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New Robotic Inspection Technology Helps ID Potentially Critical Situation
"We have not yet found a large diameter sewer too demanding for this robot system," Brousseau said. "The multiple sensor approach permits a large amount of synchronized data to be collected, and often it is the combination of sensors that allows full assessments on the pipe condition to be made in one inspection where results otherwise might be inconclusive. On this project the synchronized high resolution video, pipe ovality, robot pitch and water level data allowed us to come to very accurate conclusions about an anomaly that might otherwise not be possible."
The specific anomaly was reported to be located about 3,900 feet from the downstream manhole. The line was inspected from both directions in order to isolate the exact length of the anomaly. It was determined that the inspection could best be made during early morning hours when flows in the line would be at the lowest in order to "see" as much of the pipe as possible. Equipment was placed in the pipe about midnight to allow time to have it to the target site by about 5 a.m.
The robot weights about 650 pounds and has a 6,500 foot long, high strength tether with embedded fiber optic cable. The robot's mast can be lowered or raised to keep the 3D laser and camera out of the water for optimum visual observations and precise profiling of the inner pipe wall.
The robot is designed to fit through a standard manhole opening. It is lowered by a power winch to the base of the manhole. Once in the pipe, it is remotely controlled from a truck by the tether with a fiber optic, hydraulic and electric power cord with high a high strength external protective sheath. The robot moves on twin, independently powered tracks that permits it to traverse debris and turn around inside the pipe. The equipment normally is operated by a crew of three.
"To verify the condition of the entire trunk line we performed the inspection two times all the way to the anomaly, from both the up and downstream manholes," said Brousseau. "Each required about 10 hours to complete The robot drove upstream against the very fast flow without a hitch as we recorded excellent technical data."
The two inspections revealed an area of cracking about 262 feet in length. How the trunk line will be repaired has yet to be determined, but Brousseau said following completion of the DM Robichaud inspection, the full extent of the problem is known, allowing engineers to develop the most effective course of action.