Electric Actuators Explained: Types, Benefits, and Industrial Applications
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Introduction to Electric Actuators
Electric actuators are devices that convert electrical energy into mechanical motion to operate valves, dampers, and other flow control equipment. As industries move towards greater automation and remote operation, electric actuators have become an essential component in modern process plants, water treatment facilities, HVAC systems, and manufacturing environments. Unlike pneumatic actuators, electric actuators do not require a compressed air supply, making them particularly well-suited to locations where compressed air infrastructure is unavailable or impractical to install.
At Valves UK, we supply a comprehensive range of electric actuators from leading manufacturers including Koei, designed to deliver reliable, precise, and energy-efficient valve automation across a wide variety of industrial applications. Whether you are automating a single gate valve on a water pipeline or integrating dozens of ball valves into a fully networked control system, electric actuators offer the flexibility, accuracy, and intelligence that modern operations demand.
How Electric Actuators Work
The fundamental operating principle of an electric actuator is straightforward: an electric motor drives a gear train or lead screw mechanism to produce the torque or thrust required to open, close, or position a valve. When a control signal is received — typically 4–20mA, 0–10V, or a digital command via protocols such as MODBUS or PROFIBUS — the actuator motor energises and drives the output shaft to the commanded position. A position feedback sensor, usually a potentiometer or encoder, continuously monitors the shaft position and reports it back to the control system, enabling precise, closed-loop positioning.
Most electric actuators for valve automation are rotary devices, producing an output rotation of 90 degrees for quarter-turn valves such as ball valves and butterfly valves. Multi-turn electric actuators are used for gate valves and globe valves, which require multiple turns of the stem to travel from fully open to fully closed. Linear electric actuators convert rotary motor motion into linear thrust for valves with a rising stem or sliding plug, such as linear globe valves and pinch valves.
Types of Electric Actuators
Quarter-Turn Electric Actuators
Quarter-turn electric actuators are the most common type used in industrial valve automation. They produce a 90-degree rotation that is perfectly suited to ball valves and butterfly valves. These electric actuators are compact, reliable, and available in a wide range of torque outputs to match the operating torque requirements of different valve sizes and pressure ratings. Quarter-turn electric actuators are widely used in water treatment, chemical processing, HVAC, and general industrial applications where reliable and precise valve control is essential.
Multi-Turn Electric Actuators
Multi-turn electric actuators are designed for valves that require multiple rotations of the stem to travel between open and closed positions. Gate valves and globe valves typically fall into this category. Multi-turn electric actuators incorporate a gearbox to reduce motor speed and increase output torque, and they often feature handwheels for manual override in the event of a power failure. These actuators are common in oil and gas, water treatment, and power generation applications where gate and globe valves are frequently used for isolation and throttling control.
Linear Electric Actuators
Linear electric actuators convert the rotary motion of an electric motor into linear thrust via a lead screw or ball screw mechanism. They are used to operate linear-motion valves such as gate valves with a non-rotating stem, linear globe valves, and diaphragm valves. Linear electric actuators are valued for their precise positioning capability and are often found in pharmaceutical, food and beverage, and chemical processing applications where accurate dosing or flow control is required and where the elimination of compressed air simplifies system design considerably.
Part-Turn Electric Actuators
Part-turn electric actuators operate over a rotation range other than a full 90 degrees or multiple full turns. They are used for plug valves and some types of butterfly valves where the travel angle differs from the standard quarter-turn. Part-turn electric actuators offer the same advantages as quarter-turn models but with a configurable travel range to suit the specific valve design and application requirements.
Key Benefits of Electric Actuators
No Compressed Air Required
One of the most significant advantages of electric actuators over pneumatic actuators is that they do not require a compressed air supply. In many facilities, particularly those in remote locations or buildings without existing pneumatic infrastructure, installing compressed air pipework can be costly and complex. Electric actuators can be powered by connecting to the site's existing electrical supply, dramatically reducing installation costs and complexity. This makes electric actuators the preferred choice in many building services, water treatment, and industrial automation applications across the UK and internationally.
Precise Positioning and Modulating Control
Electric actuators excel at precise valve positioning, making them ideal for modulating control applications where the valve must be set to an intermediate position rather than simply open or closed. Using a 4–20mA or 0–10V control signal, a modulating electric actuator can position the valve to any point in its travel range with high accuracy and repeatability. This makes electric actuators invaluable in processes requiring precise flow, pressure, or temperature control, and they are commonly used in conjunction with PLC-based control systems and SCADA platforms across a wide range of industrial sectors.
Intelligent Monitoring and Diagnostics
Modern electric actuators are increasingly equipped with onboard intelligence, including position feedback, torque monitoring, motor temperature sensing, and event logging. This data can be transmitted to a SCADA system or PLC via digital fieldbus protocols, enabling plant operators to monitor valve status in real time, detect developing faults before they cause a failure, and schedule maintenance proactively. This level of diagnostic capability is difficult to replicate with purely pneumatic systems and represents a major advantage of electric actuators in complex, safety-critical industrial environments.
Energy Efficiency
Electric actuators only consume energy when they are moving. Once the valve has reached its commanded position, the motor de-energises and no power is consumed. This contrasts with pneumatic actuators, which require a continuous supply of compressed air — an energy-intensive medium to produce and distribute. In applications where valves are frequently repositioned, electric actuators can offer significant energy savings over the lifetime of the installation, contributing to overall plant efficiency and sustainability targets.
Environmental Suitability
Because electric actuators do not exhaust compressed air, they produce no noise from air exhaust and do not require venting to atmosphere. This makes them suitable for enclosed spaces, clean rooms, and environmentally sensitive locations. Electric actuators are also available in sealed enclosures with high IP ratings, making them suitable for outdoor installation and wash-down environments where exposure to rain, dust, or cleaning fluids is a routine consideration.
Electric Actuator Control Options
Electric actuators are available with a wide range of control interfaces to suit different system architectures. The most common control options include on/off control via a simple two- or three-wire connection, modulating control via a 4–20mA or 0–10V signal, and digital fieldbus control via protocols including MODBUS RTU, MODBUS TCP, PROFIBUS DP, PROFINET, DeviceNet, Foundation Fieldbus, and EtherNet/IP. The choice of control interface will depend on the complexity of the application, the existing control system infrastructure, and the level of integration and diagnostics required.
For simple on/off applications, a basic two-wire or three-wire electric actuator providing open, close, and stop commands is typically sufficient and represents the most cost-effective solution. For modulating applications, a 4–20mA input signal allows the electric actuator to be positioned anywhere in its travel range proportionally. For fully integrated plant automation systems, digital fieldbus control enables bidirectional communication, allowing the control system to command the actuator and receive position, torque, and diagnostic data in return.
Selecting the Right Electric Actuator
Torque Requirements
The first step in selecting an electric actuator is to determine the torque required to operate the valve. This depends on the valve type, size, pressure rating, and the properties of the media being controlled. Valve manufacturers typically publish torque data for their products at various operating conditions. It is important to select an electric actuator with sufficient torque output to operate the valve under worst-case conditions, including breakaway torque at maximum differential pressure. A safety factor of at least 25–30% above the maximum valve torque is generally recommended to ensure reliable long-term operation and prevent actuator stalling.
Supply Voltage
Electric actuators are available for a range of supply voltages including 24V DC, 110V AC, and 230V AC single-phase, as well as 400V AC three-phase for larger, higher-torque units. The selection of supply voltage should be based on the available power supply at the installation location. Three-phase electric actuators are generally used for larger valves requiring higher torque outputs, while single-phase and DC electric actuators are more common for smaller valves and control panel installations where space and available power may be more limited.
Enclosure and Environmental Rating
Electric actuators must be selected with an enclosure rating appropriate for the installation environment. The IP (Ingress Protection) rating describes the level of protection against solid particles and liquids. For outdoor or wash-down applications, an IP67 or IP68 rating is typically required to ensure long-term reliability. For hazardous area installations where flammable gases or dusts may be present, ATEX-rated electric actuators must be selected to prevent ignition of the hazardous atmosphere. Valves UK can supply ATEX-rated electric actuators for zone 1 and zone 2 hazardous area applications where safety is paramount.
Fail-Safe Operation
Unlike spring-return pneumatic actuators, standard electric actuators do not inherently provide a fail-safe action in the event of a power failure — the valve will simply remain in its last position. For applications where fail-safe operation is required — for example, fail-open or fail-closed — battery backup or capacitor modules can be added to the electric actuator to provide power for one complete stroke following a mains power failure. Some electric actuator designs incorporate integral spring return mechanisms to provide mechanical fail-safe operation, though these are less common than in pneumatic actuator designs and may increase overall unit size and weight.
Electric Actuators in Industrial Applications
Water and Wastewater Treatment
Electric actuators are widely used in water and wastewater treatment plants to automate the operation of isolation valves, throttling valves, and flow control valves throughout the treatment process. Their precise positioning capability is particularly valuable in dosing applications where accurate control of chemical addition is required. Electric actuators are favoured in water treatment for their clean operation — unlike pneumatic systems, they produce no exhaust air and require no oil separation or filtration of the air supply, simplifying overall system maintenance and reducing running costs over time.
HVAC and Building Services
In heating, ventilation, and air conditioning systems, electric actuators are used to control zone valves, mixing valves, and damper actuators throughout commercial and residential buildings. Their ability to modulate precisely in response to temperature control signals makes them ideal for maintaining comfort conditions and minimising energy consumption. Compact electric actuators for HVAC applications are available with 24V AC or DC power supply and simple two- or three-point control, making them easy to integrate with standard building management systems and energy management platforms.
Oil and Gas
The oil and gas industry uses electric actuators in a wide range of applications including wellhead control, pipeline isolation, and process plant valve automation. In offshore and remote onshore locations where compressed air may not be readily available, electric actuators offer a practical and reliable solution. Subsea electric actuators are also available for deepwater applications where hydraulic or pneumatic actuators are not feasible or economical. For hazardous area surface installations, ATEX-certified electric actuators are essential to maintain safe operating conditions and comply with relevant safety regulations.
Chemical and Petrochemical Processing
Chemical and petrochemical plants use electric actuators extensively for controlling process valves handling corrosive, toxic, or flammable media. The ability to precisely modulate flow rates and achieve accurate valve positioning makes electric actuators valuable in batch processing applications where recipe control is important. Their diagnostic capabilities also help maintain the high levels of plant reliability demanded in continuous process operations, where unplanned downtime is extremely costly and potentially hazardous to personnel and the environment.
Food and Beverage Manufacturing
In food and beverage manufacturing, electric actuators are often preferred over pneumatic actuators for clean-in-place (CIP) and sanitary applications. Because they do not require compressed air, there is no risk of air contamination of the product stream, and there are no compressed air lubricants or moisture to manage. Electric actuators with stainless steel or food-grade enclosures are available for hygienic applications requiring regular wash-down, making them an excellent choice for use alongside hygienic ball valves, butterfly valves, and diaphragm valves in food-grade pipework systems.
Koei Electric Actuators at Valves UK
Valves UK is proud to supply Koei electric actuators — Japanese-engineered products renowned for their precision, durability, and long-term reliability. Koei electric actuators are designed to deliver accurate valve positioning and extended service life, making them an excellent choice for demanding industrial applications. The Koei range includes quarter-turn and multi-turn electric actuator models, with options for on/off and modulating control, a variety of supply voltages, and high IP ratings for outdoor and wash-down service. Whether you are specifying a single electric actuator or a complete automated valve package, the Koei range from Valves UK offers a reliable and cost-effective solution for your valve automation needs.
Installation and Commissioning
Installing an electric actuator is generally straightforward. The actuator mounts directly to the valve using a standard ISO 5211 mounting flange, and the drive coupling connects to the valve stem or shaft. Electrical connections are made in the terminal box, which is accessed by removing the actuator cover. Before commissioning, travel limits must be set to correspond to the open and closed positions of the valve. Most modern electric actuators feature automatic limit-setting routines that can be initiated via a button or through the control system, significantly simplifying commissioning and reducing setup time in the field.
It is important to ensure that the electric actuator is correctly aligned with the valve and that the coupling does not impose side loads on the valve stem. The electrical supply should be correctly rated for the actuator's motor current draw, and appropriate overcurrent protection should be provided in accordance with the actuator manufacturer's recommendations and applicable electrical installation standards. Correct installation practices will maximise the service life of both the electric actuator and the valve it operates.
Maintenance of Electric Actuators
Electric actuators are generally low-maintenance devices, particularly compared to pneumatic actuators which require air filter maintenance and regular checking of air supply quality. The main maintenance tasks for electric actuators include periodic inspection of electrical connections for corrosion or looseness, checking the gearbox oil level if the electric actuator uses an oil-lubricated gearbox, and verifying that travel limit settings remain correct after any maintenance work on the valve assembly. Many modern electric actuators use sealed-for-life gearboxes that require no routine lubrication, further reducing maintenance requirements and total cost of ownership.
The onboard diagnostics available in intelligent electric actuators can significantly reduce maintenance costs by alerting operators to developing faults before they cause a breakdown. Monitoring of motor current, operating torque, number of operations, and actuator temperature can all provide early warning of potential issues, enabling planned maintenance to be carried out at a convenient time rather than as an emergency response to a failure in a critical process application.
Conclusion
Electric actuators represent a mature, reliable, and increasingly intelligent technology for valve automation across a huge range of industrial sectors. Their ability to deliver precise valve positioning, operate without compressed air, and provide detailed diagnostic information makes them an excellent choice for a wide range of applications. Whether you are replacing an existing pneumatic actuator system or specifying automation for a new installation, electric actuators deserve serious consideration as a flexible and cost-effective solution that can integrate seamlessly with modern industrial control systems.
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At Valves UK, our team of valve and actuator specialists can help you select the right electric actuator for your application, taking into account torque requirements, control interface, environmental conditions, and fail-safe requirements. Browse our range of electric actuators online today or contact our team for expert technical guidance and a competitive quotation tailored to your specific project needs.