When your inspection task is to survey a critical pipeline for leaks, nothing is more satisfying than trusting your technology to predict the leak location and then standing by as the client excavates the area to find a flow of water within one meter of exactly where you said it would be.
The above-described 'leak-where-predicted' recently happened with the City of Ottawa, when Pure Technologies (Pure) deployed its SmartBall® inspection platform to locate leaks along a critical transmission main, as part of a long-term condition assessment program for the municipality. Over the past five years, Pure has used its suite of platform tools, including Sahara®, PipeDiver®, and PureRobotics®, as well as the free-swimming SmartBall device, for deployment on the City’s ongoing Drinking Water Transmission Main Condition Assessment Program.
Transmission main comprised of 1220mm (48-inch) lined cylinder pipe
The City’s potable water distribution system consists of 3,728 km of both local water mains and large-diameter transmission mains that move large volumes of water throughout the capital. The City has approximately 230 kms of transmission mains ranging in diameter from 600mm to 1980mm, (24-inch to 78-inch) subdivided into 96 segments for the purpose of a risk-based prioritization.
For the subject project, the City of Ottawa retained the services of Pure to perform a SmartBall tool inspection to identify and locate leaks and pockets of trapped gas along the Baseline Road Water Transmission Main, a high priority pipeline. The 1220mm (48-inch) diameter pipeline is comprised of Lined Cylinder Pipe (LCP) mostly constructed in the 1970s.
SmartBall tool chosen for its ease of use and sensitivity to small leaks
The SmartBall tool was chosen as an inspection platform for its sensitivity to small leaks, minimal pipeline modifications required for insertion and extraction and ability to inspect long distances in one deployment. The free-swimming, acoustic-based SmartBall assembly is inserted into the flow of a pipeline, traverses the pipeline, and is captured and extracted at a point downstream.
During inspection, the SmartBall tool’s location is tracked at known points along the alignment to correlate the inspection data with specific locations. As the SmartBall tool approaches a leak, the acoustic signal will increase and crescendo at the point when the tool passes the leak.
For the City of Ottawa project, five (5) surface-mounted acoustic sensors were placed along pipeline to track the SmartBall tool during the inspection. SmartBall receivers were connected to the sensors on the pipeline at the locations indicated to track the tool during inspection.
The SmartBall device was inserted into the pipeline through a 100mm drain near a hospital. Acoustic and sensor data was collected and recorded as the SmartBall tool traversed the pipeline for more than three kilometers. The SmartBall was then extracted from a reservoir using a Remotely Operated Underwater Vehicle and data was evaluated to identify acoustic anomalies associated with leaks and pockets of trapped gas.
Verification with ground microphones turned up unexpected results
From the survey results, Pure detected one (1) acoustic anomaly characteristic of a leak and zero (0) anomalies consistent with pockets of trapped gas.
Although Pure was confident in the SmartBall leak detection data, sometimes it’s worth a try to verify an anomaly with a complimentary technology. In this instance, ground microphones, regarded as a conventional a leak detection tool, were deployed to try and detect leak sounds. Although the suspect area was marked, neither Pure nor the client could pick up leak-related sounds from the ground microphone.
Even though the leak was not picked up by the ground microphone, Pure was confident that the acoustic signature from the SmartBall was caused by a leak, based on more than 15 years of experience identifying leaks. That confidence and experience proved right, and when the suspected area was excavated, the leak was located within a meter of where data analyst calculated the leak to be.
The results gave the City of Ottawa actionable data regarding the condition of their pipeline, and the City was able to fix the leak reducing non-revenue water loss and any potentially costly damage caused by the leak. It’s a great example of a proactive utility taking efforts to improve the reliability of its services.