Relative Ranking is actually an analysis strategy rather than a single, well-defined analysis method. This strategy allows hazard analysts to compare the attributes of several processes or activities to determine whether they possess hazardous characteristics that are significant enough to warrant further study. Relative Ranking can also be used to compare several process siting, generic design, or equipment layout options, and provide information concerning which alternative appears to be the “best” option. These comparisons are based on numerical values that represent the relative level of significance that the analyst gives to each hazard, potential consequence or risk depending on the approach used. Relative ranking studies should normally be performed early in the life of an existing facility’s hazard analysis program. However, the relative ranking method can also be applied to an existing process to pinpoint the hazards of various aspects of process operation.
Reference: CCPS: guidelines for hazard evaluation procedures, third edition