Pneumatic control valve with the common matters needing attention in the automatic control

In the automatic control of modern factory, pneumatic control valve plays a very important role, the production of the factory depends on the correct allocation and control flow of the medium. These controls both the exchange of energy, pressure reducing, or is a simple container loading. Pneumatic control valve and control valve, in the field of industrial automation process control, by accepting conditioning control unit of the output control signal, from engine operation to change the medium flow rate, pressure, temperature, liquid level of the process parameters such as the final control element. From the use function choose pneumatic - valve problems that should pay attention to 1) Regulating function requirements valve moves smoothly; (2) small open degree of good regulation performance; 3. Choose the required flow characteristic; (4) meet the adjustable ratio; 5. Small resistance, flow than the big ( The rated flow parameters of valve and the ratio of the nominal diameter) ； 6. Adjust speed. 2) Leakage and differential pressure of the cut off this is inseparable, two factors are linked to each other. Leakage should meet the technological requirements, and the reliability of the sealing surface protection measures; Cut off the pressure difference ( The differential pressure valve is closed) Must be mentioned, It is a pity that many design institute of pneumatic control valve calculation specification without this parameter) , let the selected valve have enough output power to overcome it, otherwise it will cause the executing agency to choose big or small. 3) Prevent even clean medium, congestion problems, that is not clean the pipe are medium pneumatic control valve, with mountains, this is a common failure, so the valve stem performance should be considered. Usually angular travel class of pneumatic control valve pneumatic - valve stem than straight travel class performance is much better, so the Angle of stroke after class use pneumatic control valve will be more and more. 4) Corrosion resistant it includes erosion, cavitation and corrosion resistance. Mainly involves the selection of material and the service life of the valve problem, at the same time, involved in economic problems. The essence of this problem should be selected valve has good corrosion resistance and the price is reasonable. If you can choose all the four fluorine valve should not choose the corrosion resistant alloy valve; Can choose the cavitation effect is good, simple structure Angle of high pressure valve ( Meet the service life of two years or so) , you should not choose the other high pressure valve structure complex and expensive. 5) Pressure and temperature resistant this involves pneumatic - valve nominal pressure, the working temperature of the selected. High pressure side, if only the pressure is not difficult, mainly is the differential assembly produce cavitation; Aspects of heat-resistant, usually solve below 450 ℃ is very easy, and it is also easy to 450 ~ 600 ℃, but to above 600 ℃, the contradiction is prominent; When the temperature at 80 ℃ of cut class pneumatic control valve selection of soft sealing material is usually not desirable, hard seal cutting should be considered. Commonly used material of working temperature, working pressure and the relationship between the nominal pressure see table 5-1. 6) Weight and the appearance of this problem is very intuitive, must have good appearance, light weight of valve by using manufacturers welcome. Here to change a bias, think of pneumatic control valve as a 'eldest brother', a bit heavy or appearance almost, not a big deal. Now we attach great importance to it, thus put forward the pneumatic control valve should be has the characteristics of miniaturization, light-duty, instrumentation.