SIL评估中共用测量单元结构可靠性计算探讨

Investigation on the Reliability Calculation in SIL Assessment for Shared Measuring Unit Structure

近十年来,随着安全联锁系统完整性等级(SIL)评估工作在炼油、化工、电厂等装置中的开展,实际评估工作中出现了很多不同于IEC 61508和IEC 61511标准规定典型逻辑结构(如1oo1、1oo2、2oo3等)。针对多个传感器共用测量模块的特殊逻辑结构,IEC标准并未给出其可靠性计算的具体方法和公式。通过故障树分析,等效拆解特殊逻辑结构为多个典型结构,准确得到了每个安全联锁功能的安全完整性等级,避免了SIL定级计算错误可能引起的事故,为SIL评估的深入且顺利开展提供了保障与技术储备。

In recent decade,along with safety integrity level （SIL） assessment of safety interlock systems has been expanded to facilities in oil refinery,chemical and power generation plants,some typical logical structures （ e. g. , lool, 1002,2003 , etc ） which are different from those of defined in standards of IEC 61508 and IEC 61511 appear in practical assessment. For the special logical structure of multiple sensors shared measurement modules, specific method and formula of reliability calculation have not been given in these IEC standards. Through fault tree analysis （FTA） ,the special logical structure is dismantled equivalently into multiple typical structures,and precise safety integrity level of each safety interlock function is obtained, thus the accident caused by the error in calculation of grading SIL can be avoided, guarantee and technicalreserve are provided for intensively and smoothly carrying out SIL assessment.