工艺安全需求对化工异型冗余设备不可用性影响分析

Analysis of the impact of process safety demand on the unavailability of non-identical redundant equipment in chemical industry

为了准确评估工艺安全需求对异型冗余安全仪表系统(SIS)不可用性的影响,在改进β因子模型的基础上,通过利用齐次马尔可夫(Markov)链量化需求失效概率(PFD),提出考虑工艺安全需求的异型冗余设备PFD计算模型。将该模型应用于某化学反应分离单元的SIS中,利用蒙特卡洛模拟验证了模型的准确性,比较分析了异型冗余模型和同型冗余模型在不同检测周期下的PFD计算误差,最后以需求率和需求持续时间为例进行灵敏度分析。结果表明,该模型与蒙特卡洛模拟最大相对误差仅为3.36%,相对于传统的工艺安全需求Markov模型,能够提高PFD计算精度,为更合理地评估石化设备的PFD提供良好的框架。

To accurately evaluate the impact of process safety demand on the unavailability of non-identical redundant safety instrumented system(SIS),a PFD(probability of failure on demand)calculation model of non-identical redundant equipment considering process safety demand was proposed based on the improvedβfactor model using a homogeneous Markov chain to quantify PFD.The model was applied to the pressure control loop of a chemical reaction separation unit,and the accuracy of the model was verified by Monte Carlo simulation.The PFD calculation errors of non-identical redundant model and identical redundant model under different proof test periods were compared and analyzed.Finally,the sensitivity analysis of parameters such as the demand rate and demand duration was carried out.The results showed that the maximum relative error between this model and Monte Carlo simulation was only 3.36%,compared with the traditional process safety demand Markov model,it could improve the PFD calculation accuracy and provide a method for more reasonable evaluation of the PFD of petrochemical equipment.