Dot chart analysis as a means to develop a fault tree: application to a catalytic hydrogenation unit

This paper describes the application of dot chart analysis to a semicontinuous catalytic hydrogenation unit. Dot chart tables have been used as a basis for developing the recursive operability analysis and the fault trees (FTs), whose aim is to determine the safety of both the unit and its operators. The unit is formed of two reactors in parallel: the transfer of operations from one reactor to the other when its catalyst is exhausted is performed by means of the isolation systems installed for this purpose on the inlet and outlet lines. FTs assessed the expected number of leak at 3×10−3 occurrences per mission time. The study clearly showed that the operations could be regarded as safe, since, with minor modification to control system and operative procedure, these leaks would be of pressurised nitrogen and hence without consequences for the unit and its operators.