cryogenic engineering
Finalising the LNG bunkering rulebook
The growing interest in LNG- powered vessels has put pressure on shipowners and regulators to finalise a new mandatory regime governing the use of gas as marine fuel
by Mike Corkhill R
egulatory authorities are being requested to review an ever-increasing number of LNG-fuelled vessel concept designs. More and more owners and operators are considering the use of natural gas to power their ships in compliance with the tightening international regime governing emissions of atmospheric pollution from ships.
Despite several disadvantages attendant on the technology, gas-burning engines comply with all existing and anticipated restrictions on emissions of sulphur oxides (SOx) and nitrogen oxides (NOx) laid down in Annex VI to IMO’s Marine Pollution (Marpol) Convention. These include the requirements that the sulphur content of the fuel used by ships sailing in emission control areas (ECAs) be reduced from 1 to 0.1 per cent from 1 January 2015 onwards and from 3.5 to 0.5 per cent in ships sailing worldwide by either 2020 or 2025. The choice of implementation date for the latter restriction will depend on the results of an IMO review later in the decade. These concept design review requests pose challenges for regulators because of their diverse nature. The applications for LNG-fuelled ship design projects span a full range of vessel types, from passenger vessels and ferries, tankers and bulk carriers to container ships, car carriers, offshore support vessels, tugs and icebreakers. The different types of gas-burning engines also need to be considered, as do varying options for gas treatment equipment and bunker tank design and location. On top of that, the logistics of the bunkering operation is very often unique to a particular vessel. The availability of an agreed international regulatory regime will greatly facilitate the task of flag administrations in approving LNG-propelled vessel designs and the work of port and coastal states charged with verifying compliance. While the maritime industry is working hard on the development of such an
50 I Marine Propulsion I April/May 2014
The location of LNG bunker tanks on ships, not least passenger vessels, has been a key discussion topic during the development of the IGF Code
instrument – in the form of IMO’s International Code for Ships using Gas or other Low Flash- Point Fuels (IGF Code) – the use of LNG to power ships that are not LNG carriers is a relatively recent phenomenon and the code is still in draft form. Work on the IGF Code is nearing completion but a handful of contentious issues await resolution and IMO machinery is such that the provisions requiring clarification need input from several of the organisation’s sub- committees. Development of the code in its final phase is being progressed via a correspondence group. Although the group is currently also addressing the use of methanol and low flash point diesel fuels, the primary focus remains on LNG. Recent IMO sub-committee work on the code has included a review of the location of LNG bunker tanks by the Ship Design & Construction Sub-Committee and the development of STCW training requirements by the Human Element, Training & Watchkeeping Sub-Committee. Although IMO is prioritising finalisation of the IGF Code, and targeting a spring 2015
adoption date, under this timetable the new regime would still not become mandatory until sometime in the first half 2017. Once the work on the use of LNG, methanol and low flash point diesel fuels is complete, other fuels such as LPG will be addressed. Fortunately for IMO member states seeking adherence to uniform provisions governing the use of LNG as fuel, there is an interim, voluntary regime in place that is the precursor of the IGF Code. That is IMO Resolution MSC.285(86), Interim Guidelines on Safety for Natural Gas-Fuelled Engine Installations in Ships, which was published by the organisation in June 2009.
This guidance owes much to the pioneering provisions governing LNG-fuelled ships developed by the class society Det Norske Veritas (DNV, now DNV GL). DNV developed its rules to underpin the use in Norway of LNG as a fuel to propel vessels, beginning with the cross-fjord passenger ferry Glutra in 2000. Glutra is
the
global LNG-powered fleet’s pioneering vessel and amongst the 40 ships running on gas that are not LNG carriers now in service worldwide, the vast majority are operating in Norwegian waters.
www.mpropulsion.com
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