What is the difference between preventive maintenance and reliability-centered maintenance (RCM)?

• A. RCM is purely schedule-based, while PM analyzes failure modes.
• B. PM focuses on reliability while RCM focuses on cost reduction.
• C. PM is time-based; RCM analyzes failure modes to determine maintenance actions that maximize reliability.
• D. PM and RCM are identical approaches.

Answer: (C)

The main idea here is how maintenance planning is determined: by a fixed schedule or by analyzing how and why equipment might fail. Preventive maintenance is typically scheduled at fixed intervals, based on time or usage, to reduce the chance of failure by performing tasks regardless of the equipment’s current condition. Reliability-centered maintenance uses a structured analysis of failure modes and their effects (FMEA) to decide which actions will best preserve function and reliability, prioritizing critical risks and balancing cost, safety, and downtime. In that framework, maintenance actions are chosen to address the actual failure risks rather than simply happening on a calendar.

So the statement that PM is time-based and that RCM uses failure-mode analysis to determine actions that maximize reliability captures the core difference. It’s worth noting that PM can include condition-based elements, and RCM can incorporate various strategies, but the key contrast is time-driven scheduling versus failure-mode–driven decision-making focused on reliability.