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‘Never-ending’ pipe promises revolution

January 2013

An expert at the University of Arizona, US, has made a breakthrough by designing a new, lightweight underground pipe called InfinitPipe, which he says could transform the pipeline construction industry.

Mo Ehsani, professor emeritus of Civil Engineering at the university, says instead of conventional concrete or steel, InfinitPipe consists of a central layer of lightweight plastic honeycomb, similar to that used in the aerospace industry, sandwiched between layers of resin-saturated carbonfibre fabric. In combination, these materials are as strong, or stronger, than conventional steel and concrete pipes, which are time-consuming and expensive to manufacture and transport, he states.

Concrete and steel pipes are built in short sections to fit on standard 18-wheel trucks, but InfinitPipe can be built onsite as a single section of virtually infinite length, hence the product name, says a spokesman for the university.

The heavy industrial manufacturing processes, long-distance trucking, and leak-prone joints used in steel and concrete pipe construction exact a heavy toll on the environment, not to mention the bottom line, which is why Ehsani’s company, QuakeWrap, is marketing InfinitPipe as the world’s first “green” pipe.

“There are really two aspects to this invention,” says Ehsani. “The first is this new type of lightweight honeycomb pipe and the second is our ability to give clients an endless or infinite pipe, without a joint. That is a big, big breakthrough in the pipeline industry that has implications for natural gas, oil, water, and sewer pipes.”

Ehsani demonstrates carbon laminate honeycomb pipe sections of various sizes built at his facility in Tucson, Arizona.

A literally infinite pipe is, of course, not feasible, but Ehsani’s method of manufacturing could create extremely long sections of joint-free pipe. “We could make a section a mile long,” he says. “Of course, every thousand feet or so, you’d need an expansion joint so the pipe can breathe, but this would certainly not be the same concern we have today, where we have to put a joint every 20 ft.”

The secret to producing virtually endless pipe sections lies in the manufacturing methodology. Ehsani wraps the various layers of carbon fabric and honeycomb around a mandrel – a kind of tubular mould with a cross-sectional shape that matches the pipe’s internal cross-section, which is typically, but not always, circular.

“We basically start with a tube and wrap the materials on the outside,” says Ehsani. “A couple of layers of carbon fabric, then we put on the honeycomb and then a couple of layers of carbon or glass fibre on the outside. This becomes the pipe.”

After testing this manufacturing method, Ehsani had a “eureka” moment when he realised that the finished pipe could be partially slid off the mandrel, and more pipe could be added to the section of pipe remaining on the mandrel. “I thought why don’t we just slip this off of the mandrel and continue making this pipe?” Ehsani says. “Never stop.”

Carbon fibre, resin and aerospace honeycomb are all very light materials that can be transported at a fraction of the cost of conventional prefabricated steel and concrete pipe. Ehsani says he is looking for partners to develop an automated mobile unit to make the pipes onsite.

Revolutionary concept ... Ehsani’s mobile pipe-laying truck creating a pipeline of virtually infinite length.

“Imagine having a truck with a mandrel in the back,” Ehsani says. “You start making the pipe on, say, a 20-ft mandrel, and pull off 18 ft so you have two ft left on the mandrel. Then you just move the truck forward and drop the pipe in the ground, and keep adding pipe.”

Besides virtually eliminating transportation costs, slashing manufacturing costs, and reducing environmental impact, Ehsani sees this pipe technology creating jobs and boosting local economies.

“Suppose you have a pipeline project in a developing nation,” he says. “You could ship the raw materials to the workers there and they could make this pipe in their own village. No matter what size or shape they want. All they need to do is build a mandrel and make the pipe on the spot. We would be making it with local people under our supervision.”

Ehsani says he didn’t really set out to turn pipeline construction on its head, but the project took on a life of its own. “We developed this originally with the intention of fixing existing pipes. Then as we started getting into this thing I realised it could be a real game-changing breakthrough technology.”

The breakthrough did not happen overnight. In the late 1980s, Ehsani and Hamid Saadatmanesh, both of the University of Arizona’s Department of Civil Engineering and Engineering Mechanics, pioneered research into repairing and retrofitting bridges and buildings using fibre-reinforced polymers, so the technology is well established.

“There’s a lot of history on these materials,” Ehsani says, which has enabled him to refine the pipe manufacturing process to use smaller amounts of better quality materials.

“Because we’re using our materials in a smart manner, we can afford to use the higher end material. So instead of cheaper glass fabric, we use carbon; 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.”

If Ehsani’s concept for mobile pipe manufacture using lightweight components takes off, he envisions an industry freed from the shackles of heavy industrial plant.

“As a business model, a company that wants to get into pipeline manufacturing with one of these mobile trucks could have a factory anywhere in the world. You could be doing a job in Hawaii today and next week be working in Panama. You’re no longer limited by where your factory is,” he adds.

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