ABS approves LNG fueled Z-drive towboat design

Written by Nick Blenkey
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DECEMBER 2, 2014 — Morgan City, LA, headquartered Conrad Shipyard, L.L.C. and the Seabrook, TX, based Shearer Group, Inc. (TSGI) have developed the design of a 4,200 hp liquefied natural gas (LNG) fueled towboat utilizing a proven design from TSGI. The design has gained “Approval in Principle” (AIP) from ABS.

The towboat is based on TSGI’s proven azimuth drive (Z-drive) towboat design that debuted in 2008 with the Frank T. Stegbauer. To date, eight of these towboats have been built for Southern Towing Company. The original Southern Towing boats helped pioneer the use of Z-drives for brown water operations and have shown significant fuel savings relative to conventional towboats.

The new LNG fueled towboat design capitalizes on Wärtsilä’s proven dual fuel technology, but, according to TGSI, “is not wedded to it.”

TGSI says the Wärtsilä technology is the most widely accepted dual fuel technology currently in use in the domestic U.S. market. While Wärtsilä’s existing dual fuel engines are medium speed diesels, it is anticipated that future engine developments will result in lighter and smaller high speed units. The design is flexible enough to allow for the use of either engine option as determined by the operator.

“By combining two widely accepted technologies; Z-drives and Wärtsilä’s dual fuel engines and fuel system, we have mitigated most of the risks associated with being an early adopter of this novel technology” says Greg Beers, P.E., TSGI’s President. “By incorporating proven technologies, we have minimized the risks that first movers will be taking with the switch to utilizing LNG as a fuel.”

The Wärtsilä system specified is basically a smaller version of the system currently installed on the Harvey Gulf Multi Purpose Supply Vessels, and as noted above, the Z-drive towboat designs have been operating successfully since 2008.

The economic and environmental benefits of using LNG as a fuel source for high horsepower applications like towboats are widely understood. TGI says the beauty of its design is that it marries these benefits with the proven benefits of utilizing Z-drives on a towboat.

These efficiencies compound, providing an owner with operational cost savings that can exceed 35% of the cost of operating a conventional towboat. TSGI and Conrad Shipyard, believe that these savings will prove to be very attractive to towing companies,

TSGI and its sister company, Bristol Harbor Group, Inc., have been involved in LNG projects since 2009, and are currently involved in five active LNG projects, including one for the United States Army Corps of Engineers. Conrad Shipyard, L.L.C., established in 1948 and headquartered in Morgan City, Louisiana, designs, builds and overhauls tugboats, ferries, liftboats, barges, offshore supply vessels and other steel and aluminum products for both the commercial and government markets. The company provides both repair and new construction services at its five shipyards located in southern Louisiana and Texas. www.conradindustries.com.

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