BIRMINGHAM, Ala. – In a study of the effects of earthquakes on water and sewer pipe, ductile iron pipe with restrained joints proved superior to other pipe materials, according to a paper by Michael Tucker, senior sales engineer with AMERICAN Cast Iron Pipe in Tulsa, Okla. The paper was published in the May 2010 issue of the Journal of the American Water Works Association.
“Pipelines that deliver clean water and remove wastewater are essential to the well-being of our communities,” said Tucker. “Some utilities may have only one source – one lifeline – into a community. In areas of seismic activity, utilities need to consider how best to protect these lifelines from failure.”
The study reviewed data about pipe failures during modern-day earthquakes, including the following earthquakes in the U.S.: Prince William Sound, Alaska, 1964; Loma Prieta, Calif., 1989; and Northridge (San Fernando Valley), Calif., 1994.
“Earthquakes like these have demonstrated time and again the need for high-strength, flexible pipe with flexible joints,” Tucker said. “Whether the pipe and joints are flexible or rigid determines the ability of the pipeline to resist the motion and energy associated with earthquakes.”
The study shows that ductile iron pipe and joints performed the best, sustaining only minimal structural damage. Asbestos-cement pipe had the worse failure rate and plastic pipe was more likely to pull apart at the joints.
“Most mid- to large-size utilities in seismic zones in this country use ductile iron pipe and joints designed for river crossings,” Tucker said. “This application has proven very effective in withstanding the effects of earthquakes. It uses locking joints with 15 degrees deflection.”
“AMERICAN's Flex-Ring ductile iron pipe and joints meet all the criteria for seismic resistance...”
Other utilities, in particular small rural utilities, should take a close look at their systems. “Utilities in seismic zones need to evaluate the lifelines critical to their systems and give these lifelines top priority for retrofitting or replacement to ensure the greatest seismic resistance,” Tucker said.
For new developments, the time to consider system reliability is during initial planning. “While the cost of an earthquake-resistant system may be more on the front end, in addition to protecting a utility’s lifelines, it may offer considerable savings in the long run,” Tucker said.
AMERICAN, founded in 1905 and headquartered in Birmingham, Ala., is a manufacturer of ductile iron pipe, fire hydrants and valves for the waterworks industry, and electric-resistance steel pipe for the oil and gas industry. AMERICAN’s diversified product line also includes spiral-welded steel pipe in diameters up to 144 inches, fire pumps, static castings and fabricated assemblies. AMERICAN’s Flex-Ring ductile iron pipe and joints meet all the criteria for seismic resistance and are available in sizes from 4 through 64 inches in diameter.