Selection Between Single-Acting and Double-Acting Pneumatic Actuators

Selection Between Single-Acting and Double-Acting Pneumatic Actuators

When equipping pneumatic actuators for valves, the first step is to determine its operating mode: single-acting (spring-return) or double-acting. This decision directly impact system safety, reliability and control performance,  Mismatching actuator can lead to control failures. This article aims to provide guidance for selection.

Double-Acting Pneumatic Actuators:

Double-Acting pneumatic actuators use two air ports to deliver compressed air alternately supplied  both sides of the piston, actively driving the piston rod to open and close valves. Its operation controlled by external air source; if the air supply is lost, it will remain in its current position.

Product Features:

Double-Acting actuator is one of the choice for valves that require consistent output torque performance across the entire stroke. It provides stable, bidirectional output torque with adjustable control force and speed. When paired with auxiliary valves, double-acting actuators enable highly precise modulating control. However, Double-Acting actuator does not include a fail-safe (spring return) mechanism; in the event of a pressure or power loss, the actuator will remain at the position where the failure occurred.

Applications and Selection:

1. Valves requiring frequent operation-Suitable for automated pipeline systems where requires rapid and frequent opening/closing is needed.

2. Valves requiring maintenance of intermediate positions-Used for vent valves or diverting control valves that need to hold a specific opening consistently.

In these applications, the reliability and control performance of double-acting actuators are crucial. Typical applications include flow control in chemical production.

Single-Acting Pneumatic Actuators:

Single-Acting Pneumatic Actuators use one air inlet port to deliver compressed air enters from one end, driving the piston in one direction; the reverse motion relies on the elastic force of a pre-compressed spring inside the cylinder to achieve automatic reset. Therefore, in the event of a loss of air supply, it can automatically return to a pre-set safe position (fail-open or fail-closed) using spring force.

Product Features:

Single-Acting actuator is characterized by simple design and low air consumption. it incorporates a built-in "fail-safe" mechanism which ensures the actuator is automatically returned to its initial position by spring force in case of pressure loss.

Applications and Selection:

1. Emergency Shut-off Valves (ESD Valves)-Safety pipelines that must be closed or opened in a hazardous situation.

2. Critical Interlock Protection Valves: Valves that must automatically move to a safe position (fully open or closed) in a power or air supply failure.

In these situations, the "fail-safe" feature serves as the final reliable safety barrier. Common applications are found in emergency shut-off, boiler safety, natural gas pipelines, and other safety-critical pipeline process.

Are you unsure about selecting the right actuator for specific operating conditions (such as corrosive environments, explosion-proof requirements, or SIL certification)? Please contact our professional team to receive free selection advice and product solutions matches to your project's specific parameters.