HAZOP analysis (hazard and operability analysis) is one of the most widely used evaluation methods in hazard (safety) analysis of process systems (including process industries). The method comprehensively and systematically studies every element in the system, in which important parameters deviate from the hazards and operability problems caused by specified design conditions. On this basis, the results of the HAZOP analysis are verified through SIL (Safety Integrity Level) analysis and the grade is defined, thereby completing the quantitative safety evaluation of the entire production system.