SIS中考虑功能测试的Markov建模分析

Analysis of Markov Modeling Considering Functional Test for SIS

采用Markov建模方法计算安全完整性水平(SIL)时,为了使计算结果更加精确,对安全仪表系统(SIS)中带诊断电路的系统建模时加入考虑功能测试的条件进行重新建模。利用重建的模型计算出系统在功能测试后的测试时间间隔内的平均要求时失效概率,进而得出SIS的SIL等级,并与未考虑功能测试条件建模的计算结果进行比较。通过分析得出考虑功能测试条件建模时计算得到的结果相对精确,并以化工装置中的加氢装置为例进一步验证了理论研究结果的正确性和适用性。

For the system with diagnostic circuit in safety instrumented system （ SIS ）, to calculate safety integrity level （SIL） by adopting Markov modeling method, in order to improve the accuracy of calculation, the functional test condition is taken into account for model reconstruction. From the rebuilt model, the PFDavg of the system in the test interval after the functional test is calculated ; then come to the SIL of SIS. The calculated result is compared with that by using the method in which the functional test is not taken into account. Through analyzing, it is found that the method proposed obtained more accurate result, and with the hydrogenation unit in chemical industry as example, the correctness and applicability of the result of theoretical research are verified.