Utilities across the country are experiencing an increased rate of pipeline failures. In addition to problems precipitated by an aging water infrastructure, a lagging economy is affecting large-scale capital projects needed for repairing, replacing, and improving infrastructure. With funding gap estimates ranging between $200 billion and $1 trillion over the next 20 years, utilities must find cost-effective, accurate ways to identify system weaknesses and make appropriate improvements, while maintaining reliable service to customers.
For the San Diego County Water Authority (Water Authority), proactive management of their water delivery system has been an ongoing priority. The system is comprised of 5 pipelines which supply approximately 80 percent of San Diego County’s water. With little rainfall over the last few years, California is experiencing extreme drought conditions that make the reliability of supply systems like the Water Authority’s even more critical.
A major artery of the Water Authority’s system in the northern part of the county was constructed in the late 1950’s and is an important link between the Metropolitan Water District of Southern California (MWD) and the Water Authority. This link is made up of 72- and 75-inch mortar-lined and coated steel pipe. In order to ensure the structural reliability of their mortar-lined and coated steel pipelines, the Water Authority has used advanced Magnetic Flux Leakage (MFL) to assess different portions of the water delivery system since 2011. In 2013, 11 miles were assessed, while in 2011, 5 miles were completed.
In November 2014, nearly 10.5 miles of inspection were completed on the pipeline between MWD and the Water Authority using MFL. The project required close co-ordination and thorough planning, as MFL inspections provide high-resolution data about defects in the pipe wall. Verifications of the data collected during this inspection were completed and overall the pipeline was in good condition and minor repairs were made.
Each of the various pipe designs used in water networks across the United States has a specific life expectancy and operational requirements. Although some pipeline materials have well-developed, effective inspection technologies, assessing metallic water pipelines with mortar lining has historically posed a challenge for utilities. The development of MFL technology now allows operators to assess metallic mains with mortar coating and represents the highest available resolution in the market.
The technology enables non-destructive testing to detect corrosion, pitting, and wall loss in metallic pipelines. Magnets are used to temporarily magnetize the pipe, allowing magnetic field changes to be recorded and analyzed. If there are no flaws in the pipe wall, the magnetic flux is uniform. If internal or external flaws are present, such as pitting, corrosion, or other forms of damage, the magnetic flux is distorted beyond the wall of the pipe, and this distortion or leakage is measured by Hall Effect sensors.
Through the proactive assessment of its critical steel aqueduct, the Water Authority provides an excellent example for utilities looking to manage their metallic pipelines.