Pneumatic valve standard summary
1. Nominal diameter (nominal diameter), also called average diameter (mean outside diameter), symbols, is all kinds of pipe DN and pipeline fittings general caliber. The same nominal diameter of the pipe and pipe accessories all can mutual connection, interchangeable. It is not a real sense of pipe diameter or inner diameter, although its numerical with pipe diameter is relatively close to or equal, in order to make the pipe, pipe connection size uniform, the nominal diameter (also called nominal diameter and nominal diameter). Such as welded steel pipe according to thickness can be divided into thin wall steel pipe, the common steel pipe and upset steel pipe. The nominal diameter is not outside, not inside, but approximate common steel pipe diameter of a nominal size. Each nominal diameter, corresponding to a diameter, the thickness of inner diameter value with different and different. Nominal diameter can be used metric mm said, also can use English in said. Piping accessories also use nominal diameter said, meaning with tube.
2. Nominal pressure (Nominal pressure), symbols, PN in a certain temperature when application maximum allowable working pressure. For carbon steel body control valve, refer to the 200 ℃ the following application allowed maximum working pressure; The cast iron body, refer to the 120 ℃ the following application allowed maximum working pressure; To the stainless steel body control valve, refer to the 250 ℃ the following application maximum allowable working pressure. When work when the temperature rises, the body pressure will reduce. For example, nominal pressure is 6.4 MPa (PN64) carbon steel valve, used to 300 ℃ when the pressure is 5.2 MPa, with 400 ℃ when the pressure is 4.1 MPa, used to 450 ℃ when the pressure is 2.9 MPa. Therefore, the determination of nominal pressure control valve not only according to the maximum working pressure, still need according to the highest working temperature and material characteristics, not only meet the nominal pressure is greater than the working pressure.
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