In examining a baseline vibration signature and the historical record of periodic vibration analyses, what must be considered for the evaluation of rotating machinery?

Correct Answer: Option B — Maximum vibration limits and the change in vibration levels over time.

Effective vibration analysis requires monitoring both absolute maximum vibration limits, which indicate immediate mechanical distress, and the trend of vibration levels over time. A gradual increase in vibration, even if below the alarm threshold, often serves as a leading indicator of bearing wear, misalignment, or impending component failure.