Purging air from a hydraulic system is necessary when __________.

Correct Answer: Option B — the system has been drained and then filled with new oil

Air trapped in hydraulic systems causes spongy operation and erratic actuator movement. Draining and refilling introduces significant air pockets that must be purged to ensure stable, predictable control. Failure to bleed the system can lead to cavitation and damage, violating safe operational procedures for high-pressure marine hydraulic machinery.