One of the perks of working in trenchless technology is the ability to get outside and get your hands dirty while safeguarding our community’s infrastructure. That holds doubly true when working in sunny southern California in November.
Over the course of 23 days, San Diego County Water Authority (SDCWA) worked with PICA USA to inspect six miles of steel pipeline and ensure its underground assets can be operated safely for years to come.
The SDCWA owns and operates more than 310 miles of pipeline serving the San Diego region, conveying water to 24 member agencies. The WA’s pipeline network ranges in size from 39 in. to 120 in. and is comprised of a variety of materials, including PCCP, steel, RCCP and others.
SDCWA’s Pipeline 3 was built in 1959 using Pre-stressed Concrete Cylinder Pipe (PCCP). After experiencing a series of PCCP failures elsewhere in their system, in the early 1980s the WA decided to rehabilitate the pipeline by installing a steel liner within the PCCP. The finished diameter of the steel liners was 63.5 in.
To install the liner, large access portals were installed. The portals were installed intermittently and consisted of approximately 40 ft of pipe being removed, allowing 20-ft steel sections to be rammed into the existing PCCP pipe. After the relining, the access portals were finished with welded steel pipe specials of 66 to 68 in.
The WA’s Asset Management team assigned a useful service lift of 75 years to the lined steel pipe, so by 2017, the pipeline was approaching its estimated half-life. The Asset Management Program at SDCWA recommends inspecting all of their pipeline assets as they approach half their useful service life. This allows them the ability to more effectively manage capital improvement plans, while confidently knowing the condition of high consequence of failure assets.
A Request for Proposals was issued for pipeline inspection firms to provide pipe wall condition assessment reports on over five miles of both the steel lined portions of pipe, as well as the steel special access points. After reviewing multiple proposals, SDCWA selected PICA USA to pull the ElectroMagnetic Inspection Tool (EMIT) through 4.9 mile of steel liners, and use their Internal Bracelet Probe to locally scan 1,580 ft of steel specials.
PICA’s EMIT tool employs an electromagnetic inspection solution called Remote Field Testing (RFT). The EMIT is a modular tool that can be inserted piece-wise through openings as small as 18-in. diameter and assembled in the pipe. Its array of detectors is then spring loaded against the inside contour of a pipe and the entire tool is pulled by means of an above-ground winch. A winch is attached to the front of the tool and is used to pull it through the pipeline, up to 3,500 ft in a single pull.
As the tool scans, it comprehensively collects pipe wall thickness information around the circumference and every one-tenth of an inch along the pipe. Redundant odometers affixed to the tool’s suspension system track distance traveled, and an embedded Inertial Measurement Unit (IMU) detects heading changes. Data is stored onboard the tool and integrated batteries negate the need to run external power along the wireline.
PICA’s Bracelet Probe similarly employs electromagnetics and is a handheld tool that was designed to scan the internal curvature of a pipeline. Tool components are loaded piece-wise into the pipe at the nearest access point and conveyed by a three-person crew to the inspection location. The probe is then assembled at that location and used to circumferentially scan the PCCP pipe. With a width of 2 ft, multiple scans would be performed at each location to capture the extent of the PCCP at that location.
After a few months of project management and planning, the WA shutdown Pipeline 3 and allowed inspections to take place over 35 days in fall 2017. On the first day, the WA provided a 20-in. access port for EMIT insertion. Once the tool was built within the pipeline, it was conveyed approximately 2,500 ft per day. At the end of each day, batteries would be disconnected so that they may be charged offsite and the inspection tool would stay within the pipeline overnight. The next day, the batteries would be reconnected, the winches repositioned and scanning would continue down the line. The EMIT tool completed 16 scans, covering 4.9-miles over 22 days.
While the EMIT scans took place, a separate team of PICA technicians focused on the Bracelet Inspections. This inspection team would enter the pipe, perform inspections and exit the pipeline each working day. In total, 21 locations were scanned, covering 1,580 ft over 23 days.
For both sets of inspections, the WA provided confined space entry support and subcontracted traffic control when required.
Data, Results, Verification
Data analysis and reporting was delivered in two phases. It was critical to the WA that imminent failures and areas of concern were flagged immediately. This would allow for rehabilitation of the compromised areas while the pipeline was already out of service and dewatered. A dedicated data analyst was mobilized into the field with the express purpose of analyzing data and delivering a preliminary report within 48 hours.
SDCWA also wanted to validate and verify the accuracy of the inspection data. To accomplish this, WA personnel installed magnets within one of the EMIT pipe sections unbeknownst to PICA. The magnets were arrayed in the shape of a smiley-face emoji and PICA analyst was able to locate and report them, providing the WA with a degree of certainty that the inspection tool was operating as promised.
Once the fieldwork was completed, a thorough analysis of the data was performed offsite. The final report focused not only on the imminent failures but also less severe corrosion that could be addressed during subsequent pipeline shutdowns.
The SDCWA’s Asset Management Program is more than 25 years old and continues to integrate emerging technologies with tried-and-true methods. With this section of Pipeline 3 successfully inspected, the WA has been able to direct their condition assessment efforts to other high priority assets. Inspection projects like these help protect our underground infrastructure and ultimately helps safeguard our neighbors.