FMEA RPN Scores, an Alternative Approach
Mark Allen Durivage, Managing Principal Consultant, Quality Systems Compliance LLC, Lambertville, MI, USA
Keywords: FMEA, Risk, RPN
Failure mode effect analysis (FMEA) risk priority number (RPN) scores have traditionally been used to quantify risks for use, design, and process FMEAs.
FMEA helps quantify and prioritize risk using severity of the harm, probability of occurrence, and probability of detection ratings that are multiplied together to produce the RPN. Severity (S) is a measure of the seriousness of the possible consequences of a hazard. Probability of occurrence (O) is the likelihood that a harm or cause will occur and that it will induce the detrimental consequences of the associated hazard. Detection (D) is the probability that control (design, inspection, alert/warning) will eliminate, mitigate, or catch the defect. The RPN output of an FMEA is a relative risk score for each failure mode, which is used to rank the failure modes of relative risk to allow the organization to prioritize risk mitigation and reduction activities.
The Automotive Industry Action Group (AIAG) and the Verband der Automobilindustrie (VDA) jointly released an updated FMEA handbook on April 2, 2019. One of the major changes with the new AIAG-VDA FMEA process is the traditional RPN has been eliminated. The RPN has been replaced by the action priority (AP) table.
The AP tables assign one of three suggested rankings (High, Medium, and Low Priority) for each action based upon the Severity, Occurrence, and Detection values. The priorities are derived from weighted hierarchical rankings considering Severity, Occurrence, and Detection.
This presentation will compare and contrast the traditional RPN and the action priority (AP) table methods for FMEA as well as provide practical examples of the application of the action priority (AP) table method.