Probabilistic Safety Assessment of a Typical Chemical Process Plant

Abstract

Probabilistic safety assessment (PSA) of an upcoming chemical process plant handling toxic materials was carried out. The PSA includes all possible accident scenarios and their quantification in terms of release frequency and consequences. Based on the comprehensive review of various storage facilities, process systems and safety systems, major PIEs are screened-in for further quantitative analysis. The facility may cause potential hazards mainly due to the three hazardous chemicals, viz. hydrogen, chlorine and a pyrophoric material. Hydrogen leakage causes flash fire or explosion hazards; chlorine gas leakage causes toxic hazards. Adequate measures have been considered to mitigate these hazards. PSA will help in probabilistic estimation. The analysis takes into account for development of accident scenarios, considering possible failure of safety functions and human interactions. Models available in ISOGRAPH software have been used for component modelling. The events considered in fault tree are failures that are associated with component hardware failures, human errors, maintenance or breakdown unavailability that may lead to undesired state. Standard formats were used for coding basic events, common cause failure (CCF) events and human error events in the fault trees with due care were considered to ensure that the basic event clearly relates to specific component/system identification, component failure mode and type. This work will be helpful in dealing with gaseous hazards and flash fire hazard and explosion hazard.