LNG船液货系统的安全仪表系统设计方法研究

Research on Design Methods of SIS for LNG Carrier Cargo System

LNG船是在-163℃下运输液化天然气的专用船舶,是高技术、高难度、高附加值的产品。由于LNG船具有超低温沸点、易燃易爆等高危特点,因此对LNG船有着很高的安全要求。这其中LNG船液货系统又是LNG船的关键组成部分,它的安全系统设计优劣对整个LNG船的安全尤为重要。IEC61508标准是专用于指导安全系统设计的权威标准,该文将它应用到LNG船液货系统的安全设计中并取得了一定的积极效果。该文首先介绍了IEC61508标准的主要内容并引入了其中的两个重要概念:安全完整性水平和安全生命周期,然后基于IEC61508标准,采用HAZOP方法和事件树分析方法对LNG船液货安全仪表系统进行分析设计,最后通过事件树分析验证了安全仪表系统设计的有效性。

LNG carrier is a kind of large-scale ship used for transportation of LNG with temperature under -163℃,so LNG carrier is a high-tech,high challenging and high value-added product. Because of its ultra low boiling point and flammable characteristics,LNG carrier owns a higher safety requirement. As an important part of LNG carrier,the safety of cargo system is especially significant for the safety of the whole LNG carrier. Standard IEC61508 is the guideline for design of safety system. This paper applies it to the design of LNG carrier cargo system and achieves some positive results. This paper introduces the content of IEC61508 and two important concepts (safety integrity level and safety life-cycle) in it firstly,and then based on IEC61508,using HAZOP method and event tree analysis method to analyze and design SIS for LNG Carrier cargo tank. Finally,this paper verified the effectiveness of safety instrumented system design by means of the event tree analysis.