Service: Assess and Address
Client: Lake Huron Primary Water
Project Date: October 2012 - March 2013
Location: Greater London Region, ON
Type of Pipeline: Water Transmission Main
Diameter: 48-inch (1200mm)
Pipe Material: PCCP
The Lake Huron Primary Water Supply System (LHPWSS) serves about 500,000 people over eight municipalities in the London area and pumps about 44 million gallons of water per day (170 million liters). Its major transmission main was constructed in 1966 and made of 48-inch (1200-mm) Prestressed Concrete Cylinder Pipe. In October 2012, LHPWSS completed a leak detection survey and electromagnetic (EM) condition assessment of its major transmission main to proactively address deterioration on the pipeline. A subsequent verification of the EM data was completed in January 2013.
After a failure to a 48-inch (1200-millimeter) pipe in May, 2012, LHPWSS wanted to take a proactive approach in inspecting and maintaining its water transmission mains to ensure quality service delivery. This was the fourth failure on the Lake Huron pipeline; the others were in March 2010, 1988 and 1983. While 25 kilometers of the pipeline are twinned for redundancy, others are not, increasing their consequence of failure and making it important for LHPWSS to prevent a failure on a non-redundant section.
Results at a Glance
- 56 electromagnetic anomalies were identified in 47 kilometers of PipeDiver inspection
- Analysis confirmed 7 pipe sections with a high level of distress
- LHPWSS verified and replaced 3 high-risk pipe sections early in 2013
What was the Solution?
Because a large portion of Pipeline A is non-redundant, LHPWSS required inspection methods that would not require service to be shut down. To accommodate the operational conditions, LHPWSS and Pure Technologies used advanced non-destructive free-flowing technologies to inspect the transmission main for leaks, gas pockets and structural deterioration while the pipeline remained in service.
LHPWSS began its condition assessment project with a leak and gas pocket assessment using SmartBall® technology, a free-flowing tool that identifies acoustic anomalies associated with leaks and gas pockets. When acoustic anomalies are present, the data is analyzed to determine if it is a leak, gas pocket, or just an external sound. The tool is tracked using SmartBall Receivers (SBR) that are mounted along the pipeline at strategic locations.
After completing a leak detection survey, LHPWSS completed a non-destructive structural condition assessment using PipeDiver® technology, a tool used to identify wire breaks in PCCP. The tool is also tracked throughout inspection using SBR’s.
The PipeDiver tool is free-swimming and comprised of three parts – a battery module, electromagnetic (EM) module and a tracking module. The EM sensors are located on each fin and collect a magnetic signature reading for each pipe section to identify anomalies that are produced by wire breaks in PCCP, which are the main structural component for the integrity of the pipe. The tool is able to quantify the amount of wire break damage on each pipe section and is ideal for performing a baseline inspection of a PCCP pipeline that cannot be removed from service.
Before the inspections, Pure installed 33 SBR’s along the pipeline that were used to track both inspection platforms as they travelled through the pipeline.
For the SmartBall tool launch, LHPWSS and Pure mobilized at the Lake Huron Water Treatment Plant early in the morning to minimize service interruption. A small portion of the pipeline was isolated and depressurized to allow for manual insertion of the SmartBall. Once the tool was in position, the pipeline was put back into service and the tool started travelling down the pipeline. After 47 kilometers, it was retrieved in the Arva Terminal Reservoir by commercial divers.
After a day off to prepare the PipeDiver inspection platform, Pure’s staff mobilized at the Lake Huron Water Treatment Plant for the EM condition assessment. The launch, tracking and retrieval of PipeDiver technology are very similar to SmartBall leak detection.
The SmartBall survey located three leaks and eight gas pockets. Upon verification, the leaks were found to match up with existing features, such as valves and laterals, meaning the Lake Huron Pipeline had no leaks. The gas pockets were verified and likely caused by shutting down and restarting the pumps to insert the inspection tools. These pockets are expected to release themselves throughout the natural transmission cycle.
The EM inspection with the PipeDiver platform identified 58 pipe sections with electromagnetic anomalies out of approximately 10,000 pipes inspected, resulting in a distress rate of 0.6 percent, which is much less than the industry average of 4 percent.
While the majority of Pipeline A was in good condition, the inspection showed that seven pipe sections had a relatively high level of distress. Of these seven pipes, two are located within a twinned section and therefore have a lower consequence of failure. The remaining five high distress pipes are located within 3.5 kilometers of each other and are in the same vicinity of the 2010 and 2012 failures.
LHPWSS has verified and replaced the two most distressed pipes from the five that didn't have redundancy. The verification found that the pipe sections had longitudinal cracks in the mortar coating that spanned over half of the pipe, large corrosion areas centered amongst the cracks and scattered wire breaks throughout the corrosion areas.
Although Pipeline A is primarily in good shape, the identification of several high distressed pipe sections has allowed LHPWSS to proactively plan targeted rehabilitation to ensure the continued delivery of quality service and the prevention of a major pipeline failure. By determining the baseline condition of their entire primary large-diameter pipeline, LHPWSS now has a better understanding of the overall health of their system and can make informed decisions as they move forward with their pipeline management program.