Issues regarding the selection of pneumatic control valves and solenoid valves
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I’m just starting to work with valve selection, and I have questions regarding the air supply interface. Because for small ball valves and butterfly valves, it is sufficient to normally equip them with solenoid valves and pneumatic control valves of 1/4 NPT size. However, with angle-action valves of 300, 400, 500 or larger, the 1/4 NPT connection can sometimes be too small, and a larger connection may need to be used. What I want to ask is: when should one choose larger interfaces (by larger interfaces, I mean larger flow channels; it’s not just a matter of the interface size itself). What are the criteria for making such a decision, or based on experience, how should one choose larger solenoid valves, air-controlled valves, and other similar components? If we really delve into it, we would have to examine the CV values of these attachments, which is too detailed; or we could discuss how to choose the appropriate attachments based on their CV values.
First, calculate the cylinder torque required to open and close the valve based on the valve size, type, and pressure difference at which the valve closes. Then determine the cylinder diameter. Next, calculate the air consumption required for the valve to operate, using the cylinder diameter, stroke length, and air supply pressure. Finally, determine the size of the pneumatic control valve based on the air consumption and the frequency of operation. This is my personal understanding for reference only.
For large-diameter valves, electromagnets are not used directly for shutting off gas flow; they are merely used to control the opening and closing of solenoid valves, thereby controlling the operation of the valves themselves. For large-diameter valves, the air inlet of pneumatic control valves can be 1/2\" or 1\".
To become good at AE, one needs guidance from an experienced mentor in the early stages, as there is a lot that needs to be learned. First, understand the valve structure and gas circuit, before discussing the characteristics of valve selection for various processes. I’ve been an AE for twelve years; just passing by. . . .
For large-diameter valves (such as DN>350), or those with cylinders whose diameter is greater than 350, the small size of the air supply interface results in a slow flow rate of air; therefore, it is generally recommended to use an accelerator or to increase the size of the air supply interface (for example, by using 1/2” or 1” connections)
Strictly speaking, the selection must be based on the Cv or the flow curve of the valve.
The selection of solenoid valves should be based on the type of cylinder and the air consumption to choose the appropriate model. The air flow rate for different solenoid valves is indicated. The requirements for solenoid valves are generally higher than those for cylinders. The ventilation volume is related to the inner hole diameter.
Valve manufacturers will design the gas supply interface as needed. Just connect the piping according to the valve’s interface.