Case study - City of Rockville - Robotic Pipeline Inspection


Courtesy of Pure Technologies - a Xylem brand

Service: PureRobotics - Robotic Pipeline Inspection
Client: City of Rockville
Project Date: July 2010
Type of Pipeline: Water Transmission Main
Diameter: 24-inch
Pipe Material: PCCP
Length: 53,000 feet
Results: 3 pipe sections identified at risk
Insertion of Pipeline Inspection Robot

Pure Technologies (Pure) was contracted to provide robotic pipeline inspection of a critical 24-inch prestressed concrete cylinder pipe (PCCP) transmission line for the for the City of Rockville’s Department of Public Works (DPW). The City’s single 10 mile-long transmission main system traverses from the Potomac River to the Rockville city limits before branching off into the distribution network.

The PCCP transmission main was built under two separate contracts in 1957 and 1969. DPW needed to assess the condition and develop a management plan for the transmission main after it experienced a pipeline failure in early July of 2010. Approximately 53,000 feet were inspected in three phases between Mid-August and late-October utilizing closed circuit television (CCTV), electromagnetic and acoustic pipeline inspection technologies.

Pipeline Inspection Cameras

Assessing the condition of a PCCP transmission main is best performed using a combination of non-destructive testing technologies, internal visual inspection, engineering science, and experiential judgment. The primary goal of an inspection is to provide an understanding of the condition of the structural component that provides the pipe’s strength—the prestressing wire. An electromagnetic inspection provides a non-destructive method of evaluating the baseline condition of the prestressing wire and establishes a baseline of the current condition of a pipeline. This equipment is integrated into a robotic crawler system that traverses the pipe. The robotic crawler was also outfitted with three high-resolution CCTV cameras that are used for both navigation of the equipment as well as conducting a visual inspection of the pipe with the goal of identifying cracks, spalls, carbonation, and other defects.

The pipeline inspection is tethered to the surface

Analysis of the electromagnetic inspection data revealed that several pipes exhibited prestressing wire break damage. Specifically, three pipe sections were identified near the previous failure locations that exhibited electromagnetic signals consistent with wire break damage. DPW took a proactive approach to managing the transmission main by immediately replacing these sections.

In total, 3,310 pipe sections were inspected by Pure Technologies, not including special sections such as gate valves and steel pipes. A total of 21 pipe sections (0.6% of the total) were identified as having electromagnetic anomalies consistent with wire break damage. The findings of the electromagnetic and acoustic inspections created a baseline for the City of Rockville to begin management of their critical water distribution asset.

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