Seabulk Towing completes innovative four-tug order from Master Boat Builders
Seabulk Towing has completed its four-tugboat order with Master Boat Builders, adding two hybrid ship- assist tugboats and two Advanced Rotortugs (ARTs) to its Gulf Coast fleet within barely a year.
The two newest tugboats are the 98.5-foot diesel-electric hybrid Titan, which operates from the energy and petrochemical hub in Port Arthur, Texas, and the 98.5-foot ART Hermes that works from Mobile, Ala.
Robert Allan Ltd. of Vancouver, British Columbia, designed Titan and its sister tug Spartan, using plans from Robert Allan Ltd.’s RApport 3000 series of powerful escort tugboats.
The 98.5-by-43.5-foot Hermes and its sister tug Nike, meanwhile, are based on Robert Allan Ltd.’s Advanced Rotortug (ART) platform featuring three engines and three z-drives in a triangular pattern under the hull.
Nike and Hermes build on Seabulk Towing’s three existing ART tugboats delivered in 2017 and 2018. The ART platform is designed for superior power and maneuverability. They exert unusually strong power sideways, particularly at high speed when escorting a ship.
The two newer ARTs deliver 25 percent more horsepower than their predecessors thanks to three 2,375-hp Caterpillar 3512 Tier 4 main engines. The three mains are paired with Schottel SRP 430 z-drive units with fixed-pitch props. Electrical power comes from two 118-kW Cat C7.1 generators
On deck, Hermes is outfitted with a versatile winch package from JonRie InterTech. The tug is equipped with a JonRie Series 240 winch forward, while the aft deck has a burly Series 500 double-drum winch. Both winches are spooled with Samson Saturn-12 rope.
Hermes and Nike feature a spacious wheelhouse anchored by an Alphatron Integrated Bridge with four flatscreen monitors that retract when not in use. JRC supplied the four radar units, along with the AIS, compass and other navigation electronics. Icom supplied the VHF radios.
Hermes can do more than assist ships thanks to a capable off-ship firefighting package consisting of a remote-controlled FFS monitor fed by an FFS pump. At full power, the system can spray 3,000 gallons per minute.
Both Hermes and Nike operate from Mobile, Ala., a port with its share of tight slips and narrow spaces. The two new ARTs give captains the tools they need to get the job done.
Further west along the Gulf Coast, in Port Arthur, Texas, Seabulk has stationed its two new diesel-electric tugs Spartan and Titan. These powerful tugs assist and escort tankers and other big ships calling at the energy terminals and around Port Arthur, Texas.
“It handles really well,” Titan Capt. William Soileau said recently, adding that the vessel is right at home in a ship-assist role.
“We turn them, we push them and pull them and we slow them down,” he said, adding that some escort jobs take as long as three hours.
Spartan and Titan are the first hybrids in Seabulk’s towing fleet, which now has about two dozen tugboats. They also were the first hybrid project for Cat supplier Thompson Tractor, which supplied the Cat engines, generators and Berg z-drives.
The hybrid powerplant on both tugs features two 2,550-hp Caterpillar 3512 main engines, along with two 565-kW Cat C18 gensets and a third 200-kW Cat C7.1 genset. Additionally, 560-kW ABB electric motors are installed aft of each Berg MTA 628 z-drive. Total installed horsepower, including the electric motors, exceeds 6,600.
There are four main modes on Spartan and Titan’s hybrid packages: standby, eco, mechanical and power. Standby mode uses only the hotel generator for power. In eco mode, one or more generators send power to the ABB electric motors that turn the z-drives.
The system automatically spools up or down the generators as the operator demands more power, and will spread the load between multiple generators. Power mode uses electricity from the three gensets and electric motors in tandem with the two Cat main engines. Mechanical mode reverts to the twin Cat main engines and disengages the electric motors.
“It’s a really good system,” Soileau said. “It’s very efficient.”
There are multiple benefits from a hybrid propulsion system. For one, operators can downsize their engines from, say, a Cat 3516 to a Cat 3512 without impacting towing capabilities. And when transiting to a job, the tugs can disengage the mains and run entirely on electric power — reducing engine wear, saving fuel and cutting emissions.
Spartan and Titan, running in eco mode alone, can produce about 25 tons of bollard pull. But in power mode, with all systems running, that jumps to nearly 90 tons. Both tugs also contain ample space for battery banks that could be installed down the road to power the electric motors.
Spartan and Titan are blessed with enormous engine rooms that have plenty of space for the third generator and the electrical integration equipment. Engineer Buck Shoemaker III said the hybrid system and its components ultimately make his job a little easier.
“But with that comes a learning curve,” he added.
Titan and Spartan are equipped with a JonRie InterTech Series 225 winch on the bow wrapped with 600 feet of 8.5-inch Samson Saturn-12 line. The winch can generate 50,000 pounds of line pull and has a brake holding force of 720,000 pounds. The aft deck is equipped with a JonRie Series 424 hydraulic capstan with a line-pull rating of 20,000 pounds.
The wheelhouse on the hybrid tugs is nearly identical to the ARTs working in Mobile, with an Alphatron bridge, JRC radars and Icom radios. •