BELEF 3-Position Pneumatic Actuator
The 3-position pneumatic actuator is a rack-and-pinion rotary pneumatic device, distinct from conventional 2-position (open/close) actuators. It offers three fixed angular positions, with 0°-45°-90° as the standard configuration and 0°-90°-180° available upon request. The intermediate position is mechanically adjustable via an built-in auxiliary piston stop, enabling precise positioning without the need for an electrical positioner. Paired with solenoid valve assemblies, it delivers stepped flow control and is widely used with ball valves, butterfly valves, and plug valves for multi-stage flow regulation.
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Product Overview
The actuator features a dual-piston rack-and-pinion base design with an integral auxiliary limiting piston mechanism. Three-position indexing is achieved through multi-port pneumatic switching: 1.0° (fully closed): Specific air port is pressurized, pistons retract, and output shaft rotates to the closed position； 2. Intermediate position (typically 45°, adjustable): Both air ports are simultaneously pressurized. The auxiliary piston creates a mechanical stop, limiting piston stroke and locking the output shaft at the preset intermediate angle； 3. 90° (fully open): The auxiliary piston stop is released, pistons fully extend, and the output shaft reaches the fully open position. Control: Two solenoid valve assemblies form the pneumatic control circuit. Position switching is sequentially controlled via PLC signals. Double-acting 3-position: Fully air-driven throughout; holds position upon air supply failure.Spring-return 3-position: Automatically returns to a safe position (fully closed or fully open) upon air supply loss.
Product Features
1. Three Independent Mechanical Positions The intermediate position is locked by a mechanical stop, ensuring high positioning repeatability. Both adjustable end stops allow free adjustment of the intermediate angle (20°~75° as required) to meet different flow control requirements. 2. Eliminates Water Hammer The valve opens and closes in stages, allowing smooth fluid transitions and preventing water hammer caused by sudden flow changes — protecting pipelines and storage tanks. Ideal for quantitative loading of oil and chemical media.
3. Standard Universal Mounting Interface Conforms to ISO 5211, DIN3337, and NAMUR standards for direct mounting of solenoid valves, limit switches, and position feedback devices. The output shaft can be assembled in either direction for flexible rotation. 4. Durable Construction Extruded aluminum alloy cylinder body with honed internal surface for smooth operation. Internal rack and gear are precision-machined with low backlash. Fasteners are stainless steel for excellent corrosion resistance. High/low temperature seal kits are available for demanding environments.
5. Simplified Solution & Cost Advantage For applications requiring only three fixed-position control, this solution offers lower investment cost compared to electrical valve positioner schemes, with simpler commissioning and easier maintenance.
Product Specs

   Standard Rotation Angle

   0°-45°-90° (Custom 0°-90°-180° available)

   Supply Pressure

   0.4～0.7 MPa

   Operating Temperature

   Standard: -20℃ to +80℃ / Optional: High/Low Temperature Kit

   Actuation Type

   Double-Acting 3-Position / Spring-Return 3-Position

   Compatible Valves

   Ball Valves, Butterfly Valves, Plug Valves, and other 90° quarter-turn valves

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