35: Frequency Specification Issue
Definition/Typical Issues
Was the frequency of the periodic maintenance task incorrectly specified (either too frequently or not often enough)?
Note 1: This node addresses how often the periodic maintenance is supposed to be done. Implementation Issue (#36) addresses how often the task was actually performed.
Examples
Example 1
- The periodic monthly maintenance for conveyor #1 took 6 hours and accounted for 50% of the conveyor's unavailability. Conveyor #2 in a similar service in another part of the plant had the same periodic maintenance performed every 6 months. No failures had occurred on either conveyor in the past 3 years. The periodic maintenance interval for conveyor #1 was subsequently changed to once every 6 months.
Example 2
- An important control system in a nuclear power plant was tested daily to detect hidden failures. The test took about an hour to perform. As a result, the system was inoperable about 5% of the time for scheduled maintenance. After 6 months with no failures, the test frequency was modified so that it was performed once per week.
Typical Recommendations
- Review the frequency of periodic maintenance. If the same activity routinely needs to be performed between scheduled intervals, shorten the periodic maintenance interval.
- Review the frequency of periodic maintenance. Consider reducing the frequency of periodic maintenance on components if no adjustments or repairs are required during consecutive periodic maintenance tasks. Monitor equipment performance to determine the effects of a reduced frequency.
- Based on the results of tests and inspection activities, make appropriate adjustments to the inspection or test interval.
Cross-References
| Version 10 Element(s) | |
|---|---|
| Node ID | Node Name |
| 33 | Frequency LTA |
| Maritime Element(s) | |
|---|---|
| Node ID | Node Name |
| 42 | Scheduling Issue |