are restricted to tethered, in-line visual camera inspections of approximately one hundred feet in length. This requires numerous excavations at considerable cost to the industry and, ultimately, the consumer. The EXPLORER robot platform being developed removes these restrictions. The current robot design is capable of unrestricted movement in six to eight inch pipelines, which comprises the bulk of the systems distribution mains, and will provide visual images over distances of several miles. Future enhancements will permit the platform to carry other advanced sensors being designed with novel geometries and flexibility. These enhancements are currently being developed through other projects under the Delivery Reliability Program. These integrated inspection systems will be capable of long range inspection to much of the currently un-inspectable natural gas distribution pipelines. Continued development of these new inspection methods will aid in maintaining the high integrity and operation reliability of the Nation's natural gas pipeline infrastructure.

Accomplishments (most recent listed first)
  • Refined and integrated design concepts (mechanical power charge interface, wireless communication, power re-charge circuitry, and miniaturized fish-eye imager) into EXPLORER,
  • Detailed the complete design both mechanically and electrically,
  • Designed and constructed a 1,000-foot long test-circuit pipe network at CMU to simulate a typical underground run,
  • Fabricated and assembled all custom components,
  • Developed all software for the operating system,
  • Successfully tested EXPLORER in the lab and in the pipe-network at CMU,
  • Successfully conducted three demonstrations of the EXPLORER robot in high and low pressure natural gas distribution mains. EXPLORER has traveled over five miles in operating pipelines,
  • The robot design has been offered to a commercialization partner for commercial development, and
  • Under a different project, EXPLORER is being further developed to integrate advanced sensors for extended in-line pipe inspection.
Current Status

All tasks have been successfully completed and the project is in closeout.

Project Start
Project End
DOE Contribution


Performer Contribution


Contact Information

NETL – Daniel Driscoll ( or 304-285-4717)
CMU – Hagen Schempf ( or 412-268-6884)
NGA – Daphne Dzurko ( or 212-354-4790)

Additional Information

Final Report - October 2005: Distribution Gasline Robotics and Automation [PDF-2748KB]