The working principle of automatic control valves

Control wiring diagram _ valve control valve works: for control valves, the related research mostly focused on the active control, and the study of passive control is less, the passive control valve means without external power can realize the automatic control valve, the passive control valve is also referred to as a purely mechanical control valve, it has a high degree of automation, energy saving effect is good, easy to use, simple process equipment, etc. Based on the above, this paper briefly discusses the amount of pure mechanical automatic control valve design and control principle. An overview, purely mechanical automatic control valves in essence, the purely mechanical automatic control valve is a kind of without external power supply can realize the automatic control valve, the passive control valve, purely mechanical control valve research began in the 1980 s, L. Ornstein, a professor of design a called Irristat valve, the valve is a purely mechanical control valve, which has been widely applied in the water-saving irrigation of agriculture. When the soil moisture content to the expected value, the water will enter into valve, the valve internal gel, press the piston, decrease the pipe sectional area, so as to realize the control of water use [ 1] 。 And when the soil moisture content is lower than the preset value, the moisture in practice will return to the soil, the piston lose up under pressure, water flow, so as to realize the automatic control of the water flow. Second, the purely mechanical design of automatic control valve ( A) Purely mechanical automatic control valve design train of thought in this paper, on the basis of Irristat valve, soil water tension as the main design principle. Irristat automatic control valve is mainly by water balance principle, with the help of vacuum pressure gauge readings, tension meter can monitoring the soil moisture, and on the basis of the monitoring results to achieve the automatic control of the valve. In the process of the entire control, tension meter is equivalent to a soil temperature sensors, Irristat swell valve through internal gel and to judge the moisture in the soil water loss contraction, thus to realize the automatic control of the water flow through valve, to realize the automatic irrigation, not to need the computer and sensors, belongs to a kind of no derived from control valves, by purely mechanical valve automatic control [ 2] 。 （ 2) Purely mechanical automatic control valve structure design of the structure mainly includes the control element, two springs ( A buffer spring spring 1, a reset spring is spring 2) , water inlet and two outlet, through spring 1 to push the valve core is moving, when the conical surface blocking water inlet valve core, the valve closed, irrigation to stop, move backward across 2 can push valve valve core, sealed water inlet valve core of conical surface will gradually retreat, so as to realize gradually open the valve water entry, irrigation.