What is RBI? 

Risk Base Inspection (RBI) is a method for using risk as a basis  to prioritize and manage the efforts of an inspection program.

RBI provides a logical, documented, repeatable methodology for determining the optimum combination of inspection frequencies and inspection scopes.

Definition of Risk

Risk is the combination of the probability of some event occurring during a time period of interest and the consequence (generally negative) associated with the event.

RBI vs Time Based Inspection