The composition and classification of regulating valve
The regulating valve, also known as the control valve, is the main type of actuator. It changes the fluid flow by means of power operation by accepting the control signal output by the regulating control unit. The regulating valve generally consists of an actuator and a valve. According to the power used by the actuator, the regulating valve can be divided into three types: pneumatic, electric and hydraulic, namely the pneumatic regulating valve using compressed air as the power source, the electric regulating valve using electricity as the power source, and the liquid medium (such as oil, etc.) pressure-driven electro-hydraulic control valves, in addition, according to their functions and characteristics, there are solenoid valves, electronic, intelligent, fieldbus control valves, etc. There are many product types and structures of regulating valves, and they are constantly updated and changed. Generally speaking, the valve is universal, which can be matched with pneumatic actuators, electric actuators or other actuators.
2 Choice of control valve type
2.1 Valve body type selection of regulating valve The selection of valve body is a very important part in the selection of regulating valve.
There are many types of regulating valve bodies, commonly used are straight-through single-seat, straight-through double-seat, angle, diaphragm, small flow, tee, eccentric rotation, butterfly, sleeve, spherical, etc. 10 kinds. Before selecting a valve, it is necessary to carefully analyze the medium, process conditions and parameters of the control process, collect enough data, understand the requirements of the system for the regulating valve, and determine the type of valve to be used according to the collected data. In the specific selection, the following aspects can be considered:
(1) The shape and structure of the valve core are mainly considered according to the selected flow characteristics and unbalanced force.
(2) Wear resistance When the fluid medium is a suspension containing a high concentration of abrasive particles, the valve core and valve seat joint surface will be severely rubbed every time they are closed. Therefore, the flow path of the valve should be smooth, and the inner material of the valve should be hard.
(3) Corrosion resistance Since the medium is corrosive, in the case of satisfying the adjustment function, try to choose a valve with a simple structure.
(4) The temperature and pressure of the medium When the temperature and pressure of the medium are high and the change is large, the valve core and valve seat material should be selected with small changes in temperature and pressure.
(5) Prevent flash evaporation and cavitation Flash evaporation and cavitation only occur in liquid media. In the actual production process, flash evaporation and cavitation not only affect the calculation of the flow coefficient, but also form vibration and noise, which shortens the service life of the valve. Therefore, the valve should be prevented from flashing and cavitation when selecting the valve.