Classification:	Lloyd's Register of Shipping
Main engines:	2 × Wärtsilä Wärtsilä Wärtsilä is a Finnish corporation which manufactures and services power sources and other equipment in the marine and energy markets. The core products of Wärtsilä include large combustion engines...  9L38B (2 × 6,0 MW) 2 × Wärtsilä 6L38B (2 × 4.0 MW)
Auxiliary generator:	Wärtsilä 6L26A (1.7 MW)

MT Mastera is a Finnish

Finland

Finland , officially the Republic of Finland, is a Nordic country situated in the Fennoscandian region of Northern Europe. It is bordered by Sweden in the west, Norway in the north and Russia in the east, while Estonia lies to its south across the Gulf of Finland.Around 5.4 million people reside...

 Aframax

Aframax

An ' ship is an oil tanker smaller than and with a breadth above 32.31 m. The term is based on the Average Freight Rate Assessment tanker rate system. class tankers are largely used in the basins of the Black Sea, the North Sea, the Caribbean Sea, the China Sea and the Mediterranean...

 crude oil tanker operated by Neste Shipping

Neste Oil

Neste Oil is a Finnish oil refining and marketing company producing mainly transportation fuels and other refined petroleum products. Neste Oil shares are quoted on the Helsinki Stock Exchange.- History :...

. She and her sister ship, Tempera

MT Tempera

MT Tempera is a Finnish Aframax crude oil tanker operated by Neste Shipping. She was the first ship to utilize the double acting tanker concept, developed by Aker Arctic, in which the vessel is designed to travel ahead in open water and astern in severe ice conditions...

, are the first ships to utilize the double acting tanker

Double acting ship

Double acting ship is a type of icebreaking merchant ship designed to run ahead in open water and astern in ice...

 (DAT) concept, developed by Aker Arctic, in which the vessel is designed to travel ahead in open water and astern in severe ice conditions. The two icebreaking tankers are used to transport crude oil year round from the Russia

Russia

Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

n oil terminal in Primorsk

Primorsk

Primorsk may refer to:*Dənizkənarı, Azerbaijan - formerly Primorsk*Primorsk, Leningrad Oblast, a town in Leningrad Oblast, Russia, formerly Koivisto or Björkö...

 to Neste Oil refineries in Porvoo

Porvoo

Porvoo is a city and a municipality situated on the southern coast of Finland approximately east of Helsinki. Porvoo is one of the six medieval towns in Finland, first mentioned as a city in texts from 14th century...

 and Naantali

Naantali

Naantali is a city in south-western Finland, known as one of the most important tourist centres of the country. The municipality has a population of , and is located in the region of Finland Proper, west of Turku....

.

Concept

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

Slamming

Slamming is the impact of the bottom structure of a ship onto the sea surface. It is mainly observed while sailing in waves, when the bow raises from the water and subsequently impacts on it. Slamming induces extremely high loads to ship structures and is taken under consideration when designing...

 in heavy weather while a hydrodynamically efficient bulbous bow greatly increases the ice resistance. 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. These findings resulted in the adoption of bow propellers in older icebreakers operating in the Great Lakes

Great Lakes

The Great Lakes are a collection of freshwater lakes located in northeastern North America, on the Canada – United States border. Consisting of Lakes Superior, Michigan, Huron, Erie, and Ontario, they form the largest group of freshwater lakes on Earth by total surface, coming in second by volume...

 and the Baltic Sea

Baltic Sea

The Baltic Sea is a brackish mediterranean sea located in Northern Europe, from 53°N to 66°N latitude and from 20°E to 26°E longitude. It is bounded by the Scandinavian Peninsula, the mainland of Europe, and the Danish islands. It drains into the Kattegat by way of the Øresund, the Great Belt and...

, 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.

For this reason it was not until the development of electric podded propulsion, ABB's Azipod

Azipod

Azipod is the registered brand name of the ABB Group for their azimuth thruster. Originally developed in Finland jointly by Kvaerner Masa-Yards dockyards and ABB, these are marine propulsion units consisting of electrically driven propellers mounted on a steerable pod.The pod's propeller usually...

, 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 tankers Uikku

MT Varzuga

MT Varzuga is a Russian product tanker operated by Murmansk Shipping Company. After her modernization in 1993 she became the first merchant ship to be equipped with an electric azimuth thruster, Azipod.-History:...

 and Lunni

MT Indiga

MT Indiga is a Russian product tanker operated by Murmansk Shipping Company. After her modernization in 1994 she became the second merchant ship, after her sister ship Varzuga, to be equipped with an electric azimuth thruster, Azipod....

 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.

Development

Following the successful operation of the Azipod-converted tankers Uikku and Lunni in the Northern Sea Route

Northern Sea Route

The Northern Sea Route is a shipping lane officially defined by Russian legislation from the Atlantic Ocean to the Pacific Ocean specifically running along the Russian Arctic coast from Murmansk on the Barents Sea, along Siberia, to the Bering Strait and Far East. The entire route lies in 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

Pechora Sea

Pechora Sea , is a sea at the northwest of Russia, the southeastern part of the Barents Sea. The western border of the sea is off Kolguyev Island, while the eastern border is the western coasts of Vaygach Island and the Yugorsky Peninsula, and the northern border the southern end of Novaya...

 in the Russia

Russia

Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

n Arctic

Arctic

The Arctic is a region located at the northern-most part of the Earth. The Arctic consists of the Arctic Ocean and parts of Canada, Russia, Greenland, the United States, Norway, Sweden, Finland, and Iceland. The Arctic region consists of a vast, ice-covered ocean, surrounded by treeless permafrost...

, where ice conditions during winter can be considered moderate and the ships would operate mainly in astern mode, first to Murmansk

Murmansk

Murmansk is a city and the administrative center of Murmansk Oblast, Russia. It serves as a seaport and is located in the extreme northwest part of Russia, on the Kola Bay, from the Barents Sea on the northern shore of the Kola Peninsula, not far from Russia's borders with Norway and Finland...

 and then Rotterdam

Rotterdam

Rotterdam is the second-largest city in the Netherlands and one of the largest ports in the world. Starting as a dam on the Rotte river, Rotterdam has grown into a major international commercial centre...

, where most of the distance can be travelled in open water year round. 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.

In early 2000s Fortum Shipping, the transportation arm of the Finnish energy company Fortum

Fortum

Fortum Oyj is a Finnish publicly listed energy company, which focuses on the Nordic and Baltic countries, Poland and the north-west of Russia. After acquisition of Russian energy company TGC-10 in year 2008, Western Siberia has become an important operating area for Fortum. The head of the company...

, started a major fleet renewal program to increase the efficiency and reduce the average age of its vessels. The program also included replacing the company's old tankers, such as the 90,000-ton Natura, that were used to transport crude oil to the company's oil refineries in the Gulf of Finland

Gulf of Finland

The Gulf of Finland is the easternmost arm of the Baltic Sea. It extends between Finland and Estonia all the way to Saint Petersburg in Russia, where the river Neva drains into it. Other major cities around the gulf include Helsinki and Tallinn...

. The old ships had traffic restrictions during the worst part of the winter because of their lower ice class

Ice class

Ships with an Ice Class have a strengthened hull to enable them to navigate through sea ice.-History:The first requirements for merchant ships to be escorted by icebreakers were set in Finland in 1890, after winter traffic to the port of Hanko was started. In the past, different classification...

 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.

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

Sumitomo Heavy Industries

Sumitomo Heavy Industries, Ltd. is an integrated manufacturer of industrial machinery, automatic weaponry, ships, bridges and steel structure, equipment for environmental protection, including recycling, power transmission equipment, plastic molding machines, laser processing systems, particle...

 in 2001. The new ships were designed to the highest Finnish-Swedish ice class

Finnish-Swedish ice class

The Finnish-Swedish ice class is an ice class assigned to a vessel operating in first-year ice in the Baltic Sea and calling Finnish or Swedish ports...

, 1A Super, and to be capable of operating in all ice conditions encountered in the Baltic Sea

Baltic Sea

The Baltic Sea is a brackish mediterranean sea located in Northern Europe, from 53°N to 66°N latitude and from 20°E to 26°E longitude. It is bounded by the Scandinavian Peninsula, the mainland of Europe, and the Danish islands. It drains into the Kattegat by way of the Øresund, the Great Belt and...

. 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.

The world's first double acting tanker and the largest 1A Super class oil tanker at that time, Tempera, was delivered from Yokosuka shipyard

Yokosuka, Kanagawa

is a city located in Kanagawa, Japan. As of 2010, the city had an estimated population of 419,067 and a population density of 4,160 people per km². It covered an area of 100.62 km²...

 in late August 2002. She was awarded the Ship Of The Year 2002 award by the Society of Naval Architects of Japan (SNAJ). The second ship, Mastera, was delivered in the following year. Both ships were named after the company's oil products. 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 thruth". The ships were owned by ABB Credit, which leased them to Fortum for ten years. The leasing business was later sold to SEB Leasing.

Career

Since the beginning Tempera and Mastera have been 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, where they have been the only ships capable of operating without delays or problems during the harshest winters. Occasionally they have carried cargoes in the Gulf of Bothnia

Gulf of Bothnia

The Gulf of Bothnia is the northernmost arm of the Baltic Sea. It is situated between Finland's west coast and Sweden's east coast. In the south of the gulf lie the Åland Islands, between the Sea of Åland and the Archipelago Sea.-Name:...

 and even outside the Baltic Sea depending on the amount of oil in the refineries' storage tanks. 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.

In 2005 Fortum's oil division was transferred to the re-established Neste Oil

Neste Oil

Neste Oil is a Finnish oil refining and marketing company producing mainly transportation fuels and other refined petroleum products. Neste Oil shares are quoted on the Helsinki Stock Exchange.- History :...

 and the management of the ships, including the double acting tankers, was handed over to a subsidiary company Neste Shipping.

After almost a decade of successful operation without icebreaker assistance Tempera and Mastera remain the only double acting tankers operating in the Baltic Sea. While other double acting ships have been built in the recent years, the tankers operated by Neste Shipping are also 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.

General characteristics

Mastera is 252 metres (826.8 ft) long overall and 237.59 metres (779.5 ft) between perpendiculars. The moulded breadth and depth of her hull are 44 metres (144.4 ft) and 22.5 metres (73.8 ft), respectively, and from keel to mast she measured 53.1 metres (174.2 ft). Her gross tonnage

Gross tonnage

Gross tonnage is a unitless index related to a ship's overall internal volume. Gross tonnage is different from gross register tonnage...

 is 64,259 and net tonnage

Net tonnage

Net tonnage is a dimensionless index calculated from the total moulded volume of the ship's cargo spaces by using a mathematical formula...

 30,846, and the deadweight tonnage

Deadweight tonnage

Deadweight tonnage is a measure of how much weight a ship is carrying or can safely carry. It is the sum of the weights of cargo, fuel, fresh water, ballast water, provisions, passengers, and crew...

 corresponding to the draft at summer freeboard

Summer Draft

Summer draft is a naval term for the worst-case loaded draft a ship can have. This draft is corrected for the worst-case seasonal conditions . During summer the water is warmer, and thus less dense and expands slightly: see Thermal expansion. This makes ships float deeper in the water. Summer draft...

, 15.3 metres (50.2 ft), is 106,208 tons, slightly more than in Tempera. In ballast Mastera draws only 8.6 metres (28.2 ft) of water.

The foreship of Mastera is designed for open water performance with a bulbous bow

Bulbous bow

A bulbous bow is a protruding bulb at the bow of a ship just below the waterline. The bulb modifies the way the water flows around the hull, reducing drag and thus increasing speed, range, fuel efficiency, and stability...

 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 Mastera is designed to operate independently in the most severe ice conditions of the Baltic Sea

Baltic Sea

The Baltic Sea is a brackish mediterranean sea located in Northern Europe, from 53°N to 66°N latitude and from 20°E to 26°E longitude. It is bounded by the Scandinavian Peninsula, the mainland of Europe, and the Danish islands. It drains into the Kattegat by way of the Øresund, the Great Belt and...

. For this purpose the ship is also equipped with two bridges for navigating in both directions. The ship is served by a crew of 15 to 20 depending on operating conditions during winter and maintenance work during summer.

Mastera is classified by Lloyd's Register of Shipping.

Cargo tanks and handling

Mastera has six pairs of heated, partially epoxy-coated cargo tanks and one pair of fully coated slop tanks, all divided by a longitudinal center bulkhead and protected by double hull

Double hull

A double hull is a ship hull design and construction method invented by Leonardo da Vinci where the bottom and sides of the ship have two complete layers of watertight hull surface: one outer layer forming the normal hull of the ship, and a second inner hull which is some distance inboard,...

, with a combined capacity of 121158.2 cubic metres (4,278,661.4 cu ft) at 98 % filling. For cargo handling she has three electrically driven cargo oil pumps with a capacity of 3,500 m³/h × 130 m and one cargo oil stripping pump rated for 300 m³/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

Automated tank cleaning machine

An automated tank cleaning machine is a machine used to clean cargo tanks such as those found in tank trucks, railroad cars, barges, and oil tankers...

s as well as holes for portable tank cleaning machines.

The ship's ballast water capacity of 46922.4 cubic metres (1,657,048.9 cu ft) is divided into sixteen segregated ballast tanks, six pairs located in the double hull around the cargo tanks, two fore peak tanks and two aft peak tanks. She has two electrically driven ballast pumps rated at 2,500 m³/h × 35 m and 3,000 m³/h × 70 m. The ballast capacity is needed to maintain correct trim especially during drydocking — the empty ship has an aft trim of 3 metres (9.8 ft) and an uneven weight distribution may damage the hull girder.

Power and propulsion

Mastera has diesel-electric powertrain with four main generating sets, two nine-cylinder Wärtsilä

Wärtsilä

Wärtsilä is a Finnish corporation which manufactures and services power sources and other equipment in the marine and energy markets. The core products of Wärtsilä include large combustion engines...

 9L38B and two six-cylinder 6L38B four-stroke medium-speed diesel engine

Diesel engine

A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber...

s, with a combined output of 20 MW. The main engines are equipped with exhaust gas economizers. 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 1.7 MW. While underway at 13.5 knots (7.3 m/s), 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 2890.1 cubic metres (102,062.9 cu ft) of heavy fuel oil for the main engines, 308.2 cubic metres (10,884 cu ft) of diesel oil for the auxiliary generator, steam boilers and inert gas system, and 63.2 cubic metres (2,231.9 cu ft) of lubrication oil.

Mastera and her sister ship are the first tankers propelled by ABB Azipod electric azimuth thruster

Azimuth thruster

An azimuth thruster is a configuration of ship propellers placed in pods that can be rotated in any horizontal direction, making a rudder unnecessary...

s capable of rotating 360 degrees around the vertical axis. The pulling-type pods in these two ships, with a nominal output of 16 MW and 7.8 metres (25.6 ft) fixed-pitch propellers turning at 86 rpm, are the most powerful ice-strengthened Azipod units ABB has ever produced. 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

Rudder

A rudder is a device used to steer a ship, boat, submarine, hovercraft, aircraft or other conveyance that moves through a medium . On an aircraft the rudder is used primarily to counter adverse yaw and p-factor and is not the primary control used to turn the airplane...

s. The turning circle of Mastera and Tempera 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 2.5 kilometres (1.6 mi).

For maneuvering at low speeds in harbours Mastera is also equipped with two bow thruster

Bow thruster

A bow thruster is a transversal propulsion device built into, or mounted to, the bow of a ship or boat to make it more maneuverable. Bow thrusters make docking easier, since they allow the captain to turn the vessel to port or starboard without using the main propulsion mechanism which requires...

s.

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. However, this has not been intentional — when the world's largest 1A Super class ice tanker 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.

The ships have performed beyond expectations in both level ice up to 1 metres (3.3 ft) thick, which can be broken in continuous motion at 3 knots (1.6 m/s), and ridges up to 13 metres (42.7 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. 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.