How to select a pneumatic control valve?

It is not easy to get started and involves a wide range of knowledge. The quality of selection is directly related to vital issues such as the service life, accuracy and craftsmanship of the regulating valve. If you need to choose a regulating valve, I can help you choose it. Call me (ID name)

If you want to know more. The following is forwarded--The general principles that should be followed when selecting a regulating valve are as follows.

1. Structural type of regulating valve: it should be able to meet the requirements of medium temperature, pressure, fluidity, flow direction, adjustment range and tightness.

2. The flow characteristics of the regulating valve: it should be able to meet the system characteristics for reasonable compensation.

The flow characteristics of the regulating valve refer to the relationship between the relative flow rate of the medium flowing through the valve and the relative displacement of the valve stem. The mathematical expression is as follows: Q/Qmax=f (l/L), where Q/ Qmax is the relative flow rate, which is the ratio of the flow rate Q and the full-open flow rate Qmax of the regulating valve at a certain opening; l/L is the relative displacement, which is the ratio of the valve core displacement l and the full-opening displacement L when the regulating valve is at a certain opening degree. .

The general principle of selection is that the flow characteristics of the regulating valve should be opposite to the characteristics of the regulating object and the characteristics of the regulator, so that the comprehensive characteristics of the regulating system can be close to linear. The selection of flow characteristics is usually based on the requirements of the process system, but the following actual conditions should also be considered.

1. Applicable scope of linear flow characteristics: ① The change in differential pressure is small and almost constant; ② The changes in the main parameters of the process flow are linear; ③ Most of the system pressure loss is distributed on the regulating valve (changing the opening degree, the change of differential pressure on the valve is relatively small); ④ The external interference is small, the change of the given value is small, and the adjustable range requirement is small.

2. The applicable range of equal percentage characteristics: ① The actual adjustable range is large; ② When the opening changes, the differential pressure on the valve changes relatively large; ③ The pressure loss of the pipeline system is large; ④ The process system load fluctuates significantly ;⑤ The regulating valve often operates at a small opening.

3. In addition to the above two commonly used flow characteristics, there are also control valves with other flow characteristics such as parabolic characteristics and quick-opening characteristics.

3. The caliber of the regulating valve: it should be able to meet the flow requirements of the process.

Based on the known fluid conditions, calculate the necessary Kv value and select the appropriate regulating valve diameter.