Pm Frequency
PM Frequency is the predetermined time interval or usage metric (e.g., hours, cycles) at which Preventive Maintenance tasks must be executed on an asset to prevent failure. It is calculated as a fraction (typically 1/3 to 1/5) of the detectable-potential-to-failure (P-F) interval to ensure faults are found before critical failure.
In a CMMS like ServiceGrid, PM Frequency is configured as the recurrence trigger for work orders (e.g., 'Every 30 days' or 'Every 500 operating hours'), ensuring technicians perform inspections or servicing within a strict compliance window (often the '10% Rule,' meaning execution within ±10% of the due date) to maintain asset reliability and MTBF. This scheduling is critical for shop floor maintenance to prevent unexpected breakdowns and optimize maintenance costs.
How is the optimal PM frequency mathematically derived for assets with a linearly increasing hazard rate?
It is selected as the time interval between PM actions that incurs the minimal maintenance cost while guaranteeing a predetermined availability level, often calculated as 0.7N to 0.8N of the average failure time (N).
What is the relationship between PM Frequency and MTBF in critical power systems?
Increasing PM frequency (e.g., from 0 to 2 visits/year) can increase MTBF by up to 23 times, though diminishing returns occur after ~19 annual visits for certified technicians.
When should PM strategies be reviewed and frequencies adjusted?
Industry best practice recommends a formal PM Optimization review every 3–5 years, or every 12–24 months for critical equipment, to update frequencies based on failure history and operational context.