Problems of Risk Assessment Based on the Results of the HAZOP Study

Abstract

HAZOP hazard identification method, which considers the parts of a system individually, has disadvantages that limit its application to structurally complex technological systems. In these cases, the simplified risk analysis methods such as FMEA, FMECA, etc. cannot be correct. To assess the risk of complex systems, it is recommended to conduct additional studies using the methods such as FTA and ETA, and other more rigorous methods. Additional studies require a significant investment of time, which is often limited by design time. Limitations can be overcome by using the information technology. The use of the FTA and ETA methods as the methods for identifying hazards directly in HAZOP study process allows to supplement HAZOP procedure with an analysis of deviations in the characteristics of the system elements from the design goals, their causes, and hazardous consequences in the entire technological system. It becomes possible, based on the results of HAZOP studies, to automatically build and analyze a combined fault tree and event tree. To determine the permissible probability of a hazardous event, a calibrated risk graph and the results of accident modeling are used. Automated analysis of the combined fault tree and event tree will allow to consider solution options, determine the risk created by the controlled equipment, select the systems for its consistent reduction and optimal requirements for the functions and reliability of safety systems used to reduce the risk.