Attributes: type pneumatic control valve selector valve: (1) determine the nominal pressure, not with Pmax set to PN, but by temperature, pressure, material corresponding to the three conditions to find and meet the PN from the table of the selected valve PN values. (2) determine the valve type, the leakage meet process requirements. (3) determine the valve type, the working pressure should be less than the allowable differential pressure valve, such as not, it shall be considered or alternatively valve from a special perspective. (4) the temperature of the medium in the valve operating temperature range, the ambient temperature to meet the requirements. (5) consider the problem valve attempts to prevent the situation according to the medium is not clean. (6) According to the chemical properties of the medium resistance to corrosion considerations valve. (7) According to media pressure and containing a hard object, consider the problem of erosion and abrasion resistant valves. (8) the performance of the overall economic effect is considered, the price ratio. . Need to consider three questions: a simple structure (as simple as higher reliability), easy maintenance, spare parts have sources; b.T969H electric high-pressure regulating valve life; c prices. (9) a preferred order. Butterfly - single-seat valve - seat valve - sleeve valve - angle valve - three way valve - ball - eccentric rotary valve - diaphragm. Select the implementing agencies: (1) The simplest is the pneumatic diaphragm type, followed by the piston, and finally the electric.