February 16, 2010
Navy puts first of new tug series to work
The YT 802 Valiant, first of the new series of Z-Tech 4500 Class tugs for U.S. Navy pilots operating in Puget Sound, was placed in active service earlier this month.
The new series tugs are being built in Tacoma, Wash., by J. M. Martinac Shipbuilding Ltd., a sub-contractor to Pacific Tugboat Services of Long Beach, CA, the prime contractor.
The design was developed by Robert Allan Ltd. of Vancouver, Canada, and adapted to the Navy's needs based on the Z-Tech 6000 hullform originally developeds for the Port of Singapore.
Based in Bremerton and Bangor, Washington, the tugs will perform ship-handling duties for the full range of Navy surface warships and submarines. They are equipped with an extensive array of underwater fendering, as well as the typical resilient style fenders for handling surface ships.
The Z-Tech 4500 class tugs have the following particulars,:
Length Overall, 27.42 m
Beam, Molded,11.65 m
Depth, Molded, 5.00 m
Load Draft, max, 4.88 m
Propulsion machinery comprises a pair of CAT 3512C, main engines, each rated 1,350 kW (1,810 bhp) at 1,600 rpm, each driving a Schottel Model SRP 1012 steering/propulsion Z-Drive units, with 2,100 mm diameter fixed pitch propellers. This combination delivered in excess of the predicted performance, providing 42 t (92,500 lb) bollard pull ahead, 45 t (99,205 lb) astern, and a free-running speed of 12.4 knots on trials.
Electrical power is delivered by a pair of R.A. Mitchell Co. diesel gensets with a John Deere 6068SFM75 prime mover, each rated 130 ekW at 1,800 rpm.
Deck machinery fitted includes a ship-handling hawser winch forward; JonRie Series 210 Assist winch, fitted with 180 m of 175 mm line. This winch has a brake capacity of 136 t (300,000 lb), and a line pull/speed rating of 9 t (20,000 lb) at 53 m/min (175 ft/min).
The fendering is all rated "non-marking" for dealing with the gray hulls of warships, and was supplied by Shibata through Schuyler Fenders.
The tugs are configured as "day-boats" but also provide accommodations for a crew of up to six persons. One of the unique features of the layout is the complete separation of the accommodation deckhouse from the machinery casing, a configuration designed to both provide a reasonably dry access to the accommodation spaces in the notoriously damp northwest climate, as well as to provide a significant degree of noise attenuation in the crew spaces.