Double-acting pneumatic actuators operate by alternately supplying compressed air to drive pistons in both directions. This linear motion is then converted into rotational output via a gear mechanism, enabling precise opening and closing control of valves. The specific workflow is as follows:
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Valve Opening Process:
Compressed air enters the actuator cylinder housing through Port A, pushing the two pistons apart in opposite directions (towards the ends). The racks on the pistons engage with the gear connected to the output shaft, causing it to rotate 90 degrees counterclockwise, opening the valve. Simultaneously, the gas originally within the cylinder is exhausted through Port B. -
Valve Closing Process:
Compressed air enters both ends of the cylinder housing through Port B, pushing the two pistons towards the center. The racks on the pistons drive the gear on the output shaft to rotate 90 degrees clockwise, closing the valve. Simultaneously, the gas in the central region of the cylinder is exhausted through Port A.
Core Characteristics:
- No Spring Return: Unlike single-acting actuators, the double-acting type relies entirely on compressed air for movement. Upon loss of air supply or power, the actuator will remain in its last position instead of automatically returning to a default state.
- Bi-Directional Air Drive: Requires alternating air supply to the two ports (A & B) to perform opening and closing actions. Continuous air pressure is needed to maintain the valve's open or closed position.
- Adjustable Rotation Direction: The direction of rotation (clockwise-to-open or counterclockwise-to-open) can be reversed by adjusting the orientation of the gear assembly in the transmission mechanism.
- Intrinsically Safe: The purely pneumatic design eliminates the risk of electrical sparks, making it suitable for explosive environments like oil, gas, and chemical plants.
Note: The operating direction (whether Port A corresponds to open or close) can be mechanically adjusted according to actual requirements. Output torque selection must include a 20%-60% safety margin based on media characteristics (e.g., lubricity, particulate content).
