Cause(s) - hdbk11000065

DOE-HDBK-1100-2004

Cause(s). If desired, the root causes of the failure mode should be identified. Identification of

root causes provides information helpful for ranking hazards.

Operational Mode. If the equipment being analyzed is subject to different modes of operation,

each operational mode should be identified and analyzed separately.

Effects. For each identified failure mode, the PrHA team should describe the anticipated effects

of the failure on the overall system or process. The key to performing a consistent FMEA is to

assure that all equipment failures are analyzed using a common basis. Typically, analysts

evaluate effects on a worst-case basis, assuming that existing safety levels do not work.

However, more optimistic assumptions may be satisfactory as long as all equipment failure

modes are analyzed on the same basis.

Failure Detection Method. The means of failure detection should be identified, such as visual

or warning devices, automatic sensing devices, sensing instrumentation, or other indicators. The

main purpose of identifying failure detection methods is to determine whether the failure mode

is "hidden," i.e., not detectable for some period of time. If there is no means to detect failure,

"none" should be entered into the worksheet.

Compensating Provisions. For each identified failure mode, the PrHA team should describe

any design provisions, safety or relief devices, or operator actions that can reduce the likelihood

of a specific failure or mitigate the consequences.

Severity Class. The severity of the worst consequence should be specified as follows.

Category I

Catastrophic

May cause death or loss of system or process.

Category II

Critical

May cause severe injury, major property

damage, or major system damage.

Category III

Marginal

May cause minor injury, minor property

damage, or minor system damage.

Category IV

Minor

Is not serious enough to cause injury, property

damage, or system damage, but may result in

unscheduled maintenance or repair.

Remarks/Actions. For each identified failure mode, the PrHA team should suggest actions for

reducing its likelihood or mitigating its effects. The actions suggested for a particular piece of

equipment may focus on the causes or effects of specific failure modes or may apply to all of the

failure modes collectively.

If the team discovers that a single item failure is not detectable, the FMEA should be extended

to determine if the effects of a second failure in combination with the first could have