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Sunday, October 22, 2017

The Efficient Tugboat: The Efficient Tug

February 21, 2003

In many ports across the country, competition among tugboat operators is intense. The combined Port of Los Angeles and Long Beach is one such competitive environment for tug operators. Three companies vie for business that includes about 6,000 ship arrivals a year. Many of the companies utilize new tractor tugs to guide these ship movements. Foss Maritime, Crowley Marine and Millennium Maritime operate over a dozen modern tugs. Any slight edge in efficiency gives one company a competitive edge.

Foss Maritime

For example, Foss Maritime recently placed the Halter Marine-built Marshall Foss into service. The 6,200 hp tug measures 98 x 40 x 16 ft. "This vessel was purpose built as a harbor tug," said Barry Baldwin, business director for Foss Maritime. Baldwin is located in Long Beach. Foss Maritime is headquartered in Seattle, Wash. Baldwin says that shorter is better for ship handling. "Most general purpose tugs with this much horsepower would be 130-140 feet long," Baldwin added. "They can't get out of their own way when it comes to ship assist," Baldwin reported. "At 98 feet long and 40 feet wide, we have more maneuverability in harbor work," said Baldwin. Maneuverability is a key in busy harbors such as Los Angeles/Long Beach and leads to a more efficient tug operation, Baldwin believes.

Power for the tug comes from a pair of Detroit Diesel 16V4000 engines giving a 165,000-pound forward bollard pull and 11 knots speed. The engines couple to Rolls Royce Ulstein Z drives and Nautican nozzles with 106-in. propellers, which are are skewed to increase the thrust per unit of horsepower.

Other efficiencies come from the Detroit Diesel engines that are fuel efficient, and electronically controlled. The engines exceed tough California air quality standards for low emissions. Although not designed for towing, Foss Maritime decided to put a towing winch on the stern to give the vessel some rescue capability.

Harley Marine Services

Harley Marine Services is a major force in the Los Angeles/Long Beach ship assist market. Through their subsidiary Millennium Maritime, Harley has brought a new tractor tug to the market, the Millennium Dawn.

The 108- x 36- x 16-ft. tug is a tractor tug with Z drives. Caterpillar 3516B diesels provide total hp of 4,400 and work into Rolls Royce Z drives and Nautican nozzles and propellers. "We think that Z-drives gives our tugs more pulling power than cycloidal powered tugs on a horsepower versus horsepower basis," said Doug Houghton of Millennium Maritime. The Millennium Dawn is one of three identical tractor tugs used by Millennium in the Port of Los Angeles/Long Beach. "Our tugs do both towing and ship assist work and some ocean towing as well," Houghton said. Marco Shipyard in Seattle built all three tugs.

Crowley Marine Services

Crowley Marine provides extensive ship assist and escort services in the Port of Los Angeles/ Long Beach. Crowley uses a fleet of Z-drive tugs and also tractor tugs using cycloidal drive. The 360 degrees of omni-directional thrust permit the tugs to perform a number of maneuvers without repositioning themselves.

In the last six years Crowley has added eight new tractor tugs to its fleet. Two are 120 ft. long with 5,500 hp and the six newest are 105-ft. long with 4,800 hp. All are cycloidal drive units. The newest tugs are called the Harbor Class and feature 120 tons of indirect bollard pull at 10 knots. The State if California has declared the Harbor Class capable of the most difficult tanker escort work in the Los Angeles/Long Beach harbor.

Crowley also has three Z-drive tugs that are 140 ft. long and feature 10,192 hp each. These tugs work in Valdez Harbor and Prince William Sound, Alaska.

Crescent Towing

The New Orleans harbor is one of the busiest in the nation. Crescent towing dominates this market with 24 tugs performing ship assist, ship escort and towing work. Crescent also has an operation in Savannah, Ga. and the company's newest tug is located in this east coast port.

The Savannah is the second Z- drive tug in the Crescent Towing fleet. It is 96 ft. long with a 34-ft. beam and a 14.75-ft. depth. Power is from a pair of Caterpillar 3516B diesels for a total of 4,000 hp. They drive two Ulstein Z-drives connected to Nibral propellers in nozzles. The Z-drives feature 360-degree maneuverability giving exceptional maneuverability and eliminating the need for rudders.

The term "Z-Drive" comes from the drive shaft configuration, which is horizontal out of the engine, vertical through the hull and horizontal again at the propeller, roughly outlining a "Z"

The ships in the Savannah harbor are growing in size. "This vessel and its technology are needed here," said Ed Bazemore, Crescent Towing vice president and port manager in Savannah. The vessel went to work right away assisting LNG and container ships.

It was designed by Jensen Maritime Consultants, inc., Seattle, Wash. and built by Bollinger Shipyards, Lockport, La. Bollinger is also in the process of upgrading eight Crescent tugs to twin screw power and a new pilothouse with enhanced electronics and 360 degree visibility.

The vessel is outfitted with a Coastal Marine Equipment double drum winch at the bow and single capstan winch on her aft deck. "This vessel is amazing," said Larry Ohler, vice president and port engineer for Crescent Towing.

"The vessel is so powerful it can push a ship in any direction," Ohler said. For example the Savannah can pull up parallel to the port or starboard side of a vessel and pull it away from the dock, Ohler indicated.

"The Savannah can also have a line attached to the port side of a vessel and without disconnecting the line, swing over to the starboard side of the vessel, Ohler added..

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