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Many Factors Essential In Completion Of Ohio Gas Main Replacement Project
Planning, Cooperation & Carefully Controlled Logistics
Mears used an American Augers DD-330 developing 330,000 pounds of pullback, he explained. The drill unit was set up in an entry pit and began drilling with a jet assembly and 9 7/8-inch mill tooth bit. The majority of crossing was through sand and gravel, not ideal for HDD applications.
“For drilling through the descending curve,” said DeCraene, ”conditions were deemed too hard for the bit set-up, and the decision was made to trip out and install a 6¾-inch mud motor and 9 7/8-inch TCI bit. The pilot hole had 25 feet of cover beneath the river bottom. The sand and gravel conditions made it essential to implement a drilling fluid program to ensure the hole remained open throughout the installation.”
The pilot bore required six days, including mobilization and set up. Upon pilot hole completion, 24-inch and 34-inch reaming passes were performed prior to making a swab and cleaning pass before product pullback.
“Four product pipe strings were strung out in Clinton-Como Park during drilling and reaming. Pullback of the 20-inch, .500 wall thick X-52 steel pipe was completed in one day,” DeCraene related. “Pullback force peaked at 70,000 pounds and rotary torque remained low, confirming the hole was ideally prepared.”
The frame and axel mounted DD-330 drill rig is powered by a 500-horsepower diesel engine. In addition to 330,000 pounds of pullback, it develops maximum rotary torque of 48,000 foot pounds. The mud motor employed was a 6 3/4-inch Adtech with a 2.1-degree bend. A Rockmaster MCS 750 mud cleaning system was capable of pumping 500 gpm.
A Paratrack II guidance system was used. “Survey surface wire was laid out on each side of the river to track location and depth as the drill progressed,” DeCraene said. “Wire was not allowed to be placed under the river, so the crew relied on the azimuth behind the bit to steer laterally across the unwired portion of drill path.”
From the time equipment arrived on site, until pipe was pulled into place, was 13 days.
Safety always is a priority for InfraSource, and a complex project such as this one which involved multiple companies always is challenging.