Estimation of occurrence frequencies of chemical plant equipment failure accident end events during preliminary design stage

Abstract

The occurrence frequencies estimation of chemical plant accident end events is a critical component in risk estimation, as the tolerability of risk depends on it. This estimation becomes challenging during the preliminary design stage of chemical process plant development, as the data available at this stage are limited. This paper presents a methodology to estimate occurrence frequencies of fire, explosion, toxic gas release and toxic liquid release end events resulting from chemical plant equipment failure accidents, during the preliminary design stage. The major equipment in the plant are considered. They are reactors, separators and storage vessels. The methodology presented is generic and estimates the occurrence frequencies of chemical plant accident end events using the bow-tie technique considering the total loss of containment in the equipment. The proposed methodology was applied on major process equipment involved in an acetone manufacturing plant. The highest occurrence frequency was observed in toxic liquid release end event due to release of cumene resulting from the failure of chemical reactor. Accidents caused by storage tank showed the lowest occurrence frequencies compared to other process equipment.