TANKEROperator � January/February 201240

TECHNOLOGY - PROPULSION SYSTEMS

The conversion project wasundertaken under the supervisionof Hamburg-based class societyGermanischer Lloyd (GL). Once

converted, the tanker has become a dual-fuelvessel, able to burn fuel oil, or liquefiednatural gas (LNG).Ronnie-Torsten Westerman, GL’s business

development manager, writing in the classsociety’s magazine ‘Nonstop’, explained:“The project started with a kick-off meeting ofrepresentatives from Wärtsilä, the ownerTarbit Shipping and GL in April 2010.”Manufacturing of various new components

began in early 2011. They were thentransported to the shipyard in Landskrona,Sweden. “The Bit Viking arrived at the yard ontime and the conversion commenced inAugust,” said Westerman. Upon her arrival,the new equipment necessary for LNGoperation was installed in the vessel. GL’s staff played a critical role in this

process by monitoring the manufacture andinstallation of the components, such as piping,valves, safety equipment and LNG tanks andensuring safe construction, use of suitablematerials and application of appropriatewelding methods.

The two main engines were converted fromWärtsilä VASA type 46 D to type 50 DF.Westerman said: “Virtually everything wasreplaced except the crankshafts and frames.” The Bit Viking was then taken to

Risavika/Stavanger for completion of the pipeinstallation, the testing and calibration of thenewly installed equipment. She was thenready for her first bunkering of LNG. “Thefirst time we prepared for bunkering we had tocool down the LNG storage tanks on the foredeck using liquid nitrogen at –192 deg C”,explained Westerman. She then successfully bunkered LNG, which

has a temperature of –162 deg C, for a main

engine test run at the pier. By the end ofOctober, the Bit Viking was finally ready forher official sea trials. “She performed as expected and no major

discrepancies were noted. GL had twosurveyors on board during the sea trial. Thetechnical challenge in steering the conversionprocess was immense,” said Westerman. Key concerns were the proper interpretation

of class rules for safe construction, ensuring thatthe equipment manufacturers clearly understoodthe class rules and anticipating how the flagadministration (Sweden) would understand andaccept the required risk analysis. “Particularfocus was on bunkering and how it should beperformed, since this is a somewhat criticaloperation that requires special knowledge andequipment,” Westerman said.

Testing the rulesThe conversion of the Bit Viking also provideda good opportunity to put the GL rules for gasas ship fuel (see box) to the test. Followingthe successful conversion, Westermanexpressed optimism; “The existing rules aresufficient for a conversion such as that of theBit Viking. However, some modifications willbe made in the future as regulations, such asMarpol, are updated to reflect the option ofgas as a ship fuel.”

First L!G-fuelledretrofit resumesserviceThe 24,783 dwt chemical tanker Bit Viking was the world’s first vessel converted to run on L!G while in service. After successful sea trials under GL supervision,

the vessel has resumed commercial trading.

Bit Viking was built at theEdwards Shanghai shipyard inChina with double enginerooms, propellers, steeringgears, rudders and controlsystems – a full redundancypackage. Having previously been powered by two 6-cylinder in-line Wärtsilä 46 enginesrunning on heavy fuel oil, the conversion

has changed these to 6-cylinder in-lineWärtsilä 50DF dual fuel engines, capableof operating on LNG supplied from two500 cu m LNG storage tanks on the foredeck.The 24,783 dwt chemical tanker is

currently on long term charter to Statoil,trading on and around Norway’s westcoast, thus qualifying for Norway’semission tax rebate.

Bit Viking fact file

General arrangement drawing showing the deck layout.

TECHNOLOGY - PROPULSION SYSTEMS

January/February 2012 � TANKEROperator 41

While the advantages of LNG-fuelled shipengines are well known, there are a fewperformance drawbacks compared to fuel oil.Furthermore, the two 500 cu m capacity LNGtanks and the associated piping and valves addseveral hundred tonnes to the weight of thevessel. On the other hand, the ship enjoysincreased buoyancy and lifting cargo capacity.Westerman said;” You clearly win on theenvironmental side.”An LNG-powered vessel at this

developmental stage is slightly moreexpensive than a conventionally poweredequivalent, which increases capital costs. Yetwith the advent of cash incentives for loweremissions in some Scandinavian countries,notably Norway where the vessel is tradingunder a charter to Statoil, ship operators canalso save money via rebates.Where Scandinavia has taken the lead,

others will follow, GL said. Under rules drawnup by IMO, vessels must cut SOx emissionsfrom 1% currently to 0.1% by January 2015.“Within the short period of operation since

her conversion, the Bit Viking has alreadyachieved considerable benefits for theenvironment,” said Westerman. “Greenhousegases have been reduced by 20% to 25%,NOx gases by 9 %, sulphur output has beencut entirely and particle emissions have beenbrought down by 99%. “An official emissions measurement has

been conducted, but the final results havenot yet been publicised. However, theseestimates should be pretty close to the actual

outcome,” he said.According to GL, Tarbit Shipping is very

pleased with the environmental footprint of itsnewly converted vessel and all projectpartners expressed their appreciation of thegood spirit of co-operation. “We all held firmand stayed focused on the quality and safetyoutcome of the project,” said Westerman. “It

was the final result that counted. This wasvery important, since there is no room forerrors in dealing with an LNG plant!”Bit Viking resumed commercial trading on

25th October 2011. Ever since, she has beenperforming as expected and the crew hassuccessfully refuelled her from the shore,GL said.

GL has prepared guidelines for gas as aship fuel. Developed by the IMO sub-committee on Bulk Liquid andGases (BLG) with GL assistance over the past few years,the interim guidelines are the first step towards theenvisioned general code for gas as a ship fuel, the so-calledIGF Code.This Code is currently under development by the IMO

and is expected to enter into force conjointly with therevision of SOLAS 2014. The GL guidelines will help shipowners and yards

prepare for the introduction of gas as a ship fuel. They provide criteria for the design arrangements and

installation of propulsion and auxiliary machinery poweredby natural gas to ensure a level of integrity, safety,reliability and dependability equivalent to that ofcomparable, state-of-the-art machinery burningconventional fuel oil, GL said.

GL Guidelines for Gasas Ship Fuel

The gas tanks clearly seen on deck.

The vessel has been operating successfully as a gas-powered vesselsince October last year.

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