The control valve consists of two main assemblies: valve body assembly and actuator assembly (or actuator system), which are divided into four series: single-seat series control valve, double-seat series control valve, sleeve series control valve and self-operated series control valve. Variations of the four types of valves can lead to many different applicable configurations, each with its own specific applications, features, advantages and disadvantages. While some control valves are used in a wider range of applications than others, control valves are not suitable for all applications to work together to create the best solution for enhanced performance and reduced cost.
(1) There are various types of control valves, and their applicable occasions are different. Therefore, the type of control valve should be reasonably selected according to the requirements of the technological production process.
(2) Pneumatic control valves are divided into two types: air-on and air-off. The air-to-open control valve is closed in a fault state, and the air-to-close control valve is opened in a fault state. Some auxiliary equipment can be used to form a retaining valve or make the control valve self-locking, that is, the control valve maintains the valve opening before the failure when the fault occurs.
(3) The way of air opening and air closing can be realized by the combination of positive and negative actuator types and positive and negative valves. When using a valve positioner, it can also be realized by a valve positioner.
(4) Various control valves have different structures and have their own characteristics.
There are many types of valve bodies for control valves. Common control valve types include straight-through single-seat, straight-through double-seat, angle, diaphragm, small flow, three-way, eccentric rotation, butterfly, sleeve, spherical, etc. When making specific choices, consider the following:
(1) It is mainly considered according to the selected flow characteristics and unbalanced force.
(2) When the fluid medium is a suspension containing a high concentration of abrasive particles, the internal material of the valve should be hard.
(3) Since the medium is corrosive, try to choose a valve with a simple structure.
(4) When the temperature and pressure of the medium are high and the change is large, the material of the valve core and the valve seat should be selected with a small change in temperature and pressure.
(5) Flash evaporation and cavitation only occur in liquid media. In the actual production process, flashing and cavitation will form vibration and noise, which will shorten the service life of the valve. Therefore, the valve should be prevented from flashing and cavitation when selecting the valve.
The hydraulic water level control valve has the function of automatically opening and closing the valve pipeline to control the water level. It is suitable for the automatic water supply system of various water towers (pools) in industrial and mining enterprises and civil buildings, and can be used as a circulating water supply control valve for atmospheric boilers. The valve is small in size, easy installation, high activation sensitivity, small head loss, no water hammer phenomenon, controlled by small floating balls can greatly improve the utilization rate of the water tower, for the newly built water tower, due to the reduction in the volume of the floating ball, the upper part of the water tower is left for the floating ball to float freely, and the required height is reduced to reduce the cost of the water tower to overcome the disadvantages of the old screw float valve, such as large size, easy damage, low working pressure, and a large amount of overflow.