Control valve control valve is also called, is the main type of actuator, control unit regulating the output by receiving the control signal, using power-operated to change the fluid flow. Regulating valve and valves are generally composed of the implementing agencies. If you press it with the implementing agencies to use power, control valve can be divided into pneumatic, electric, hydraulic three kinds, namely, the source of compressed air-powered pneumatic control valve, to electric power source for electric control valve in order to liquid medium (eg oil) pressure-powered electric hydraulic control valve addition, according to their functions and features points, as well as solenoid valves, electronic, intelligent, fieldbus-type regulating valve.
Control Valve Body type selection
Many different types of control valve body, often there are through single-seat, through two-seater, angular, diaphragm, small flow, three-, eccentric rotation, butterfly, sleeve type, ball and so on. Specific selection, do the following considerations:
(1)阀芯中形结构
Mainly based on the selected traffic characteristics and take into account factors such as unbalanced force.
(2) The wear resistance
When the fluid medium that contain high concentrations of abrasive particles in suspension, the valve's internal materials to be hard.
(3) corrosion resistance
As the medium is corrosive, as we choose simple valve.
(4) medium temperature, pressure,
When the medium temperature and pressure variation in high and when the valve core and valve seat should use the material by the temperature and pressure changes in the small valve.
(5) Prevention of flashing and cavitation
Flashing and cavitation produced only in liquid medium. In the actual production process, the flashing and cavitation will form vibration and noise, shorten the life of the valve, so the choice should be to prevent the valve produces flash valve and cavitation.
Control valve selection of implementing agencies
In order to control valve to work, with executive body used to be able to generate sufficient output power to ensure a high degree of sealing and the valve opening.
For the double-acting pneumatic, hydraulic, electric actuator, generally do not reset spring. The size of the force direction has nothing to do with its operation, therefore, selecting executing agencies is the key to understand the maximum output power and the motor rotational torque. For single role of the pneumatic actuator, the output force and the opening of the valve, regulating valve on the emergence of the force will also affect the motion characteristics, thus requiring the entire range of control valve opening to establish the force balance.
Implementing agencies to determine the type of
Output force of the implementing agencies to determine, based on the use of environmental requirements, process, select the appropriate enforcement agency. For the scene, where explosion-proof requirements, should use pneumatic actuator. From the energy-saving considerations, should try to use electric actuator. If the adjustment of high precision, optional hydraulic enforcement agency. Speed machines such as power plants and transparent regulation, the refinery's catalytic cracking unit reactor temperature adjustment control.
Mode of action of regulating valve selection
Mode of action of control valve selection of pneumatic actuator only when they left, their mode of action through the pros and cons of the role of implementing agencies and valve combination of positive and negative role in the formation. There are four kinds of combination that is precisely (gas off type), the pros and cons (gas open type), anyway (gas open type), anti-anti-(gas off type), through the formation of these four combined mode of action of a gas control valve Open off two kinds of gas. For the choice of mode of action of control valve, the main three-pronged approach to consider: a) process production safety; b) characteristics of the medium; c) to ensure product quality, minimize economic losses.
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