Parameter Definition Of Pneumatic Valves

1. Nominal diameter, also known as mean outer diameter, represents the symbol DN, which is the universal diameter for various pipes and pipeline accessories. Pipes and pipeline accessories with the same nominal diameter can be connected to each other and have interchangeability. It is not the actual outer diameter or inner diameter of the pipeline, although its value is relatively close to or equal to the inner diameter of the pipeline. In order to unify the connection size of pipes and fittings, nominal diameter, also known as nominal diameter or nominal diameter, is used. For example, welded steel pipes can be divided into thin-walled steel pipes, ordinary steel pipes, and thickened steel pipes according to their thickness. Its nominal diameter is not the outer diameter or the inner diameter, but a nominal size that approximates the inner diameter of a regular steel pipe. Each nominal diameter corresponds to an outer diameter, and its inner diameter value varies with thickness. The nominal diameter can be expressed in metric millimeters or in English inches. Pipeline accessories are also represented by nominal diameter, which is the same as slotted pipes.
2. Nominal pressure: (Nominal pressure), representing the symbol PN, the maximum allowable working pressure when applied at a certain temperature. For control valves with carbon steel valve bodies, it refers to the maximum allowable working pressure for applications below 300 ℃; For cast iron valve bodies, it refers to the maximum allowable working pressure for applications below 120 ℃; For control valves with stainless steel valve bodies, it refers to the maximum allowable working pressure for applications below 250 ℃. When the working temperature increases, the pressure resistance of the valve body will decrease. For example, a carbon steel control valve with a nominal pressure of 6.4MPa (PN64) has a pressure resistance of 5.2MPa at 300 ℃, 4.1MPa at 400 ℃, and 2.9MPa at 450 ℃. Therefore, the determination of the nominal pressure of the control valve should not only be based on the highest working pressure, but also on the highest working temperature and material characteristics, rather than just meeting the requirement that the nominal pressure is greater than the working pressure.