Valve actuators are automated mechanical devices that adjust the position of valves. This mechanism is driven through pressure by means of motion that controls the valve position. The motion generated by the actuator can be linear (straight horizontal or vertical movement) or rotary (around a fixed axis).There are different types of valve actuators. However, the most common classification falls into electric and pneumatic.
Pneumatic actuators use air pressure (or any other gas, depending on the application) as the main energy source to produce motion to control the valve. For example, in the diaphragm actuator, air is pumped into a hollow housing where the pressure acts on a flexible rubber diaphragm that deflects it to its original position. Also, connected to a valve stem, the diaphragm rises and falls in order to adjust the pneumatic electric valve disc and control the flow. Although pneumatic actuators produce linear motion, they also generate rotary motion.
Through an electric motor and by means of motion and pressure, electric actuators transform energy for application in various processes. They are classified as solenoid or motor-driven actuators. In solenoid actuators, the electric current, through a coil, generates a magnetic field that moves the metal stem and adjusts the position of the electric valve disc. Motor-driven actuators, on the other hand, have an AC or DC servomotor for the purpose of moving the valve to the desired position.
Applications and benefits of pneumatic actuators
Pneumatic actuators produce some of the highest closing forces of all actuator types. They reach a maximum pressure of 250 PSI according to the specific design: 85PSI to 250. Generates forces up to 40,000 lb. They are also noted for their relatively fast closing speeds of up to 2 m/s, where both actuator speed and force can be easily matched by adjusting a system of pressure relief valves or flow regulators.
The cost of pneumatic actuators is low, as are their components. Pneumatic cylinders are easily adjusted to larger diameters and large air compressors are ideal for powering large groups of pneumatic devices.
These actuators are known for their clean operation, lack of ignition source and high reliability, making them suitable for application in ventilation systems, pumps, service in flammable environments and internal combustion engines.
Applications and benefits of electric actuators
The positioning control of the actuators is very precise. Intermediate and stop positions can be pre- programmed, allowing them to be positioned anywhere on the basis of their function for a given input. Of most devices, this one offers very fast movements (speeds up to 10 m/s).
The separation of the electric power supply from the actuator makes it possible to reduce costs in terms of maintenance and replacement of parts. And, despite having an electric motor, electric actuators have a low percentage of noise pollution, producing little noise, making them ideal for environments where low frequencies are needed.
Electric actuators are applied in machinery (forklifts, dump trucks, excavators, etc.), and smaller actuators are often used for mobile robotics and manufacturing automation.
Choosing the right actuator
It is necessary to know the specific applications you require for your electric and pneumatic actuators, so that the features and advantages listed in the previous paragraphs benefit your processes.