View source for MT Petali

{{Short description|Aframax crude oil tanker}}
{|{{Infobox ship begin}}
{{Infobox ship image
| Ship image               = [[File:Mastera 20JUN07 p06.JPG|300px|MT Mastera]]
| Ship caption             = ''Petali'' (as ''Mastera'') outside the [[Port of Rotterdam]]
}}
{{Infobox ship career
| Hide header              = 
| Ship name                = * ''Mastera'' (2003–January 2022)
* ''Mikines'' (January–June 2022)
* ''Alma'' (June 2022–2023)
* ''Petali'' (2023–present)<ref name="seaweb">{{csr|register=SEAWEB|id=9235892|shipname=Alma|accessdate=26 June 2022}}</ref>
| Ship owner               = * [[ABB|ABB Credit]] (2003–2006)<ref name="equasis" />
* [[SEB Group|SEB Leasing]] (2006–2014)<ref name="vapalahti">Vapalahti, H: Finnish illustrated List of Ships 2007. Judicor Oy, 2008.</ref>
* SSC Maslaiva (2014–2019)<ref name="equasis">{{csr|register=E|id=9235892|shipname=Mikines|accessdate=19 March 2022}}</ref>
* SEB Leasing (2019–January 2022)<ref name="2019ownerchange">{{cite web|url=https://www.iltalehti.fi/talous/a/bbf276e3-8881-40fc-bbb7-72c78d38b116|title=Suomen suurin öljytankkeri ruotsalaisomistukseen: "Merimiehet huutavat liikenneministeri Sanna Marinin ja pääministeri Antti Rinteen perään"|language=fi|work=Iltalehti|publisher=Alma Media Suomi Oy|date=5 August 2019|accessdate=6 August 2019}}</ref>
* Neste Shipping (January 2022)<ref name="equasis" />
* Omega Shipmanagement (January–February 2022)<ref name="equasis" />
* Neptune Seaway (February–June 2022)<ref name="equasis" />
* Zenaida Seaways (June 2022–2023)<ref name="seaweb" />
* Lauriane Shipping Corp (2023–present)<ref name="seaweb" />
| Ship operator            = * [[Neste Oil|Neste Shipping]] (2003–2014)
* OSM Ship Management (2014–2015)<ref name="equasis" />
* Neste Shipping (2014–January 2022)<ref name="equasis" />
* Chemikalien Seetransport (January–February 2022)<ref name="equasis" />
* Neptune Seaway (February–June 2022)<ref name="equasis" />
* Zenaida Seaways (June 2022–)<ref name="seaweb" />
* Lauriane Shipping Corp (2023–present)<ref name="seaweb" />
| Ship registry            = * [[Porvoo]], {{FIN}} (2002–2021)
* [[Arendal]], {{NOR}} (2021–2022)<ref name="norflag">{{cite web|url=https://www.sdir.no/skipssok/?fbclid=IwAR3N3IBZU9VmdHsQL9IDdljqxXO1Jn7EOJ9f2i9w08Yk75QHAIooScReMQY#/shipdetails/105445/1|title=Fartøyet LAOI8 MASTERA|website=Norwegian Maritime Authority|accessdate=21 September 2021}}</ref>
* [[Monrovia]], {{LBR}} (2022–)
| Ship route               = [[Primorsk, Leningrad Oblast|Primorsk]]–Porvoo–[[Naantali]] (until January 2022)<ref name="smu">Remmiä kaulan ympärillä kiristetään jatkuvasti. [http://www.smu.fi/@Bin/2164313/MS_3-10_touko.pdf Merimies - Sjömannen, 3/10]{{Dead link|date=March 2020 |bot=InternetArchiveBot |fix-attempted=yes }}. Suomen Merimies-Unioni. {{retrieved | accessdate=2011-09-20}}</ref>
| Ship ordered             = 2001<ref name="akerarctic">[http://www.akerarctic.fi/publications/pdf/Poac01XNewDAS.pdf The development of the new double acting ships for ice operation] {{webarchive|url=https://web.archive.org/web/20120303021431/http://www.akerarctic.fi/publications/pdf/Poac01XNewDAS.pdf |date=2012-03-03 }}. [[Aker Arctic]], 2001.</ref>
| Ship builder             = [[Sumitomo Heavy Industries|Sumitomo Heavy Industries Ltd.]], [[Yokosuka, Kanagawa|Yokosuka]], [[Japan]]<ref name="nesteoil">{{cite web|title=Mastera/Tempera |url=http://www.nesteoil.com/binary.asp?GUID=1A6F31A4-6C93-4D6D-B791-61D99C5AF75F |publisher=Neste Oil |year=2004 |accessdate=20 September 2011 |url-status=dead |archiveurl=https://web.archive.org/web/20110929062316/http://www.nesteoil.com/binary.asp?GUID=1A6F31A4-6C93-4D6D-B791-61D99C5AF75F |archivedate=29 September 2011 }}</ref>
| Ship original cost       = 60–70 million euro (estimate)<ref name="tt" />
| Ship yard number         = 
| Ship way number          = 
| Ship laid down           = 
| Ship launched            = 30 September 2002<ref>{{csr|register=MSI|id=9235892|shipname=Mastera |accessdate=13 March 2020}}</ref>
| Ship completed           = 8 January 2003<ref name="seaweb" />
| Ship christened          = 
| Ship acquired            = 
| Ship maiden voyage       = 
| Ship in service          = 2003–<ref name="nesteoil" />
| Ship out of service      = 
| Ship identification      =*[[Maritime call sign|Call sign]]: 5LEL4<ref name="equasis" />
*{{IMO Number|9235892}}<ref name="equasis" />
*{{MMSI Number|636021543}}<ref name="equasis" />
| Ship fate                = 
| Ship status              = In service<ref name="equasis" />
| Ship notes               = 
}}
{{Infobox ship characteristics
| Hide header              = 
| Header caption           = <ref name="nesteoil" />
| Ship class=
| Ship type = [[Crude oil tanker]]
{{Infobox|child=yes
| label1 = Classification
| data1 = [[Lloyd's Register of Shipping]]
}}}}
{{Infobox ship characteristics
| Hide header              = yes
| Ship tonnage             =*{{GT|64,259}}
*{{NetT|30,846}}
*{{DWT|106,208}}
| Ship displacement        = 
| Ship length              = {{convert|252.0|m|ft|2|abbr=on}} ([[Length overall|overall]])
| Ship beam                = {{convert|44.0|m|ft|abbr=on}}
| Ship height              = {{convert|53.1|m|ft|abbr=on}}
| Ship draught             =*{{convert|15.3|m|ft|abbr=on}} (summer)
*{{convert|8.6|m|ft|abbr=on}} (ballast)
| Ship draft               = 
| Ship depth               = {{convert|22.5|m|ft|abbr=on}}
| Ship decks               = 
| Ship deck clearance      = 
| Ship ramps               = 
| Ship ice class           = 1A Super
| Ship sail plan           = 
| Ship power               =*2 × [[Wärtsilä]] 9L38B<ref name="vapalahti" /> (2&nbsp;×&nbsp;6,0&nbsp;MW)
*2 × Wärtsilä 6L38B<ref name="vapalahti" /> (2&nbsp;×&nbsp;4.0&nbsp;MW)
| Ship propulsion          =*[[ABB]] [[Azipod]] (16 MW)
*Two [[bow thruster]]s (2{{nbsp}}×{{nbsp}}1,750{{nbsp}}kW)<ref name="signships">MASTERA: double-acting tanker for Arctic routes. Significant Ships 2003, page 66.</ref>
| Ship speed               =*{{convert|15.2|kn}} (max)<ref name="vapalahti" />
*{{convert|13.5|kn}} (service)
*{{convert|3|kn}} ({{convert|1|m|ft|abbr=on}} ice)<ref name="abb_tempera">[http://www05.abb.com/global/scot/scot293.nsf/veritydisplay/85132e39bb90c45ac1257b1a005b7845/$file/Tempera.pdf Fortum ́s Double Acting Tankers] {{Webarchive|url=https://web.archive.org/web/20140407085539/http://www05.abb.com/global/scot/scot293.nsf/veritydisplay/85132e39bb90c45ac1257b1a005b7845/$file/Tempera.pdf |date=2014-04-07 }}. ABB. {{retrieved|accessdate=2014-04-03}}</ref>
| Ship capacity            = 
| Ship crew                = 15–20<ref name="vapaavahti42010" /><ref name="refine107" />
| Ship notes               = 
}}
|}

'''MT ''Petali''''' is an [[Aframax]] [[crude oil tanker]]. Formerly known as '''''Mastera''''' for almost two decades and briefly as '''''Mikines''''' in early 2022 and '''''Alma''''' until September 2023, she and her sister ship [[MT Tempera|''Tempera'']] were the first ships to utilize the [[double acting ship|double acting tanker]] (DAT) concept in which the vessel is designed to travel ahead in open water and astern in severe ice conditions.<ref name="akerarctic" /><ref name="tekniikkajatal" /> The icebreaking tanker was built to transport crude oil year-round from the [[Russia]]n oil terminal in [[Primorsk, Leningrad Oblast|Primorsk]] to Neste Oil refineries in [[Porvoo]] and [[Naantali]].<ref name="smu" />

== Concept ==
{{Main|Double acting ship}}

Although icebreaking cargo ships had been built in the past, their hull forms were always compromises between open water performance and icebreaking capability. A good icebreaking bow, designed to break the ice by bending it under the ship's weight, has very poor open water characteristics and is subjected to [[slamming]] in heavy weather while a hydrodynamically efficient bulbous bow greatly increases the ice resistance.<ref name="kujala">Kujala, P and [[Kaj Riska|Riska, K]]: Talvimerenkulku (TKK-AM-13). Department of Applied Mechanics, Helsinki University of Technology, 2010.</ref> However, already in the late 1800s captains operating ships in icebound waters discovered that sometimes it was easier to break through ice by running their vessels astern. This was because the forward-facing propellers generated a water flow that lowered the resistance by reducing friction between the ship's hull and ice.<ref name="arcticaborg">Aker Arctic Technology Inc.: [http://www.akerarctic.fi/publications/pdf/aker%20arc_arctica.pdf Icebreaking Supply Vessels Arcticaborg and Antarcticaborg] {{webarchive|url=https://web.archive.org/web/20110718163440/http://www.akerarctic.fi/publications/pdf/aker%20arc_arctica.pdf |date=2011-07-18 }}. {{Retrieved | accessdate=2010-02-08 }}</ref> These findings resulted in the adoption of bow propellers in older icebreakers operating in the [[Great Lakes]] and the [[Baltic Sea]], but as forward-facing propellers have a very low propulsion efficiency and the steering ability of a ship is greatly reduced when running astern, it could not be considered a main operating mode for merchant ships.<ref name="poac95">Juurmaa, K et al.: [http://www.akerarctic.fi/publications/pdf/Poac95NewDAT.pdf New ice breaking tanker concept for the arctic (DAT)] {{webarchive|url=https://web.archive.org/web/20120303021749/http://www.akerarctic.fi/publications/pdf/Poac95NewDAT.pdf |date=2012-03-03 }}. Kvaerner Masa-Yards Arctic Technology, 1995.</ref><ref name="dat">Juurmaa, K et al.: The development of the new double acting ships for ice operation. Kvaerner Masa-Yards Arctic Technology, [http://www.akerarctic.fi/publications/pdf/Poac01XNewDAS.pdf 2001] {{webarchive|url=https://web.archive.org/web/20120303021431/http://www.akerarctic.fi/publications/pdf/Poac01XNewDAS.pdf |date=2012-03-03 }} and [http://www.akerarctic.fi/publications/pdf/MombXDat.pdf 2002] {{webarchive|url=https://web.archive.org/web/20120904220420/http://www.akerarctic.fi/publications/pdf/MombXDat.pdf |date=2012-09-04 }}.</ref>

For this reason it was not until the development of electric podded propulsion, [[ABB]]'s [[Azipod]], that the concept of double acting ships became feasible. The superiority of podded propulsion in icebreaking merchant ships, especially when running astern, was proved when Finnish [[product tanker]]s [[MT Varzuga|''Uikku'']] and [[MT Indiga|''Lunni'']] were converted to Azipod propulsion in 1993 and 1994, respectively. Even though the ships were originally designed with icebreaking capability in mind, after the conversion ice resistance in level ice when running astern was only 40% of that when breaking ice ahead despite the ships being equipped with an icebreaking bow and not designed to break ice astern.<ref name="poac95" /><ref name="dat" />

== History ==

=== Development ===

Following the successful operation of the Azipod-converted tankers ''Uikku'' and ''Lunni'' in the [[Northern Sea Route]], [[Aker Arctic|Kværner Masa-Yards Arctic Research Centre]] developed the first double acting tanker concept in the early 1990s. The 90,000 DWT tankers were designed to transport oil and gas condensate from the [[Pechora Sea]] in the [[Russia]]n [[Arctic]], where ice conditions during winter can be considered moderate and the ships would operate mainly in astern mode, first to [[Murmansk]] and then [[Rotterdam]], where most of the distance can be travelled in open water year round.<ref name="poac95" /> Other early double acting concepts included a similar ship with an icebreaking bow that would be utilized in summer time when the ship was traveling in areas with low ice concentration but with a risk of colliding with multi-year ice blocks.<ref name="dat" />

In early 2000s Fortum Shipping, the transportation arm of the Finnish energy company [[Fortum]], started a major fleet renewal program to increase the efficiency and reduce the average age of its vessels.<ref name="refine206">NextStop - Merten valtiaat. [http://www.nesteoil.com/binary.asp?GUID=2CD7FAB0-9F8E-4956-821B-3E59F7D9827A Refine 2/06] {{Webarchive|url=https://web.archive.org/web/20130814184114/http://www.nesteoil.com/binary.asp?GUID=2CD7FAB0-9F8E-4956-821B-3E59F7D9827A |date=2013-08-14 }}, page 24. Neste Oil, 2006.</ref> The program also included replacing the company's old tankers, such as the 90,000-ton [[MT Natura|''Natura'']], that were used to transport crude oil to the company's oil refineries in the [[Gulf of Finland]]. The old ships had traffic restrictions during the worst part of the winter because of their lower [[ice class]] of 1C and could not deliver their cargo all the way to the refineries in Porvoo and Naantali because they were denied icebreaker assistance. When this happened, the oil had to be transported to smaller ships of higher ice class at the edge of the ice — a practice that was both uneconomical and hazardous.<ref name="dat" />

To solve these problems Kværner Masa-Yards Arctic Research Centre developed a new 100,000 DWT Aframax tanker concept together with Fortum Shipping, which ordered two vessels from [[Sumitomo Heavy Industries]] in 2001. The new ships were designed to the highest [[Finnish-Swedish ice class]], 1A Super, and to be capable of operating in all ice conditions encountered in the [[Baltic Sea]]. The possibility to operate in the Pechora Sea was also taken into account in the design process. Extensive ice model tests confirmed the vessel's operational capability in level ice, rubble fields, ice channels and ridges.<ref name="dat" />

The world's first double acting tanker and the largest 1A Super class oil tanker at that time, ''Tempera'', was delivered from [[Yokosuka, Kanagawa|Yokosuka shipyard]] in late August 2002.<ref name="themotorship">[http://www.motorship.com/news101/tempera-tanker-double-act TEMPERA Tanker double act] {{Webarchive|url=https://web.archive.org/web/20120331042251/http://www.motorship.com/news101/tempera-tanker-double-act |date=2012-03-31 }}.  The Motor Ship, 1 October 2002. {{retrieved | accessdate=2011-09-26}}</ref><ref name="1asuper">[http://193.25.186.69/upload/presentations/Icebriefing20190404.pdf Ice-class tankers] {{Webarchive|url=https://web.archive.org/web/20140716020353/http://193.25.186.69/upload/presentations/Icebriefing20190404.pdf |date=2014-07-16 }}. Lloyd's Register, 16 April 2004. {{retrieved | accessdate=2011-09-26}}</ref> She was awarded the Ship Of The Year 2002 award by the Society of Naval Architects of Japan (SNAJ).<ref name="snaj">[http://www.jsea.or.jp/VariableJ/Sea300.pdf The Ship of The Year 2002 Award goes to the Tempera] {{Webarchive|url=https://web.archive.org/web/20050214095334/http://www.jsea.or.jp/VariableJ/Sea300.pdf |date=2005-02-14 }}. SEA Japan No. 300, August–September 2003.</ref> The second ship, ''Mastera'', was delivered in the following year.<ref name="akerarctic" /><ref name="nesteoil" /> Both ships were named after the company's oil products.<ref name="refine108">Refine 1/08, page 23. Neste Oil, 2008.</ref> While the price of the contract was not made public, the company later admitted that the 60–70 million euro estimate was "quite close to the truth". The ships were owned by ABB Credit, which leased them to Fortum for ten years.<ref name="tt" /> The leasing business was later sold to SEB Leasing.

=== Career ===
[[File:MT Mastera in 2020.jpg|thumb|left|MT ''Mastera'' in 2020 near Primorsk]]
Since the beginning, ''Tempera'' and ''Mastera'' were used mainly for year-round transportation of crude oil from the Russian oil terminal of Primorsk to company's own oil terminals in Porvoo and Naantali,<ref name="smu" /> where they were the only ships capable of operating without delays or problems during the harshest winters.<ref name="htf2">[http://www.hightech.fi/direct.aspx?area=htf&prm1=113&prm2=article Opening up Arctic oil resources] {{Webarchive|url=https://web.archive.org/web/20120401202102/http://www.hightech.fi/direct.aspx?area=htf&prm1=113&prm2=article |date=2012-04-01 }}. High Technology Finland 2006. {{retrieved | accessdate=2011-09-26}}</ref> Occasionally they also carried cargoes in the [[Gulf of Bothnia]] and even outside the Baltic Sea depending on the amount of oil in the refineries' storage tanks.<ref name="refine107">Varmoilla jäillä. [http://ir-service.funkton.com/view/agppci1zZXJ2aWNlchYLEg5GaWxlQXR0YWNobWVudBiZvxIM Refine 1/07] {{Webarchive|url=https://web.archive.org/web/20120402232308/http://ir-service.funkton.com/view/agppci1zZXJ2aWNlchYLEg5GaWxlQXR0YWNobWVudBiZvxIM |date=2012-04-02 }}, pages 25-27. Neste oil, 2007.</ref><ref name="rannikko">[http://www.rannikkoseutu.fi/cs/Satellite/Uutiset/1194674595987/artikkeli/ahteri+edella+primorskiin.html Ahteri edellä Primorskiin] {{Webarchive|url=https://web.archive.org/web/20120402232312/http://www.rannikkoseutu.fi/cs/Satellite/Uutiset/1194674595987/artikkeli/ahteri+edella+primorskiin.html |date=2012-04-02 }}. Rannikkoseutu, 13 April 2011. {{retrieved | accessdate=2011-09-26}}</ref> However, due to draft restrictions the ships could not carry a full cargo of 100,000 tons to the port of Naantali until April 2010 — they had to stop at Porvoo on the way and unload 20,000 tons of oil to reduce the draft of the vessel.<ref name="hs_syva">[http://www.hs.fi/kotimaa/artikkeli/Neste+Oilin+tankkialus+ajoi+ensimm%C3%A4isen%C3%A4+uutta+syv%C3%A4v%C3%A4yl%C3%A4%C3%A4+Naantaliin/1135256386344 Neste Oilin tankkialus ajoi ensimmäisenä uutta syväväylää Naantaliin]. Helsingin Sanomat, 25 April 2010. {{retrieved | accessdate=2011-09-26}}</ref>

In 2005 Fortum's oil division was transferred to the re-established [[Neste Oil]] and the management of the ships, including the double acting tankers, was handed over to a subsidiary company Neste Shipping. On 19 September 2013, Neste Oil announced that it would sell its shipping business and the majority of its ships, including ''Mastera'', to a new company owned by the Finnish insurance company [[Ilmarinen (insurance company)|Ilmarinen]] and the [[National Emergency Supply Agency]].<ref>[http://www.taloussanomat.fi/energia/2013/09/19/ilmarinen-varustamobisneksesta-riskit-minimoitu/201313099/12 Ilmarinen varustamobisneksestä: Riskit minimoitu]. Taloussanomat, 19 September 2013. {{retrieved|accessdate=2013-09-19}}</ref> In 2019, ''Mastera'' was resold back to SEB Leasing.<ref name="2019ownerchange" />

Since 2017, ''Mastera'' was the only double acting tanker operating in the Baltic Sea after ''Tempera'' was sold overseas.<ref name="htf3">[http://www.hightech.fi/direct.aspx?area=htf&prm1=1059&prm2=article A passion for ice.] {{Webarchive|url=https://web.archive.org/web/20120401202108/http://www.hightech.fi/direct.aspx?area=htf&prm1=1059&prm2=article |date=2012-04-01 }} High Tech Finland 2011. {{retrieved | accessdate=2011-09-26}}</ref> While other double acting ships have been built, the tankers operated by Neste Shipping were the only ones equipped with a bulbous bow designed primarily with open water performance in mind — the tankers and container ships built for the Russian Arctic have a more traditional icebreaking bow due to the more severe ice conditions.<ref name="norilsk_powerpoint" />

In September 2021, ''Mastera'' was transferred to the [[Norwegian International Ship Register]].<ref name="norflag" /> In January 2022, she was renamed ''Mikines'' and reflagged to Liberia.<ref name="equasis" /> In March 2022, the 19-year-old ''Mikines'' appeared on list of tonnage sold for [[shipbreaking|demolition]],<ref>{{cite web|url=https://www.hellenicshippingnews.com/wp-content/uploads/2022/03/Weekly-SP-Market-Report-Week-ending-March-11th-2022-Week-10-Report-No-10.22-1.pdf|title=Weekly S&P market report|date=11 March 2022|accessdate=19 March 2022}}</ref> but resumed trading and was renamed ''Alma'' in June 2022.<ref name="seaweb" />

In May 2023, ''Alma'' was recognized as one of the oil tankers transmitting a falsified [[automatic identification system]] (AIS) to circumvent the [[2022 Russian crude oil price cap sanctions]].<ref>{{cite web|url=https://www.nytimes.com/interactive/2023/05/30/world/asia/russia-oil-ships-sanctions.html|title=Fake Signals and American Insurance: How a Dark Fleet Moves Russian Oil|work=New York Times|date=30 May 2023|accessdate=26 June 2023}}</ref>

In September 2023, the ship was renamed ''Petali''.<ref name="seaweb" />

== Design ==

=== General characteristics ===

The double acting Aframax tanker is {{convert|252.0|m|ft}} [[length overall|long overall]] and {{convert|237.59|m|ft}} [[length between perpendiculars|between perpendiculars]]. The moulded breadth and depth of her hull are {{convert|44.0|m|ft}} and {{convert|22.5|m|ft}}, respectively, and from keel to mast she measures {{convert|53.1|m|ft}}. Her [[gross tonnage]] is 64,259 and [[net tonnage]] 30,846, and the [[deadweight tonnage]] corresponding to the [[summer draft|draft at summer freeboard]], {{convert|15.3|m|ft}}, is 106,208 tons, slightly more than that of her sister ship. In ballast, the ship draws only {{convert|8.6|m|ft}} of water.<ref name="nesteoil" />

The foreship of the tanker is designed for open water performance with a [[bulbous bow]] to maximize the hydrodynamic efficiency. The ship is, just like any other ice-strengthened vessel, also capable of running ahead in light ice conditions. The stern is, however, shaped like an icebreaker's bow, and the vessel is designed to operate independently in the most severe ice conditions of the [[Baltic Sea]].<ref name="akerarctic" /> For this purpose the ship is also equipped with two [[Bridge (nautical)|bridges]] for navigating in both directions.<ref name="nesteoil" /> The ship is served by a crew of 15 to 20 depending on operating conditions during winter and maintenance work during summer.<ref name="vapaavahti42010" /><ref name="refine107" />

The ship is classified by [[Lloyd's Register of Shipping]].<ref name="nesteoil" />

=== Cargo tanks and handling ===

The ship has six pairs of heated, partially epoxy-coated cargo tanks and one pair of fully coated [[slop tank]]s, all divided by a longitudinal center bulkhead and protected by [[double hull]], with a combined capacity of {{convert|121,158.2|m3}} at 98% filling. For cargo handling she has three electrically driven cargo oil pumps with a capacity of 3,500 m<sup>3</sup>/h × 130 m and one cargo oil stripping pump rated for 300 m<sup>3</sup>/h × 130 m. The cargo can be loaded in 10 hours and discharged in 12 hours. Each cargo tank has two and both slop tanks one [[automated tank cleaning machine]]s as well as holes for portable tank cleaning machines.<ref name="nesteoil" />

The ship's ballast water capacity of {{convert|46922.4|m3}} is divided into sixteen segregated ballast tanks, six pairs in the double hull around the cargo tanks, two fore peak tanks and two aft peak tanks.<ref name="themotorship" /> She has two electrically driven ballast pumps rated at 2,500 m<sup>3</sup>/h × 35 m and 3,000 m<sup>3</sup>/h × 70 m.<ref name="nesteoil" /> The ballast capacity is needed to maintain correct trim especially during drydocking — the empty ship has an aft trim of {{convert|3|m|ft}} and an uneven weight distribution may damage the hull girder.<ref name="vapaavahti42010">Tempera telakalla. [http://www.mepa.fi/2010vv4.pdf Vapaavahti 4/2010] {{Webarchive|url=https://web.archive.org/web/20120402232130/http://www.mepa.fi/2010vv4.pdf |date=2012-04-02 }}, pages 4-7. Merimiespalvelutoimisto, 2010.</ref>

=== Power and propulsion ===

The ship has [[diesel-electric transmission|diesel-electric]] powertrain with four main generating sets, two [[straight-nine engine|nine-cylinder]] [[Wärtsilä]] 9L38B and two [[straight-six engine|six-cylinder]] 6L38B four-stroke medium-speed [[diesel engine]]s, with a combined output of {{convert|20|MW|hp|abbr=on}}. The main engines are equipped with [[exhaust gas economizer]]s. In addition ''Mastera'' has one auxiliary diesel generator that can be used when the ship is at port. The auxiliary generator, six-cylinder Wärtsilä 6L26A, has an output of {{convert|1.7|MW|hp|abbr=on}}. While underway at {{convert|13.5|kn}}, the fuel consumption of the ship's main engines is 56 tons of [[heavy fuel oil]] per day when loaded and 40 tons per day in ballast. Her tanks can store {{convert|2890.1|m3}} of heavy fuel oil for the main engines, {{convert|308.2|m3}} of diesel oil for the auxiliary generator, steam boilers and [[inert gas system]], and {{convert|63.2|m3}} of lubrication oil.<ref name="nesteoil" />

When built, ''Mastera'' and her sister ship were the first tankers propelled by ABB Azipod electric [[azimuth thruster]]s capable of rotating 360 degrees around the vertical axis. The pulling-type VI2500 pods in these two ships, with a nominal output of 16 MW and {{convert|7.8|m|ft|adj=on}} fixed-pitch propellers turning at 86 rpm, are the most powerful ice-strengthened Azipod units ABB has ever produced.<ref name="tt">[http://www.tekniikkatalous.fi/metalli/potkurikeksinto+heratti+kilpailijat/a33864 Potkurikeksintö herätti kilpailijat] {{Webarchive|url=https://web.archive.org/web/20120401135439/http://www.tekniikkatalous.fi/metalli/potkurikeksinto+heratti+kilpailijat/a33864 |date=2012-04-01 }}. Tekniikka & Talous, 9 October 2003. {{retrieved | accessdate=2011-09-19}}</ref><ref name="abb_reflist">[https://library.e.abb.com/public/98a7ddd74d7ecb3bc1257b09004c14ab/ABB%20Propulsion%20Products%20reference%20list%202013.pdf References - Propulsion Products]. ABB. {{retrieved|accessdate=2015-05-28}}</ref> The forward-facing propeller increases the propulsion efficiency due to optimal water flow to the propeller and thus improves fuel efficiency. In addition an azimuthing thruster's ability to direct thrust to any direction also results in excellent manoeuvrability characteristics that exceeds those of ships utilizing traditional mechanical shaftlines and [[rudder]]s.<ref name="abb">[http://www.abb.com/industries/db0003db002805/c12571f4002ab83dc1256fdf003b2929.aspx?tabKey=2 Azipod Propulsion], ABB</ref> The turning circle of the Azipod-equipped double acting ships is only half a kilometer at full speed, half of that of a traditional oil tanker of the same size. This is a significant safety factor as the stopping distance of a traditional tanker can be up to {{convert|2.5|km|mi}}.<ref name="tekniikkajatal">[http://www.tekniikkatalous.fi/rakennus/fortum+toi+itamerelle+ketteran+oljytankkerin/a40810 Fortum toi Itämerelle ketterän öljytankkerin], Tekniikka & Talous, 2002-11-14</ref>

For maneuvering at low speeds in harbours, the ship is also equipped with two 1,750{{nbsp}}kW [[bow thruster]]s.<ref name="signships" />

=== Icebreaking capability ===

The icebreaking capability of the double acting tankers proved to be superior to other ships since the beginning — in shuttle service between Primorsk, Russia, and the Finnish refineries the tankers require no icebreaker assistance and have even acted as an icebreaker for other merchant ships that have utilized the wide channel opened by the Aframax tanker.<ref name="tt" /><ref name="norilsk_powerpoint">Anatoly Gorshkovskij & Göran Wilkman: [http://www.akerarctic.fi/2ndAkerArcticPassionSeminar/Norilsk.pdf "Norilskiy Nickel" a Breakthrough in Cost Efficient Arctic Transports] {{webarchive|url=https://web.archive.org/web/20071010035717/http://www.akerarctic.fi/2ndAkerArcticPassionSeminar/Norilsk.pdf |date=2007-10-10 }}. Aker Arctic Technology Inc, 2007. {{Retrieved | accessdate=2010-06-07}}</ref> However, this has not been intentional — when the world's largest 1A Super class ice tanker [[MT Stena Arctica|''Stena Arctica'']], also owned by Neste Shipping, became stuck in ice outside the port of Primorsk during the winter of 2009–2010, a decision was made to leave the assisting to Russian icebreakers.<ref name="vapaavahti42010" />

The ships have performed beyond expectations in both level ice up to {{convert|1|m|ft}} thick, which can be broken in continuous motion at {{convert|3|kn}},<ref name="abb_tempera" /> and ridges up to {{convert|13|m|ft}} deep, which can be penetrated by either allowing the forward-facing propeller to mill (crush) the ice or breaking the ridge apart with the propeller wash.<ref name="dat" /><ref name="htf1">[http://www.htf.fi/direct.aspx?area=htf&prm1=336&prm2=article Opening up the Arctic] {{Webarchive|url=https://web.archive.org/web/20120402232303/http://www.htf.fi/direct.aspx?area=htf&prm1=336&prm2=article |date=2012-04-02 }}. High Technology Finland 2005. {{retrieved | accessdate=2010-09-26}}</ref> While the vessels have been immobilized occasionally by pack ice, they have been able to free themselves by using the rotating propeller pod to clear the ice around the hull.<ref name="hs2">[http://www2.hs.fi/english/archive/news.asp?id=20030401IE18 Oil Tanker Maestra cuts backward course through solid ice] {{Webarchive|url=https://web.archive.org/web/20120329011936/http://www2.hs.fi/english/archive/news.asp?id=20030401IE18 |date=2012-03-29 }}. Helsingin Sanomat International Edition, 1 April 2003. {{retrieved | accessdate=2011-09-26}}</ref>

== References ==
{{Commons category|IMO 9235892|''Mastera''}}
{{reflist}}

{{Authority control}}

{{DEFAULTSORT:Petali}}
[[Category:Oil tankers]]
[[Category:2002 ships]]
[[Category:Ships built by Sumitomo Heavy Industries]]
[[Category:Double acting ships]]