Electric driven multi turn actuators are one of the commonly used and reliable types of actuators. Using a single-phase or three-phase motor to drive gears or worm gears and drive the valve stem nut, the valve stem nut moves the valve stem to open or close the valve.
Multi turn electric actuators can quickly drive large-sized valves. In order to protect the valve from damage, the limit switch installed at the end of the valve stroke will cut off the motor power supply. At the same time, when the safety torque is exceeded, the torque sensing device will also cut off the motor power supply. The position switch is used to indicate the on/off status of the valve. The handwheel mechanism installed with the clutch device can manually operate the valve in case of power failure.
The main advantage of this type of actuator is that all components are installed in one housing, which integrates all basic and advanced functions within this waterproof, dustproof, and explosion-proof shell. The main disadvantage is that in the event of a power failure, the valve can only remain in its original position, and only with the use of a backup power system can the valve achieve a fail safe position (fail open or fail closed)
2. Electric single rotary actuator
This type of actuator is similar to an electric multi turn actuator, with the main difference being that the actuator outputs a motion of 1/4 turn to 90 degrees. The new generation of electric single turn actuators combines the complex functions of most multi turn actuators, such as parameter setting and diagnostic functions using a non intrusive user-friendly interface.
The single turn actuator has a compact structure and can be installed on small-sized valves, with a typical output torque of up to 800 kilograms per meter. Additionally, due to the small required power supply, they can be equipped with batteries to achieve safe operation in case of failure.
3. Fluid driven multi turn or linear output actuators
This type of actuator is often used to operate straight through valves (globe valves) and gate valves, which use pneumatic or hydraulic operation methods. The structure is simple, the work is reliable, and it is easy to implement a fault safe operation mode.
Usually, people use electric multi turn actuators to drive gate valves and globe valves, and only consider using hydraulic or pneumatic actuators when there is no power supply.
4. Fluid driven single rotary actuator
Pneumatic and hydraulic single turn actuators are very versatile, they do not require power and have a simple structure with reliable performance. They have a wide range of applications. Usually, the output ranges from a few kilograms of meters to tens of thousands of kilograms of meters. They use cylinders and transmission devices to convert linear motion into right angle output. The transmission devices usually include forks, gears and racks, and levers. Gears and racks output the same torque throughout the entire stroke range, making them highly suitable for small-sized valves. Forks have high efficiency and high torque output at the beginning of the stroke, making them ideal for large-diameter valves. Pneumatic actuators are generally equipped with accessories such as solenoid valves, positioners, or position switches to control and monitor valves.
This type of actuator is easy to implement a fail safe operating mode.