Abstract: In a fluid catalytic cracking process, catalyst migration through the vapor line from a reactor to a distillation column is controlled. Catalyst migration is controlled by detection, isolation, and removal of catalyst from the vapor line before entering the distillation column. Upon detection of a predetermined amount of catalyst in the vapor line, a signal is generated to close the valves in the vapor line, the catalyst feedstock line, and the regenerator/reactor line substantially simultaneously. Further, the distillation column can be isolated from the reactor for blind installation.