Industrial stent-like repairs for failing pipelines
and heat-treated to create strips about 0.025 inches thick.
“It works like a stent,” Ehsani said. “We coil the laminate around what is essentially a balloon with wheels and insert it into the pipe.” The area to be fixed might be 1,000 feet away from the pipe entry point, Ehsani said, which means that pipe can be treated even if it’s buried under buildings or roads.
“When the balloon is at the repair area, we pump in air and the laminate unravels and presses against the pipe,” he said. “After the epoxy has dried, we deflate the balloon and remove it.”
The superlaminates created at Ehsani’s production facility in Tucson, Arizona, are shipped in rolls hundreds of feet long, ready for insertion into leaky pipes. The main advantage of Ehsani’s laminates over most current methods is that prefabrication enables them to be strength-tested and gives them rigidity. This allows the laminates to be inserted into pipes in cylindrical coil form, which is retained as the balloon presses the laminate against the inside of the pipe.
Currently, most pipe fixes use the “wet lay-up” method, which involves soaking fiber in resin, applying it manually to the problem area, and waiting for it to set, or cure. Precise control is not possible and the strength of the repair cannot be determined until curing is complete, when samples of the cured fiber-resin can be tested to determine whether the fix is up to specification.
Unlike Ehsani’s laminates, the wet fiber-resin mix is too squashy to fix large areas. Health and safety are also a problem with wet lay-up because of harmful volatile organic compounds from the resin and associated accelerators and catalysts.
PipeMedic can be used to strengthen pipes, culverts, and aqueducts made from steel, cast iron, corrugated metal, clay, brick, concrete, and wood. The GTI test showed, however, that this superlaminate could actually replace, rather than strengthen, old pipes.
The release notes that many old gas pipelines have “drip pots” every 1,000 feet or so to collect condensation, which is then pumped out.
Modern gas pipelines do not need drip pots, and when gas companies upgrade older gas lines by inserting thin liners, the old drip pots leave 2-foot breaks in the original pipe. The liners prevent corrosion of pipe joints but depend on the structural integrity of the pipe to be effective. Without supporting pipeline, the liners balloon out of the gaps and explode.
The GTI test showed that PipeMedic could be installed as a standalone section of pipe, bridging the gap left by an old drip pot or T-junction, and withstand pressures more than four times those used in modern pipeline operation.
Utility owners are thinking about the next generation of subsurface pipework. Some want to line all new pipe with extra-thick superlaminates, so that when the external pipe eventually fails, the superlaminate becomes the de facto new pipe, but with no new construction.
“Carbon is much too expensive to construct a half-inch thick superlaminate liner that could withstand soil pressures and traffic loads,” Ehsani said. “So we have taken a page from the book of the aerospace industry and built a liner using an internal honeycomb structure.” This product, called StifPipe, is already in use in a rain catchment system in Brooklyn Bridge Park in New York.
