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Detailed pneumatic control valve principle and maintenance instructions


Release time:

2021-07-22

Pneumatic control valveIt uses compressed air as the power source, uses the cylinder as the actuator, and uses the electric valve positioner, converter, solenoid valve, holding valve and other accessories to drive the valve to complete the switch or proportional adjustment, and receives the control signal of the industrial automation control system to complete the adjustment of the flow rate, pressure, temperature and other process parameters of the pipeline medium. Pneumatic control valve is characterized by simple control, rapid response, and intrinsically safe, no need to adopt other explosion-proof methods.

Detailed pneumatic control valve principle and maintenance instructions

Pneumatic control valveIt uses compressed air as the power source, uses the cylinder as the actuator, and uses the electric valve positioner, converter, solenoid valve, holding valve and other accessories to drive the valve to complete the switch or proportional adjustment, and receives the control signal of the industrial automation control system to complete the adjustment of the flow rate, pressure, temperature and other process parameters of the pipeline medium. Pneumatic control valve is characterized by simple control, rapid response, and intrinsically safe, no need to adopt other explosion-proof methods.
Pneumatic control valve classification and the use of pneumatic control valve action split gas open type and gas closed type two. Air open type (AirtoOpen) is when the air pressure on the diaphragm head increases, the valve moves in the direction of increasing opening, and when the upper limit of the input air pressure is reached, the valve is fully open.
Conversely, when the air pressure decreases, the valve moves in the closed direction, and when there is no input air, the valve is fully closed. Therefore, sometimes the gas open type valve is also called the fault closed type (FailtoCloseFC).
The air-off type (AirtoClose) moves in the opposite direction to the air-on type. When the air pressure increases, the valve moves in the closed direction; when the air pressure decreases or does not, the valve moves in the open direction or fully open. Therefore, it is sometimes called the open type (FailtoOpenFO). Pneumatic control valve gas on or off, usually through the positive and negative action of the actuator and valve structure of different assembly methods to complete.
The choice of gas on and off is considered from the safety point of view of the process. When the gas supply is cut off, is the control valve in the closed position safe or the open position safe? For example, for the incineration control of a heating furnace, the control valve is installed on the fuel gas pipe to control the fuel supply according to the temperature of the furnace or the temperature of the heated material at the outlet of the heating furnace.
At this time, it is safer to choose a gas open valve, because once the gas supply is stopped, the valve is closed than the valve is fully open. If the air supply is stopped and the fuel valve is fully opened, there is a risk of excessive heating.
Another example is a heat exchange equipment cooled by cooling water. The hot material is cooled by heat exchange with cooling water in the heat exchanger. The regulating valve is installed on the cooling water pipe, and the temperature of the heat-exchanged material is used to control the cooling water volume. When the air source is stopped, the regulating valve should be in an open position and safer. Air-closed (FO) regulating valve should be selected.