When it comes to electric valve actuators, there are a few things you need to take into account to ensure you're choosing the right one for the job. In this blog post, we'll run through what you need to consider, from the application requirements to the environment the actuator will be used in. By the end, you'll be equipped with the knowledge you need to choose the perfect electric valve actuator for your needs.
Identify the application requirements
When choosing electric valve actuators, the first step is to identify the application requirements. This will ensure that you select a product that is fit for purpose and will meet the needs of your specific application.
There are a few key considerations to bear in mind when identifying the requirements for your application, including:
The type of medium that will be flowing through the valve (e.g. water, air, oil, gas, etc.)
The operating conditions (e.g. temperature, pressure, flow rate)
The required control signal (e.g. 4-20mA, 0-10V)
The power supply available (e.g. 24Vdc, 110Vac)
Once you have considered all of these factors, you will be able to narrow down your search and choose an electric valve actuator that is suitable for your application.
Select the proper output
When choosing electric valve actuators, one of the most important considerations is the type of output required. There are three main types of output: linear, rotary and scotch yoke. Each has its own advantages and disadvantages, so it is important to select the one that is best suited to the application.
Linear actuators are the most common type of electric valve actuator. They produce a linear force, which is then converted into torque by the actuator. Linear actuators are typically used for applications where a high degree of accuracy is required, such as in control valves. They are also relatively compact and have a high power-to-weight ratio.
Rotary actuators are less common than linear actuators, but they offer some advantages over their linear counterparts. Rotary actuators produce a rotating force, which can be used to directly drive a valve or other load. This type of actuator is often used in larger valves or where a high degree of torque is required.
Scotch yoke actuators are the least common type of electric valve actuator. They use a reciprocating motion to generate torque, rather than a rotating or linear force. Scotch yoke actuators are typically used in very large valves or where an extremely high degree of torque is required.
Calculate the required torque
The required torque for an electric valve actuator is dependent on a number of factors, including the type of actuator, the size of the valve, and the application.
Linear actuators typically require less torque than rotary or scotch yoke actuators, as they produce a linear force that is converted into torque by the actuator. The required torque for a linear actuator is typically calculated using the following equation:
T = F * r
where:
T = required torque (Nm)
F = applied force (N)
r = radius of rotation (m)
For rotary actuators, the required torque is typically calculated using the following equation:
T = F * r * sin(θ)
where:
T = required torque (Nm)
F = applied force (N)
r = radius of rotation (m)
θ = angle of rotation (radians)
Scotch yoke actuators typically require more torque than linear or rotary actuators, as they use a reciprocating motion to generate torque. The required torque for a scotch yoke actuator is typically calculated using the following equation:
T= F * r * sin(θ/2)^2
where: T= required torque (Nm), F= applied force (N), r= radius of rotation (m), and θ= angle of rotation (radians).
Consider the environment
When selecting an electric valve actuator, it is important to consider the environment in which it will be used. Factors such as temperature, humidity and vibration can all affect the performance of the actuator.
Temperature is a particularly important consideration, as extreme temperatures can cause the actuator to fail. The maximum and minimum operating temperatures of the actuator should be within the range of the expected temperature extremes in the application.
Humidity can also affect the performance of electric valve actuators. High humidity levels can cause corrosion, while low humidity levels can cause the actuator to become dry and brittle.
Vibration can also adversely affect electric valve actuators. Vibrating loads can cause wear and tear on the actuator, leading to premature failure.