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University Prof. Develops Lightweight Pipeline Material

Mo Ehsani holds a section of lightweight pipe. (University of Arizona)

Mo Ehsani holds a section of lightweight pipe. (University of Arizona)

A University of Arizona engineering professor designed a new, lightweight underground pipe material, with a company he founded taking the invention, as well as the innovative manufacturing methods, to market. Mo Ehsani, Professor Emeritus of Civil Engineering at Arizona (pictured left), will discuss the new pipe material next week at American Society of Civil Engineers Pipelines 2012 Conference in Miami Beach, Florida.

Ehsani devised not only the material for the underground pipe, but also a manufacturing process with the potential to turn the economics of the pipeline business on its head. Most underground pipelines today are made of concrete or steel, which are heavy and difficult to manufacture and transport. Because of their weight, concrete and steel pipes are built in short sections to fit on standard 18-wheel trucks.

Ehsani’s new pipe, on the other hand, consists of a central layer of lightweight plastic honeycomb, similar to that used in the aerospace industry, sandwiched between layers of resin-saturated carbon fiber fabric. Ehsani says these materials in combination are as strong, or stronger, than conventional steel and concrete pipes. Moreover, the new pipe can be built at a construction site as a single section of virtually infinite length, rather than shipped in small pieces.

While an infinite length of pipe may not be feasible, very long lengths of pipe — measure in hundreds or thousand of feet — are possible, says Ehsani, requiring a small fraction of the number of joints needed today to connect 20-foot sections of pipe. The secret is in the manufacturing method, which would layer the carbon fabric, honeycomb plastic, and glass fiber around a tubular mold called a mandrel. The pipe would be manufactured on site by simultaneously adding more material at one end of the mandrel, while sliding off the finished pipe at the other end of the mandrel.

The carbon fiber, resin and plastic honeycomb are all very light materials that can be transported to the job site, with the mandrel on a flatbed truck platform that could continuously make and lay the pipe in one operation. “You start making the pipe on, say, a 20-foot mandrel, and pull off 18 feet so you have two feet left on the mandrel,” says Ehsani. “Then you just move the truck forward and drop the pipe in the ground, and keep adding pipe.”

This simultaneous manufacturing and installation method would change the economics of today’s pipeline industry. The carbon fiber, resin and plastic honeycomb can be transported at a fraction of the cost of conventional prefabricated steel and concrete pipe, sharply reducing both the manufacturing and transportation costs. “That is a big, big breakthrough in the pipeline industry that has implications for natural gas, oil, water, and sewer pipes,” says Ehsani.

The genesis of the discovery goes back to the 1980s, when Ehsani and Arizona engineering colleague Hamid Saadatmanesh conducted research into repairing and retrofitting bridges and buildings using fiber-reinforced polymers. Over the years Ehsani has refined the process to use smaller amounts of higher-quality materials. “So instead of cheaper glass fabric, we use carbon,” Ehsani notes. “Instead of polyester resin, we use epoxy. Because we don’t have a solid core, we can afford to put the expensive material on the skin.”

Ehsani founded the company QuakeWrap in 1994 as an engineering services and fiber reinforced materials business in Tucson. Ehsani retired from the full-time Arizona faculty in 2009. Because of the potential to manufacture and install underground pipes in infinite lengths, QuakeWrap calls the new pipe InfinitPipe. Ehsani says he is looking for partners to develop an automated mobile unit to make the pipes onsite.

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