Recent regulatory requirements for shipping emissions control have led to the adoption of Liquefied Natural Gas (LNG) as a marine fuel and the design of LNG-fuelled vessels. Considering the potential safety implications due to system failure/unavailability, this study aims at the safety analysis of a low-pressure LNG fuel feeding system using a novel model-based methodology. The proposed methodology is based on the functional system modelling, leading to the failure diagrams development, and combines the use of Failure Modes, Effects, and Criticality Analysis (FMECA) and Fault Tree Analysis (FTA), which are performed in MADe™ and PTC Windchill software environments. The FMECA results are employed to identify the investigated system critical components and failures as well as specifying the top events for the subsequently performed FTA, which evaluates the top events failure rates. The system critical components identification leads to the system design modification targeting reduced safety metrics. This study results demonstrate that the evaporator, pressure build-up unit, sensors, and cryogenic valve assemblies are the most critical components of the investigated system, whilst the enhanced system design exhibits a failure rate reduced by 69% in comparison to the baseline system. This study reveals the advantages of the developed methodology along with some limitations of the employed tools and contributes to the quantitative safety analysis and design of ship complex systems.

中文翻译：

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船用液化天然气燃料输送系统的基于模型的安全性分析和设计增强

最近有关船舶排放控制的法规要求导致采用液化天然气（LNG）作为船用燃料和设计以LNG为燃料的船舶。考虑到由于系统故障/不可用而带来的潜在安全隐患，本研究旨在使用基于模型的新型方法对低压LNG燃料供料系统进行安全性分析。所提出的方法基于功能系统建模，从而导致故障图的发展，并且结合了在MADe™和PTC中执行的故障模式，影响和临界分析（FMECA）和故障树分析（FTA）的使用Windchill软件环境。FMECA结果用于确定所调查的系统关键组件和故障，并指定随后执行的FTA的主要事件，评估最重要事件的失败率。系统关键组件的识别导致针对降低的安全指标的系统设计修改。这项研究结果表明，蒸发器，压力累积单元，传感器和低温阀组件是所研究系统的最关键组件，而增强型系统设计的故障率与基准系统相比降低了69％。这项研究揭示了所开发方法的优点以及所用工具的一些局限性，并有助于船舶复杂系统的定量安全性分析和设计。压力累积单元，传感器和低温阀组件是所研究系统的最关键组件，而增强型系统设计的故障率与基准系统相比降低了69％。这项研究揭示了所开发方法的优点以及所用工具的一些局限性，并有助于船舶复杂系统的定量安全性分析和设计。压力累积单元，传感器和低温阀组件是所研究系统的最关键组件，而增强型系统设计的故障率与基准系统相比降低了69％。这项研究揭示了所开发方法的优势以及所用工具的某些局限性，并有助于船舶复杂系统的定量安全性分析和设计。