MIL-STD-1629-RevA - Barringer and Associates, Inc.

MIL-STD- 1629ATASK 102CRITICALITYANALYSIS1. Purpose. The purpose of the criticality analysis (CA) isto rank each potential failure mode identified in the FMEA Task 101,according to the combined influence of severity classification and itsprobability of occurrence based upon the best available data.1.1 Application. The CA, Task 102, supplements the FMEA,Task .101, and shall not be imposed without the imposition of Task 101.2. Documents referenced in Task 102:llANDBOOKSMilitarvMIL-HDBK-217 Reliability Prediction of Electronic Equipment3. Analysis approach. One approach from the two specifiedin 3.1 and 3.2 of Task 102 shall be selected. The availability ofspecific parts configuration data and failure rate data will determinethe analysis approach to be used. The qualitative approach is appropriatewhen specific failure rate data arc not available. The failure probabilitylevels, when used, should be modified as L})esystem is better defined.As parts configuration data and failure race data become available,criticality numbers should be calculated and incorporated in the analysis.3.1 Qualitative approach. Failure modes identified in theFMEA are assessed in terms of probabili~y of occurrence when specificparts configuration or failure rate data are not available. Individualfailure mode probabilities of occurrence should be grouped into distinct,logically defined levels, h’hich establish cllequali~ative failure probabilitylevel for entry into the appropriate CA worksheet column. ProbabilityOf Occurrence Ieve]s are defined as follows:a. Level A - Frequent. A higl]probability of occurrenceduring the item operating time interval. Highprobability may be defined as a single failure modeprobability greater than 0.20 of tl]eoverall probabilityot failure during the item operating time interval.b. Level B - Reasonably probable. A moderate probabilityof occurrence during the item operating time interval .Probable may be defined as a single failure modep~(lhability Of (j~~(jrr~~]]~~ w!li~j~is m~re Ll)an (J.1ObuL less than 0.20 of the overall probability offailure during the item operating time. .-. -——-— —....= — — —=-.—.-—.=-_>_—_-—_—_—— —.