Scotch Yoke Pneumatic Actuator
A Scotch yoke pneumatic actuator is a mechanism that converts the linear motion of a piston, driven by compressed air, into a rotational motion. This is achieved through a scotch yoke mechanism, which uses a slider and a yoke to translate the linear movement into a rotary movement, typically a quarter-turn rotation. These actuators are commonly used to automate quarter-turn valves, like ball and butterfly valves, in various industrial applications.
Key features and working principle:
Scotch Yoke Mechanism:
The core of the actuator is the scotch yoke mechanism. It consists of a piston rod connected to a slider that moves within a yoke, converting the linear motion of the piston into a rotating motion of the yoke.
Pneumatic Power:
Compressed air is used to drive the piston, providing the force needed for the linear motion.
Quarter-Turn Rotation:
The scotch yoke mechanism typically provides a 90-degree (quarter-turn) rotation, suitable for controlling quarter-turn valves.
High Torque:
Scotch yoke actuators are known for generating high torque, especially at the beginning and end of the stroke, which is beneficial for overcoming initial resistance when starting valve rotation or when the valve is nearly closed.
Applications:
Automation of Quarter-Turn Valves:
Scotch yoke pneumatic actuators are frequently used to automate the operation of ball valves, butterfly valves, and plug valves, which require a quarter-turn motion to open or close.
Industrial Settings:
They are commonly found in industries like oil and gas, water and wastewater treatment, chemical processing, and power generation, where reliable and efficient valve control is essential.
Hazardous Environments:
Due to their enclosed design and ability to be powered by compressed air, they are suitable for use in hazardous environments where electrical sparks could pose a risk.
Advantages:
• High Torque: Provides strong torque, particularly at the start and end of the stroke.
• Reliability: The simple design of the scotch yoke mechanism contributes to its reliability and durability.
• Suitability for Quarter-Turn Valves: Effectively automates valves requiring a quarter-turn motion.
• Can be used in Hazardous environments: Some sources indicate they are suitable for hazardous environments due to their air powered nature.
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