Otso (icebreaker): Difference between revisions
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{{short description|Finnish icebreaker}} |
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{{Use dmy dates|date=February 2019}} |
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{|{{Infobox ship begin}} |
{|{{Infobox ship begin}} |
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{{Infobox ship image |
{{Infobox ship image |
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| Ship image= |
| Ship image=File:Finnish icebreaker Otso 2012-01-18.jpg |
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| Ship caption=''Otso'' returning from sea trials to the icebreaker base at Katajanokka, Helsinki, on 18 January 2012. |
| Ship caption=''Otso'' returning from sea trials to the icebreaker base at Katajanokka, Helsinki, on 18 January 2012. |
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{{Infobox ship career |
{{Infobox ship career |
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| Ship country=Finland |
| Ship country= Finland |
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| Ship flag= |
| Ship flag= {{shipboxflag|Finland}} |
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| Ship name=''Otso'' |
| Ship name=''Otso'' |
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| Ship namesake=[[Finnish language|Finnish]] |
| Ship namesake=[[Finnish language|Finnish]] term for [[bear]] |
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| Ship owner=[[Finnish Maritime Administration]]<ref group="Note">Finnish National Board of Navigation until 1998.</ref> (1986–2004) |
| Ship owner=* [[Finnish Maritime Administration]]<ref group="Note">Finnish National Board of Navigation until 1998.</ref> (1986–2004) |
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* [[Finstaship]] (2004–2010) |
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* [[Arctia Icebreaking]]<ref name="equasis" /> (2010–) |
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| Ship operator= |
| Ship operator= |
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| Ship registry=[[Helsinki]], {{FIN}} |
| Ship registry=[[Helsinki]], {{FIN}} |
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| Ship maiden voyage= |
| Ship maiden voyage= |
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| Ship in service=1986–present |
| Ship in service=1986–present |
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| Ship identification={{IMO number|8405880}} |
| Ship identification=* {{IMO number|8405880}} |
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* [[Maritime call sign|Call sign]]: OIRT |
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* {{MMSI|230252000}}<ref name="equasis">{{csr|register=E|id=8405880|shipname=Otso|accessdate=14 October 2012}}</ref> |
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| Ship captured= |
| Ship captured= |
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| Ship status=In service |
| Ship status=In service |
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{{Infobox ship characteristics |
{{Infobox ship characteristics |
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| Header caption=<ref name="arctia"> |
| Header caption=<ref name="arctia">{{cite web |url=http://arctia.fi/ship/otso/ |url-status=dead |archive-url=https://web.archive.org/web/20190228130413/http://arctia.fi/ship/otso/ |archive-date=28 February 2019 |title=IB Otso |publisher=Arctia Oy |place=Helsinki |lang=fi}}</ref><ref name="motorship">{{cite magazine |title=Finland's latest icebreaker uses ac/ac diesel-electric propulsion |magazine=The Motor Ship |volume=67 |issue=791 |date=June 1986 |pages=21–24}}</ref> |
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| Ship class= |
| Ship class= |
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| Ship type=[[Icebreaker]] |
| Ship type=[[Icebreaker]] |
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| Ship tonnage={{GT|7, |
| Ship tonnage=* {{GT|7,189}} |
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* {{NetT|2,157}} |
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| Ship displacement=9, |
| Ship displacement=9,222 tonnes |
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| Ship length={{convert|99|m|ftin|abbr=on}} |
| Ship length={{convert|99|m|ftin|abbr=on}} |
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| Ship beam={{convert|24.2|m|ftin|abbr=on}} |
| Ship beam={{convert|24.2|m|ftin|abbr=on}} |
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| Ship draft={{convert|8|m|ftin|abbr=on}} (maximum) |
| Ship draft={{convert|8|m|ftin|abbr=on}} (maximum) |
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| Ship depth= |
| Ship depth= |
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| Ship ice class= |
| Ship ice class=[[Polar Class 4]] (2015–) |
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| Ship power=4{{nbsp}} |
| Ship power=4{{nbsp}}×{{nbsp}}[[Wärtsilä]] Vasa 16V32 (4{{nbsp}}×{{nbsp}}5,460{{nbsp}}kW) |
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| Ship propulsion=[[Diesel-electric#Ships|Diesel-electric]] (AC/AC) |
| Ship propulsion=* [[Diesel-electric#Ships|Diesel-electric]] (AC/AC) |
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* Two shafts (2{{nbsp}}×{{nbsp}}7,500{{nbsp}}kW) |
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| Ship speed={{convert|18.5|kn}} |
| Ship speed=* {{convert|18.5|kn}} |
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* {{convert|10|kn}} in {{convert|0.8|m|in|abbr=on}} level ice |
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| Ship range= |
| Ship range= |
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| Ship endurance= |
| Ship endurance= |
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| Ship crew=20 |
| Ship crew=20 |
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| Ship aircraft facilities= |
| Ship aircraft facilities=Helicopter landing area |
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| Ship notes= |
| Ship notes= |
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== Development and construction == |
== Development and construction == |
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In the early 1980s, the [[Finnish National Board of Navigation]] began looking for a replacement for the aging ''Karhu''-class icebreakers [[Finnish icebreaker Karhu|''Karhu'']], [[Finnish icebreaker Murtaja (1959)|''Murtaja'']] and [[Sampo (1960 icebreaker)|''Sampo'']] which had been built in the late 1950s and were no longer wide enough to escort modern merchant ships.<ref name="sws">Karhu II - A new-generation icebreaker |
In the early 1980s, the [[Finnish National Board of Navigation]] began looking for a replacement for the aging ''Karhu''-class icebreakers [[Finnish icebreaker Karhu|''Karhu'']], [[Finnish icebreaker Murtaja (1959)|''Murtaja'']] and [[Sampo (1960 icebreaker)|''Sampo'']] which had been built in the late 1950s and were no longer wide enough to escort modern merchant ships.<ref name="sws">{{cite magazine |title=Karhu II - A new-generation icebreaker |magazine=Shipping World & Shipbuilder |date=October 1985}}</ref> Furthermore, the old icebreakers were expensive to operate and, despite their small size, required a relatively large crew of 53.<ref name="kaukiainen">{{harvnb|Kaukiainen|1992|p=330}}</ref> The development of the new class of icebreakers, dubbed ''Karhu II'' in the preliminary papers, intensified when Wärtsilä opened [[Aker Arctic|a new ice model test facility]] in 1983. The tenth post-war icebreaker of Finland was ordered from [[Wärtsilä]] [[Hietalahti shipyard|Helsinki shipyard]] on 19 March 1984 with a price of [[Finnish markka|FIM]] 235 million.<ref name="sws" /><ref>{{cite magazine |title=Uusi murtaja tilattu |trans-title=New icebreaker ordered |magazine=Suomen Merenkulku |date=June 1984 |page=43 |lang=fi}}</ref> The ship was launched on 12 July 1985 and delivered to the owners on 30 January 1986.<ref>{{cite news |newspaper=Helsingin Sanomat |date=31 January 1986}}</ref>{{full citation needed|date=June 2023}} Her name, ''Otso'', is one of the many terms for [[bear]] in the [[Finnish language]]. In January 1987, ''Otso'' was followed by a similarly-named sister ship, ''Kontio'', after which the three ''Karhu''-class icebreakers were decommissioned and sold.<ref name="kaukiainen" /> |
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During extensive ice trials in the [[Bothnian Bay]] in March 1986, ''Otso'' was put through a series of test to determine her icebreaking capability. In a race against the 1975-built [[Finnish icebreaker Urho (1975)|''Urho'']] in {{convert|0.8|m|in|adj=on}} level ice, ''Otso'' beat the older but more powerful four-propelled icebreaker by more than a ship's length,<ref> |
During extensive ice trials in the [[Bothnian Bay]] in March 1986, ''Otso'' was put through a series of test to determine her icebreaking capability. In a race against the 1975-built [[Finnish icebreaker Urho (1975)|''Urho'']] in {{convert|0.8|m|in|adj=on}} level ice, ''Otso'' beat the older but more powerful four-propelled icebreaker by more than a ship's length,<ref>{{cite news |url=http://www.hs.fi/paivanlehti/20072016/a1468895009893 |title=Talvimerenkulun taitaja oli ennen kaikkea merimies |trans-title=A master of winter seafaring was above all a sailor |newspaper=Helsingin Sanomat |date=20 July 2016 |last=Kotiranta |first=Erkki |url-status=dead |archive-url=https://web.archive.org/web/20170205135721/http://www.hs.fi/ihmiset/art-2000002911632.html |archive-date=5 February 2017 |lang=fi}}</ref><ref name="turunen37-39">{{harvnb|Turunen|Partanen|2011|pp=37–39}}</ref> showing that in terms of ice resistance the new icebreaker was superior to her predecessor.<ref name="kaukiainen" /><ref name="navigator6-1986">{{cite magazine |title=Telakoiden vaikein vuosi menossa |magazine=Navigator |date=June 1986 |lang=fi}}</ref> In {{convert|40|cm|in|adj=on}} ice, she could easily maintain a speed of {{convert|16|kn}} and small ice ridges along the way appeared to be of no consequence to the vessel. However, the strength of the new icebreaker was put to the ultimate test when she encountered a large pressure ridge reaching all the way to the seafloor some {{convert|20|m|ft|0}} below the surface. After preparations, ''Otso'' was accelerated to a speed of {{convert|14|kn}} and rammed into the ridge at full power. Since the new icebreaker had a smooth inclined [[Stem (ship)|stem]] and lacked the bow propellers of her predecessors, she rode up the ridge and began listing to the port side as the hull rose from the water. After coming to a stop, ''Otso'' slid back by herself without utilizing the engines, and the ridge was penetrated on the second charge.<ref name="motorship" /><ref name="turunen37-39" /> The robustness of the ship and its propulsion system were further proven when the icebreaker was backed into a ridge at {{convert|10|kn}} "to prove to the customer it doesn't break".<ref name="popularmechanics">{{cite magazine |url=https://books.google.com/books?id=KOQDAAAAMBAJ&pg=PP94 |title=Icebreakers! |magazine=Popular Mechanics |place=New York |date=February 1989 |volume=166 |number=2 |pages=58–59}} </ref> |
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Considered to be a successful design that incorporated the latest Finnish icebreaker technology, ''Otso'' was later used as a design basis for the [[United States Coast Guard]] icebreaker [[USCGC Healy (WAGB-20)|''Healy'']].<ref>Strong Finnish involvement in U.S. icebreakers |
Considered to be a successful design that incorporated the latest Finnish icebreaker technology, ''Otso'' was later used as a design basis for the [[United States Coast Guard]] icebreaker [[USCGC Healy (WAGB-20)|''Healy'']].<ref>{{cite magazine |title=Strong Finnish involvement in U.S. icebreakers |magazine=Navigator Yearbook 2016 |page=20}}</ref>{ |
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== Technical details == |
== Technical details == |
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=== General characteristics === |
=== General characteristics === |
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[[File:Otso Raahe 2011.jpg|thumb|left|''Otso'' in unbroken level ice outside [[Raahe]] in February 2011.]] |
[[File:Otso Raahe 2011.jpg|thumb|left|''Otso'' in unbroken level ice outside [[Raahe]] in February 2011.]] |
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Although the {{convert|99|m|ft|0|adj=on}} ''Otso'' is slightly shorter than her predecessors ''Urho'' and ''Sisu'', she is slightly wider and was, at the time of her delivery, the widest subarctic icebreaker in the world with a beam of {{convert|24.2|m|ft}}.<ref name="sws" /> However, with a maximum draft of {{convert|8|m|ft}} and a minimum operating draft of only {{convert|7.3|m|ft}}, ''Otso'' is able to escort ships to shallower ports than her predecessors.<ref name="navigator6-1986" |
Although the {{convert|99|m|ft|0|adj=on}} ''Otso'' is slightly shorter than her predecessors ''Urho'' and ''Sisu'', she is slightly wider and was, at the time of her delivery, the widest subarctic icebreaker in the world with a beam of {{convert|24.2|m|ft}}.<ref name="sws" /> However, with a maximum draft of {{convert|8|m|ft}} and a minimum operating draft of only {{convert|7.3|m|ft}}, ''Otso'' is able to escort ships to shallower ports than her predecessors.<ref name="navigator6-1986" /> The displacement of the icebreaker is 9,222 tonnes.<ref name="arctia" /> |
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In many ways, ''Otso'' was a significant departure from the traditional Finnish icebreaker design. The extended [[bridge wing]]s on top of the stylish superstructure feature full-depth all-round windows that provide almost 360 degree visibility from the main steering position, which has been moved to the starboard bridge wing from the centerline.<ref name="motorship" /><ref name="smk2-85" /> Furthermore, the traditional colours dating back to the [[Russian Empire|Imperial Russian]] era, yellow and black, were replaced with the colors of the [[flag of Finland]], blue and white. Due to the extensive use of advanced automation, which allowed everything ranging from starting and stopping the main engines to raising and lowering the flag to be done remotely from the bridge, ''Otso'' had the smallest crew among Finnish state-owned icebreakers when she entered service in 1986.<ref name="kaukiainen" /> Later her crew has been further reduced to 20.<ref name="arctia" /> ''Otso'' was also the first icebreaker in which the [[Lifeboat (shipboard)| |
In many ways, ''Otso'' was a significant departure from the traditional Finnish icebreaker design. The extended [[bridge wing]]s on top of the stylish superstructure feature full-depth all-round windows that provide almost 360 degree visibility from the main steering position, which has been moved to the starboard bridge wing from the centerline.<ref name="motorship" /><ref name="smk2-85" /> Furthermore, the traditional colours dating back to the [[Russian Empire|Imperial Russian]] era, yellow and black, were replaced with the colors of the [[flag of Finland]], blue and white. Due to the extensive use of advanced automation, which allowed everything ranging from starting and stopping the main engines to raising and lowering the flag to be done remotely from the bridge, ''Otso'' had the smallest crew among Finnish state-owned icebreakers when she entered service in 1986.<ref name="kaukiainen" /> Later her crew has been further reduced to 20.<ref name="arctia" /> ''Otso'' was also the first icebreaker in which the [[Lifeboat (shipboard)|lifeboats]], unusable in ice-covered waters, were replaced with inflatable life rafts that could be lowered on the ice.<ref name="smk2-85" /> |
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While ''Otso'' holds the highest [[Finnish-Swedish ice class]], 1A Super,<ref name="arctia" /> it has hardly any meaning for icebreakers which are of considerably stronger build than merchant ships operating in their care. Coated with low-friction [[Inerta 160|Inerta{{nbsp}}160]] epoxy paint, the hull plating has thickness of over {{convert|30|mm|in}} in the bow and the waterline is protected by an [[Explosion welding|explosion welded]] [[stainless steel]] compound plating that further reduces ice friction and resists abrasion.<ref name="motorship" /><ref name="popularmechanics" /> [[Galvanic corrosion]] is prevented by active [[cathodic protection]].<ref name="arctia" /> |
While ''Otso'' holds the highest [[Finnish-Swedish ice class]], 1A Super,<ref name="arctia" /> it has hardly any meaning for icebreakers which are of considerably stronger build than merchant ships operating in their care. Coated with low-friction [[Inerta 160|Inerta{{nbsp}}160]] epoxy paint, the hull plating has thickness of over {{convert|30|mm|in}} in the bow and the waterline is protected by an [[Explosion welding|explosion welded]] [[stainless steel]] compound plating that further reduces ice friction and resists abrasion.<ref name="motorship" /><ref name="popularmechanics" /> [[Galvanic corrosion]] is prevented by active [[cathodic protection]].<ref name="arctia" /> |
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=== Power and propulsion === |
=== Power and propulsion === |
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Like all modern Finnish icebreakers, ''Otso'' has a [[diesel-electric#Ships|diesel-electric]] propulsion system. It utilizes the so-called power plant principle in which the main generators provide electricity for all shipboard consumers through a common [[busbar]]. Her main generators, four [[V16 engine|16-cylinder]] Wärtsilä Vasa 16V32 four-stroke medium-speed [[diesel engine]]s producing 5,460{{nbsp}}kW each and driving 7,540 kVA Kymi-[[Strömberg (company)|Strömberg]] [[alternator]]s, are located on the upper deck beneath the helicopter platform.<ref name="motorship" /><ref name="cyclo">Cycloconverters for the new icebreaker from Kymmene-Strömberg |
Like all modern Finnish icebreakers, ''Otso'' has a [[diesel-electric#Ships|diesel-electric]] propulsion system. It utilizes the so-called power plant principle in which the main generators provide electricity for all shipboard consumers through a common [[busbar]]. Her main generators, four [[V16 engine|16-cylinder]] Wärtsilä Vasa 16V32 four-stroke medium-speed [[diesel engine]]s producing 5,460{{nbsp}}kW each and driving 7,540 kVA Kymi-[[Strömberg (company)|Strömberg]] [[alternator]]s, are located on the upper deck beneath the helicopter platform.<ref name="motorship" /><ref name="cyclo">{{cite magazine |title=Cycloconverters for the new icebreaker from Kymmene-Strömberg |magazine=Navigator |date=1985}}</ref>{{volume needed|date=June 2023|vol=no}} In addition, she has two smaller Wärtsilä 4R22/26 generators with an output of 350{{nbsp}}kW for use in ports.<ref name="smk2-85">{{cite magazine |title=Jäänmurtajalaivastoa uusitaan |magazine=Suomen Merenkulku |date=February 1985 |pages=6–8 |lang=fi}}</ref> The uncommon location of the engine room was chosen to improve the seakeeping characteristics of the icebreaker by moving the [[center of gravity]] higher to calm the ship's motions in heavy weather. In addition, the maintenance of the main engines is easier as the heavy engine components can be handled with the ship's main crane and the [[heavy fuel oil]] tanks could be placed amidships to reduce the probability of an oil spill in case of grounding.<ref name="navigator6-1986" /> {{Asof|2013}}, ''Otso'' and her sister ship ''Kontio'' are the only Finnish icebreakers running on heavy fuel oil which, being the cheapest fuel available, reduces operational costs of the icebreaker.<ref>{{cite news |url=http://www.demari.fi/politiikka/uutiset/15683-arctia-shippingin-luottamusmiehet-ruotsalaisille-annettu-etua |title=Arctia Shippingin luottamusmiehet: Ruotsalaisille annettu etua |trans-title=Trustees of Arctia Shipping: Advantage given to Swedes |work=Demari.fi |date=15 October 2013 |archive-url=https://web.archive.org/web/20140714191404/http://www.demari.fi/politiikka/uutiset/15683-arctia-shippingin-luottamusmiehet-ruotsalaisille-annettu-etua |archive-date=14 July 2014 |url-status=dead |publisher=Kustannus Oy |place=Helsinki |lang=fi}}</ref> |
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''Otso'' was the first icebreaker in the world to utilize [[cycloconverter]]s and [[alternating current]] (AC) propulsion motors.<ref name="motorship" /> Although electrical propulsion had already been used in Finnish icebreakers for almost five decades due to its flexibility and good torque characteristics at low propeller speeds, the older vessels had [[direct current]] (DC) propulsion motors which were very heavy and bulky at such power levels. Although it would have been possible to use two smaller DC motors in tandem, recent advances in drive and control technology as well as excellent experiences from a prototype installation on board the Finnish research vessel [[Katarina (1953 ship)|''Aranda'']] were in favor of the new type of propulsion system. As a result, ''Otso'' was fitted with two Kymi-Strömberg [[Synchronous motor|synchronous]] AC motors rated at 7,500{{nbsp}}kW. The maximum power is available at propeller speeds ranging from 115 to 220{{nbsp}}rpm to both directions and at lower speeds the propulsion motors are capable of providing 130% of the rated torque to prevent the four-bladed stainless steel propellers from jamming in severe ice conditions.<ref name="motorship" /><ref name="cyclo" /> The [[bollard pull]] of ''Otso'' is 160{{nbsp}} |
''Otso'' was the first icebreaker in the world to utilize [[cycloconverter]]s and [[alternating current]] (AC) propulsion motors.<ref name="motorship" /> Although electrical propulsion had already been used in Finnish icebreakers for almost five decades due to its flexibility and good torque characteristics at low propeller speeds, the older vessels had [[direct current]] (DC) propulsion motors which were very heavy and bulky at such power levels. Although it would have been possible to use two smaller DC motors in tandem, recent advances in drive and control technology as well as excellent experiences from a prototype installation on board the Finnish research vessel [[Katarina (1953 ship)|''Aranda'']] were in favor of the new type of propulsion system. As a result, ''Otso'' was fitted with two Kymi-Strömberg [[Synchronous motor|synchronous]] AC motors rated at 7,500{{nbsp}}kW. The maximum power is available at propeller speeds ranging from 115 to 220{{nbsp}}rpm to both directions and at lower speeds the propulsion motors are capable of providing 130% of the rated torque to prevent the four-bladed stainless steel propellers from jamming in severe ice conditions.<ref name="motorship" /><ref name="cyclo" /> The [[bollard pull]] of ''Otso'' is 160{{nbsp}}tonnes.<ref name="arctia" /> |
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Prior to the construction of ''Otso'', all Finnish state-owned icebreakers built after the [[Second World War]] had been fitted with two bow propellers to reduce the friction between ice and the hull of the vessel in difficult ice conditions. However, the quad-shaft propulsion system was expensive to build and maintain, and the forward propeller bossings considerably increased the resistance of the ship. Although Finnish icebreaker captains voiced their concerns about the maneuverability and icebreaking capability of a vessel without bow propellers especially in heavy ice ridges and at crawling speeds,<ref name="smk4-86">Otso osoittautui kelpo murtajaksi |
Prior to the construction of ''Otso'', all Finnish state-owned icebreakers built after the [[Second World War]] had been fitted with two bow propellers to reduce the friction between ice and the hull of the vessel in difficult ice conditions. However, the quad-shaft propulsion system was expensive to build and maintain, and the forward propeller bossings considerably increased the resistance of the ship. Although Finnish icebreaker captains voiced their concerns about the maneuverability and icebreaking capability of a vessel without bow propellers especially in heavy ice ridges and at crawling speeds,<ref name="smk4-86">{{cite magazine |title=Otso osoittautui kelpo murtajaksi |magazine=Suomen Merenkulku |date=April 1986 |pages=22–24 |lang=fi}}</ref> extensive model testing at Wärtsilä's new ice model test basin showed that the ice resistance could be reduced by replacing the bow propellers with a "clean" hull and adopting an air bubbling system to lubricate the hull.<ref name="motorship" /> The patented [[Wärtsilä Air Bubbling System]] (WABS) onboard ''Otso'' consists of three compressors with a combined output of 1,900{{nbsp}}kW that pump air through 46 nozzles located below the waterline on both sides of the vessel. At low speeds, the system can also be used for manoeuvering. In addition, she has large ballast tanks and high-capacity pumps that can be used for rapid heeling and trimming to release the icebreaker if she is immobilized by compressive pack ice.<ref name="smk2-85" /> |
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In 1996, ''Otso'' was fitted with a [[bow thruster]] to assist manoeuvering while the icebreaker was drydocked at [[Vuosaari shipyard]].<ref>Häkkinen |
In 1996, ''Otso'' was fitted with a [[bow thruster]] to assist manoeuvering while the icebreaker was drydocked at [[Vuosaari shipyard]].<ref>{{cite book |last=Häkkinen |first=Pentti |date=2009 |title=Muistiinpanot JM Otson vierailusta 18.11.2009 |publisher=Teknillinen Korkeakoulu |url=https://noppa.aalto.fi/noppa/kurssi/kul-24.4420/materiaali/Kul-24_4420_otson_vierailu.doc |lang=fi}}{{Dead link|date=June 2023|fix-attempted=y}}</ref> |
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== Career == |
== Career == |
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Before ''Otso'' entered service in 1986, the Finnish icebreaker captains were sceptical about the ability of an icebreaker without bow propellers to operate successfully in the shallow Finnish waters characterized by heavy ice ridges. However, after the early [[teething problem]]s and successful ice trials, the opinions changed and the performance of the "Bubbler of the Bothnian Bay" was generally deemed to be satisfactory.<ref name="smk4-86" /> Over the years, ''Otso'' and her sister ship ''Kontio'' have proved to be very cost-efficient and for that reason they are the first Finnish state-owned icebreakers to be deployed for icebreaking in the [[Gulf of Bothnia]] every winter.<ref name="arctia" /> |
Before ''Otso'' entered service in 1986, the Finnish icebreaker captains were sceptical about the ability of an icebreaker without bow propellers to operate successfully in the shallow Finnish waters characterized by heavy ice ridges. However, after the early [[teething problem]]s and successful ice trials, the opinions changed and the performance of the "Bubbler of the Bothnian Bay" was generally deemed to be satisfactory.<ref name="smk4-86" /> Over the years, ''Otso'' and her sister ship ''Kontio'' have proved to be very cost-efficient and for that reason they are the first Finnish state-owned icebreakers to be deployed for icebreaking in the [[Gulf of Bothnia]] every winter.<ref name="arctia" /> |
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Until 2015, ''Otso'' and ''Kontio'' were the last Finnish icebreakers designed solely for escorting merchant ships through |
Until 2015, ''Otso'' and ''Kontio'' were the last Finnish icebreakers designed solely for escorting merchant ships through iced-over waters.<ref name="kaukiainen" /> In the 1990s, the Finnish Maritime Administration commissioned three multipurpose icebreakers with a secondary role in [[Offshore drilling|offshore]] construction projects during the summer months. However, due to the criticism of the multipurpose icebreakers and Arctic offshore drilling in general, [[Polaris (icebreaker)|the new icebreaker]] that will replace the aging [[Voima (1952 icebreaker)|''Voima'']] in 2015 will be a traditional one.<ref>{{cite news |url=http://www.lvm.fi/web/fi/tiedote/-/view/4118574 |title=Liikenne- ja viestintäministeriön budjettiehdotus |trans-title=Budget proposal of the Ministry of Transport and Communications |publisher=Liikenne- ja viestintäministeriö |place=Helsinki |date=8 August 2012 |archive-url=https://web.archive.org/web/20131023004531/http://www.lvm.fi/tiedote/-/view/4118574 |archive-date=23 October 2013 |lang=fi}}</ref><ref>{{cite news |url=http://yle.fi/uutiset/ministeri_ja_varustamo_eri_linjoilla_uudesta_jaanmurtajasta/5236137 |title=Ministeri ja varustamo eri linjoilla uudesta jäänmurtajasta |trans-title=The minister and the shipping company are on different lines about the new icebreaker |publisher=YLE |date=2 April 2012 |access-date=21 August 2012 |lang=fi}}</ref> |
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In April 2015, Arctia Shipping announced that ''Otso'' |
In April 2015, Arctia Shipping announced that ''Otso'' had been chartered to an unnamed client to support seismic surveys in the Arctic for two years with an option of two additional years. The vessel was upgraded for service in the northern latitudes by increasing her ice strengthening, previously adequate only for icebreaking in the Baltic Sea, to ''[[Polar Class 4]]'' (PC 4) which is intended for vessels operating year-round in thick first-year ice which may include old ice inclusions. Furthermore, a {{convert|250|m3|cuft|adj=on}} anti-rolling tank was installed to improve her open water characteristics. Other additions included lifeboats to allow unrestricted worldwide service as well as a new helideck. The modifications were carried out by [[Rauma Marine Constructions]]. After the summer season in the Arctic, ''Otso'' would return to the Baltic Sea icebreaking duty by November as mandated by the icebreaking contract between Arctia Shipping and the Finnish Transport Agency.<ref>{{cite news |url=http://www.talouselama.fi/uutiset/otson-kylkiin-terasta-kannelle-helikopterikentta-ja-vesiallas-miehistolle-arktiset-palkanlisat-3474552 |title=Otson kylkiin terästä, kannelle helikopterikenttä ja vesiallas – miehistölle arktiset palkanlisät |trans-title=Steel on the sides, a helipad and a pool of water on the deck - arctic bonuses for the crew |work=Talouselämä |date=10 April 2015 |last=Lundén |first=Kimmo |publisher=Talentum Media Oy |place=Helsinki |archive-url=https://web.archive.org/web/20160304035614/http://www.talouselama.fi/uutiset/otson-kylkiin-terasta-kannelle-helikopterikentta-ja-vesiallas-miehistolle-arktiset-palkanlisat-3474552 |archive-date=4 March 2016 |lang=fi}}</ref> |
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*{{cite book |last= Kaukiainen |first= Yrjö |title= Navigare Necesse—Merenkulkulaitos 1917–1992 |publisher=Gummerus Kirjapaino Oy | location = Jyväskylä |year= 1992 |isbn= 951-47-6776-4}} |
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*{{cite book |last=Kaukiainen |first=Yrjö |title=Navigare Necesse – Merenkulkulaitos 1917–1992 |trans-title=Navigare Necesse – The Maritime Administration 1917–1992|publisher=Gummerus Kirjapaino Oy |location= Jyväskylä |year=1992 |isbn= 951-47-6776-4 |lang=fi}} |
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*{{cite book |last1=Turunen |first1=Ari |last2=Partanen |first2=Petja |title=Raakaa voimaa – Suomalaisen jäänmurtamisen tarina |trans-title=Raw power – The story of Finnish icebreaking |publisher=Atena Kustannus Oy |location=Jyväskylä |year=2011 |isbn=978-951-796-762-4 |lang=fi}} |
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{{Icebreakers of Finland}} |
{{Icebreakers of Finland}} |
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Latest revision as of 06:29, 2 July 2023
 Otso returning from sea trials to the icebreaker base at Katajanokka, Helsinki, on 18 January 2012.
| |
| History | |
|---|---|
 Finnland | |
| Name | Otso |
| Namesake | Finnish term for bear |
| Owner |
|
| Port of registry | Helsinki,  Finnland |
| Ordered | 19 March 1984 |
| Builder | Wärtsilä Helsinki Shipyard, Finland |
| Cost | FIM 235 million |
| Yard number | 472 |
| Launched | 12 July 1985 |
| Completed | 30 January 1986 |
| In service | 1986–present |
| Identification | |
| Status | In service |
| General characteristics [2][3] | |
| Typ | Icebreaker |
| Tonnage | |
| Displacement | 9,222 tonnes |
| Length | 99 m (324 ft 10 in) |
| Beam | 24.2 m (79 ft 5 in) |
| Draft | 8 m (26 ft 3 in) (maximum) |
| Ice class | Polar Class 4 (2015–) |
| Installed power | 4 × Wärtsilä Vasa 16V32 (4 × 5,460 kW) |
| Propulsion |
|
| Speed |
|
| Crew | 20 |
| Aviation facilities | Helicopter landing area |
Otso is a Finnish state-owned icebreaker. Built by Wärtsilä Helsinki shipyard in 1986 to replace the aging Karhu-class icebreakers, she was the first Finnish post-war icebreaker to be built without bow propellers. Otso has an identical sister ship, Kontio, which was delivered in 1987.
Development and construction
[edit]In the early 1980s, the Finnish National Board of Navigation began looking for a replacement for the aging Karhu-class icebreakers Karhu, Murtaja and Sampo which had been built in the late 1950s and were no longer wide enough to escort modern merchant ships.[4] Furthermore, the old icebreakers were expensive to operate and, despite their small size, required a relatively large crew of 53.[5] The development of the new class of icebreakers, dubbed Karhu II in the preliminary papers, intensified when Wärtsilä opened a new ice model test facility in 1983. The tenth post-war icebreaker of Finland was ordered from Wärtsilä Helsinki shipyard on 19 March 1984 with a price of FIM 235 million.[4][6] The ship was launched on 12 July 1985 and delivered to the owners on 30 January 1986.[7][full citation needed] Her name, Otso, is one of the many terms for bear in the Finnish language. In January 1987, Otso was followed by a similarly-named sister ship, Kontio, after which the three Karhu-class icebreakers were decommissioned and sold.[5]
During extensive ice trials in the Bothnian Bay in March 1986, Otso was put through a series of test to determine her icebreaking capability. In a race against the 1975-built Urho in 0.8-metre (31 in) level ice, Otso beat the older but more powerful four-propelled icebreaker by more than a ship's length,[8][9] showing that in terms of ice resistance the new icebreaker was superior to her predecessor.[5][10] In 40-centimetre (16 in) ice, she could easily maintain a speed of 16 knots (30 km/h; 18 mph) and small ice ridges along the way appeared to be of no consequence to the vessel. However, the strength of the new icebreaker was put to the ultimate test when she encountered a large pressure ridge reaching all the way to the seafloor some 20 metres (66 ft) below the surface. After preparations, Otso was accelerated to a speed of 14 knots (26 km/h; 16 mph) and rammed into the ridge at full power. Since the new icebreaker had a smooth inclined stem and lacked the bow propellers of her predecessors, she rode up the ridge and began listing to the port side as the hull rose from the water. After coming to a stop, Otso slid back by herself without utilizing the engines, and the ridge was penetrated on the second charge.[3][9] The robustness of the ship and its propulsion system were further proven when the icebreaker was backed into a ridge at 10 knots (19 km/h; 12 mph) "to prove to the customer it doesn't break".[11]
Considered to be a successful design that incorporated the latest Finnish icebreaker technology, Otso was later used as a design basis for the United States Coast Guard icebreaker Healy.[12]{
Technical details
[edit]General characteristics
[edit]
Although the 99-metre (325 ft) Otso is slightly shorter than her predecessors Urho and Sisu, she is slightly wider and was, at the time of her delivery, the widest subarctic icebreaker in the world with a beam of 24.2 metres (79 ft).[4] However, with a maximum draft of 8 metres (26 ft) and a minimum operating draft of only 7.3 metres (24 ft), Otso is able to escort ships to shallower ports than her predecessors.[10] The displacement of the icebreaker is 9,222 tonnes.[2]
In many ways, Otso was a significant departure from the traditional Finnish icebreaker design. The extended bridge wings on top of the stylish superstructure feature full-depth all-round windows that provide almost 360 degree visibility from the main steering position, which has been moved to the starboard bridge wing from the centerline.[3][13] Furthermore, the traditional colours dating back to the Imperial Russian era, yellow and black, were replaced with the colors of the flag of Finland, blue and white. Due to the extensive use of advanced automation, which allowed everything ranging from starting and stopping the main engines to raising and lowering the flag to be done remotely from the bridge, Otso had the smallest crew among Finnish state-owned icebreakers when she entered service in 1986.[5] Later her crew has been further reduced to 20.[2] Otso was also the first icebreaker in which the lifeboats, unusable in ice-covered waters, were replaced with inflatable life rafts that could be lowered on the ice.[13]
While Otso holds the highest Finnish-Swedish ice class, 1A Super,[2] it has hardly any meaning for icebreakers which are of considerably stronger build than merchant ships operating in their care. Coated with low-friction Inerta 160 epoxy paint, the hull plating has thickness of over 30 millimetres (1.2 in) in the bow and the waterline is protected by an explosion welded stainless steel compound plating that further reduces ice friction and resists abrasion.[3][11] Galvanic corrosion is prevented by active cathodic protection.[2]
Power and propulsion
[edit]Like all modern Finnish icebreakers, Otso has a diesel-electric propulsion system. It utilizes the so-called power plant principle in which the main generators provide electricity for all shipboard consumers through a common busbar. Her main generators, four 16-cylinder Wärtsilä Vasa 16V32 four-stroke medium-speed diesel engines producing 5,460 kW each and driving 7,540 kVA Kymi-Strömberg alternators, are located on the upper deck beneath the helicopter platform.[3][14][issue needed] In addition, she has two smaller Wärtsilä 4R22/26 generators with an output of 350 kW for use in ports.[13] The uncommon location of the engine room was chosen to improve the seakeeping characteristics of the icebreaker by moving the center of gravity higher to calm the ship's motions in heavy weather. In addition, the maintenance of the main engines is easier as the heavy engine components can be handled with the ship's main crane and the heavy fuel oil tanks could be placed amidships to reduce the probability of an oil spill in case of grounding.[10] As of 2013[update], Otso and her sister ship Kontio are the only Finnish icebreakers running on heavy fuel oil which, being the cheapest fuel available, reduces operational costs of the icebreaker.[15]
Otso was the first icebreaker in the world to utilize cycloconverters and alternating current (AC) propulsion motors.[3] Although electrical propulsion had already been used in Finnish icebreakers for almost five decades due to its flexibility and good torque characteristics at low propeller speeds, the older vessels had direct current (DC) propulsion motors which were very heavy and bulky at such power levels. Although it would have been possible to use two smaller DC motors in tandem, recent advances in drive and control technology as well as excellent experiences from a prototype installation on board the Finnish research vessel Aranda were in favor of the new type of propulsion system. As a result, Otso was fitted with two Kymi-Strömberg synchronous AC motors rated at 7,500 kW. The maximum power is available at propeller speeds ranging from 115 to 220 rpm to both directions and at lower speeds the propulsion motors are capable of providing 130% of the rated torque to prevent the four-bladed stainless steel propellers from jamming in severe ice conditions.[3][14] The bollard pull of Otso is 160 tonnes.[2]
Prior to the construction of Otso, all Finnish state-owned icebreakers built after the Second World War had been fitted with two bow propellers to reduce the friction between ice and the hull of the vessel in difficult ice conditions. However, the quad-shaft propulsion system was expensive to build and maintain, and the forward propeller bossings considerably increased the resistance of the ship. Although Finnish icebreaker captains voiced their concerns about the maneuverability and icebreaking capability of a vessel without bow propellers especially in heavy ice ridges and at crawling speeds,[16] extensive model testing at Wärtsilä's new ice model test basin showed that the ice resistance could be reduced by replacing the bow propellers with a "clean" hull and adopting an air bubbling system to lubricate the hull.[3] The patented Wärtsilä Air Bubbling System (WABS) onboard Otso consists of three compressors with a combined output of 1,900 kW that pump air through 46 nozzles located below the waterline on both sides of the vessel. At low speeds, the system can also be used for manoeuvering. In addition, she has large ballast tanks and high-capacity pumps that can be used for rapid heeling and trimming to release the icebreaker if she is immobilized by compressive pack ice.[13]
In 1996, Otso was fitted with a bow thruster to assist manoeuvering while the icebreaker was drydocked at Vuosaari shipyard.[17]
Career
[edit]
Before Otso entered service in 1986, the Finnish icebreaker captains were sceptical about the ability of an icebreaker without bow propellers to operate successfully in the shallow Finnish waters characterized by heavy ice ridges. However, after the early teething problems and successful ice trials, the opinions changed and the performance of the "Bubbler of the Bothnian Bay" was generally deemed to be satisfactory.[16] Over the years, Otso and her sister ship Kontio have proved to be very cost-efficient and for that reason they are the first Finnish state-owned icebreakers to be deployed for icebreaking in the Gulf of Bothnia every winter.[2]
Until 2015, Otso and Kontio were the last Finnish icebreakers designed solely for escorting merchant ships through iced-over waters.[5] In the 1990s, the Finnish Maritime Administration commissioned three multipurpose icebreakers with a secondary role in offshore construction projects during the summer months. However, due to the criticism of the multipurpose icebreakers and Arctic offshore drilling in general, the new icebreaker that will replace the aging Voima in 2015 will be a traditional one.[18][19]
In April 2015, Arctia Shipping announced that Otso had been chartered to an unnamed client to support seismic surveys in the Arctic for two years with an option of two additional years. The vessel was upgraded for service in the northern latitudes by increasing her ice strengthening, previously adequate only for icebreaking in the Baltic Sea, to Polar Class 4 (PC 4) which is intended for vessels operating year-round in thick first-year ice which may include old ice inclusions. Furthermore, a 250-cubic-metre (8,800 cu ft) anti-rolling tank was installed to improve her open water characteristics. Other additions included lifeboats to allow unrestricted worldwide service as well as a new helideck. The modifications were carried out by Rauma Marine Constructions. After the summer season in the Arctic, Otso would return to the Baltic Sea icebreaking duty by November as mandated by the icebreaking contract between Arctia Shipping and the Finnish Transport Agency.[20]
Notes
[edit]- ^ Finnish National Board of Navigation until 1998.
References
[edit]
- ^ a b "Otso (8405880)". Equasis. Ministry of Ecology, Sustainable Development and Energy. Retrieved 14 October 2012.
- ^ a b c d e f g "IB Otso" (in Finnish). Helsinki: Arctia Oy. Archived from the original on 28 February 2019.
- ^ a b c d e f g h "Finland's latest icebreaker uses ac/ac diesel-electric propulsion". The Motor Ship. Vol. 67, no. 791. June 1986. pp. 21–24.
- ^ a b c "Karhu II - A new-generation icebreaker". Shipping World & Shipbuilder. October 1985.
- ^ a b c d e Kaukiainen 1992, p. 330
- ^ "Uusi murtaja tilattu" [New icebreaker ordered]. Suomen Merenkulku (in Finnish). June 1984. p. 43.
- ^ Helsingin Sanomat. 31 January 1986.
{{cite news}}: Missing or empty|title=(help) - ^ Kotiranta, Erkki (20 July 2016). "Talvimerenkulun taitaja oli ennen kaikkea merimies" [A master of winter seafaring was above all a sailor]. Helsingin Sanomat (in Finnish). Archived from the original on 5 February 2017.
- ^ a b Turunen & Partanen 2011, pp. 37–39
- ^ a b "Icebreakers!". Popular Mechanics. Vol. 166, no. 2. New York. February 1989. pp. 58–59.
- ^ "Strong Finnish involvement in U.S. icebreakers". Navigator Yearbook 2016. p. 20.
- ^ a b c d "Jäänmurtajalaivastoa uusitaan". Suomen Merenkulku (in Finnish). February 1985. pp. 6–8.
- ^ a b "Cycloconverters for the new icebreaker from Kymmene-Strömberg". Navigator. 1985.
- ^ "Arctia Shippingin luottamusmiehet: Ruotsalaisille annettu etua" [Trustees of Arctia Shipping: Advantage given to Swedes]. Demari.fi (in Finnish). Helsinki: Kustannus Oy. 15 October 2013. Archived from the original on 14 July 2014.
- ^ a b "Otso osoittautui kelpo murtajaksi". Suomen Merenkulku (in Finnish). April 1986. pp. 22–24.
- ^ Häkkinen, Pentti (2009). Muistiinpanot JM Otson vierailusta 18.11.2009 (in Finnish). Teknillinen Korkeakoulu.[permanent dead link]
- ^ "Liikenne- ja viestintäministeriön budjettiehdotus" [Budget proposal of the Ministry of Transport and Communications] (in Finnish). Helsinki: Liikenne- ja viestintäministeriö. 8 August 2012. Archived from the original on 23 October 2013.
- ^ "Ministeri ja varustamo eri linjoilla uudesta jäänmurtajasta" [The minister and the shipping company are on different lines about the new icebreaker] (in Finnish). YLE. 2 April 2012. Retrieved 21 August 2012.
- ^ Lundén, Kimmo (10 April 2015). "Otson kylkiin terästä, kannelle helikopterikenttä ja vesiallas – miehistölle arktiset palkanlisät" [Steel on the sides, a helipad and a pool of water on the deck - arctic bonuses for the crew]. Talouselämä (in Finnish). Helsinki: Talentum Media Oy. Archived from the original on 4 March 2016.
Sources
[edit]- Kaukiainen, Yrjö (1992). Navigare Necesse – Merenkulkulaitos 1917–1992 [Navigare Necesse – The Maritime Administration 1917–1992] (in Finnish). Jyväskylä: Gummerus Kirjapaino Oy. ISBN 951-47-6776-4.
- Turunen, Ari; Partanen, Petja (2011). Raakaa voimaa – Suomalaisen jäänmurtamisen tarina [Raw power – The story of Finnish icebreaking] (in Finnish). Jyväskylä: Atena Kustannus Oy. ISBN 978-951-796-762-4.