Built in 2003, by Washburn and Doughty Associates, Incorporated of East Boothbay, Maine (hull #78) as the Liberty for Boston Towing and Transportation of Boston, Massachusetts. A subsidiary of Reinauer Transportation Companies of Staten Island, New York.
She was the second in a series of two 4,400 horsepower "z-drive" (also known as an Azimuthing Stern Drive (ASD) tugs built for the Boston Towing and Transportation Company of Boston, Massachusetts, a division of Reinauer Transportation Companies of Staten Island, New York.
The tug was designed primarily to fulfill Boston Towing's contract with Tractebel LNG Shipping of North America LLC.
Powered by two Caterpillar 3516B electronic injection main engines rated at 2,200 horsepower at 1,600 RPM producing an estimated bollard pull of 110,000 lbs ahead and 105,000 lbs astern. Turning two Rolls Royce 1650H z drives equipped with 86(in) stainless steel propellers mounted in kort nozzles lined with stainless steel.
The "z-drives" are modular to allow for removal through soft patches on the main deck. Her electrical service is provided by two 99KW generators driven by two Caterpillar 3304 engines turning at 1,800 RPM for 120/208 volts, 3 phase with auto transfer. One generator is normally online while the other is on standby.
The Liberty is outfitted with two 3,000 gallon per minute Alco fire monitors and Aurora model 411 centrifugal pumps driven by Caterpillar 3406TA engines rated 480 horsepower at 2,100 RPM. The systems are designed to allow the crew to start and stop the pump engines remotely from the pilothouse. Additionally, the tug features a deluge systems designed to provide water spray coverage over the entire tug. The main engines, pump engine and the "z-drives" are keel cooled by Fernstrum grid coolers. The generators are keel cooled using the skeg on the underbelly of the tug as a cooler.
The tug's towing gear consists of a Markey type DEPCF-50 75 horsepower electric hawser winch, mounted on the bow; outfitted with 500(ft) of 9(in) synthetic line. With a line pull up to 44,000 lbs and a line speed (up to) 393(ft) per minute, and a drum brake holding capacity of 400,000 lbs. The Markey level wind spools the line in such a way as to minimize pull-down during high-tension operations, and a line tension display system provides the operator with an active display of line tension while executing ship docking or escort maneuvers. The winch is operated via all electrical controls, including controls that allow the operator to freewheel the drum at any time, whether loaded or unloaded, the winch also features Markey's constant tension "hands-free" render-recover system.
The stern is fitted with a Markey type TES-32 75 horsepwoer electric towing winch, fitted with 2,100(ft) of 2(in) wire plus three layers flange-margin for synthetic line. The two speed towing winch features a line pull up to 156,000 lbs, with line speeds up to 86' (ft) per minute, and a drum brake holding capacity of 400,000 lbs. The standard Markey towing winch level wind spools the wire rope smoothly and consistently the winch also includes an integrated towing bitt for special operations that require manual line handling and tie off, also a warping head with line-speeds to 60(ft) minute, and a super-compact design as required for stern installation on z drive tugs. The winch is operated with all electrical controls, including controls that allow the operator to freewheel the drum at any time, whether loaded or unloaded, and Markey's constant tension "hands-free" render-recover system. The Markey electrical drive and control system is based on two 75 horsepower AC Variable frequency drives which can be switched between either the bow hawser winch, or the stern towing winch.
Boston Towing has strict fendering requirements for its ship assist and barge handling tugs. The upper bow course is Viking 14(in) molded square fender. Below it is Viking 17(in) enhanced soft loop to the deck level; Viking 12(in) by 14(in) square fender at the deck line; Viking 17(in) enhanced soft loop below the deck line to the waterline; and four courses of 18(in) flanged Viking fender below the waterline. Viking 12 (in) black rubber "D" fender is fitted at the main deck from the bow fenders at the sides and around the stern. Additional courses of 8(in) of "D" fendering are strategically located at different points on the hull and tires are used to cover the forward sides. Stainless steel pins are used to fasten the "D" fendering.
The Siemens machinery alarm system consists of an integrated multi channel alarm system complete with sensors and local/remote alarm indicators. All components are completely modular and plug into a single dedicated backbone running fore and aft through the vessel. Navigation and communications equipment include a Furuno GP-37 DGPS; a Robertson AP9MK3 autopilot; a Furuno SC-60 satellite compass; a Standard LH5 loud hailer; a Simrad RA53-4-24V radar with a 64 NM range; a Furuno 1953 C/NT-4 scan radar; a Furuno RD-30 depth sounder; and two Standard Omni VHF radios.
(Washburn and Doughty Associates)