Mudyug () is a Russian icebreaker and the lead ship of a series of three subarctic icebreakers built at Wärtsilä Helsinki shipyard in Finland in 1982–1983. The vessel's non-rebuilt sister ships are Magadan and Dikson.
Mudyug was rebuilt with a new Thyssen-Waas icebreaking bow at Nordseewerke in 1986.
Design
Mudyug was originally built with a overall length of , or if the towing notch is included, and a maximum beam of . However, the 1986 conversion increased the vessel's hull length to and beam to at the widest point of the hull. When loaded to the maximum draught of , the icebreaker has a displacement of , about 30% greater than that of the non-rebuilt sister ships. The vessel's ice class, LL4, is intended for icebreaking operations primarily in ports and coastal areas.
Unlike most icebreakers, Mudyug has a diesel-mechanical propulsion system where the vessel's four 8-cylinder Wärtsilä 8R32 medium-speed main engines are coupled in pairs through Lohmann & Stolterfoht Navilus twin-input/single-output single-stage reduction gearboxes to propeller shafts driving four-bladed stainless steel KaMeWa controllable pitch propellers. In order to protect the main engines from large torque variations during icebreaking operations and to prevent the propellers from stopping when the blades come in contact with ice, each shaft has a flywheel to increase rotational inertia of the drivetrain. Onboard electrical power is generated by three Wärtsilä-Vasa 624TS auxiliary diesel engines with 960 kVA alternators. Mudyugs icebreaking capability is further increased by a hull lubrication system and an active heeling system. During the 1986 conversion, the original Wärtsilä Air Bubbling System (WABS) was replaced with a Jastram-HSVA water deluge system.
Mudyugs bollard pull is when operating with a continuous propulsion power of . However, for short-term operation the icebreaker can use its maximum shaft output of to generate a bollard pull of . The vessel has a service speed of in open water and, prior to rebuilding its icebreaking bow, could maintain a continuous speed of when breaking thick level ice.
History
Development and construction
In 1977, Wärtsilä began developing a new icebreaker concept in close co-operation with experts from the Soviet Union. Although the Finnish shipbuilder had delivered more icebreaking vessels than any other shipyard in the world, they had all been diesel-electric vessels where diesel generators powered electric propulsion motors driving fixed-pitch propellers. In the new icebreakers, this fairly expensive specialized drivetrain would be replaced with cheaper and more efficient mechanical transmission where the main diesel engines would be connected to controllable pitch propellers through a reduction gearbox. An extensive research program was initiated by Wärtsilä Arctic Design and Marketing (WADAM) to ensure that the new concept was viable and that the problems encountered the recently commissioned United States Coast Guard Polar-class icebreakers would be avoided.
In April 1980, Wärtsilä and the Soviet Union signed a FIM 400 million shipbuilding contract for the construction of three icebreakers to escort ships in the freezing subarctic ports. The vessels, first of which would be delivered in late 1982 and the two following ones in 1983, would be stationed in the Barents Sea, Sea of Okhotsk and Baltic Sea.
The lead ship, Mudyug, was laid down at Hietalahti shipyard on 30 December 1980 and launched together with the second icebreaker of the series, Magadan, on 16 April 1982. Shortely before the delivery of the vessel on 29 October 1982, Mudyugs engine room accidentally flooded with water at quayside due to a faulty seacock.
1986 rebuilding
In October 1986, Mudyug was retrofitted with new bow with the intention of improving the vessel's icebreaking capability by a factor of 1.5 without increasing its propulsion power. The icebreaker's traditional wedge-shaped bow was replaced with a so-called Thyssen-Waas bow developed by Thyssen Nordseewerke in cooperation with the Hamburg Ship Model Basin (Hamburgische Schiffbau-Versuchsanstalt; HSVA). The pontoon-shaped bow, which broke ice by shearing instead of traditional bending, had been previously tested in the early 1980s on the German icebreaker Max Waldeck.