ABS publishes white paper on LNG as a marine fuel

The new sustainability report offers ‘practical pointers’ for the use of marine LNG, and includes a firm focus on the issues and processes associated with bunkering the fuel.

The white paper is intended to supplement the American Bureau of Shipping’s Advisory on Gas and Other Low Flashpoint Fuels.

The document emphasises that the bunkering process should be considered at the conceptual design stage of an LNG-fuelled vessel. If the trading route of the planned vessel is already known and bunkering locations can be identified, ‘measures/contracts can be established to ensure the parameters of the LNG vessel during bunkering and the supplier/bunker vessel are aligned and procedures of bunkering standardised’.

If trading routes and bunkering locations are not known at the design stage, then ABS suggest that ‘it might be beneficial to increasing the equipment limits on the ship to ensure issues arising from bunkering are handled correctly’.

The report also highlights the differences in design between gas and fuel oil systems – notably from a fuel tank perspective.

According to the white paper: ‘The design thought process needs to shift from handling a static liquid fuel that does not significantly alter if left alone to that of a dynamic liquefied gas fuel which is actively trying to get back into a gaseous state.’

It continues: ‘It is typical to think about consumptions or flows in tonnes and m3 and although this can also be done for LNG it is not to be forgotten that LNG is an energy source that has different characteristics depending on pressure and temperature and is constantly changing.

‘Factors such as loading capacity, energy value received and measuring the amount of energy received need to be considered when bunkering.

ABS also broaches the subject of contractual agreements, such as charter parties and bunker supply contracts, in relation to marine LNG.

It notes: ‘Shipowners must specify fuel supply contracts that reflect the requirements for safely storing and holding LNG fuel within the operating parameters of their ship containment and fuel gas supply system.

‘For example, tank operating pressure limits should reflect the expected condition at the time of bunkering, not the tank maker specified design minimum temperature. The LNG supply contract should specify, for example, a maximum acceptable saturated vapour pressure.’

The class society refers to the Society for Gas as a Marine Fuel (SGMF) contractual guidelines which may be used as a resource.

In respect of charter party terms, the white paper advises that these should account for ‘potential voyage management issues that facilitate fuel tank conditioning prior to bunkering that fits with the vessel port schedule and minimises fuel waste, delay or results in fuel management issues that adversely affect ship performance.

‘LNG fuel operations, technical and safety management training/familiarisation should be conducted for shore staff, managers and executives that may be in a decision making capacity to ensure they are familiar with the specific contract terms and more importantly the implications for safe operation of the gas fuelled ship.’

The full report can be accessed here

Lesley Bankes-Hughes

Lesley Bankes-Hughes