University of Arizona professor invents lightweight infinite pipeline

A University of Arizona professor has invented a theoretically infinite pipe that promises to bring down the costs of laying pipelines while reducing environmental damage. Developed by Mo Ehsani, Professor Emeritus of Civil Engineering at the University of Arizona, the new pipe, called InfinitiPipe, is of a lightweight plastic aerospace honeycomb under layers of resin-saturated carbon fiber fabric put together by a new fabricating process that allows pipes to be built in indefinite lengths on site.

Because they’re out of sight, we sometimes forget how much pipe lies buried under our feet. Spreading throughout and between towns and cities there are thousands, if not millions of miles of pipeline carrying fuel, water, sewage, cables and all manner of other things that make up the veins and arteries of modern civilization. The problem is that any large pipe intended to have any strength, such as those made out steel, concrete or heavy plastic, can only be made in very short lengths. This is partly due to the weight of some materials, but mainly because they’re transported on trucks.

This means that a pipeline, no matter how long, is made up of a series of short sections with hundreds or thousands of joints – each one a potential leak. It also means that the pipes often have to be manufactured at distant locations and then shipped and hauled to construction sites over great distances and at great cost.

Ehsani’s InfinitiPipe addresses this problem by moving the manufacturing process to the site itself. He had originally been working on a method to reinforce existing pipes using composite materials. This led to his creating a method for making composite pipes that involved wrapping layers of carbon fabric and plastic honeycomb around a mold called a mandrel. As the pipe was partially finished, it would be slipped down the mandrel while the next length was made.

Then Ehsani realized that he was on to something. “I thought, why don’t we just slip this off of the mandrel and continue making this pipe?” Ehsani said. “Never stop.”

This meant that the composite pipe could be theoretically infinite – just keep adding honeycomb and fabric, keep moving the pipe down the way and there’s no end to it. In practice, however, there are limits. “We could make a section a mile long,” he said. “Of course, every thousand feet (304.8 m) 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 feet (6.09 m).”

Since the InfinitiPipe is made of lightweight materials, transportation costs are much cheaper than for concrete or steel. This makes on site manufacturing an economical proposition. Ehsani envisions a manufacturing unit installed inside of a truck where the pipe would be fabricated and the truck moving forward as the pipeline if fed out.

According to Ehsani, this would have a large impact on both commercial operations, which could move their pipe fabricating trucks anywhere in the world to follow demand, and in the developing world. “Suppose you have a pipeline project in a developing nation,” Ehsani said. “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 is presenting a paper on his new pipe technology at the American Society of Civil Engineers Pipelines 2012 Conference, Aug. 19-22 in Miami.