The Southwest Research Institute (SwRI) (San Antonio, Texas) has patented a new technology to inspect coatings on pipelines installed through horizontal directional drilling (HDD), a trenchless technology that has gained widespread acceptance over the past 20 years.
The technology can determine both the extent and the configuration of any damage to the coating that occurs during HDD installation, according to SwRI officials.
“Our system provides a significant improvement over existing technologies that are only capable of estimating the extent of coating damage but do not provide information about the configuration of that damage,” says Pavan Shukla, one of the two SwRI engineers who invented the technology.
Traditionally, workers install pipelines in open trenches—a method that disturbs roads, sidewalks, and environmentally sensitive areas, according to the institute. With this installation method, coating damage can be detected through various conventional techniques from the surface above the pipeline.
HDD, however, is used for pipelines that run under surface features, such as rivers, roadways, and railways—where trenching is not desirable or practical. Special methods and devices to detect coating damage and corrosion of HDD-installed pipelines are necessary, SwRI explains, because access to the surface above the pipeline is limited.
Additionally, the HDD installation tends to damage coatings, as pipeline segments are pulled through a borehole and come in contact with soil, rock, and other debris. SwRI says its technology can determine damage to the coating along both the length and around the circumference of a pipeline.
According to SwRI, the technology should be used to inspect pipeline segments for coating damage immediately after HDD installation. Engineers place a magnetic field sensor array within the pipeline, with the array generally matching the interior profile of the pipeline but at a smaller size.
As the array moves along the pipeline, engineers analyze the output from each sensor to determine the location, configuration, and extent of coating damage.
“It is important to determine the condition of the coating on the pipeline segment immediately after installation,” says Jay Fisher, the co-inventor of the technology. “Understanding the extent of any damage to the coating will help determine if it is too severe to be protected by a cathodic protection system—which inhibits the oxidation process and prevents corrosion—or whether it can be repaired or needs to be replaced before it is placed into service.”
Additional field testing is needed before the technology can be licensed for commercial use, according to SwRI officials.
Source: SwRI, swri.org.