This work aims to present, in a practical approach, the application of Process Safety basic principles and management elements to the major turnaround of an Olefins Plant in the year 2011. This application can be understood and emphasized in the various stages of a turnaround: planning, pre-turnaround, shutdown and decontamination, maintenance itself, commissioning, and startup of the plant. (c) 2013 American Institute of Chemical Engineers Process Saf Prog 32: 264-267, 2013