Describe the difference between preventive maintenance task intervals and condition-based maintenance triggers.

• A. Preventive maintenance uses fixed calendars or usage; condition-based triggers are based on sensor data or condition indicators.
• B. Preventive maintenance relies on sensors; condition-based relies on calendar schedules.
• C. They are the same; different terminology.
• D. Preventive uses manufacturer recommendations; condition-based uses OEM alerts.

Answer: (D)

Preventive maintenance task intervals are fixed in advance, usually set by a calendar or by cumulative usage (miles, hours, cycles). Condition-based maintenance triggers, on the other hand, are driven by the actual condition of the equipment, detected through sensor data or other condition indicators, and they prompt maintenance when a threshold is reached.

This distinction matters because PM keeps components serviced on a schedule to prevent failures, regardless of current wear, while CBM relies on real-time or periodic condition monitoring to act only when needed, often saving time and cost while maintaining reliability. For example, replacing a part every 6,000 miles is PM, whereas replacing or servicing based on vibration, temperature, or oil condition readings is CBM.

The description that pairs fixed schedules with sensor/condition indicators is the most accurate representation. Reversing these roles, suggesting PM relies on sensors and CBM on calendars, isn’t correct. Saying they are the same ignores the different drivers (time/usage vs. condition). Relying only on manufacturer recommendations or OEM alerts can be part of PM or CBM, but doesn’t capture the fundamental difference in how each approach is triggered.