Explain MTBF and its use in maintenance planning.

• A. MTBF is the average time between potential faults.
• B. MTBF is the total operational time of equipment.
• C. MTBF is the reliability probability at a given time.
• D. MTBF is the average time between failures; used to set maintenance intervals and anticipate component replacements.

Answer: (D)

Mean Time Between Failures is the average time the equipment runs before a failure occurs in repairable systems. This measure guides maintenance planning by showing how often you can expect failures to happen, so you can set preventive maintenance intervals, schedule inspections, and anticipate component replacements based on historical data. It’s calculated from total uptime across many cycles divided by the number of failures, and a higher MTBF means longer average uptime between failures. It’s not the total operational time, nor a probability of surviving to a certain moment, nor a description of potential faults—it's an average interval between actual failures used for planning and stocking parts.