Failure Modes失效模式.pptVIP

Failure Modes David L. Andra, Jr. Science and Operations Officer WFO Norman, Oklahoma Failure Mode: The manner in which a system fails. Examples Technology - WSR-88D klystron fails preventing access to critical data. Conceptual – Forecaster fails to recognize small storm as mini-supercell. Organizational – Absence of well defined job roles and mission priorities leads to failure in SA. Failure Mode and Effects Analysis A technique employed by engineers to improve system performance. Failure Mode and Effects Analysis 1. Define failure mode. 2. Identify cause of failure. 3. Identify effects of failure. 4. Corrective action. An Example Failure mode: Conceptual Cause: Failed to identify mini-SC Mini-SC characteristics not understood by forecaster Effects: Injuries and loss of life Correction: Training for staff on mini-SC structure and evolution Strategy to Improve Try to eliminate the failure mode. Minimize the severity of the failure. Reduce the occurrence of the failure mode. Improve the detection. Other Considerations Some failures are more preventable than others! Examples Relatively easy to prevent: Failure mode: Conceptual Cause: Classic SC not recognized Forecaster only uses 0.5 deg R product Effect: Loss of life, feature on Dateline Correction: Training, etc. Examples Nearly impossible to prevent: Failure mode: Technological Cause: mini-SC at long range and embedded stratiform pcpn, night, sparse population. Brief tornado. Effect: mobile home destroyed with loss of life. Correction: maybe better VCPs or new radar? Ten Recent Disasters(since 1989) By Failure Mode Failure Mode and Effects Analysis (FMEA) is only a tool to identify potential or actual points of failure and identify corrective action. A Case Analysis A nearly unwarned tornado in OKC metro area WFO Norman October 22, 2000 Surface 00Z 00Z OUN Raob 00Z OUN Hodograph Considerations Tornado day before Midday AC “NO SVR” Tornado watch by early evening Dayshif