Use of FMECA Method for Leakage Analysis of LNG Fueled Vessels

Abstract

Liquefied natural gas (LNG), a cleaner energy resource compared to heavy fuel oil (HFO), has been utilized as an energy source by vessels of various types, e.g., ferries, cargo vessels and platform supply vessels (PSV), notably after the release of International Maritime Organization (IMO) interim guideline MSC. 285(86) which officially authorized the natural gas as a marine fuel for merchant vessels in June 2009. LNG fuel is expected to have a promising prospect in green shipping industry with advantages in decreasing the emissions of NOX, SOX, and particulate material. However, as an inflammable and explosive energy source, safety issues of LNG should also be taken into account, especially under the circumstances of fuel leakage during a long voyage. In this paper, failure mode, effects and criticality analysis (FMECA) is conducted for the study on leakage failure modes of LNG fueled vessels. The criticalities of LNG leakage modes are calculated and ranked by taking failure rate, causes and effects (consequence probability and associated severity) of each failure mode into consideration. Event tree analysis (ETA) approach is utilized to identify possible failure consequences and estimate associated probabilities of occurrence, while computational fluid dynamics (CFD) modeling and simulation are applied for the consequence analysis of each failure mode. A typical Chinese LNG powered cargo ship in the Yangtze River is studied for critical leakage modes identification and risk control options (RCOs) provision so as to provide recommendations on the daily operations and safety managements of LNG fueled vessels.