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24

2023

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04

Valve driven hydraulic actuator - Selection considerations 1

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【Summary description】The size of the swing angle determines the parameters during design. That is to say, the maximum swing angle of a selected manufacturer or structural actuator has been determined. So it mainly depends on whether the maximum swing angle can meet the application requirements. For example, if the full open angle of a butterfly valve is 90 degrees, choosing an actuator with a maximum angle of 94 degrees can basically meet its requirements

As a hydraulic actuator for controlling valve switches, regardless of the structure, the selection time should follow the following precautions: 1. The size of the swing angle; 2. Output torque and working pressure; 3. Starting pressure and internal leakage; 4. Cushioning and braking, etc. Below is a brief description of 1/2 points.

1: Swing angle size

Generally speaking, the size of the swing angle determines the parameters during design. That is to say, the maximum swing angle of a selected manufacturer or structural actuator has been determined. So it mainly depends on whether the maximum swing angle can meet the application requirements. For example, if the full opening angle of a butterfly valve is 90 degrees, choosing an actuator with a maximum angle of 94 degrees can basically meet its requirements. Assuming that a certain valve only needs to be opened 70 degrees to meet the requirements, when we select a group of actuators with a maximum angle of 94 degrees, one solution is to match the travel switch. When the angle is turned to 70 degrees, the travel switch triggers an action to stop or reverse the action. For example, the following image.

 

Of course, there are other solutions, such as matching an angle sensor. When the angle is turned to the set angle parameter, the sensor triggers to achieve action control.

2: Output torque and working pressure

The output torque and working pressure are also parameters that are determined at the time of product structure design. The output torque mainly depends on the pressure supplied by the system and the mechanical efficiency of the actuator. Before selecting the output torque, there are several things to understand:

The torque required for valve control to open and close, generally speaking, the valve manufacturer needs to conduct experiments to obtain accurate parameters. So first, it is necessary to understand whether this parameter is theoretical or actually required.

For example, when calculating the opening torque of butterfly valves, it is basically to calculate the friction torque between the sealing components, the friction torque between the packing and the valve stem, and the friction torque between the bearing and the valve stem; In addition, the torque caused by the load and the torque required to make the load obtain angular acceleration. These calculations are also complex or inaccurate, and the torque obtained from experimental testing is a relatively accurate parameter. In actual parameters, the principle of selecting a simple coefficient of valve opening torque X1.3-1.5 is used to select actuator parameters.

Assuming that the actual obtained butterfly valve opening torque parameter is 700 Nm, follow the principle of simple parameters. 700X1.3-1.5=910-1050 Nm. We selected an actuator of 1000 Nm to meet the requirements. As shown in the following figure

Another issue to note is whether the system supply pressure meets the requirements, for example, 1000 Nm of torque is the system working pressure of 150 Bar If the system pressure meets this condition, the output torque of the actuator cannot reach the required torque of 1000 Nm. If the on-site pressure of 150 kilograms cannot be provided, the actual pressure and the manufacturer's parameters should be referred to for selection. Generally, manufacturers have similar parameters as follows:

Assuming that only 80Bar pressure can be provided on site, in order to meet the parameter of 1000 Nm, it is necessary to select 200 series products.

In addition, it is necessary to refer to the ISO5211 parameters to see the flange specifications of the valve or actuator. The flange specifications must at least meet the requirements for flanges above F12.