TUGS & BARGES
his year, some of the first escort tugs to be fitted with the marine industry’s cleanest-burning diesels yet will begin operating in the U.S. One of those is 5,300-hp tractor tug Earl W Redd, which recently joined the fleet of Seattle-based Harley Marine Services. Shown on this month’s cover, the 120 ft Earl W Redd was built by Diversified Marine, Portland, OR, and is fitted with two Caterpillar 3516 main engines that will each produce 2,675 horsepower at 1,600 rev/min. In order to comply with the U.S. Environmental Protection Agency’s Tier 4 Final emissions standards, the Cat engines are fitted with a Selective Catalytic Reduction (SCR) after treatment system. SCR uses a urea-based solution called Diesel Exhaust Fluid (DEF) to reduce nitrogen oxide (NOx) contained in diesel exhaust down to nitrogen and water vapor. Cat says that there are several cost and operational advantages of using the SCR system. “Harley Marine should save over $1 million across a 15-year lifecycle on total fluid consumption (diesel plus DEF) costs for this newbuild compared to an equivalent Tier 2-powered vessel,” says Ryan Darnell of Caterpillar’s Large Power Systems division. “They are able to deliver an increased level of performance due
to the higher power rating with increased efficiency,” says Ryan Darnell of Caterpillar’s Large Power Systems division. “That’s a direct result of engine fuel efficiency improvements that our SCR technology allows us to make by reducing NOx downstream of the engine combustion process.” Earl W Redd’s main engines drive Rolls Royce US 255-P30-FP azimuth thrusters to give the tug a bollard pull capability of 75 tons. The Earl W Redd will be able to carry about 8,200 gal of urea. The tug has specially designed bow winches for shiphandling and escort supplied by Markey Machinery and fendering from Schuyler Rubber. Meanwhile, early next month, McAllister Towing & Transportation, New York, NY, is expected to add the first of two Z-drive escort tugs that will be fitted with EPA Tier 4-compliant engines. Named the Brian A. McAllister—after company Chairman Capt. Brian A. McAllister—the tug was recently launched by Horizon Shipbuilding, Bayou La Batre, AL. This summer, Horizon Shipbuilding is expected to deliver the tug’s sister ship, the Rosemary McAllister, named for Mr. McAllister’s wife. The tugs will be used to assist postPanamax and ultra-large vessels. Designed by Jensen Maritime, Seattle, WA, each of the 100 ft x 40 ft escort tugs will be powered by two Caterpillar 3516E Tier 4 engines with Schottel SRP4000 FP azimuth 18 Marine Log // April 2017
Photo Credit: Robert Allan Ltd.
Harley Marine should save $1 million across a 15-year lifecycle on total fluid consumption costs for this newbuild
New escort tugs with Tier 4 compliant engines join the fleet; first U.S.-built Rotortug added by Seabulk