Selection of valve type of regulating valve of Shanghai Yi Fan Valve Manufacturing Co., Ltd.
There are many kinds of valves for regulating valves. There are many kinds of valves commonly used, such as straight through single seat, straight through double seat, angular, diaphragm, small flow, three way, eccentric rotation, butterfly shape, sleeve type, ball and so on. In the specific choice, the following consideration can be made:
(1) the shape structure of the valve core
It is mainly considered according to the selected flow characteristics and unbalance force.
(2) wear resistance
When the fluid medium is a suspension containing high concentration of abrasive particles, the internal material of the valve should be hard.
(3) corrosion resistance
As the medium is corrosive, choose the simple valve as far as possible.
(4) the temperature and pressure of the medium
When the temperature and pressure of the medium are high and varied, the valve with small change in temperature and pressure should be selected for the material of the valve core and the valve seat.
(5) prevention of flash and cavitation
Flash and cavitation are produced only in liquid medium. In the actual production process, flash and cavitation will form vibration and noise, shorten the service life of valves, so we should prevent flashing and cavitation of valves when selecting valves.
Selection of regulating valve actuator
In order to make the valve work properly, the actuating actuator is able to produce enough output to ensure the high seal and valve opening.
For double acting pneumatic, hydraulic and electric actuators, there is generally no reset spring. The size of the force has nothing to do with the direction of its operation, so the key to the selection of the actuator is to find out the maximum output force and the torque of the motor. For a single acting pneumatic actuator, the output force is related to the opening of the valve. The force on the regulating valve will also affect the motion characteristics, so we need to establish the balance of force in the opening range of the control valve.
Determination of the type of executive organization
After determining the output power of the executing agency, the corresponding executing agency should be selected according to the requirements of the process environment. The pneumatic actuator should be selected when the site has explosion-proof requirements. In terms of energy saving, the electric actuator should be chosen as far as possible. If the adjustment precision is high, the hydraulic actuator can be selected. Such as the speed regulation of the transparent machine in the power plant, the temperature regulation and control of the catalytic reactor of the refinery.
Selection of function mode of regulating valve
The action way of regulating valve is only when selecting pneumatic actuator, and its action mode is formed through the positive and negative actions of actuator and the positive and negative actions of valve. There are 4 combinations: positive (air close), positive and negative (gas open), reverse (gas open), reverse reverse (gas shut type). Through these four combinations of regulating valves, there are two ways to control valves. The choice of the action mode of the regulating valve is mainly considered from three aspects.
A) process production safety;
B) the properties of the medium;
C) guarantee the quality of the product and the minimum economic loss
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