Risk Priority Number(RPN)

A rating of the worst potential consequence of a failure mode, scored on a scale of 1 (negligible) to 10 (catastrophic/hazardous without warning). Severity considers the impact on safety, environment, operations, and financial loss. Severity ratings should only change if the design or process is fundamentally altered to eliminate or mitigate the failure effect.

A rating of the likelihood that a specific failure mode will occur, scored on a scale of 1 (extremely unlikely) to 10 (almost certain/inevitable). Occurrence is based on historical failure data, engineering judgment, or generic reliability databases. It represents the probability of the failure cause generating the failure mode during the defined assessment period.

A rating of the ability of current controls to detect the failure mode or its cause before the failure reaches the end user or causes harm, scored on a scale of 1 (almost certain detection) to 10 (no detection capability). Detection evaluates the effectiveness of existing inspection, monitoring, and testing methods. Lower detection scores indicate better detection capability.

A systematic, proactive methodology for evaluating a process, product, or design to identify all possible failure modes, determine their effects on system performance, rank them by risk priority, and recommend actions to reduce or eliminate the highest risks. FMEA examines each component's potential failure modes, their causes, effects at local/system/end levels, current controls, and risk priority numbers.

An extension of FMEA that adds a criticality analysis step to quantify the combined frequency and severity of each failure mode's consequences. FMECA augments FMEA by calculating a criticality number for each failure mode based on the failure effect probability, failure mode ratio, part failure rate, and operating time, enabling a more rigorous mathematical prioritization than RPN alone.

A structured evaluation to determine the relative importance (criticality) of equipment items based on the consequences of their failure. Criticality analysis considers safety, environmental, production, and cost impacts to classify equipment into criticality categories that drive maintenance strategy, inspection priority, and spare parts stocking decisions.