Liquefied Natural Gas as Fuel Design Considerations

The global cap for airborne emissions from ships continues to grow more stringent year after year. The revised regulations within Annex VI to the International Convention for the Prevention of Pollution from Ships (MARPOL Convention) have driven industry to adopt new technologies to control pollution, including the use of natural gas as fuel. To address the safety challenges presented from natural gas fueled ships, the International Maritime Organization adopted the International Code of Safety for Ships using Gases or other Low-flashpoint Fuels (IGF Code), which came into force January 1, 2017. The IGF Code makes special note of construction, arrangement, design, and installations, including alternatives, taking into account the unique nature of the fuel. This paper presents the major design considerations for a natural gas fueled ship that are fundamentally different from a diesel fueled vessel. Naval architects must consider LNG design requirements early in the process because these requirements drive the arrangement and stability of a vessel more so than more traditional designs. Specific hazards unique to natural gas and LNG use on board ships outlined in this paper require special attention by ship designers to ensure safe operation. The particular design requirements to mitigate these hazards include: the requirement to conduct a risk assessment, machinery space safety concepts, the role of hazardous area classification, and fuel containment and distribution requirements. The goal of this paper is not to restate the regulations, but rather to highlight major considerations for designers weighing the use of natural gas when developing new vessel concepts.