October 21, 2016Utilities Kingston (UK) prides itself in its openness to explore assessment options to understand the condition of its pipeline network. If a new inspection technology deserves a test, bring it on.
The message was brought home this year when UK agreed to pilot a new technology during a comprehensive condition assessment on its Dalton Avenue (North End) Pump Station Force Mains.
Conducting a condition assessment can pose a particular challenge if the pipe material is unknown, as each pipe type exhibits specific characteristics that affect its structural integrity. Despite the challenge, UK managed to work around the issue thanks to assistance from Pure Technologies, bringing its innovative technologies and engineering expertise to survey the pipeline for leaks, gas pockets and wire breaks.
RELATED: Pure Technologies at Forefront of Infrastructure Management
Utilities Kingston is unique in Ontario, combining water, wastewater, gas and electrical services, and a broadband fibre optics provider under one company. UK’s engineering and public works departments provide water and wastewater collection and treatment to 36,000 customers. The utility owns and operates more than 550 km (342 miles) of water mains, 500 km (311 miles ) of sewer mains, two water treatment plants and three wastewater treatment plants needed to service the local population of nearly 125,000.
With an average age of 35 years, each of its pipeline assets is entering a critical stage in its life-cycle. The subject pipeline had experienced a failure and as a result, the utility was interested in exploring technologies to help them implement a comprehensive asset management program for their network.Condition Assessment Deploys Various Screening TechnologiesUK retained Pure to perform a condition assessment inspection, consisting of a SmartBall leak detection survey, followed by a PipeDiver electromagnetic inspection and a transient pressure monitoring on the Dalton Avenue Sewage Pump Force Mains. The pipelines are both approximately 1,550 m (5,085 ft) long and follow a parallel route for approximately 1 km.
The older of the two force mains is 450 mm (18 in.) in diameter, constructed of ductile iron built in the late 1950s, and had failed several times over its lifetime. The newer of the two force mains is 600 mm (24 in.) in diameter, built from an unspecified concrete pipe from the early 1960s. As the pipe material specifics were still unknown at the time of the inspection, Pure elected to conduct a PipeDiver run to accommodate both possible types of pipe material – assumed by all to be bar wrapped pipe (BWP) and prestressed concrete cylinder pipe (PCCP).
Metallic Force Mains Typically Difficult to Assess
Historically, it has proven challenging to assess the condition of pressurized mains that carry sewage, especially those made with ferrous material. Metallic force mains have operational challenges that don’t apply to gravity sewer systems, and due to the presence of solids in the flow, force mains represent a far more abrasive environment than potable water systems.
In a 2009 report published by to the Water Environment Research Foundation (WERF), internal corrosion is rated as the major cause of failure in metallic force mains 26 percent of the time, ahead of all other causes. External corrosion (19.2 percent) and third-party damage (19.4 percent) round out the next most common sources of failures in metallic force mains.
RELATED: Pure Technologies Unveils Third Generation of Robotics Crawler (Video)
Utilities Kingston began the force main condition assessment by deploying the SmartBall platform, a free-flowing tool used to identify a variety of conditions in pressurized pipelines. The SmartBall tool travels untethered with the product flow for up to 14 hours, collecting information on anomalies associated with leaks and gas pockets.
The tool requires only two access points for insertion and extraction, and is tracked throughout the inspection at predetermined locations along the pipeline.
Following the SmartBall survey, UK deployed the free-swimming PipeDiver assessment tool, which features collapsible fins that allow it to pass through sharp bends, diameter reductions and butterfly valves as it is carried by the product flow.
The PipeDiver platform uses electromagnetic (EM) sensors to evaluate the existing condition of the pre-stressing wires, and is arguably the best available technology to determine the baseline condition of PCCP mains. EM inspections collect a magnetic signature for each pipe section to identify anomalies that indicate zones of wall loss and wire break damage. The presence of wire breaks in concrete pressure pipe is often a sign of impending failure.
During a forensics exercise on the 600-mm force main using 12-detector PipeDiver technology, it was revealed that the actual pipe material included 102 suspected metallic pipes, which were not identified as such in the original plan and profile drawings.
This included ductile iron, steel and unexpectedly, reinforced concrete pipe (RCP), which is not usually used in pressurized environments. Electromagnetic inspection of the RCP can only reveal anomalies on the circumferential cage and not the longitudinal bars.
Pure deployed its electromagnetic PipeDiver tool to conduct a quality analysis of the 450-mm pipe. The purpose of the inspection was to locate and identify steel and ductile iron pipes that have indications of wall loss.
This marked the first condition assessment of metallic pipe using the 24-detector PipeDiver in wastewater, an exercise that confirmed the validity of the tool’s sensor technology.
RELATED: PipeDiver Sets New Distance Record for the Inspection of a Live Water Main.
Results Lead to Actionable Information Regarding Rehabilitation In the end, one acoustic anomaly characteristic of transient gas on the 450-mm forcemain was identified during the analysis of the data collected during the SmartBall inspections. No anomalies resembling leaks were identified within the 600-mm forcemain.
Of the 650 pipes inspected with the PipeDiver tool, a total of 55 pipes in the 450-mm Dalton Avenue Pump Station Force Main had electromagnetic anomalies characteristic of localized wall loss. These results represent a high percentage of distress along the length of the pipeline and indicate a high risk of failure.
The data collected from both the inspections and transient pressure monitoring gave Utilities Kingston a better understanding of their real, not assumed assets. The results, which included a DIP risk of failure analysis, were used to complete a structural evaluation of the force mains, and have provided UK with actionable information regarding any necessary repairs or rehabilitation.