Actuators are used for the automation of industrial valves and can be found in all kinds of technical process plants: they are used in wastewater treatment plants, power plants and even refineries. This is where they play a major part in automating process control. The valves to be automated vary both in design and dimension. The diameters of the valves range from a few inches to a few metres.
Depending on their type of supply, the actuators may be classified as pneumatic, hydraulic, or electric actuators.
Currently there is no international standard describing linear actuators or linear thrust units. A typical representative of the valves to be automated is the control valve. Just like the plug in the bathtub is pressed into the drain, the plug is pressed into the plug seat by a stroke movement. The pressure of the medium acts upon the plug while the thrust unit has to provide the same amount of thrust to be able to hold and move the plug against this pressure.
Most of the linear actuators used are pneumatic diaphragm actuators. They are characterised by a simple design principle and are therefore cost-effective. A compressed air supply is a prerequisite for their use. In case this is not possible, the use of thrust units is recommended which can easily be supplied with power.