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Bloem Water Proactively Manages Bulk Pipeline Smartball

TRA Verification
Leaks on small-diameter distribution pipelines are the most common leaks a utility encounters. However, locating and repairing leaks on large-diameter transmission pipelines is also important in maintaining safe and reliable service delivery. These leaks are often more sparse, and therefore more difficult to locate which can lead to prolonged leakage and extensive water loss.

Utilities that have a leak detection program in place for their large-diameter transmission mains often achieve greater reductions in Non-Revenue Water (NRW), which is the amount of water lost before it reaches the customer. Furthermore, a leak detection inspection is a valuable step as part of a condition assessment program. Utilities can avoid expensive capital replacement programs by gathering real data on the condition of their pipelines, and addressing problems as they arise.

Bloem Water, who provides water services to the central region of South Africa, recently implemented an asset condition assessment project that included a comprehensive leak detection program using inline methods on a strategic 1200-millimeter (48-inch) Prestressed Concrete Pipe (PCP) that supplies the City of Bloemfontein with roughly 60 percent of its drinking water.

Inline leak detection is the most accurate method of locating leaks because it brings the acoustic sensor directly to the leak source, unlike traditional methods, such as correlators and listening sticks. These techniques lack the accuracy needed to locate leaks in larger pipes because the sound of a leak dissipates rapidly in large-diameter pipes.

Both SmartBall® and Sahara® leak detection technologies were successfully applied for Bloem Water. The total inspection covered 103 kilometers between De Hoek Reservoir and Brandkop Reservoir and identified 30 leaks.

To maximize efficiency, the SmartBall tool was used first to cover large sections of the distance in single deployments. The tool is a free-swimming leak detection platform that operates while the pipeline remains in service. It is equipped with an acoustic sensor that identifies acoustic anomalies associated with leaks; the acoustic signature is then analyzed to determine if it is a leak, air pocket, or an external noise.

SmartBall tool before insertion

The SmartBall tool prior to insertion.

Staff during tool extraction

Staff retrieving the tool at the end of inspection.

To maximize efficiency, the SmartBall tool was used first to cover large sections of the distance in single deployments. The tool is a free-swimming leak detection platform that operates while the pipeline remains in service. It is equipped with an acoustic sensor that identifies acoustic anomalies associated with leaks; the acoustic signature is then analyzed to determine if it is a leak, air pocket, or an external noise.

The SmartBall inspections were followed by selective Sahara audio and visual surveys to provide visual confirmation on the location of the leaks in order to aid in the interpretation of findings and plan interventions. The Sahara tool is a tethered inline leak location and condition assessment technology that pinpoints the location of leaks while at the same time inspecting the internal condition of the pipeline and verifying the cause of leakage using a combined acoustic hydrophone with an integrated CCTV camera.

Visual leak verification was also performed at all accessible components along the pipeline.

The leaks were identified and classified as either pipeline leaks (i.e. on the pipe barrel itself), component leaks (i.e. at valves, air valves, scour valves, etc.) or off-take leaks. The majority of the leaks were found to be at components while pipeline leaks were detected mainly on joints (i.e. where the PCP was connected with prefabricated steel joint pieces). Some of the leaks on these joints may be attributed to poor bedding, improper VJ connections, among other things.

The estimated water loss based on indicative leak sizing categories amounts to approximately 1200 kiloliters per day. Interestingly, of the pipeline leaks detected, only three leaks showed any surface signs of leakage. This reiterates the importance of not relying on surface inspections as the only means of detecting large-diameter pipeline leaks.

The findings of the latest leak detection surveys were compared to that of a previous Sahara leak detection inspection project performed in 2007-2009 to establish trends. This information, combined with a first order engineering evaluation of available pipeline design and manufacturing data, the failure history of the pipeline, operating records and the hydraulic behavior of the system were incorporated into a risk assessment model for the pipeline.

The leak detection findings, engineering evaluation and risk assessment were factored into the development of a pipeline-specific management strategy. Bloem Water can now implement this strategy as a guideline to proactively manage this valuable asset in order to prolong its remaining useful life, avoiding expensive capital replacement of the asset.

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