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Wärtsilä completes conversion of tanker Bit Viking from heavy fuel oil to LNG

Bit Viking
The converted Bit Viking. The twin LNG tanks are mounted on the deck. Click to enlarge.

Wärtsilä Corporation has completed the conversion of the 25,000 dwt product tanker Bit Viking from heavy fuel oil to liquefied natural gas (LNG) operation. The conversion enables the Bit Viking to qualify for lower nitrogen oxides (NOx) emission taxes under the Norwegian NOx fund scheme.

In August 2010, Wärtsilä signed a turnkey project with Tarbit Shipping to convert the Bit Viking to LNG operation. The Bit Viking has twin screw propulsion, with each screw originally powered by a 6-cylinder in-line Wärtsilä 46 engine running on heavy fuel oil (HFO). The conversion involved changing these to 6-cylinder in-line Wärtsilä 50DF dual-fuel engines that operate on LNG.

Wärtsilä dual-fuel engines in gas mode produce roughly 80% less NOx compared to IMO Tier I levels and practically zero SOx and particulates. When gas is used in a dual-fuel engine, CO2 emissions are reduced by about 20% compared to liquid fuels.

The scope of the conversion package from Wärtsilä included deck-mounted gas fuel systems, piping, two two six-cylinder Wärtsilä 46 engines converted to Wärtsilä 50DF units with related control systems and all adjustments to the ship’s systems necessitated by the conversion. The vessel’s classification certificate was also updated.

The engines are connected directly to the propeller shafts through a reduction gearbox, thus avoiding the electrical losses that are an unavoidable feature of diesel-electric configurations. This enables a significant improvement in propulsion efficiency, reduced fuel consumption, and corresponding reductions in emissions. This is the first LNG fueled vessel to be classified by Germanischer Lloyd.

The Bit Viking utilizes Wärtsilä’s new LNGPac system, which enables the safe and convenient onboard storage of LNG. The two 500 cubic meter LNG storage tanks are mounted on the deck to facilitate bunkering operations and permit the bunkering of LNG at a rate of 430 cubic meters per hour.

The LNGPac tanks are insulated with perlite/vacuum and consist of a stainless steel inner vessel, which is designed for an internal pressure, and an outer vessel that acts as a secondary barrier. The outer vessel can be made of either stainless steel or carbon steel.

The storage tanks provide the vessel with 12 days of autonomous operation at 80% load, with the option to switch to marine gas oil if an extended range is required. When visiting EU ports, which have a 0.1% limit on sulfur emissions, the vessel operates on gas.

This is the first marine installation to involve converting Wärtsilä 46 engines to Wärtsilä 50DF engines, and the first 50DF marine installation with mechanical propulsion.

The vessel was handed over to the customer, Tarbit Shipping, in October. The re-commissioned vessel is operated by Statoil along the Norwegian coastline.

The Norwegian NOx fund is a cooperative effort whereby participating companies may apply for financial support in return for introducing NOx reducing measures.

This is a major step for Wärtsilä in consolidating its market leading position in LNG solutions for the shipping industry. The successful sea trials with this vessel provide yet further validation of the viability of LNG as the marine fuel of the future. We anticipate that this development will rapidly accelerate during the coming few years.

—Sören Karlsson, General Manager, Gas Applications, Ship Power Technology


  • Sören Karlsson, and Leonardo Sonzio (2010)Enabling the safe storage of gas onboard ships with the Wärtsilä LNGPac. Wärtsilä Technical Journal 01.2010


Account Deleted

A global shipping infrastructure for LNG fueling could be setup quickly if you made a dedicated ship for storage of LNG and fueling of other LNG ships. From a security point of view it also makes sense to fuel LNG ships off-shore. 100 of these LNG refueling ships could cover some 80% of all international shipping routes.

LNG is taking over in shipping as the cost of LNG ranges from 4 to 15 USD per million BTU whereas the price for bunker oil is 18 USD per million BTU when a barrel of oil is 100 USD.


Why have refueling ships? Look at the picture - there is plenty of space for more tanks. Four more tanks = a month's worth of fuel at 100% load +/-.

"The storage tanks provide the vessel with 12 days of autonomous operation at 80 per cent load, with the option to switch to marine gas oil if an extended range is required."


LNG could and/or is current being stock near many major ports. With enough large customers, LNG suppliers would make their product readily available. Isolated refueling stations could increase safety put would delay most ships for a few hours.

With more and more shale gas being produced worldwide and cost as low as $4/million BTU in many places, this could be a good interim solution, at least until such time as large ships are equipped with on-board clean e-energy power plants.


Henrik, that's quite a savings. How about the carbon dioxide and methane emissions? LNG vs Bunker.

Account Deleted


LNG produces less CO2 per million BTU than bunker oil as methane is less carbon intensive. However, only a dedicated LNG engine will not emit more unburned methane than an engine running on bunker fuel. I think only MAN Diesel & Turbo can deliver a LNG engine that solves that problem right now but the other engine makers are not far behind. Legislation is needed just to be sure that a solution to the NOX and the SOX problems is not creating a new methane emission problem.

A burning LNG tanker could blow up creating a fireball for several miles. You don’t want that to happen in a populated area. The few LNG fueling facilities that exist globally are all miles away from everything else including cargo loading and unloading facilities on a special off-shore pier. You may just as well take it entirely off-shore.


Henrik...I agree with you that added safety is worth the two hours or so required to refuel at an isolated place. Two hours every 12 days for refueling is probably acceptable and could be partially of fully offset by lower fuel cost.

Henry Gibson

What is the present energy cost of producing liquid natural gas or liquid methane. Norway sometimes has a surplus of hydro power but it may also make or import fossil power directly from the Netherlands via undersea cables. This power may even be made with natural gas exported to Europe from Norway by undersea pipelines.

It is also interesting to know the minimum energy cost of making LNG from the gas. This cost reduces the CO2 savings of the use of natural gas.

Both NOx and SO2 can be used by farms to increase production of crops or by forests to increase tree growth if properly neutralized, and it is well known by many people that CO2 is necessary for plant growth and the release of CO2 is necessary for plant and animal metabolism.

Norway, even, may have many places where the Waterboxx from Groasis can establish tree growth to capture much CO2. ..HG..


Henry Gibson - your comments do not fit the narrative of the media/Democratic party.

Alex Kovnat

I have a question for anybody familiar with Norway: Have any large numbers or percentage of their trucks been converted from Diesel to LNG/CNG? Seems like you would reduce NOx just as much that way, as by using LNG for ships.

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