Industrial processes rely on continuous and reliable supply from the grid to achieve optimal operation and output. In the case of large sites, local generation is also used to ensure the continuous operation of critical equipment. Heavy disturbances occurring in the grid, such as blackouts and faults, can force the site to switch to islanded operation to maintain the functioning of critical equipment. This paper presents a load shedding approach based on Monte-Carlo simulation applied to a large industrial site in Romania, used to manage the safe islanding of a set of critical consumers in the presence of local generation. A case study shows that, for a load sampling rate of 1 second, stable operating configurations can be found for a time interval of up to 30 minutes.