Gothenburg is Sweden’s second largest city after Stockholm, located between Oslo and Copenhagen in a low-lying estuary area near the Gota River, the primary source of drinking water for the port city. The City’s Sustainable Waste and Water Department serves a population of over 500,000 and manages 1750 km of potable water pipeline.
As part of a pre-emptive program to address non-revenue water loss and understand the condition of their pipes, Gothenburg wanted to conduct a condition assessment and leak detection survey on a series of large diameter transmission mains. The three pipelines were built in the 1960s and made of cement and steel, ranging in size from 1000 mm to 1200 mm.
Detecting leaks in large diameter transmission mains is challenging using conventional tools. Behroz Haidarian, Superintendent of the City’s Sustainable Waste and Water Department, took on the challenge with confidence.
“We selected the pipelines to inspect because these are critical for our drinking water supply, and had a history of breaks. These are large diameter supply lines, making it more difficult to detect leaks using conventional technology.”
The Gothenburg team recognized the value of detecting leaks, however small, to prevent these from developing into greater problems. While leaks occur most frequently on small-diameter distribution mains, leaks and ruptures on trunk mains are a much bigger concern for operators due to the relatively higher consequence of a pipeline failure.
In addition to physical losses of water caused by small leaks, the escaping water can eventually erode the surrounding soil making the area more prone to washouts or sinkholes, a major headache especially in densely populated areas. Leaking water can eventually find its way to the surface, or into sewers, overburdening the system. Unplanned excavations to repair breaks and unforeseen leaks can also erode consumer confidence in a public utility.
Gothenburg wished to avoid costly failures and unplanned repairs by gathering actionable data on the condition of their pipelines and addressing problems as they arise. They wanted to accurately identify leaks and pockets of trapped air, gather CCTV footage to identify visual anomalies, and take GPS points at select locations to improve their GIS data—without disrupting service.
Xylem applied its Decision Intelligence approach by recommending its highly reliable and precise Sahara leak detection solution for the condition assessment.
The Sahara platform comes with a variety of sensor tools to perform the inspection. This includes an acoustic sensor that performs leak and air pocket detection, and high-resolution video camera to assess internal pipe conditions, and in many instances, identify the type of leak and other details helpful for planning a repair before excavating.
“The Sahara tool’s CCTV function enabled us to go beyond leak detection and provided us with a condition assessment of the pipelines…overall we are satisfied with the useful and applicable results of the inspection….”
Behroz Haidarian, Superintendent, Sustainable Waste and Water Department
Because the Sahara tool is drawn by product flow via a small drag chute and is tethered to a data acquisition unit on the surface, it gives the operator close control to confirm suspected leaks, air pockets and other visual anomalies. The tool can visually confirm pipe irregularities, continuously recording, allowing for both real-time and post-processing analysis.
The inspections took place over four days, with the Sahara solution identifying seven leaks in 5.5 kilometers of pipe. The leak locations were marked above ground. After verifying and confirming the first three leaks, the tool’s accuracy was confirmed. This gave the City the confidence that the remaining four leaks would be verified and choose to replace the entire 1200 mm pipeline to avoid any potential failures.
Interestingly, of the pipeline leaks detected, none showed any signs of surface leaking. This reiterates the importance of not relying on surface inspections as the only means of detecting large-diameter pipeline leaks.
Based upon the accuracy of the Sahara technology and recommendations provided by Xylem, Gothenburg was able to avoid a costly failure while gathering valuable data regarding the overall condition of their pipelines. They are now better equipped to reduce water loss and make the best pipeline management decisions to aid in future capital planning
That’s the power of decision intelligence.