(128b) A Methodological Approach to Perform Process Hazard Analysis (PHA) for START-up of Chemical Processes.

A Pre-Startup Safety review (PSSR) is performed as a final activity to verify that there are safe conditions in a Chemical Process before the startup. PSSR also verifies that process equipment and their safeguards are installed consistently with the design intent as well as reviewing other important Process Safety Management elements are in place, well-executed or correctly installed previous to the start-up.

One item reviewed by PSSR is that Process Hazard Analysis (PHA) recommendations have been implemented or resolved before startup. From our consulting perspective, a more formal practice or approach is required to review potential and credible hazards during startup stage of Chemical Plants in order to complement PSSR. There are a lot of cases showing that a significant number of accidents have ocurred and will continue ocurring at the startup stage. We propose in this paper a methodological approach to perfom hazard analysis in the startup stage of Chemical Plants.

During a startup, a set of actions could be critical because an error, sudden process upsets or non-identified anomalies can appear and be be able to compromise the startup sequence or create potential hazard conditions impacting the safety of personnel, the environment or damaging process equipment.

The proposed approach considers a startup as a set of different transition states, so as the startup sequence runs, the safety conditions changes in each transition state. Transitions states can be represented using a graph called State and Transitions Diagrams. This graph are used to plan and exectue Process Hazards Analysis (PHA) in the startup stage. This approach is exemplified reviewing a startup sequence for a chemical reactor.