FRP the key to 12 miles of large-diameter pipe
For an irrigation project commissioned by the Los Angeles Dept. of Water and Power (LADWP) at Owens Lake in California's High Sierra Desert, Ameron International (Houston Texas, U.S.A.), manufactured, hydrotested and delivered more than 63,360 ft of 30-, 42- and 48-inch diameter FRP pipe within a tight seven-month schedule.
Due to the corrosive soils, LADWP specified FRP pipe, which was designed to American Water Works Assn. (AWWA) C950 specifications. Ameron's Fiberglass Composite Pipe division met the challenge at its Burkburnett, Texas facility, using large-diameter, NC-controlled filament winding equipment custom-built to meet the job requirements by Ameron subsidiary Hope Composites (Atlanta, Ga., U.S.A.). On custom mandrels built by Ameron, the nominal 40-ft lengths of pipe were each wound over a Schmelzer Industries' Pearlveil 110-12, 10-mil, 37.67 g/m2 (0.124 oz/ft2) veil liner (Somerset, Ohio, U.S.A., select 248), using 518 AS 113-yield continuous fiberglass roving from Johns-Manville (Denver, Colo,, U.S.A., select 249) wetout with ARAPOL 7334 isophthalic unsaturated polyester resin from Ashland Specialty Chemical Co., Composite Polymers Division (Columbus, Ohio, U.S.A., select 250), chosen for its toughness and corrosion resistance.
In the lakebed, where most of the pipe was to be laid, soil was expected to be unstable, says Ameron's vice president of corporate research and engineering Rocky Friedrich. "The joints needed to be able to articulate, so you didn't get unusual bending loads applied to the pipe sections." Ameron-designed "bell"-forming tooling enabled manufacture of self-sealing, double O-ring type insertion joints capable of articulating up to 2° without leakage to accommodate both mild changes in terrain and planned pipe curvature. (Tested at 2° misalignment, the pipe joints passed ASTM D 2412 specifications.)
Installers needed to lay 40 to 50 joints a day to meet schedule, but the simple joint and special clamps on the contractor's backhoe equipment allowed crews to join as many as 100 lengths per day. The pipe spigot (small end) was machined with two locator grooves, allowing crews to visually confirm proper insertion of the spigot into the bell. "If the bell end landed anywhere between the two grooves, we knew they'd be secure," says Friedrich.
Ameron hydrotested 100 percent of the pipe to 300 psi at the factory - double the design operating pressure of 150 psi (maximum surge pressure of 192 psi), then the pipe was retested after installation, to 211 psi.