Consequence analysis: comparison of methodologies under api standard and commercial software

In this study the procedure for conducting the consequence analysis according to API RBI is presented. The guidelines of API methodology are reported in the document API 581. The calculation of consequences was carried out by Inspection Manager tool (IM), thanks to the implementation of RBI analysis in this software developed in a previous work (Vianello et al. 2013), and Phast, a commercial software package for the estimation consequences modelling. Through the software, two example of quantitative consequence analysis was conducted by taking into account the consequences of releases both of flammable-explosive and toxic compound based on real process operating conditions. In both methods, the results are determined as an affected impact area and are useful to establish a comparison between the two software, in order to putting out the differences in the calculation of the consequences. Finally, it is important to highlight that API approach is greatly simplified procedure and the consequence areas calculated using API methodology are not intended to be employed during unit design and other safety purposes, but only to establish a relative risk ranking of equipment items on the basis of risk, in RBI assessment.