Bigger containerships, prospects for increased U.S. grain exports and worldwide expansion in the liquefied natural gas trade are helping drive tugboat design and construction to the next levels of power and sophistication.
With that demand come additional challenges — fitting bigger, heavier engines and drives into the new tugs. For these high-horsepower vessels, the advent of Tier 4 emission standards brings additional complexity and space requirements for emission controls.
That new generation will be emerging from shipyards in the first half of 2017. In Bayou La Batre, Ala., Horizon Shipbuilding is working to complete the Capt. Brian A. McAllister, first in a series of four 100'×40', 6,770-hp escort tugs for New York-based McAllister Towing and Transportation Co. Inc. With a bollard pull of around 90 short tons, they are designed to handle bigger containerships that pass through the widened Panama Canal.
They will be among the biggest tugs in McAllister’s East Coast fleet, a hull design from the minds at Jensen Maritime. Another next-generation design from the Seattle architects, a 110'×40', 6,770-hp multipurpose tractor tug under construction by JT Marine, Vancouver, Wash., is scheduled for delivery to Vessel Chartering LLC, a subsidiary of Baydelta Maritime, San Francisco, later this year.
Jensen says the vessel’s 110' length gives it the towing performance and range of larger oceangoing tugs, with a bollard pull of 93 to 95 short tons, while still providing the deft ship assist and escort touch of smaller harbor tugs. The escort capability was enhanced in anticipation of bigger containerships up to 18,000 TEUs coming to West Coast ports.
It is the third Jensen tug design to tackle the Environmental Protection Agency’s Tier 4 emissions requirements, using exhaust treatment systems to achieve the further 74% reduction in nitrogen oxides and 82% cut in particulate matter demanded in the new rules.
That takes some doing. Vessel designers and engineers say Tier 4 equipment can require two to three times the internal space of older exhaust systems. The Baydelta tug will carry up to 4,500 gals. of urea to treat exhaust gases — more than its 4,300 gals. tankage for fresh water.
“The development of the Tier  engines for this tug demonstrates our commitment to innovative, environmentally friendly design while continuing to deliver powerful, high-quality performance,” Johan Sperling, Jensen’s vice president, said when the project was announced. “This tug will meet our industry’s demands for strong, yet nimble vessels with the quality design people expect from us.”
The Jensen designs are close in size and power. Propulsion on the McAllister tugs will be pairs of Caterpillar 3516E Tier 4 engines running Schottel SRP4000 FP azimuth thrusters, with 80 metric tons of bollard pull. They will be classified ABS Maltese Cross A-1 Towing, Escort Service, FiFi 1 and Maltese Cross AMS.
The Baydelta tug will likewise be powered by two Cat 3516Es. With its deck machinery — an electrically powered Rapp Marine double-drum tow winch aft and an electrically powered hawser winch forward by Markey Machinery — the tug will have a calculated 93-to-95 short-ton bollard pull. Having both winches run on electrical power removes the chances of a hydraulic oil spill on deck.
Jensen designers came up with another low-cost solution for environmental and regulatory issues with ballast water. With new rules pending to treat ballast water for the control of invasive marine species, they simply got rid of ballast water tanks. The Baydelta tug will move its 123,000 gals. fuel capacity around tanks to maintain trim.
With the Tier 4 emission requirements fast approaching, builders and operators have been adding vessels just before the new EPA threshold kicks in.
Washburn & Doughty Associates Inc., East Boothbay, Maine, continues to build 93'×38'×15'6", 6,000-hp Z-drive tugs for New Canaan, Conn.-based Moran Towing Corp. Powered by twin EMD 12-710G7C or Caterpillar 3516B engines, they have been Moran’s preferred newbuilds since 2013, with the Maxwell Paul Moran hitting the water Sept. 30. Moran now has 11 6,000-hp Z-drive harbor tugs in its fleet and two more under construction, according to its website. Moran also has two LNG 6,000-hp tugs under charter.
Based on Washburn & Doughty’s earlier 92'×32' design, the 93' tugs accommodate more horsepower while maintaining good handling characteristics. Executive vice president Bruce Washburn said the company is preparing for the Tier 4 generation, but the 6,500-hp level and above represents a new design frontier beyond recent 95' to 100' docking tugs.
Tug designs from the prolific Robert Allan Ltd. (RAL), Vancouver, British Columbia, are favored worldwide and have been prominent additions to U.S. harbor fleets in recent months. In December E.N. Bisso & Son Inc. took delivery of the 80'×38'×15', 5,362-hp azimuth stern drive (ASD) tug Gladys B from Signet Shipbuilding & Repair, Pascagoula, Miss.
New Orleans-based Bisso decided to build the ASD tug before the Tier 4 emission requirements took effect in 2017. The Gladys B Tier 3 propulsion package is made up of two MTU 16V4000 M64 diesels that produce 2,681 hp each, turning Rolls-Royce US205 fixed-pitch Z-drives. That combination provides bollard pulls of 60 metric tons forward and 56 metric tons astern.
Built on the lines of the RApport 2400 class, it was the 10th RAL tug design for Signet Maritime Corp., and the fourth to be built at Signet’s Pascagoula yard. A sistership, the Signet Magic, has been in the company’s fleet for three years.
Based on that design, the Gladys B differs in its increased helm beam, modified skeg, and the addition of bilge keels. That makes it fully ABS class compliant for escort operations, according to the designers. “This powerful steel titan will serve her owner well. Built in America, built by Americans and built for progress. She will soon be known in Louisiana as the Maserati of the river,” Signet president J. Barry Snyder said in remarks at an Oct. 12 christening.
Eastern Shipbuilding Group, Panama City, Fla., launched a similarly sized series of RAL-designed Z-Tech 2400-class terminal and escort tugs for Bay-Houston Towing Co. and Suderman & Young Towing Co. — eight vessels in all to assist ships that call at Texas ports.
Along with larger containerships, prospects for U.S. export growth of grain and LNG are factoring into tug operators’ planning and building programs.
In its year-end Grain Transportation Report, the U.S. Department of Agriculture called 2016 a “remarkable” year, with barge movements of grain up 19% from the year before and strong export activity out of the Pacific Northwest and Gulf of Mexico ports.
Those expectations led Crescent Towing to add three new Z-drive ship assist and escort tugs for its operations in New Orleans, Mobile, Ala., and Savannah, Ga. The 92'×38'×17', 5,500-hp Mardi Gras, Arkansas and South Carolina, a Jensen Maritime design built by Steiner Shipyard, Bayou La Batre, Ala., were all delivered by the end of 2016.