Engineers, designers, and manufacturers that deal with designing in flow and valve engineering, mostly have an essential need to understand the aspects and the processes of using a particular product.
In most simple terms, a pneumatic actuator is a device that transforms air pressure into motion. For example, to open and close a ball valve, the pneumatic actuator mechanically generates a rotary motion. In comparison with hydraulic and electric actuators, pneumatic actuators are the most common actuators in the valve market and can be found in many industrial applications. A pneumatic actuator, also known as an air cylinder, is typically made of metal. Its action is based on the motion of an air cylinder. The torque of an actuator depends on the size (area) of its cylinder and the air pressure. The larger the piston and the higher the pressure, the more powerful is the torque. The ratio between the actuator torque and its size, represents the efficiency of the actuator. The higher the ratio, the more efficient it is, as is its manufacturing cost.The animation below shows how a pneumatic actuator works.
There are two major types of a pneumatic actuators: Double Acting and Single Acting actuator. The double acting actuator uses two air pressure chambers, one for movement in each direction, as shown in the animation. A single acting actuator uses a single air pressure chamber to move the piston in one direction, while compressing a spring. When the air pressure is released, the compressed spring returns the actuator to its original position. This type of actuator is also called a "Spring Return" actuator.
Selecting the correctly sized actuator for a specific valve or application is very important, both functionally and economically. On one hand, it is necessary to to select an actuator that is powerful enough to operate the valve; but on the other hand, one doesn’t want to spend the money on an actuator that is too big for the job.
Here are some of the parameters to consider when “sizing” an actuator:
The nominal torque values of a valve, at the starting point and at the end point, both in the two movement directions.
The application conditions: pressure, temperature, media viscosity, operating frequency.
Actuator features: type (double or single acting) and operating air pressure.
Ingenieure, Entwurfsgestalter und Hersteller, zu deren Aufgaben das Design im Bereich Durchfluss- und Ventiltechnik gehört, müssen unbedingt die Aspekte und Prozesse verstehen, die mit der Verwendung eines bestimmten Produkt verbunden sind.
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