Ocean TundraJul 2, 2014 02:40 PM
Quebec company comes up with a big versatile tug ready for all seasons
Ocean Tundra, with a bollard pull of 113 tons, is billed as the most powerful tug in Canadian registry.
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Gordon Bain calls his big new tug “the beast.”
Bain is president and founder of Ocean, the Quebec-based marine services company. The official name of his company’s newest tug is Ocean Tundra. At 118 feet in length, this twin z-drive, 8,160-hp boat generates a bollard pull of 113 metric tons. Those stats are the basis of the claim that Ocean Tundra is the most powerful harbor tug ever built in Canada.
However, when Bain calls the tug a beast, he is not thinking about raw power alone, but also the vessel’s ability to perform safely in extreme northern environments. With an ice class certification of 1AS FS, Ocean Tundra routinely performs icebreaking duties on the St. Lawrence River.
“This tug is really a mean machine,” Bain said, recounting a ride he took on Ocean Tundra this winter near the company’s Quebec City base, where the St. Charles River joins the St. Lawrence. At the time, the rivers were encased in ice, including an ice ridge in the St. Lawrence about 15 feet thick. The boat, he said, was able to “crush the ice without any trouble.”
Capt. Rejean Blais at the controls.
The boat went through the ice ridge, continued up the St. Charles, then backed out, crushing ice all the way. The ice, he said, went through the propellers of the z-drives “like slush, no noise, no vibration.”
The z-drive’s stainless steel props are just under 10 feet in diameter. After going through the props, the biggest pieces of ice left behind in the boat’s wake were only about 9 inches square, Bain said.
“What comes through the propellers, comes out like that,” he said, making a sweeping motion with his hand. “It outperformed anything I thought it would.”
Ocean Tundra was not designed just as an icebreaker. The company calls it a multipurpose coastal tug capable of icebreaking, ship escorting and docking, firefighting and even some ship rescue or salvage work.
“There are many reasons we built Tundra,” Bain said. “We try to get as much versatility as possible.”
The boat was designed by the Vancouver design firm of Robert Allan Ltd. The initial mandate of the design team was to create a boat with significant icebreaking and escorting capabilities that could work with LNG carriers and petroleum tankers for an extended season in the lower St. Lawrence River, according to Robert Allan, the head of the design firm. However, when various LNG terminals did not materialize, the tug was reconfigured for a more multifunctional role.
While it might not be suitable for year-round operations in the high Arctic, it could work “just about anywhere in the Arctic in the summer and shoulder seasons,” according to Allan.
“This a pretty serious icebreaking boat,” he said. “Within Canada, it could work anywhere in the St. Lawrence and Great Lakes throughout the winter…It’s the most capable tug in the St. Lawrence system. I can say that with assurance. Our press release calls it the most powerful tug in Canadian registry.”
The tug in mid-March on the St. Lawrence River near Quebec City.
The tug’s z-drives give it advantages in the ice. While a conventionally powered tug will create a channel about the same width as its beam, a z-drive tug can create a path one and a half times its beam. By angling the z-drive’s props outboard, the operator can “vector the ice away from the boat.” This also creates a clearer channel behind the tug, as the broken ice pieces are pushed below the adjacent ice sheet.
Yet another advantage is the ability of the z-drive to generate almost as much thrust in reverse as ahead. When moving astern, Ocean Tundra can exert 95 percent as much thrust, while a boat with a prop in a fixed nozzle can exert at best 50 percent. So a tug like Ocean Tundra is much less likely to get stuck in the ice, and when it does, it can extract itself more easily.
“We know from a lot of experience and model testing, z-drives are a huge advantage when you’re working in ice,” Allan said.
The towing pin system and stern roller.
Ocean Tundra also needed to be able to escort large tankers and bulk carriers. “The biggest challenge for us was to combine high icebreaking capability with a significant escort capability,” Allan said.
The two roles are in some ways conflicting. The ideal icebreaker has a bow that allows it to ride up on the ice, while an escort vessel needs to have a hull that can generate powerful lateral forces, especially focused on maximum area low and forward in the hull.
The tug is powered by two 4,080-hp MAK 9M25C diesels.
“You should move the center of effort as far forward as possible,” Allan explained. “The centroid of all the underwater area is as far forward as practicable. That’s what generates the indirect forces. However this is directly contrary to the form for most efficient icebreaking, so a delicate balance is necessary between these two contrary design objectives.”
The problem is not a new one for the design firm. Robert Allan Ltd. designed four similar tugs for escort work at a Russian LNG terminal on Sakhalin Island in the Pacific, a place with what Allan called “a pretty high ice regime.”
Ocean Tundra is a “slightly scaled-up model” of a “well-proven prototype,” Allan said.
Central to the boat’s duties are its winches, which must operate reliably in a very challenging northern climate.
On the bow is a Markey DESDF-48 200-hp electric escort hawser winch with render/recover capability. The winch has a 202-metric-ton pulling capacity and 307-metric-ton braking capacity. The brakes and clutches on the winch are actuated by a pneumatic system.
Markey came up with several modifications of its standard designs to ensure reliability in extreme cold. Ocean Tundra’s escort winch has an attached heated enclosure to protect those items that could be affected by the cold. They include the electric motor, water-cooled slip-brake, pneumatic logic panel and lube pump.
“The most vulnerable elements are housed in a nice environment,” said Scott Kreis, Markey’s vice president of sales.