Types of industrial actuators
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There are many types of industrial actuators. In my understanding, the various types of actuators can be classified, with brief explanations of their advantages and disadvantages. 1. Diaphragm actuator (also known as diaphragm head or diaphragm cylinder): Structure – In a double-acting type, there is a composite rubber diaphragm inside the green head, with a valve stem shaft connected to it; in a single-acting type, a spring is included. Operation principle: Instrument air enters the diaphragm head, driving the diaphragm to stretch and thereby moving the valve stem up and down, thus operating the valve to open or close for regulation. Advantages: Fast response, small space requirement, low cost; almost all valve manufacturers can produce them, and the technical complexity is low. Disadvantages: The available operating space is limited, so it can only be used on valves with small diameters. It was originally used primarily for valves that require precise proportional control, and it is now also used for small-diameter gate valves and stop valves in the chemical industry. Common manufacturers include Fisher, Memmert, Samson, Fox; among domestic manufacturers, there are Wuzhong Instruments, Chuanyi, Shanghai Instrument Factory No. 7, Wuxi Intelligence, etc. Larger valve manufacturers almost always produce their own components rather than purchasing them from outside.
2. Fork-type pneumatic actuator (also known as: fork cylinder). Structure: Single-acting type consists of a piston chamber, a fork chamber, and a spring chamber; double-acting type does not have a spring chamber. Some manufacturers use a modular design for production, allowing modules of the same model to be fully interchangeable. Operation principle: Instrument air enters the piston chamber, driving the piston plate and tensioning the spring. The piston then causes the fork to rotate; this fork is connected to the valve stem shaft, and its rotation leads to the closure of the valve. Advantages: High output torque, exceeding 1 million Nm for single-acting types; long service life, with over 1 million operations possible. The U-shaped arc output is more suitable for the curved motion trajectory of valves, allowing it to be used in various applications. Disadvantages: High price, large size. Common manufacturers and origins: BETTIS in Tianjin, BIFFI in Chengdu, ROTORK in Shanghai, ProControl in Italy. AUTOMAX Suzhou Service life: Over 5 years with one maintenance
3. Gear-rack pneumatic actuator (also known as a gear-rack cylinder or aluminum alloy cylinder): The piston and spring move within an aluminum alloy cylinder. Working principle: Instrument air enters the cylinder to drive the piston; the piston is integrated with a rack, which in turn drives the gear, and the gear causes the valve stem to move so that the valve closes. Advantages: Low price, small size. Disadvantages: Low output torque and short service life, generally less than 300,000 cycles; domestic versions last around 100,000 cycles. Not applicable to control ball valves or butterfly valves. Common manufacturers and origins: ProControl – Italy. Nimitoco-Suzhou, STI-Shanghai, C-MAX-Chengdu, Saint Hans-Wuxi. Service life: over 2 years per maintenance cycle, with a total lifespan of less than 300,000 cycles.
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