Never Assume: Ontario utility surprised to find unexpected pipe material during force main condition assessment
The familiar adage, “never assume anything” certainly applies to the water and wastewater pipeline industry. The message was brought home to Utilities Kingston (UK) early this year when the utility was surprised to find unexpected pipe material on sections of pipe during a condition assessment on its Dalton Avenue (North End) Pump Station force mains.
Conducting a condition assessment on a pipeline 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 move forward thanks to assistance from Pure Technologies, bringing its inspection, risk assessment and engineering analysis services, along with its comprehensive suite of technologies to survey the pipeline for leaks, gas pockets and wire breaks.
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 potable water and wastewater collection and treatment to 36,000 customers. The utility owns and operates approximately 550 kilometres of water mains and 500 kilometres of sewer mains to service the local population of nearly 125,000.
With an average age of 35 years, each of their 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 pipelines.
Condition assessment includes various screening technologies
UK retained Pure to perform a condition assessment inspection, consisting of a SmartBall® leak detection survey, a PipeDiver® electromagnetic inspection and a transient pressure monitoring on the Dalton Avenue Sewage Pump 450-millimeter and 600-millimeter force mains. The two sewage force mains are both approximately 1,550 meters long and follow a parallel route for approximately 1 kilometer.
The older of the two force mains is 450-mm (18-inch) in diameter, constructed of ductile iron, was built in the late 1950s, and had failed several times over its lifetime. The newer of the two force mains is 600-mm (24-inch) in diameter was 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 free-swimming PipeDiver electromagnetic run to accommodate both possible types of pipe material – assumed by all to be bar wrapped pipe (BWP) and prestressed concrete cylinder pipe (PCCP). The PipeDiver inspection platform uses electromagnetic (EM) sensors to evaluate the existing condition of the pre-stressing wires. EM inspections collect a magnetic signature for each pipe section to identify anomalies that indicate zones of wire break damage. The presence of wire breaks in concrete pressure pipe is often a sign of impending failure.
Pure’s SmartBall tool was deployed on both pipes, checking for leaks and gas pockets.
Force main defects can vary from one pipe material to another
During a forensics exercise on the 600-mm force main using 12-detector PipeDiver technology, it was revealed that rather than BWP or PCCP, the actual pipe material included 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.
Furthermore, the inspection identified 102 suspected metallic pipes, which were not identified as such in the original plan and profile drawings.
Pure first: metallic pipe condition assessment using mini PipeDiver tool in wastewater
Pure deployed its electromagnetic 24-detector mini PipeDiver tool to conduct a condition assessment of the 450-mm pipe. The purpose of the enhanced electromagnetic inspection is to locate and identify steel and ductile iron pipes that have indications of wall loss.
Results lead to actionable information regarding rehabilitation
In the end, one (1) acoustic anomaly characteristic of transient gas on the 450-mm forcemain was identified during the analysis of the data collected during the SmartBall tool inspections.
No anomalies resembling leaks were identified within the 600-mm force main.
Of the 650 pipes inspected, a total of 55 pipes in the 450-mm Dalton Avenue Pump Station force main had electromagnetic anomalies characteristic of localized wall loss (DIP). 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 transit pressure monitoring gave Utilities Kingston a better understanding of their real, not assumed assets. The results were used to complete a structural evaluation of the force mains, and have provided UK with actionable information regarding any necessary repairs or rehabilitation.