Signet Shipbuilding & Repair, Pascagoula, Miss., delivered the Signet Sirius, the first of two 7,725-hp ART 92-32W Rotortugs, to Signet Maritime, Houston, late last year..
This is the first ART Rotortug that Signet has built and operated in their fleet. Designed by Robert Allan Ltd. (RAL) in collaboration with RotorTug BV, the Advanced Rotortugs (ART) incorporate the patented triple Z-drive Rotortug propulsion layout, featuring omni-directional maneuverability, and the benefits of a fully redundant and precise propulsion machinery configuration, RAL said. The Rotortug concept, RAL said, offers increased redundancy for shiphandling, terminal support, and escort towing, as well as enhanced crew safety.
The tugs were named the Boat of the Year for 2023 by WorkBoat at December's International WorkBoat Show.
Signet Sirius and Signet Capella specifications:
Length overall: 103'4"
Beam, moulded: 45'-6"
Depth, moulded: 15'-7"
Maximum draft (overall): 21'6"
Power: (3) MTU 12V4000 M65L, 2,575 hp
U.S. gross tonnage: 299
Bollard pull: 92 metric tons
The tugs are classed by American Bureau of Shipping, with the following notations:
Signet Sirius and Signet Capella are built for close-quarter operations in narrow marine terminal slips and can shoulder indirect and accelerate assist maneuver deep-draft VLCCs not otherwise possible.
A hull breach in any space will keep the vessel upright. In addition, the tugs will carry custom-designed, modular ultra-high-performance polyurethane elastomer fenders from Buoyant Works. The fenders are 30% lighter than materials normally used and can be individually replaced. This eliminates the need to replace an entire fender because of damage to one area.
Main propulsion comes from three MTU 12V4000 M65L Tier 4 marine engines producing a total of 7,725 hp. The mains connect to Kongsberg US 205 controllable pitch Z- drives with 2,500mm-dia., 4-bladed nibral propellers in nozzles.
Ship’s service power comes from a pair of Tier 3 John Deere 6135 AFM85 gensets, sparking 300 kW of electrical power each.
The tugs have two Markey Machine winches each on deck — a DESF-52 AGILE, 200-hp, electric winch on the bow; and a TESF-32 AGILE, 200-hp, electric winch on the stern. These were complete winch redesigns. Both winches transition between gears for increased line tension and speed to protect the vessel from high pitch and roll moments in two-meter, six-second seas and protect ship and tug from shock loads and zero-tension (slack line) issues.
Also on deck, the tug is equipped with a Fire Fighting Systems AS (FFS) SFP 1,000-kW centrifugal fire pump, and two FFS 1200LB remotely operated monitors with 10,600-gpm flow and a range of 400'.
The new tugs have a three-thruster design — two forward and one aft — making them able to steer and affect line tension in different directions.
