FMEA Basis

An FMEA, or Failure Modes and Effects Analysis, is a systematic approach to identify failure modes (causes) that could either directly result in, or contribute significantly to an identified accident scenario. An FMEA is used to identify causes and effects as well as safeguards for accident scenarios.

Each cause is evaluated for adequate design safety and potential effect on the system. A qualitative risk category is then assigned to each failure cause according to the guidelines found in MIL STD 882C. This qualitative ranking is determined by considering both the severity and frequency of occurrence.

Critical areas of the process are identified and studied to determine the possibility of a major incident. Management can then use this information to control the potential risk, and avoid the accident scenario. A block flow diagram of the FMEA process is given below:
FMEA flow

The following terms are typically used in the FMEA process and in the FMEA table (see downloadable pdf file at right):

  • Line No. – consists of an “Operation/Item” number and a single letter identifying the specific “Failure Cause” (e.g., 1A, 1B, 2A…).
  • Operation/Item – the operation or item of concern in the scenario.
  • Failure Mode – the potential problem stimulus.
  • Failure Cause – events that cause the effects.
  • Potential Effects – potential effects in the system or subsystem.
  • Safeguards – those features of a system that will prevent the Failure Mode from occurring. Any deficiencies in design safety will be reflected in the Recommendation column.
  • Hazard Category – an assessment of the hazard risk of the operation. In most analyses, we have used the MIL-STD-882B, “Hazard Risk Assessment Matrix.”
  • Recommendations – recommended corrective actions. Deficiencies in design safety are corrected by implementing the recommendations in the Recommendation column.