Preventive Maintenance Task Selection - Continued

DOE-STD-1052-93

Effectiveness requirements for a task depend on the

consequences and cost of the failure (i.e., operational, safety, or

economic), To be effective, a task selected for a failure mode

with safety consequences shall reduce the likelihood of failure

within cost and implementation consideration. An example of

an implementation consideration is the impact of performing a

task "on-line," thereby increasing the time a system is

unavailable (i.e., LCO time), or performing it during an outage

with the associated impact on outage workload and duration.

A task to identify hidden failures with safety consequences, a

failure-finding task, shall reduce the likelihood of a multiple

failure, also within identified constraints. The hidden failure

shall be discovered before another failure occurs that would

result in loss of a system function or a safety system challenge.

NOTE:

The effectiveness of a new PM task should be

dependent on the existing material condition of

the component. If a component is in a degraded

material condition (eg., a safety-related motor

operating with excessive vibration), it may fail

before the new PM task is able to prevent the

failure as designed because much of the service

life of the component has been expended. The

component may need to be repaired, overhauled,

or replaced to establish an acceptable material

condition baseline. The new PM should then be

effective in controlling the expected failure mode.

For failure modes that have operational or economic

consequences, the selected task shall be cost-effective (i.e., the

cost of preventive maintenance shall be less than the cost of the

operational loss and/or cost of repair). Cost-effectiveness is

evaluated by performing an economic trade-off study. This study

should compare the cost of performing the proposed task (e.g.,

labor, materials, and spare parts) with the cost of the

consequences of not performing the task. The present-value cost

of the PM shall be less than the present-value cost of not doing the

task. The cost-effectiveness of a recommended PM task should

be evaluated before the task is implemented.

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