The BW Double-Cylinder Double-Acting Scotch-Yoke Pneumatic Actuator is a heavy-duty quarter-turn pneumatic actuator designed for high-torque rotary valve applications. It features a dual-cylinder, dual-piston configuration with a symmetrical scotch-yoke mechanism, serving as an upgraded design based on the AW series.
Powered by compressed air, the actuator drives two pistons in linear motion and converts this motion into 90° rotary output torque through the scotch-yoke mechanism. It is suitable for ball valves, butterfly valves, plug valves and other high-torque quarter-turn valves used in demanding industrial applications.
Compared with conventional AT rack-and-pinion pneumatic actuators, the BW scotch-yoke design provides higher torque output and is better suited for large-diameter, high-pressure and heavy-duty valves requiring substantial breakaway and seating torque.
BW Double-Cylinder Double-Acting Pneumatic Actuator – Working Principle
Valve Opening：When compressed air enters the Port A of both cylinders, it drives the two pistons toward the center of the actuator. Through the pin-and-scotch-yoke mechanism, the linear piston movement is converted into rotary motion, driving the central output shaft to rotate and open the valve.
At the same time, the air inside the opposite chambers is exhausted through Port B. The synchronized movement of the two pistons ensures smooth actuator operation, allowing the output shaft to rotate accurately to the fully open position.
Valve Closing：When compressed air enters Port B of both cylinders, the two pistons move outward toward the ends of the cylinders. The pistons drive the scotch-yoke mechanism in the opposite direction, causing the central output shaft to rotate in reverse and close the valve.
Meanwhile, the air inside the opposite chambers is discharged through Port A. The synchronized piston movement enables the output shaft to return accurately to the fully closed position.
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 | H | Q | U | V | Q2 | |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 13 | XLX-B13-2D | 240 | 120 | 250 | 740 | 10 | 146 | 283 | 62 | 310 | |
| 17 | XLX-B17-2D | 328 | 164 | 325 | 978 | 18 | 190 | 342 | 86 | 350 | |
| 20 | XLX-B20-2D | 373 | 187 | 363 | 1100 | 18 | 223 | 352 | 100 | 375 | |
| 25 | XLX-B25-2D | 373 | 187 | 389 | 1151 | 92 | 372 | 352 | 100 | 375 | |
| 28 | XLX-B28-2D | 436 | 218 | 425 | 1281 | 94 | 392 | 415 | 118 | 385 | |
| 30 | XLX-B30-2D | 436 | 218 | 433 | 1302 | 112 | 426 | 415 | 118 | 385 | |
| 35 | XLX-B35-2D | 474 | 237 | 450 | 1754 | 118 | 480 | 225 | 148 | 360 | |
| 40 | XLX-B40-2D | 474 | 237 | 484 | 1877 | 147 | 540 | 225 | 148 | 360 | |
| 50 | XLX-B50-2D | 710 | 355 | 654 | 2617 | 140 | 590 | 390 | 210 | 360 | |
| 60 | XLX-B60-2D | 780 | 390 | 675 | 2752 | 187 | 700 | 415 | 221 | 360 | |
| 70 | XLX-B70-2D | 780 | 390 | 700 | 2845 | 237 | 800 | 415 | 221 | 360 |
BW Double-Cylinder Double-Acting Scotch-Yoke Pneumatic Actuator – Key Advantages
Variable-Torque Scotch-Yoke Mechanism for High Breakaway Torque：The symmetrical dual-piston scotch-yoke mechanism provides a naturally variable torque output profile, with high torque available near the 0° and 90° end positions. This torque characteristic closely matches the operating requirements of ball valves and butterfly valves, which typically require higher breakaway and seating torque during opening and closing.Compared with conventional rack-and-pinion pneumatic actuators, the BW scotch-yoke actuator can deliver higher breakaway torque at the same cylinder diameter, helping overcome valve sticking and resistance caused by high differential pressure.
Heavy-Duty Construction for Large-Diameter and High-Pressure Valves：The dual-cylinder synchronized drive system provides balanced load distribution and high mechanical capacity. The actuator is particularly suitable for large-diameter, high-pressure and high-differential-pressure valves, including heavy-duty on-off valves used in demanding industrial applications.It is widely applicable in petrochemical plants, power generation, pulp and paper, municipal pipeline systems and other heavy-duty process industries.
Robust Construction, High Impact Resistance and Long Service Life：The major transmission components feature large load-bearing surfaces, reducing contact stress and improving resistance to mechanical impact. Optimized internal lubrication of the moving components helps minimize friction and wear, extending actuator service life.Adjustable mechanical travel stops are provided at both ends, allowing accurate positioning at the 0° and 90° end positions. The travel stops are easy to adjust, making commissioning and maintenance more convenient.
