The BW Single-Cylinder Double-Acting Scotch-Yoke Pneumatic Actuator is a compact variable-torque pneumatic actuator designed for quarter-turn valve automation. It features a single-cylinder piston and scotch-yoke mechanism, delivering high torque at both ends of the actuator stroke to meet the breakaway and seating torque requirements of ball valves, butterfly valves and other quarter-turn valves.
With its compact design, reliable torque output and flexible configuration, the BW single-cylinder scotch-yoke actuator is well suited for general process automation, water treatment, HVAC systems and medium-duty industrial valve applications.
BW Single-Cylinder Double-Acting Scotch-Yoke Pneumatic Actuator – Working Principle
Valve Opening：Compressed air enters the actuator through Port A, driving the piston to move to the left, while the exhaust air is discharged through Port B. The piston drives the scotch-yoke mechanism counterclockwise, rotating the output shaft and opening the valve.
Valve Closing：Compressed air enters through Port B, driving the piston to move to the right, while the exhaust air is discharged through Port A. The piston drives the scotch-yoke mechanism clockwise, rotating the output shaft in the reverse direction and closing the valve.
A pneumatic actuator converts the energy of compressed air into mechanical motion, enabling the valve to open, close, or continuously modulate its position for reliable and automated valve control. For pneumatic actuator selection and procurement, please contact our technical team and provide the relevant operating parameters so that we can recommend the most suitable actuator model for your application. （Unit: mm）
| Size | Part No | L | L1 | L2 | L3 | L4 | H | Q | U | V | Q2 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 17 | XLX-B17-1D | 328 | 164 | 335 | 1047 | 687 | 62 | 278 | 260 | 260 | 260 | |
| 20 | XLX-B20-1D | 373 | 187 | 389 | 1176 | 790 | 92 | 372 | 260 | 260 | 260 | |
| 25 | XLX-B25-1D | 373 | 187 | 394 | 1183 | 795 | 148 | 484 | 260 | 260 | 260 | |
| 28 | XLX-B28-1D | 436 | 218 | 438 | 1330 | 905 | 163 | 534 | 320 | 320 | 320 | |
| 30 | XLX-B30-1D | 436 | 218 | 464 | 1355 | 931 | 191 | 584 | 320 | 320 | 320 | |
| 35 | XLX-B35-1D | 474 | 237 | 460 | 1320 | 968 | 200 | 645 | 225 | 720 | 360 | |
| 40 | XLX-B40-1D | 474 | 237 | 460 | 1320 | 968 | 227 | 700 | 225 | 720 | 360 | |
| 50 | XLX-B50-1D | 710 | 355 | 633 | 1878 | 1375 | 225 | 760 | 390 | 760 | 360 | |
| 60 | XLX-B60-1D | 780 | 390 | 650 | 2127 | 1521 | 295 | 915 | 415 | 785 | 360 | |
| 70 | XLX-B70-1D | 780 | 390 | 650 | 2127 | 1521 | 370 | 1066 | 415 | 785 | 360 |
BW Single-Cylinder Double-Acting Scotch-Yoke Pneumatic Actuator – Key Advantages
Variable-Torque Scotch-Yoke Design for High Breakaway Torque：The single-piston scotch-yoke mechanism provides a naturally variable torque output profile, with peak torque available at the 0° and 90° end positions. This torque characteristic closely matches the operating requirements of ball valves and butterfly valves, providing sufficient breakaway and seating torque. Compared with a rack-and-pinion actuator of the same size, the BW scotch-yoke design can more effectively overcome valve sticking and resistance caused by high differential pressure.
Compact Design for Space-Constrained Installations：Compared with the BW double-cylinder scotch-yoke actuator, the single-cylinder configuration offers a smaller overall footprint and shorter axial length, making it ideal for applications with limited installation space.
The hard-anodized aluminum alloy cylinder housing combines low weight with excellent corrosion and wear resistance, providing a good balance between mechanical strength and lightweight construction.
Robust Transmission Mechanism for Reliable, Long-Term Operation：The scotch-yoke mechanism features a large load-bearing contact area, which reduces contact stress and improves resistance to mechanical impact. Optimized lubrication of the moving components minimizes friction and wear, helping extend the actuator’s service life.
Adjustable mechanical travel stops are provided at both ends of the cylinder, allowing precise positioning at the fully open and fully closed positions and simplifying on-site commissioning.
Standard Interfaces for Flexible Accessory Integration：The actuator output mounting flange complies with ISO 5211, while the accessory interface is compatible with the NAMUR standard. This allows direct installation on ball valves, butterfly valves, plug valves and other quarter-turn valves.
The actuator can be easily equipped with solenoid valves, limit switches, valve positioners and air filter regulators for remote automatic valve control, position feedback and pneumatic system management.
Cost-Effective Solution for Medium-Duty Applications：Compared with double-cylinder scotch-yoke actuators with similar torque ratings, the BW single-cylinder design offers a more economical solution for small- and medium-diameter valves and medium differential-pressure on-off applications.
It is widely used for valve automation in water treatment systems, HVAC pipelines, general chemical processing, municipal pipelines and other medium-duty industrial applications.
