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Quebec Bulletin
June - July 2015/Volume 18/Number 3

Icebreakers: How Do They Work?

The CCGS Amundsen dry-docked.

To be considered an icebreaker, a vessel must have three characteristics:

  • a reinforced hull for moving through ice;
  • a more tapered bow; and
  • sufficient power to move forward through ice.

The hull of an icebreaker is designed to keep the vessel as stable as possible. On Canadian Coast Guard icebreakers, the hull is reinforced with special frames called the vessel's ice belt. Located at the water line, the frames are meant to withstand the pressure exerted by the ice.

An icebreaker can break ice in two ways:

  • by using its power and weight to force its way through; or
  • by forcing its bow onto the ice to break it with its weight, while pushing broken pieces to the sides to prevent them from piling up in the front.
Mechanic in front of one of the CCGS Pierre Radisson engines.
Mechanic in front of a CCGS Pierre Radisson engines.

During icebreaking operations, the propeller shafts—key components of the propulsion system—are highly stressed. They sustain numerous vibrations as a result of the vessel's movement through the ice and must withstand shocks from the vessel's hard accelerations and decelerations. These parts are therefore more durable and oversized compared to those in other vessels.

The City of Québec is the home port for three Canadian Coast Guard icebreakers powered by this impressive system:

This article was written in collaboration with the Chief Engineer of the CCGS Pierre Radisson, Stéphane Belzile.

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Julie Lemoine

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