Valve Actuators
Valve actuators are mounted on valves and use an external power source to move a valve to the desired position in response to a signal. Choosing the right valve actuator helps enhance plant uptime, save maintenance costs, and improve plant safety.
Most valve actuators are permanently maintained and perform best when properly selected and installed.
As per the Method of Actuation, the valve actuators are classified into four types: manual, electric, pneumatic, and hydraulic. They can also come with location-sensing technology, digital communication capabilities, and motor protection.
- Manual valve actuators do not usually require electricity. They utilize a handwheel or lever to operate a set of gears, the ratio of which produces a larger output torque than the input (manual) torque.
- Electric valve actuators in order to create the appropriate torque level, employ a single-phase or three-phase alternating current (AC) or direct current (DC) motor to drive a set of gears.
- Pneumatic valve actuators by translating air pressure into linear or rotational motion, change the position of a valve.
- Electrohydraulic valve actuators and hydraulic valve actuators similarly, transform the supply of fluid pressure into linear or rotational motion.
Chart Credit: Wikipedia.
|
Actuator Type |
Advantages |
Disadvantages |
|
Mechanical |
Cheap. Repeatable. No power source required. Self-contained. Identical behavior extending or retracting. |
Manual operation only. No automation. |
|
Electro-mechanical |
Cheap. Repeatable. Operation can be automated. Self-contained. Identical behavior extending or retracting. DC or stepping motors. Position feedback possible. Can be remotely controlled. |
Many moving parts prone to wear. |
|
Linear motor |
Simple design. Minimum of moving parts. High speeds possible. Self-contained. Identical behavior extending or retracting. |
Low force. |
|
Piezoelectric |
Very small motions possible. |
Requires position feedback to be repeatable. Short travel. Low speed. High voltages required. Expensive. Good in compression only, not in tension. |
|
Hydraulic |
Very high forces possible. |
Can leak. Requires position feedback for repeatability. External hydraulic pump required. Some designs perform well in compression only. |
|
Pneumatic |
Strong, light, simple, fast. |
Precise position control impossible except at full stops |
