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What is the nominal diameter?
Date:2019-05-29      Views:259Time      Label:What is the nominal diameter?
Generally, the diameter of the tube can be divided into outer diameter, inner diameter, and nominal diameter. The outer diameter of the pipe whose pipe is seamless steel pipe is indicated by the letter D, for example, the seamless steel pipe with outer diameter of 108, the wall thickness is 5MM, represented by D108*5, other such as reinforced concrete pipe, cast iron pipe, galvanized steel pipe, etc. outer diameter are represented by DN. Generally, the nominal diameter is used in the design drawings. 

The nominal diameter of the pipe is not equal to its inner or outer diameters. For example, there are several kinds of seamless steel pipes with a nominal diameter of 100 mm, such as 102*5, 108*5, etc. 108 is the outer diameter of the pipe, and 5 is the wall thickness of the pipe. Therefore, the inner diameter of the steel pipe is (108-5*2)=98MM, but the nominal diameter is not completely equal to the difference between the outer diameter of the steel pipe and the double wall thickness. It can also be said that the nominal diameter is close to the inner diameter, but not equal to the inner diameter. The name of a pipe diameter specification, in the design drawings, the nominal diameter is used. The purpose is to determine the structural dimensions and connection dimensions of pipes, fittings, valves, flanges, gaskets, etc. according to the nominal diameter. The nominal diameter is the symbol DN. It is indicated that if the outer diameter is used in the design drawing, a pipe specification comparison table should also be made to indicate the nominal diameter and wall thickness of a certain pipe.