LOSS OF SAFETY FOR INSTRUMENTED SYSTEM INCLUDING DIVERSE REDUNDANT COMPONENT

The transmitter, logic solver and final element of safety instrumented system(SIS) are always composed of non-identical redundant components. How to calculate the loss of safety for safety instrumented system including diverse redundancy was studied. Firstly, based on the loss of safety from different period, i.e. PFD, TIF and DTU, the models on loss of safety for SIS were set up. Secondly, The common cause failure became reduced because of the diverse redundancy. The common cause factor of diverse redundancy and the qualitative method on determining the diversity correction factor k were put forward. At last, The formulas for reliability of the applied safety instrumented system were given out. But how to accurately determine k needs to be farther studied.