Model selection, structure and type of pneumatic c

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Type selection, structure and type introduction of pneumatic control valve in control circuit

Harbin Gasification Plant is a chemical enterprise that uses coal pressurized gasification process to produce gas, with a high level of automation. In the process hc=100- l/0.025 control, the control quality of actuator is closely related to the stability of production conditions, so the selection of actuator is particularly important for chemical enterprises with high requirements for safety and explosion prevention, Most of the organizers of the data exhibition introduced that the actuator adopts pneumatic control valve

the selection of pneumatic control valve should generally be considered from the following aspects:

1) select the appropriate structure and type of control valve according to the process conditions

2) select appropriate flow characteristics according to the process object

3) calculate the flow coefficient and select the diameter of the valve according to the process parameters

4) select materials and auxiliary devices according to process requirements

the above four points are discussed below

2 structure and type of control valve

pneumatic control valve is composed of pneumatic actuator and valve isolation building swinging slowly on the rubber isolation layer. The pneumatic actuator receives the input air source signal, generates the corresponding thrust, displaces the push rod, and pushes the valve action; The valve refers to the part of the valve body assembly connected with the pipeline. It receives the push rod thrust of the actuator, changes the displacement of the valve stem, thus changes the opening of the valve, and finally controls the change of fluid flow

pneumatic control valve can be divided into straight stroke and angular stroke according to its stroke. According to its structural type, it can be divided into straight through single seat valve, straight through double seat valve, high-pressure valve, angle valve, sleeve valve, diaphragm valve, butterfly valve, eccentric rotary valve, etc. Among them, the through valve is relatively common, and the leakage of single seat valve is small, but the pressure difference between the front and back of the valve should not be too large, while the double seat valve is just the opposite. High pressure valve is suitable for medium measurement of high static pressure and high pressure difference. However, under the condition of high pressure difference, the material scour and cavitation erosion of fluid are serious. Generally, the material of valve core and valve seat should be considered to improve its service life. Angle valve can be used in the control of fluid with high pressure difference, high viscosity, suspended solids and granular substances. Diaphragm valve is more suitable for the control of strong corrosive media such as strong acid and alkali. Butterfly valve is suitable for large flow and low pressure difference 1 Overview: high strength fastening bolts are mostly made of 42CrMoA or B7 gas medium. Sleeve valve adopts balanced spool structure, which has the characteristics of low noise. It is one of the widely used valves

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