Failure Mode Analysis
FMEA & FTA
•FMEA/FMECA
•Fault Tree Analysis
Arnljot Hoyland, Marvin Rausand, System Reliability Theory,
John Wiley & Sons, Inc., 1994, ISBN 0-471-59397-4
Meng-Lai Yin
1
FMEA (Failure Mode and Effects
Analysis)
• Qualitative analysis
• Purpose: identify design areas where improvements are needed to meet reliability requirements
• One of the first systematic techniques for failure analysis
• Developed in the late 50s to study problems that might arise from malfunctions of military systems
• Often used as the first step of a system reliability study
• An FMEA becomes a failure mode, effects, and criticality analysis (FMECA) if criticalities or priorities are assigned
• Information can be found in: MIL-STD-1629, IEC 812,
SAE ARP 926, IEEE std. 352
Meng-Lai Yin
2
FMEA Example Sheet
Syetem:
Ref. drawing no.:
Ref. No.
Description of unit
Function Operational
Mode
Performed by:
Date:
Page: of
Description of Failure
Effect of Failure
Ont the
Failure mode Failure
Detection of On
Mechanisms Failure
Components system function in the subsystem Meng-Lai Yin
Failure rate
Severity ranking Risk reducing measures
Comments
3
Bottom-up Approach
• Bottom-up (commonly used)
– Starting at the component level and expanding upward
– The challenge: to decide which component level the analysis should be conducted, since the workload could be overwhelming
– A general rule: at a level where failure rate estimates are available or can be obtained
Meng-Lai Yin
4
Top-down Approach
• The analysis is carried out in one or two stages
• The first stage: split the system into a number of subsystems, and to identify possible failure modes and failure effects of each subsystem based on knowledge of the subsystem’s required functions or on experience with similar equipment • If the subsystem has no failure modes that are critical, then no further analysis of that subsystem needs to be
•FMEA/FMECA
•Fault Tree Analysis
Arnljot Hoyland, Marvin Rausand, System Reliability Theory,
John Wiley & Sons, Inc., 1994, ISBN 0-471-59397-4
Meng-Lai Yin
1
FMEA (Failure Mode and Effects
Analysis)
• Qualitative analysis
• Purpose: identify design areas where improvements are needed to meet reliability requirements
• One of the first systematic techniques for failure analysis
• Developed in the late 50s to study problems that might arise from malfunctions of military systems
• Often used as the first step of a system reliability study
• An FMEA becomes a failure mode, effects, and criticality analysis (FMECA) if criticalities or priorities are assigned
• Information can be found in: MIL-STD-1629, IEC 812,
SAE ARP 926, IEEE std. 352
Meng-Lai Yin
2
FMEA Example Sheet
Syetem:
Ref. drawing no.:
Ref. No.
Description of unit
Function Operational
Mode
Performed by:
Date:
Page: of
Description of Failure
Effect of Failure
Ont the
Failure mode Failure
Detection of On
Mechanisms Failure
Components system function in the subsystem Meng-Lai Yin
Failure rate
Severity ranking Risk reducing measures
Comments
3
Bottom-up Approach
• Bottom-up (commonly used)
– Starting at the component level and expanding upward
– The challenge: to decide which component level the analysis should be conducted, since the workload could be overwhelming
– A general rule: at a level where failure rate estimates are available or can be obtained
Meng-Lai Yin
4
Top-down Approach
• The analysis is carried out in one or two stages
• The first stage: split the system into a number of subsystems, and to identify possible failure modes and failure effects of each subsystem based on knowledge of the subsystem’s required functions or on experience with similar equipment • If the subsystem has no failure modes that are critical, then no further analysis of that subsystem needs to be