Pneumatic Actuators

Pneumatic actuators are devices that convert compressed air into mechanical motion. In a water or wastewater treatment plant, they play a fundamental role in controlling the operation of valves, which regulate the flow and treatment of water. They work by using the energy in the compressed air to move a piston or diaphragm, which in turn moves the valve stem, opening or closing the valve.

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By providing a reliable and efficient means of valve operation, pneumatic actuators contribute significantly to the automated processes in treatment facilities. Their design allows for adaptability to various valve types and usage conditions, ensuring optimal performance in diverse settings.

• Controlling the flow of water into and out of treatment tanks.
• Regulating the addition of chemicals for treatment.
• Managing the operation of sludge dewatering equipment.

• Daily tasks may include checking for leaks and ensuring the actuator is functioning properly.
• Regular maintenance involves cleaning and lubricating the actuator and its components, as well as checking and adjusting the air pressure as needed.
• In terms of safety, operators need to be aware of the risk of injury from the sudden release of compressed air, and should be alert for signs of wear or damage that could lead to actuator failure.

• Cylinder: This houses the piston and the compressed air. Its size and material can affect the actuator's performance and lifespan.
• Piston: This moves back and forth in the cylinder due to the pressure of the compressed air, driving the actuator's motion.
• Springs: These return the piston to its original position when the air pressure is released. The number and strength of the springs can affect the actuator's speed and force.
• Valve stem connector: This connects the actuator to the valve stem. Its design must match the valve's requirements.

• Sizing Parameters: Include the required force (in N), the stroke length (in mm), and the operating pressure (in psi or bar).
• The required force is usually determined by the size and type of valve the actuator will be operating.

• MasterFormat Division 40 - Process Interconnections, Section 401123 - Actuators

• Emerson (Fisher 657 and 667 Diaphragm Actuators)
• Rotork (CP range)
• Festo (DFPD range)

• Electric Actuators: These use an electric motor instead of compressed air. They may be preferred in situations where electricity is more readily available, or where more precise control is needed.
• Hydraulic Actuators: These use a fluid to generate motion. They can provide greater force than pneumatic actuators, but are typically more complex and costly to install and maintain.