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How to Select and Maintain Control Valves

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Jeawin Huang
How to Select and Maintain Control Valves

The control valve is the actuator in the automatic control system, and its quality directly affects the control quality of the whole system. As a terminal component in the process control, people have an updated understanding of its importance. The quality of the product itself will affect the application of the control valve. And whether the valve is properly installed, used and maintained will also affect its application. In addition, it is also important to select an appropriate control valve. If the control valve is not suitable for the system, it may cause the system to work intermittently and even make the system unusable.
Selection of Control Valves

1. According to the conditions of processing, select the control valve with appropriate structure, such as ball valves, butterfly valves. At the same time, pay attention to the material of the valve to prevent the valve from being easily damaged during use.

2. According to the features of the process, select the control valve with appropriate flow characteristics. 

3. According to the operating parameters of the process, select the control valve with a proper caliber. 

4. According to the requirements of the process, select the required auxiliary device.

5. Select the appropriate actuator, and the response speed of the actuator should be able to meet the requirements of the system. 

The selected control valve should be able to meet the requirements of valve stroke and process for the leakage class. In some cases, if the pressure control valve is to be selected, proper increase in the actual possible differential pressure should be considered, that is, the actuator is required to provide a large force. Otherwise, when there is an abnormal situation in the process and the actual differential pressure of the control valve is large, the risk that the valve can not be opened or closed may occur.

Maintenance of the Control Valve

The control valve is in direct contact with the medium and its performance directly affects the efficiency of the whole system, so the control valve must be maintained regularly. Here are some valve parts that should be inspected emphatically.

1. Inner surface of the valve body: If the medium in the valve is corrosive, the inner surface of the valve body and the diaphragm of the diaphragm valve will often be corroded by the medium, so the anti-corrosion of the valve must be checked emphatically.

2. The valve seat: When the control valve is working, the inner surface of the screw thread used to fix the valve seat is easy to be corroded due to the seepage of the medium. For valves working at high differential pressure, the sealing surface of the seat should also be checked for damage.

3. Spool: The spool is most vulnerable to the impact and corrosion of the medium, and it is necessary to carefully check whether each part of the spool is corroded and worn when the valve is maintained. The spool working at high differential pressure is worn more seriously due to cavitation. And the spool should be replaced when it is damaged seriously.

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Jeawin Huang
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