International Dredging Review

International Dredging Review
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Norfolk Dredging Company has upgraded the clamshell dredge Atlantic which is working on the Charleston Harbor deepening project along with the company’s other clamshell dredge Virginian.

The dredge made history in 1986 when one of the first of Caterpillar’s new 3600 model diesel engines was installed by then-owners Smith-Rice Company of Alameda California. The 3606 powered a 900 kW DC General Electric generator rated at 2150 horsepower. Over the years the electrical system had become outdated and unreliable and Norfolk who has owned the dredge since December 1998 contracted with OEM of Houston to design and install a digital DC to DC drive system. The Atlantic went into drydock on June 5 2000 and Kevin Williams of OEM and Jim Garaghty of Industrial Logic Systems (ILS) of Brea California installed the system. The dredge was back at work on June 17 and Williams and Garaghty stayed on board to trouble shoot until June 23 when the system was running smoothly.

The digital drive system is a state-of-the-art prototype said Williams. The system can be tuned to be more precise and smoother to operate. Norfolk is getting better production because the operator is not fatigued at the end of the shift he said. Another feature is the ability to plug a cell phone into the drive and call OEM or ILS who can trouble shoot the system over the phone he said.

“It was a fantastic improvement it has been working fine ever since” said Jerry Dundlow superintendent of the Atlantic.

The upgrade increased the torque 25 percent on the hauling gear and the swing power by 20 percent said Doug Kimbro chief engineer. A 900 kW DC generator drives the 825 hp electric motor for the main hoist which produces 1570 horsepower.

Norfolk also rebuilt all the swing generators and motors and rearranged the deckhouse.

The Atlantic is a Paceco crane rated at 300000 pounds. Norfolk purchased an 18 cubic yard Hawco bucket for the Charleston project.

This fall the two Norfolk dredges are working in Cooper River deepening the former 40- to 42-foot channel to 49 feet. The material ranges from sand to Charleston marl (a hard-packed clay) to ledge rock which Norfolk will dredge using a hard rock bucket.

The dredges are loading into five split hopper barges that are 3000 4000 and 5000 cubic yards. Placement is in a designated offshore facility three miles south of the entrance to the harbor.

The contract started when the Atlantic arrived in Charleston on July 3 1999. The Virginian which had been working in Puerto Rico arrived in October of that year. The dredges are expected to be in Charleston for another year.

Paul Lougheed is project superintendent working out of the Charleston field office assisted by his wife Karen who is office manager. Kirk Twiford is superintendent of the Virginian and Casey Jones is chief engineer of the Virginian. Daniel Cahoon is deck captain of the Atlantic.