Employees of Island Tug & Barge, Ltd., Vancouver, British Columbia, like to say that they don’t know much about bollard pull ratings — for them its much more about barge pulling. That, they say, is what they do.
Almost the entire revenue stream of this family-operated company comes from pulling and pushing barges filled with various petroleum products. The company recently converted its largest tug to an Intercon articulated-connection system, and now it has introduced a smaller tug that seems ideally designed for moving medium-sized oil barges.
The 85-foot Island Scout is built with about as much redundancy as is possible in a conventionally powered twin-screw tug.
“Aside from using modern double-hull barges and creating a no-spill culture among its employees, the best thing that a towing company can do is to build systems into its tugboats to reduce the possibility of an accident that might cause loss of control,” said Bob Shields, president of the company with a 75-year history and a current fleet of eight tugs and 10 barges.
“Transporting of refined petroleum products by barge is 90 percent of our business,” said Shields. “Our business is growing and this new tug will be able to handle any towing assignment we give her, except maybe dealing with our largest barge.”
The hull of this newest tug in the Island Tug fleet was built at the Jinling Shipyard in Nanjing, China, to a design originally generated in the 1970s for Seaspan’s C-Class tugs. These vessels, including Seaspan Cavalier, Crusader and Cutlass, are still in operation and are known as seakindly vessels.
Island Scout being built in the 21st century is almost unique in that it has been constructed with a round bilge hull similar to that of her predecessor Seaspan tugs. The hull arrived in Vancouver atop one of Island Tug’s new double-hulled barges in 2001 and it has been a work in progress ever since.
“There’s no replacement for the rounded hull when you are trying to achieve optimum water flow to the propellers,” said Shields. “Boats with hard chines are just not the same.”
Round hulls are fast and they can be fuel efficient, depending on how they are operated, said project supervisor Marc McAllister of McAllister Marine Survey & Design Ltd. A major drawback to the round-bilge design, of course, is a tendency to roll. That’s why Island Scout is built with a substantial stabilizer fin — called a “rolling chock” in Canada — along most of its length on either side of the hull.
“Any good shipyard can build a round bilge hull form, but it’s very labor intensive and not many people today want to pay that kind of money,” said McAllister. “That’s one of the advantages of building in China where you can do that kind of thing without a financial penalty.”
Island Scout, or the hull, at least, is the fourth vessel built for this company in China, the others being barges. The company recently completed design work on a pair of 25,000-barrel, clean oil barges which, according to plan, will also be built in China.
Island Scout’s hull, to conform to Canadian regulations requiring crew accommodation to be above the vessel’s waterline, features a raised focsle deck that allows for accommodations in three cabins on the main deck level and two cabins on the boat deck level. The boat deck is part of an aluminum two story house that has been added by Island Tug’s shore crew. The aluminum house, designed by naval architects at Robert Allan Ltd., provides for an elevated wheelhouse to allow the tug operators good visibility when pushing a light oil barge. The aluminum house is attached to the steel deck using the Datacouple bonding system.
Designed for both pushing and towing, the boat is fitted with a custom designed headline winch on its bow with a 50,000 pound line pull. On the aft deck there is a massive Burrard Iron Works single-drum towing winch wrapped with 2,600 feet of 1 3/4-inch towing wire. On the stern is a package of hydraulic towing gear — hold-down hook, triple pins and roller — all provided by Western Machine Works of Vancouver. These retractable items are powered by their own electro-hydraulic pump with remote controls.
The bow winch on this tug is used not for ship-assist work, but for headline work with a barge. “They run the headline up through the bullnose on the bow and rig it for slip around a cleat on the side of the barge. That way they can pull a barge off a dock and then slip the line without having to send a man up onto the barge,” said McAllister.
Since the tug will spend most of its time pushing in the shallow notch of medium-sized barges, its stern gear includes heavy sheaves at each corner and on the centerline as turning blocks for wire push gear that will be kept tight by the towing winch.
In the engine room, a pair of Cummins KTA38 main engines, with dual 800/500 hp ratings, are linked by Centalink flexible coupling to Twin Disc MG 5222 gears with 6.10:1 reduction. While compensating for any misalignment between the soft mounted engines and the hard mounted gears, these couplings also reduce gear noise.
Just behind the gears, dual-caliber Kobelt shaft brakes are mounted on the seven-inch steel propeller shafts. Both the engines and gears are electronically controlled, and the shaft brakes can be programmed to accommodate any desired delay time between gears. The disc brakes on each shaft help to compensate for the momentum of the long, steel shafts and the heavy Kaplan-style 78-inch propellers.
The 78-inch-by-60-inch, four-bladed propellers are considered oversized for a vessel of this horsepower range. The company estimates that Island Scout will generate either 32,000 pounds or 50,000 pounds of bollard pull, depending on power setting but, as they say, “Who’s keeping track?”
Canadian regulations require a tug of more than 1,000 hp to carry an engineer, so by using the lower power setting for much of its work in the south, Island Scout will normally sail with a four-person crew. For longer trips in more open water to the north, however, it has accommodation for the fifth crewmember.
Both the main engines and the auxiliary power engines are mounted on rubber, vibration-reducing isolation mounts from Sound Design in Massachusetts. These, combined with the Centalink flexible shaft couplings, are intended to help reduce noise and vibration throughout the vessel.
A pair of 99 Kw Caterpillar 3306 gensets with hydraulic power take-offs from each engine rounds out the engine room machinery. The towing winch, headline winch and anchor winch will be driven hydraulically, as will the 150 hp, 26-inch bow thruster.
The props are in nozzles with double rudder blades behind each. The fully redundant Jastram steering system allows the rudders to be operated independently or in synchronized mode.
“Here is where we really get into the redundancy,” said McAllister. “We have two completely separate and independent steering systems for the boat that also can be synchronized. You can operate them singly or together. But when you are operating in synchronized mode, they are linked electronically, so you might be using just one steering lever in the wheelhouse. If you desire, you can operate each rudder system on its own with two levers.”
Each steering system has its own AC-powered hydraulic pump, but in case of AC power failure, each system also has a back-up DC pump fed by the banks of engine batteries which are constantly being charged by the engines.
“So as long as there is an engine running, you’ll be able to steer this boat,” he added. All diesel engines on the boat are battery started, as is common on many new Canadian tugs.
The tug’s pilothouse, with fore and aft controls plus full controls on either bridge wing, is outfitted with electronics provided mostly by Japan Radio Co., Ltd. (JRC). The navigation system includes both an ECDIS electronic charting system as well as full paper charts.
From the soft-mounted engines to the main deck level accommodations, the company’s commitment to crew comfort and fatigue reduction is evident. Flooring throughout the deck house consists of several layers of sound- and vibration-deadening material, while bulkheads and other surfaces in accommodation spaces are coated with no acoustic insulation material. Engineers have made extra efforts to isolate and quiet the exhaust systems, according to McAllister.
The Cummins main engines come with two options which make life easier for crewmembers. The Cummins ‘Eliminator’ oil purification system does away with the need for conventional oil filters, saving service time and disposal problems. An oversize oil pan, combined with the Cummins Eliminator and Centinel oil management systems, extends the time between oil changes beyond the typical 250 hours to 4,000 hours, according to the manufacturer. The ‘Centinel’ system is an oil burn system which, in conjunction with the Eliminator, eradicates the need for oil changes and costly disposal problems. One other tug in the Island Tug & Barge fleet has the same systems installed, said McAllister.
Shields said he is proud of his company’s reputation for environmental precautions, as reflected by a recent industry recognition. In 2005 Island Tug was the first Canadian tug and barge company to be awarded the Exceptional Compliance Program Award (ECOPRO) from the Washington State Department of Ecology for excellence in marine safety and environmental stewardship.
“We’re growing and we’re expanding our oil trade into new regions including the Canadian Arctic and across the border into the U.S.,” Shields said.