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Mo Ehsani, professor emeritus of civil engineering at the University of
Arizona, has designed a new, lightweight underground pipe he says could
transform the pipeline construction industry.
Instead of conventional concrete or steel, Ehsani’s new pipe 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.
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.
Concrete and steel pipes are built in short sections to fit on standard
18-wheel trucks, but Ehsani’s new pipe can be built onsite as a single section
of virtually infinite length, hence the product name InfinitPipe.
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 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,” Ehsani says.
“One is this new type of lightweight honeycomb pipe. 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.”
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 of 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 mold 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,”
Ehsani says. “A couple of layers of carbon fabric, then we put on the
honeycomb and then a couple of layers of carbon or glass fiber on the outside.
This becomes the pipe.”
After testing this manufacturing method, Ehsani had a “eureka”
moment when he realized 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 fiber, 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, and Ehsani says he is looking for partners to develop
an automated mobile unit to make the pipes onsite.
“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 feet left on the mandrel,” he says. “Then you just move the
truck forward and drop the pipe in the ground, and keep adding pipe.”
As if virtually eliminating transportation costs, slashing manufacturing
costs, and reducing environmental impact weren’t enough, Ehsani sees this pipe
technology creating jobs and boosting local economies.
“Suppose you have a pipeline project in a developing nation,”
Ehsani 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.”
Closer to home, Ehsani cites the recently awarded $10.7 million contract to
build the first four miles of pipe for the billion dollar Navajo-Gallup water
supply project, which involves building a 280-mile pipeline to supply water to
more than 40 Navajo communities in New Mexico and Arizona.
“The contractor is making a 42-in diameter pipe for four miles, which
works out to $507 a foot,” Ehsani says. “Really, we could have that
pipe built faster with the help of local labor and put it in place sooner,
without having to wait to order it and ship it, and all of that expense.”
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,” he says.
“Then as we started getting into this thing I realized 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 UA department of civil engineering and
engineering mechanics, pioneered research into repairing and retrofitting
bridges and buildings using fiber-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,” Ehsani says.
“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,” he says. “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.”
Source: University of Arizona
