Electric Valve Actuator - How They Work

Figure 1: JP fluid control AG series (left) and AW series (right) electric valve actuator

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Electric quarter-turn valve actuators are electro-mechanical devices used to remotely control quarter-turn valves, such as ball and butterfly valves. Compared to their pneumatic and hydraulic counterparts, electric valve actuators offer a more energy-efficient, clean, and quiet method of valve control. These actuators can be purchased together with the valve as a package or separately and added to an existing quarter-turn valve.

Electric Valve Actuator Design

Electric actuators for quarter-turn valves are a type of rotary motorized valve actuator. They convert electric energy into rotary force, allowing for a 90-degree turn. The electric motor generates torque that is transmitted to turn the valve through an output drive. Motor voltage options include AC (alternating current), DC (direct current), or both. The motor is housed in a robust, compact enclosure that also contains other actuator components such as gearings, limit switches, wiring, etc. The assembly is connected to a valve through a compatible connection interface, such as an ISO 5211 standard.

Torque

Quarter-turn valves require a 90° turn to fully open or close. Torque, the rotational equivalent of linear force, is needed to turn the valve. The electric actuator generates this torque and transmits it to its output shaft, which then connects to the valve’s stem or shaft. This rotates the valve’s ball or disc to open or close the flow. The amount of torque generated by an actuator depends on its gearing and motor capacity. The motor capacity (torque) needs to be higher than the valve’s required torque to ensure it can open and close the valve.

Breakaway Torque

The torque required to "break free" from an open or closed position is called breakaway torque. This is the amount of torque necessary to initially move a valve from a rest position, typically higher than the run torque due to factors like media buildup in the ball cavity or increased friction from scratched valve seats. A suitable quarter-turn valve actuator should generate a torque higher than the valve’s breakaway torque.

Response Time

Response time refers to the time it takes for an actuator to turn the valve a full 90 degrees (i.e., fully open or close the valve). This time is influenced by the actuator's gearing and motor power. Torque and speed of an actuator are inversely proportional and dependent on gear arrangements. For a given motor capacity, a higher gear ratio results in more torque and a slower response time than a lower gear ratio.

Control Method

Electric valve actuators come with either 2-point control (on/off) or 3-point control, both having 3 wires. Each control method provides a different way to manage valve positioning.

Voltage

Electric actuators can be powered by DC or AC. Common voltage options include 12, 24, and 48V for direct current and 24, 48, 120, 130, 240V for alternating current.

Mounting

Quarter-turn actuators have a connection interface that connects them to the valve, consisting of an output drive, a shaft square or stem, and a flange. This interface can be brand-specific or standardized to ISO 5211. For instance, JP fluid controls' AW1 series actuators have brand-specific interfaces, while the AG series uses the standard ISO 5211, making them compatible with any valve with an ISO 5211 flange.

Electric Valve Actuator Features

Position Indicators

Position indicators show whether an actuator is open or closed. They can be visual (e.g., Figure 3) or equipped with electric feedback systems to send the position back to a controller. They use mechanical or proximity (non-contact) switches to indicate the position and may display fully or partially opened/closed states.

Manual Override

Most actuators feature a manual override for safety, typically a mechanical handwheel or handle to manually operate a valve during power failure or emergencies.

Limit Switches

Limit switches are electromechanical components that stop electricity to the actuator at the end positions to prevent further movement. They consist of open and close limit switch cams that move with the actuator. Some actuators allow these switches to be adjusted to set custom end positions.

Duty Cycle

The duty cycle defines the usage time of an actuator between cycles, expressed as a ratio of on-time to off-time. For example, if it takes an actuator 10 seconds to open, 20 seconds to close, and rests for 30 seconds, the duty cycle would be (10+20 / 10+20+30) × 100 = 50%.

Fail-Safe

A fail-safe feature is vital for automated valve actuators, designed to open or close a valve during power failure. This requires energy storage, such as a spring or a battery. Typically, the fail-safe mechanism will close the valve, but certain applications may require it to open, like cooling with cold water to prevent overheating in a heat exchanger.

Modulation

Some electric valve actuators can modulate control, often referred to as DPS (digital positioning system), allowing for precise positioning between fully opened and fully closed states. This is essential for applications requiring variable flow rates.

Electrical Wiring

This section explains wiring possibilities for 2- and 3-point electric valve actuators, which vary significantly.

• 2-point (on/off) control actuators: These actuators have three wires for +, -, and a control wire. To rotate the valve, the control wire needs to be powered to open and un-powered to close or vice-versa. For example, the AW1-R series from JP Fluid Control uses this wiring scheme.
• 3-point control actuators: These actuators have three wires - one for -, and two for + control wires. One control signal opens or closes the valve depending on which one is powered. The ability for intermediate stops is also possible. It's crucial never to power both control wires simultaneously to avoid damaging the actuator. For instance, the AW1 series from JP Fluid Control uses this wiring scheme.

Before installation, verify that the actuator code matches the connection diagram to avoid potential damage or dangerous situations. Actuators consume energy only during opening or closing due to internal position switches.

2-Point AW1 DC Electric Actuator

Connecting the control wire (blue) opens the valve in 6 seconds. Once the control wire shuts down, the valve closes in 6 seconds, consuming energy only during these actions.

Figure 4: Wiring diagram for a 2-point DC electric actuator

3-Point AW1 AC Electric Actuator

Connecting the blue control wire opens the valve in 16 seconds. Connecting the brown control wire closes the valve in 16 seconds. With both control wires disconnected, the valve remains in the current position. Never connect both control wires simultaneously to prevent actuator damage. The actuator consumes energy only during opening and closing.

Figure 5: Wiring diagram for a 3-point AC electric actuator

2-Point AW1 AC Electric Actuator

Connecting the control wire (black) opens the valve in 16 seconds. Once the control wire shuts down, the valve closes in 16 seconds, consuming energy only during these actions.

Figure 6: Wiring diagram for a 2-point AC electric actuator

3-Point AW1 DC Electric Actuator

Connecting the brown control wire closes the valve in 6 seconds. Connecting the black control wire opens the valve in 6 seconds. If both control wires are connected, the valve remains in its current position. Never connect both control wires simultaneously to prevent damage. The actuator consumes energy only during opening and closing.

Figure 7: Wiring diagram for a 3-point DC electric actuator

Standards

IP Protection Grade (IEC 60529)

Electric valve actuators have an IP (ingress protection) rating, indicating their protection against dust, water, and environmental hazards. For instance, the IP 54 rating of AW series ball valve actuators indicates partial protection from dust and water spray.

Duty Type (IEC 60034-1)

This international IEC standard for rotating electric devices specifies the duty type and duty cycle for electric motors in actuators. An actuator rated S2 30min can operate continuously for 30 minutes before requiring a cool-down period.

ATEX

ATEX directives indicate which equipment can operate safely in explosive atmospheres. ATEX-certified actuators are explosion-proof in specified environments.

Low Voltage Directive (LVD) 2014/35/EU

LVD certification ensures that low voltage electrical equipment like actuators provides sufficient protection for users.

Electromagnetic Compatibility (EMC) 2014/30/EU

EMC-certified actuators neither generate nor are affected by electromagnetic disturbances.

Material

Actuator components are housed in compact enclosures made of materials like plastic and aluminum. Special applications might require other materials.

Electric Valve Actuator Applications

Electric quarter-turn actuators are used for remotely controlling ball and butterfly valves, providing automated control and sufficient torque for high-torque valves. They are prevalent in industrial automation, irrigation, water supply, fluid dosing, heating systems, and fluid transportation.

Electric Valve Actuator Selection Criteria

• Torque
• Power
• Valve mounting compatibility
• Temperature
• IP rating
• ATEX requirement
• Fail-safe
• Modulation
• Duty type and duty cycle

FAQ

How to Wire and Install Electric Valve Actuators?

Installation and wiring methods for electric actuators vary by model. Detailed wiring and installation instructions for the AW and AG series actuators can be found here.

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