Control valve is used to regulate the flow, pressure and liquid level of media. According to the regulating signals, it can automatically control the opening degree so as to achieve the regulation of flow, pressure and liquid level.
There are three classifications of control valves: electric control valve, pneumatic control valve and hydraulic control valve.
Electric control valve is an important execution unit instrumentation in the industrial automation process. As the degree of automation industry is higher and higher, it is being increasingly used in various industrial fields. Compared with conventional pneumatic control valve, electric control valve has obvious advantages: energy saving (only consumes power when working), environmental protection (carbon-free emission), quick and easy installation (without complicated pneumatic piping and pump stations).
With compressed air used as the power source and cylinder used as the actuator, pneumatic control valve is driven by means of locator, converter, solenoid valve, lock-up valve and other attachments to implement switch or proportional regulation and to receive the control signals of industrial automatic control system so as to complete the regulation of flow, pressure, temperature and other process parameters of pipeline media. Pneumatic control valve is characterized by simple control, rapid response, and intrinsic safety, without additional exploration-proof measures.
Automatic control valve can be dated back to the self-regulating valve which includes a spherical valve with a weight bar which is used to balance the spool force so as to achieve some degree of regulation .Another from of early self-regulating valve is pressure balanced control valve.
