Control valves are composed of two main components: valve body assembly and actuator assembly (or actuation system), which are divided into four series: single seat control valve, double-seated series control valves, sleeve series control valves, and self operated control valve. Variations of the four types of valves can lead to many different applicable structures, each with its own special applications, characteristics, advantages, and disadvantages. Although some control valves have broader application conditions than other valves, control valves cannot be applied to all conditions. The best solution to build performance and reduce costs together.
Control valves have various types, and their application conditions are different. Therefore, control valve types should be selected reasonably according to the requirements of the process production process.
Pneumatic control valves are divided into two categories: air-open and air-close. The air-open control valve closes in case of failure, and the air-close control valve opens in case of failure. Some auxiliary equipment can be used to form a position protection valve or make the control valve self-locking, which means the control valve maintains the valve opening before the failure.
The air-open and air-close methods can be realized through the combination of positive and negative executing mechanism types and positive and negative body valves. When using a valve positioner, it can also be achieved through the valve positioner.
Different types of control valve structures have different characteristics. Utmost control valve factory can customize all selections of control valves according to your demands.
Control valves have the characteristics of simple structure and reliable operation, but because they are in direct contact with the process medium, their performance directly affects system quality and environmental pollution. Therefore, control valves must be maintained regularly and checked regularly. Maintenance work should be pay more attention to the conditions with harsh working conditions and important occasions. Key inspection areas:
Valve body inner wall
For control valves used in high differential pressure and corrosive medium environments, the valve body inner wall and the diaphragm of the diaphragm valve are often impacted and corroded by the medium, so the pressure-resistant and corrosion-resistant conditions must be checked.
When the control valve is working, the fixed valve seat is easily corroded due to the infiltration of the medium, and attention should be paid to inspection. For valves that work under high differential pressure, the sealing surface of the valve seat should also be checked to ensure that there is no damage.
The valve stem is a movable component in the working process. It is most severely affected by medium erosion and corrosion. Check whether each part of the valve stem is corroded or worn carefully during maintenance, especially when the valve stem is severely worn under high differential pressure (due to cavitation phenomenon), attention should be paid. When the valve stem is severely damaged, it should be replaced. In addition, attention should be paid to whether the valve stem is similar to the phenomenon of connection with the valve stem, or whether it is loose.
"O"-ring and other sealing gaskets. Check whether the diaphragm and "O"-ring sealing gasket in the control valve are aged or cracked.
Attention should be paid to whether the polytetrafluoroethylene filler and sealing lubricating grease are aging, whether the matching surface is damaged, and should be replaced if necessary. The regulating valve, also known as the control valve, is the main type of actuator. By accepting control signals output from the control unit, the flow rate of the fluid is changed through dynamic operation. The regulating valve generally consists of an actuator and a valve. If the power used by its equipped actuator is used, the regulating valve can be divided into three types: pneumatic, electric, and hydraulic, that is, pneumatic regulating valve with compressed air as the power source, electric regulating valve with electric power source, electric liquid regulating valve using liquid medium (such as oil) pressure as the power source. In addition, according to its function and characteristics, there are also electromagnetic valves, electronic, intelligent, and fieldbus-type regulating valves.