FMEA worksheet

Record one row per failure mode, numbered under its item, for example 100.1. Record its cause, its effect locally, at the next level up and at the end, how it is found, and its severity, occurrence, detection and RPN.

Rank the failure modes by RPN, highest first, and list them by severity as well. At a high severity, immediate corrective action may be needed whatever the RPN.

Where a maker’s manual or a local authority sets the failure modes, intervals or ratings for the equipment, it governs instead.

Severity (S)

S	Effect	Criterion
1	None	No reason to expect the failure to affect safety, health, the environment or operations.
2	Very low	Minor disruption to facility function. Repair to failure can be done during a routine service call.
3	Low	Minor disruption to facility function. Repair to failure takes longer than a routine service call but does not delay operations.
4	Low to moderate	Moderate disruption to facility function. Some work may need redoing, or the process may be delayed.
5	Moderate	Moderate disruption to facility function. All of the operation may need redoing, or the process may be delayed.
6	Moderate to high	Moderate disruption to facility function. Some of the operation is lost. Moderate delay in restoring function.
7	High	High disruption to facility function. Some of the operation is lost. Significant delay in restoring function.
8	Very high	High disruption to facility function. All of the operation is lost. Significant delay in restoring function.
9	Hazard	Potential safety, health or environmental issue. Failure will occur with warning.
10	Hazard	Potential safety, health or environmental issue. Failure will occur without warning.

Occurrence (O)

Adjust the failure rates to the equipment, in hours, days or cycles.

O	Failure rate	Criterion
1	1 in 10,000	Remote probability; failure is unlikely to be expected.
2	1 in 5,000	Very low failure rate, like similar equipment that has had low failure rates under the same volume and load.
3	1 in 2,000	Low failure rate, like similar equipment under the same volume and load.
4	1 in 1,000	Occasional failure rate, like similar equipment that has had similar failure rates.
5	1 in 500	Moderate failure rate, like similar equipment that has had moderate failure rates.
6	1 in 200	Moderate to high failure rate, like similar equipment that has had moderate failure rates.
7	1 in 100	High failure rate; similar equipment has had frequent failures that caused problems.
8	1 in 50	High failure rate; similar equipment has had frequent failures that caused problems.
9	1 in 20	Very high failure rate; almost certain to cause problems.
10	1 in 10 or more	Very high failure rate; almost certain to cause problems.

Detection (D)

D	Detection	Criterion
1	Almost certain	Current checks are almost certain to detect the failure. Reliable checks are known for similar equipment.
2	Very high	Very high likelihood current checks will detect the failure.
3	High	High likelihood current checks will detect the failure.
4	Moderately high	Moderately high likelihood current checks will detect the failure.
5	Moderate	Moderate likelihood current checks will detect the failure.
6	Low	Low likelihood current checks will detect the failure.
7	Very low	Very low likelihood current checks will detect the failure.
8	Remote	Remote likelihood current checks will detect the failure.
9	Very remote	Very remote likelihood current checks will detect the failure.
10	Almost impossible	No known check is available to detect the failure.

Risk priority number (RPN)

RPN is severity times occurrence. Where detection is ranked, RPN is severity times occurrence times detection.

Sources

• Department of the Army: TM 5-698-4, Failure Modes, Effects and Criticality Analyses (FMECA) for C4ISR Facilities