Scotch Yoke Actuator

A Scotch Yoke Actuator is a quarter-turn pneumatic drive in which a linear cylinder piston pushes a slotted yoke that converts piston motion into a 90-degree rotation of the output shaft. The yoke geometry delivers a high starting torque near the open and closed ends and a steady torque through mid-stroke, which is exactly the curve a large ball, butterfly or eccentric rotary valve needs to overcome seat friction at the ends of travel. Compared with a rack-and-pinion actuator of the same envelope, the scotch yoke design produces substantially higher torque, with output available from 50 up to 10,000 N·m across segmented sizes. Low-friction wear-resistant bushings in the yoke slots keep backlash small so the shaft lands accurately on each travel point. Two action types are offered: double-acting for continuous modulation and general isolation, and single-acting with an integrated return spring that drives the valve to a safe open or closed position on loss of air supply. The housing is hard-anodized aluminum alloy, rated IP65, so the unit tolerates outdoor and humid plants, and it accepts valve positioners, solenoid valves and limit switch boxes as bolt-on accessories.

Buyers of large-bore ball and butterfly valves worry most about torque consistency: an undersized yoke stalls the valve at the seat, while batch-to-batch torque variation makes spring-return fail-safe response unpredictable. We machine the yoke, piston and shaft on our own CNC centers instead of assembling generic cast parts, and every unit is torque-tested, air-tightness tested and endurance-cycled before release. The result is a torque curve that is reproducible across the batch and matched to the actual valve breakaway and seating torque.

Large chemical shut-off valves

Large-bore isolation valves need high breakaway torque to unseat tight metal or soft seals; the scotch yoke's peak torque at the travel ends provides that force inside a compact envelope that a rack-and-pinion cannot match.

Power plant high-temperature butterfly valves

The rigid yoke-and-piston structure and IP65 anodized housing hold up under elevated ambient temperatures and outdoor ducting where a lighter actuator would drift or leak.

Long-distance oil and gas pipeline ball valves

The single-acting spring-return variant drives the ball to a defined fail-safe position on instrument-air failure, which is the safety requirement for remotely located pipeline isolation stations.

• Double-acting or single-acting spring-return (fail-open / fail-closed) selection
• Torque class selected against valve breakaway, seating and operating torque
• Accessory package: valve positioner, solenoid valve, limit switch box, filter regulator
• Supplied matched to our ball valve, butterfly valve, eccentric rotary valve or slurry valve

Actuators are packed in export wooden cases with the output shaft protected by a plastic cover and air ports capped. We run torque and air-tightness checks on each unit and provide test videos, packing photos, a packing list and customs documents with the shipment.

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