Construction is underway on the first self-propelled, removable icebreaking bow to create shipping channels in a key Scandinavian inland waterway
BLRT Grupp is building a revolutionary removable bow designed by naval architects at ILS Ship Design & Engineering for an icebreaking project in Finland. It is under construction at a shipyard in Klaipeda, Lithuania, and scheduled to be attached to a tug during Q4 2019. ILS has designed two versions of these temporary bows that can be attached to vessels for icebreaking requirements.
According to ILS general manager Kristian Lehtonen, the first self-propelled, removable bow module will be transferred from Lithuania to BLRT-owned Turku Repair Yard facilities in Turku, Finland, for outfitting on to an azimuth stern drive (ASD) pusher tug later this year.
“We have designed and ice-model tested two removable bow sizes,” Mr Lehtonen told Tug Technology & Business. “What is now under construction is the smaller one, intended for inland waterways icebreaking.”
“We have designed and ice-model tested two removable bow sizes”
He confirmed that this first attachable bow will be installed on to Alfons Håkans-operated ASD tugboat Calypso, scheduled to operate in Finland for the winter season from the end of this year and into 2020.
“Alfons Håkans was awarded a 10-year contract by the Finnish Transport Agency to conduct inland waterway icebreaking in Lake Saimaa area with our first removable bow,” said Mr Lehtonen. This involves keeping inland waterways in east Finland open to shipping throughout the year.
In preparation, ILS created 3D illustrations covering the combined tug Calypso and icebreaking bow for the Finnish Transport Agency. This bow should effectively convert a conventional tug into an icebreaker at a fraction of the cost of building a new vessel for this contract.
ILS estimates the investment cost of the bow is about 25% of the price of a purpose-built icebreaker. Plus, the construction and conversion periods are shorter than for a newbuilding project and the pusher vessel can be deployed for other duties when there is no ice to break.
This ILS P999 self-propelled, icebreaking and attachable bow has a maximum length of 25.3 m, moulded breadth of 12.6 m and moulded depth of 3.4 m. The tug and bow combined will have a maximum length of 41 m. It will be able to break 80 cm of level ice at a speed of 2 knots. If the speed is increased to 6 knots, the tug-bow combination can break 40 cm of level ice in inland waterways.
ILS also designed a larger self-propelled attachable icebreaking bow for operations in open sea, such as the Baltic Sea. This has an overall length of 56.1 m, moulded breadth of 25.1 m and propulsion power of two x 3 MW. When combined with a vessel, it could break 87 cm of level ice at a speed of 5.3 knots.
Both self-propelled removable bow models are designed with a minimum ice class of 1A Super. They have a fixed coupling between the bow and the pusher tug. Mr Lehtonen said the propulsion system on each involves two propellers with angled shaftlines, located both sides at the reamer area.
The reamer propellers assist in generating icebreaking force and in manoeuvring the bow-vessel combination. “The benefit of the reamer propellers is that they are far from each other,” said Mr Lehtonen. “Therefore, they generate a big turning momentum when thrusting to opposite directions, which makes it possible to turn almost on the spot.” They are useful when the vessel is breaking out of its own channel and breaking ridges of ice.
“Reamers increase the width of the ice channel, and thus reduce frictional resistance in the aft-ship, as well as improve the ship’s manoeuvrability in ice,” said Mr Lehtonen. “The channel made by the combined vessel and removable bow is quite wide so the aft can move and the turning occurs when one propeller is pushing and the other pulling.”
This performance was demonstrated during ice model trials at Aker Arctic’s testing facilities. During these tests, ILS identified how the reamer propellers interacted with ice. There was a suction and flush effect that broke ice ridges efficiently enabling the vessel to sail through them in one attempt both ahead and astern.
ILS developed the removable icebreaking bows with funding from the European Union’s Winter Navigation Motorways of the Sea (WINMOS) programme.
The B24 version for the Baltic Sea was developed in the first phase of the programme. The second phase involves testing the smaller B12 version in Lake Saimaa when it is connected to Calypso. The basic requirements for this are a pusher ice class of 1A Super, ability to break 70 cm of ice at 2 knots, 40 cm at 6 knots and to sail through a 1.5 m consolidated ice channel at 7 knots. The total propulsion power of the pusher tug and removable bow will be about 2.6 MW.
ILS has started marketing its attachable bows for icebreaking operations in Canada, Russia and Sweden as there are shallow waterways that are frozen during winter. It has also conducted high profile consulting commissions for Russian and Finnish customers, which are of a classified nature, said Mr Lehtonen, adding that ILS has also completed feasibility studies, repair designs, bollard pull testing and inclination experiments.
ILS also designed a new icebreaking escort tug for operations offshore Sakhalin in the far east of Siberia. The vessel is being built in a shipyard in Yangzhong, China, and was due to be delivered in Q1 2019. Mr Lehtonen said the project is on schedule, with the vessel launched at the Chinese shipyard. It is based on the design of 2014-built harbour icebreaker and escort tug IB Ahto.
In the past five years, ILS has worked with shipowners and shipyards worldwide on icebreaking vessels and provided designs to Baltic Workboats.
ILS removable bow details
Length, oa: 25.3 m
Breadth, moulded: 12.6 m
Depth, moulded: 3.6 m
Icebreaking: 80 cm, 2 knots
Higher speed: 40 cm, 6 knots
Length, oa: 56.1 m
Breadth, moulded: 25.1 m
Depth, moulded: 6 m
Icebreaking: 87 cm at 5.3 knots
Propulsion power 2 x 3 MW