Abstract: This paper proposes the necessity of hazard and operability study (HAZOP) and safety integrity level (SIL) assessment in safety design for complete sets of equipment in petrochemical plants. It sorts out and summarizes the work process, methods and key points of HAZOP and SIL for complete sets of equipment. The work sequence is to conduct HAZOP and then SIL assessment followed by SIL verification. The purpose of HAZOP and SIL assessment for complete sets of equipment is to control the accident risk to acceptable level through design work. But it does not mean that accidents can be avoided completely. HAZOP and SIL assessment are analysis activities through brainstorming. The completeness of documents, the involvement and professional and knowledge levels of the team members and the sufficient preparation and analysis time will affect the quality and effects of the analysis directly.

Key words: hazard and operability study/HAZOP, safety integrity level/SIL, complete sets of equipment, petrochemical plant