What does bleeding air from a pneumatic system involve, and when should it be performed?

• A. Increasing air pressure to push air out.
• B. Adding moisture to lines to flush air.
• C. Replacing all hoses to remove air pockets.
• D. Releasing trapped air from lines and actuators by opening bleed screws or adjusting fittings; perform with system depressurized and power off as required.

Answer: (D)

Bleeding air means releasing trapped air (and any moisture) from lines and actuators so the system operates reliably. You do this by opening bleed screws or loosening fittings at designated bleed points to vent the air until only dry air comes out. The goal is to purge pockets of air that can compress and cause slow, uneven, or erratic actuator action.

Do it with the system depressurized and power off as required to prevent sudden movement and injury, then re‑pressurize and test the circuit. Bleeding is typically done after maintenance, installation, or whenever an actuator feels soft or inconsistent due to air pockets.