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Bollard pull is a conventional measure of the pulling (or towing) power of a watercraft.It is defined as the force (usually in tonnes-force or kilonewtons (kN)) exerted by a vessel under full power, on a shore-mounted bollard through a tow-line, commonly measured in a practical test (but sometimes simulated) under test conditions that include calm water, no tide, level trim, and sufficient ...
Bollard pull can increase up to 30% with ducts. With decelerating ducts, the circulation opposite of the Kort nozzle, resulting in a negative thrust of the duct. This type is used for high speed vessels with increased exposure to cavitation and vessels that want to reduce noise levels, such as warships.
A tugboat is typically rated by its engine's power output and its overall bollard pull. The largest commercial harbour tugboats in the 2000s–2010s, used for towing container ships or similar, had around 60 to 65 short tons-force (530–580 kN) of bollard pull, which is described as 15 short tons-force (130 kN) above "normal" tugboats. [5] [6]
The icebreaker is propelled by two 5-megawatt (6,700 hp) ABB Azipod azimuth thrusters that produce a bollard pull of 115 tonnes-force (127 short tons-force; 1,130 kN) in ahead and 95 tonnes-force (105 short tons-force; 930 kN) in astern direction, [4] and enable the vessel to break up to 1.5 metres (4.9 ft) thick ice.
Each vessel is 28.5 metres long and has a beam of 9.5 metres and a draught of 2.8 metres. Each tug in the class has a capacity of 25 tonnes bollard pull.The vessel are fitted with a pair of V-12 cylinder Cummins KTA38M2 engines, each generating 1200 HP continuous duty at 1800 RPM.
The Voith Schneider propeller was originally a design for a hydro-electric turbine. [2] Its Austrian inventor, Ernst Schneider, had a chance meeting on a train with a manager at Voith's subsidiary St. Pölten works; this led to the turbine being investigated by Voith's engineers, who discovered that although it was no more efficient than other water turbines, Schneider's design worked well as ...
The vessel's twin shaft lines with controllable pitch propellers can be driven with a maximum power of 18,800 kW (25,200 hp) and, when used in boost mode together with the 1,200 kW (1,600 hp) drop-down azimuthing bow thruster, generate a bollard pull of 307 tonnes (338 short tons). [7]
However, for short-term operation the icebreaker can use its maximum shaft output of 9,100 kilowatts (12,200 hp) to generate a bollard pull of 1,400 kilonewtons (140 tf). [ 6 ] [ 8 ] The vessel has a service speed of 16.5 knots (30.6 km/h; 19.0 mph) in open water [ 5 ] and maintain a continuous speed of 2 knots (3.7 km/h; 2.3 mph) when breaking ...