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Composite Technology
[Print Article: July 2003, by ] In 1975 a team of nine American mountain climbers painstakingly trudged, heaved and gasped their way up the heretofore never attempted northwest route of the Himalayas' K2, the world's second tallest -- and some say deadliest -- mountain.
Strapped to the mountaineers were composite-reinforced oxygen tanks filled by NASA to 4,000 pounds per square inch (psi). The experimental tanks enabled the climbers to carry three times the amount of oxygen at half the weight.
Unfortunately, before the adventurers reached the summit, their porters went on "strike," the climbers suffered altitude sickness, bad weather set in and to top it all off, the route became seemingly impassable due to three massive pinnacles.
The Americans made it as far as 22,000 feet up the 28,250-foot mountain before they decided to turn around and go home.
The idea behind composite-reinforced gas containers, however, carried on. The same technology used in the climbers' oxygen tanks is now being tested in natural gas pipelines, and its proponents say it significantly extends the pressure capability of comparable steel pipe while reducing weight and increasing resistance to fracture propagation.
TransCanada PipeLines Limited (TCPL) is working on a method of wrapping composite material around line pipe, leading to a decrease in a pipeline project's total costs by between four and 12% over the equivalent-strength, all-steel pipe.
Composite Reinforced Line Pipe (CRLP) is a patented process that draws high-strength fibreglass through a proprietary polyester resin bath and then winds it over the circumference of the external surface of the steel. The technology was developed by NCF Industries Inc. of California and is licensed in Canada to TCPL.
If you've ever tried to tear fibreglass tape with your bare hands, you'll have some idea of the strength behind the idea.
"We see it as an alternative to imported high-strength steel. It's a North American solution for any high-strength, high-pressure pipeline to be built," says Gary Stephen, TCPL's vice-president for composite pipe technologies. Currently much of Canada's high-strength steel line pipe comes from Japan and Germany.
And, he says, the technology may be just the ticket to someday bring gas from the Arctic, via either the proposed Alaska or Mackenzie Delta pipelines, and to ship compressed gas overseas in gas transport modules, which are pressure vessels built from sections of CRLP and installed on barges or ships (see previous story).
The company is working with a potential manufacturer with the aim of having CRLP made in Canada and is also conducting a number of economic studies.
TCPL, which has a network of about 38 000 kilometres of pipeline that transports natural gas from Western Canada to elsewhere in Canada and to the United States, most recently tested seven sections of a 100-metre, X-70 strength, 48-inch CRLP on the Saratoga loop section of the western Alberta system mainline expansion in September 2002. The test employed pressure of 1,260 psi, testing it to 1,740 psi in 11.7 millimetres of steel and five millimetres of composite material. The project's success, says TCPL, is proof the technology can be used on a commercial scale. The pipe is now part of a natural gas pipeline operating at 960 psi, and has the capability of running at 1,260 psi.
Nor is transportation an issue, says Stephen. The pipes were made by IPSCO in Regina, shipped to California for wrapping and then sent back up to Canada for installation, with nary a hitch.
He says benefits include good fracture control properties that arrest any propagating fractures, called "leak-before-burst," that would stop breaks before they turn into a catastrophic event. On the other hand, if an all-steel pipe were to burst from, say, too much pressure, in a lot of cases it would split like a banana.
Also, because the pipe is wrapped with the composite, less steel is needed, leading to a reduction in weight of about 40%, and there is less handling cost. Additionally, because the wrap is placed on the pipe's exterior, CRLP has about five to eight per cent more throughput capacity. And it's tough -- tougher than fusion bond epoxy coatings, says Stephen.
A 2001 field trial of CRLP near Buffalo Creek, north of Edmonton, tested two kilometres of 24-inch, X-70 strength pipe. TCPL found it could bend the pipe up to 14 degrees in minus 30 degrees Celsius weather, without the requirement of special equipment, so it appears to be suitable for northern pipeline conditions, says Stephen. Test objectives also confirmed its constructability and joining capability, its long-term performance, its manufacturing process and its cost savings in the frozen north, says TCPL.
Also that year, the pipeline company tested 50 metres of 24-inch pipe for long-term performance, constructability, bending and joining, and long-term corrosion resistance at Russell Creek in northern Alberta, using 1,440 psi in 6.4 millimetres of steel and five millimetres of composite.
It was also tested in Kingston, Ontario, in 1998, on 100 metres of 20-inch pipe. All these pipes are still underground, transporting natural gas. In addition, a test loop has been done on X-100 pipe, but not by TCPL.
No test installations are being done currently simply because no projects are going in the ground right now, says Stephen. CRLP is undergoing the Canada Standards Association approval process so that it can be installed under the pipeline code. This is expected to take two years.
The above-mentioned test sections have been installed with special permits from the Alberta Energy and Utilities Board. "We've tested them to a high pressure but we're not operating under as high a pressure as if they were code-approved, so to be able to install them and operate them under design conditions they would have to be in the pipeline code," explains Greg Cano, TCPL's director, gas transportation modules.
According to TransCanada, the ratio of composite to steel can vary, depending on the application. The thickness of the layer of composite varies from one-quarter inch to one inch depending on the size of the pipe and at what pressure it is operating under.
The new way of getting gas to markets begins with a conventional steel liner and, says Stephen, it's important to note that as steel technology improves, CRLP will benefit, as a large component of this is the steel liner. This liner is prepared the same way it would be for a normal coating process, with shot blasting to create an anchor pattern, pre-heating, acid wash and rinse.
A primer, specifically designed to affix the composite to the steel, is then applied to the pipe surface, followed by the fibreglass layer. This could represent up to 50% of the pipe wall thickness.
The final layer is the outer wrap, which includes a reinforcing fabric matte as well as a resin-rich gel coat surface. The armour fabric is designed to protect the load-bearing fibres from any type of surface abrasion or mechanical damage. The gel coat is employed to create a resin-rich surface that prevents moisture uptake and ensures long-term performance, similar to the coatings on fibreglass boats.
In addition to all-steel and steel-and-composite line pipe, there is the choice of all-composite, but it can only be used for small diameters and low pressures, says Stephen, and it is about four times the price of the steel-and-composite.
The technology still has some bugs that need to be worked out, though. According to a July 2002 study sponsored by the Natural Gas Pipeline Infrastructure Reliability Program, conducted by the U.S. National Energy Technology Laboratory for the U.S. Department of Energy, there needs to be greater understanding of large diameter composite material pipe under varying loading and environmental conditions.
Bearing in mind the study was done prior to TCPL's September 2002 field trial, it says more needs to be known about external damage from handling and transportation of composite pipe, and external damage from punctures and abrasions during or after field installation and handling. Furthermore, says the study, the joining and valving of composite pipe used for high-pressure operations needs to be more reliable and less expensive. Another of the barriers that limit consideration of composites for natural gas transmission pipelines is the susceptibility to damage from digging, according to the study.
CONTACT FOR MORE INFORMATION
Gary Stephen, TransCanada, Tel: (403) 920-2025, E-mail: [email protected]
- IT'S A WRAP Pipeline wrapped with high-strength fibreglass drawn through a proprietary polyester resin is stronger, lighter and demonstrates improved fracture control properties. TransCanada PipeLines is conducting economic evaluations of CRLP and investigating having it manufacturing in Canada.
