We know that the torque required for valve opening and closing determines the output torque of the precision electric actuator. Generally, it is proposed by the user or selected by the valve manufacturer. As a precision electric actuator manufacturer, it is only responsible for the output torque of the actuator. The torque required for normal valve opening and closing is determined by factors such as valve diameter size and working pressure, but there are differences in processing accuracy and assembly technology among valve manufacturers.
1.Torque magnitude
For valves with a 90 degree rotation, such as ball valves, disc valves, and plug valves, the corresponding valve torque is obtained from the valve manufacturer. Most valve manufacturers test the required operating torque of the valve at rated pressure and provide this torque to customers. For multi turn valves, the situation is different. These valves can be divided into: reciprocating (lift) motion - valve stem non rotation, reciprocating motion - valve stem rotation, non reciprocating - valve stem rotation. The diameter of the valve stem must be measured, and the size of the valve stem connection thread determines the actuator specification.
2.Drive energy
The commonly used driving energy sources are power sources or fluid sources. If a power source is chosen as the driving energy source, a three-phase power source is generally used for large-sized valves, while a single-phase power source can be used for small-sized valves. Generally, electric actuators can have multiple types of power sources to choose from. Sometimes DC power supply is also optional, and in this case, power failure safe operation can be achieved by installing batteries. There are many types of fluid sources. Firstly, they can be different media such as compressed air, nitrogen, natural gas, hydraulic fluids, etc. Secondly, they can have various pressures. Thirdly, the actuator has various sizes to provide output force and torque.
3.Valve type
When choosing a valve actuator, it is necessary to know the type of valve in order to select the correct actuator type. Some valves require multi turn drive, some require single turn drive, and some require reciprocating drive, which affect the selection of actuator types. Usually, multi turn pneumatic actuators are more expensive than electric multi turn actuators, but reciprocating linear output pneumatic actuators are cheaper than electric multi turn actuators.
4.Selection of execution mechanism
Once the type of actuator and the required driving torque for the valve are determined, the data sheet or selection software provided by the actuator manufacturer can be used for selection. Sometimes the speed and frequency of valve operation also need to be considered.
The fluid driven actuator can adjust the stroke speed, but the electric actuator with three-phase power supply only has a fixed stroke time. Some small-sized DC electric single turn actuators can adjust their travel speed.
