Electric Actuator is a device that converts incoming electrical energy into kinetic energy, that is, into mechanical movement. It can be understood in a simpler way as a motor, or switch, operated remotely, allowing a wide range of movements in a remote mode where its face-to-face operation could pose risks to the operator due to the unhealthy environment where it is located, or because it is present in a place of difficult access or in applications that require high torque outputs. Valve actuators, for example, play an important role in automating process control.
Electric actuators e.g., Danfoss are widely used in various applications such as door, opening, and gate controllers, valve actuation, and machining processes. They are used in wastewater treatment plants, power plants, refineries, mining and nuclear processes, food factories, and pipelines.
Types Of Electric Actuators
Electric actuators, according to their movement, can be LINEAR or ROTARY.
Linear Electric Actuator converts the rotary movement at continuous low voltage into a translational movement, also called LINEAR. That is the movement of pushing and pulling. It does not have full rotation. Most Linear Actuators use a combination of gears to retract or extend the drive arm. These actuators are used with gate and guillotine-type valves.
In the ROTARY Electric Actuator, gears, direct connections, or cams are also used in the transfer of movement; depending on the application torque, the movement performed is rotational or rotary, and this type of actuator has completed or infinite rotation. The rotary actuators are used with a ball and butterfly valve.
According to the opening system, electric actuators are classified as ON-OFF and PROPORTIONAL. The On-Off type allows only the opening or closing position of the flow. The Proportional type allows the adjustment of the opening in different positions according to the need.
An essential characteristic of electric actuators is the Degree of Protection IP (International Protection), which are standards defined by the international standard IEC 60529 that classifies and evaluates the level of protection of electronic products against intrusion (parts of the body such as hands and fingers), dust, accidental contact, and water. This degree of protection is assessed using two digits. The first digit, which ranges from 0 to 6, refers to solid particles (dust), and the second digit, which ranges from 0 to 9, corresponds to the liquid medium.
Electric actuators are used in the automation of various types of valves. Ball Valves and Butterfly Valves, operated by ¼ turn, also valves operated by multiturn, such as globe and gate valves, in addition to replacing Pneumatic Actuators in places where compressed air is not available.
Ball valves are economical and widely used to block the passage of fluids in the pipelines. Its wide use in the industry is due to its ability to block the flow with only ¼ turn and withstanding various pressure levels and various types of fluids; this blockage is quite efficient because, in addition to being immediate, it involves only a minimal loss inflow. The material of the construction of the valve varies according to the need, such as temperature, pressure, the corrosion of the circulating fluid in the pipeline, and the external conditions (submerged, acidic environment, etc.).
Like the Ball Valve, the Butterfly Valve also regulates or isolates the flow of fluid within a network and belongs to the group of fast-moving valves (¼ turn). The device that controls the flow is a disc called butterfly, from where the name “Butterfly Valve” comes for this type of valve. This disk rotates about its axis limited to 90 °. When it is in a position in parallel with the tube, it will allow the flow to pass, and in the perpendicular position, it will block the flow. Unlike the Ball Valve, the disc, or butterfly, remains within the flow with minimal pressure loss.