Abstract: Double wall pipe ventilation system is an important system to ensure the safety of gas supply for LNG powered ships. The system can detect the leakage in time and dilute the leaked gas rapidly in case of gas leakage. The failure mode, effects and criticality analysis (FMECA) method is used to assess the risk of the double wall pipe ventilation system, identify the failure mode and cause of each element, and detect and analyze the existing safety barriers and failure effects, as well as evaluate the failure frequency, consequence severity and detection difficulty. The risk priority is then calculated for the risk classification and the design optimization is carried out for high-risk failures. New safety barriers are finally installed to reduce the risk. A total of 13 failures are identified from the design scheme of the original double wall pipe ventilation system, of which 5 were high risk. The risk level is reduced to an acceptable range through optimal design such as arranging the air flow switch in the air inlet duct, setting up independent fan rooms and dual power supply for the fan.

Key words: failure mode, effects and criticality analysis (FMECA), risk assessment, double wall pipe, ventilation system, optimal design

摘要： 双壁管通风系统是保障LNG动力船燃气供气安全的重要系统,当出现燃气泄漏时可以及时检测到泄漏情况并迅速稀释泄漏的燃气。该文运用故障模式、影响及危害性分析（FMECA）法对双壁管通风系统进行风险评估,识别各个元件的失效模式、失效原因和失效检测,分析现有的安全栅和失效影响,并评价失效频率、后果严重度和检测难度;然后计算风险优先级 ,进行风险分级,对高风险的失效进行设计优化,最终通过增加新安全栅来减轻风险。从原双壁管通风系统的设计方案中共识别13条失效,其中高风险5条,通过在进风管布置风量开关、设置独立风机房和风机双电源供电等优化设计,把风险等级降低到可以接受的范围内。

关键词: 故障模式、影响及危害性分析, 风险评估, 双壁管, 通风系统, 优化设计