安全系统的故障分析

以可靠性研究为基础,分析独立和冗余配置的安全系统的故障状态,给出独立配置和冗余配置时安全系统的显性故障率、隐性故障率以及系统可用度的定量模型。以该模型对以紧急停车系统(ESD)和生产监控系统(DCS)构成的组合安全系统进行了比较和分析。笔者认为:ESD单独设置时,应注意降低隐性故障率、提高其修复率;ESD与DCS冗余配置时,无论是并联冗余还是串联冗余,安全保护功能都是增加的,但同时显性故障率有所增加,隐形故障率大大减少。因此,用ESD补充DCS的安全保护功能而不是简单的重复其功能,对提高系统的整体安全水平将是十分明显的。

Analyses on the Failure of Safety System

Based on the reliability theory,the fault modes of self-contained safety system and redundant safety system are analyzed;the quantitative calculation models for the explicit failure rate,implicit failure rate and availability of those systems are given.Comparison and analysis is made on the safety system comprising ESD(Emergency Shutdown System)and DCS(Distributed Control System)by using those models.It is considered that when the ESD is used independently,attention should be paid to reducing implicit failure rate and improving its repairing rate,and that when ESD and DCS are equipped redundantly-no matter they are installed in parallel or series,the safety protection function of the system increases,but the explicit failure rate increases and the implicit failure rate reduces.Therefore,using ESD to supplement DCS is not simple function repetition;it will be of great importance in raising the whole safety level.