New Technology Leads To Successful Electric Transmission Project

By Erin Boudreaux, Hobas Pipe USA | April 2013, Vol. 68 No. 4
Workers installed the 30-inch carrier pipe by jacking methods.

Before construction began, Boyer performed a trial installation to ensure that the line would grout correctly. “Grouting on this project was important; you need complete coverage around the conduit because of the heat that is generated when the line is energized,” explained Barry Buse, project manager, Boyer.

The installation depth ranged from 20 to 30 feet. Boyer purchased an Akkerman 4812, Guided Boring Machine, built specially for this project. Customary tunneling and jacking machines use diesel motors, which cause loud noise when in use. Because of the project location, in an urban environment with noise pollution codes, Boyer needed an unobtrusive option. Akkerman built this particular unit to run electrically for noise reduction.

Boyer jacked the casing pipe in runs of 400 to 500 LF sections between pits. “We had high confidence in the quality of the Hobas casing, despite it having to endure some pretty high crushing forces from the guided bore machine,” stated Erich Schoennagel, manger-transmission project engineering, CenterPoint Energy.

Once the casing pipe was in place, their worker, using a trolley system designed for the project, entered the pipe and installed a Unistrut rail system along the inside top of the pipe. With the casing pipe and Unistrut in place, Boyer installed a bundle of three 8-inch and three 4-inch PVC pipes in a spacer designed to support the weight of the product along with its accompanying grout and vent tubes. The owner insisted on conduits completely encased in thermal grout, so installers paid particular attention to the grouting process to ensure maximum grouting of the annular space inside the carrier pipe.

“The circuit was energized to the new capacity rating in late April 2012 and is performing well,” Schoennagel said.

Hobas manufactures pipe is in sizes from 18 inches to 126 inches in pressure and non-pressure classes.

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