Edia/News And Articles/Magnetic Flux Leakage Tool Advances Mortar Lined Steel Pipeline Inspection
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, including the San Francisco Public Utilities Commission (SFPUC).
Without a reliable way to assess the condition of cement-mortar-lined pipelines, the San Francisco Public Utilities Commission set out to develop its own technology.
The third-largest municipal utility in California, SFPUC operates and maintains a large, complex water-delivery system for 2.6 million people and businesses in San Francisco, Alameda, Santa Clara, and San Mateo counties. The gravity-fed system reliably delivers water across the state without using energy-intensive pumping. Eighty-five percent of this water comes from the Upper Tuolumne River Watershed in the Sierra Nevada Mountains, where it’s stored in the Hetch Hetchy Reservoir and then transported 47.5 miles via the San Joaquin Pipeline (SJPL) across California’s Central Valley to the Bay Area. The SJPL system includes three large-diameter pipelines (56–78 in.), generally consisting of cement–mortar-lined steel that have been operating for more than 80 years. The pipelines can deliver 300 mgd.
To minimize the number of unplanned outages and determine the remaining pipeline life, SFPUC sought a technology that could assess the wall thickness of steel pipelines. Unfortunately, no technology was available, so SFPUC funded research to develop such technology. The project focused on SJPL. Because capital improvement funds were limited, however, SFPUC officials knew they needed a technology that would do the job and allow the utility to efficiently administer SJPL rehabilitation funds, according to Margaret Hannaford with the Hetch Hetchy Water and Power Project (HHWP), SFPUC.
In the August issue of AWWA Opflow, read about how SFPUC developed Magnetic Flux Leakage technology for reliable assessment of mortar-lined steel water pipelines.
Magnetic flux leakage (MFL) is an electromagnetic method of nondestructive testing that is used to detect corrosion, pitting and wall loss in lined and unlined metallic pipelines.
Without a reliable way to assess the condition of cement-mortar-lined pipelines, the San Francisco Public Utilities Commission set out to develop its own technology. In a project from 2007 to 2010, SFPUC developed and used MFL technology to inspect its critical San Joaquin Pipeline.