Pneumatic valve parameter definition
1. Nominal size: ( 公称直径) , also known as the average diameter ( 平均外径) , said sign DN, it is general diameter of various kinds of pipe and pipe accessories. The same nominal diameter of the pipe and pipeline fittings can connect each other, are interchangeable. It is not on the actual meaning of pipe diameter or inner diameter, although its value with the pipe diameter is relatively close to or equal to, in order to make the pipe, tube connection dimension is unified, in nominal diameter ( Also known as nominal diameter and nominal diameter) 。 For example, welded steel pipe can be divided by the thickness of the thin wall steel tube, ordinary steel pipe and increasing pipe. Its nominal diameter rather than outside diameter, diameter, but the approximate ordinary steel pipe inner diameter of a nominal size. Each nominal diameter, corresponds to a diameter, its inner value varies with the thickness. Nominal diameter available metric mm said, also can use English in said. Piping accessories also expressed in nominal diameter, meaning is the same tube. 2. Nominal pressure: 公称压力) , said symbol PN, under a certain temperature applications allow maximum working pressure. Control valve for carbon steel body, refers to the application under 300 ℃ maximum allowable working pressure; For cast iron valve body, the point at which the application under 120 ℃ maximum allowable working pressure; Control valve for stainless steel body, refers to the application under 250 ℃ maximum allowable working pressure. When working temperature, the body pressure is reduced. For example, nominal pressure is 6. 4MPa（ PN64) Carbon steel valves, pressure of 5 to 300 ℃. 2 mpa, 400 ℃ when the pressure of 4. 1 mpa, to 450 ℃ when the pressure of 2. 9MPa。 Control valve, therefore, the determination of nominal pressure not only according to the maximum working pressure, still need according to the maximum operating temperature and material characteristics, not only meet the nominal pressure is greater than the pressure of work.