What is the flange DN in the flange type electric heating pipe referring to the inner diameter?

What is the flange DN in the flange type electric heating pipe referring to the inner diameter?

The flange DN in the flange type electric heating pipe refers to the international nominal size PN, which is the pressure nominal size

The flange DN in flange type electric heating pipes is expressed in MPa in the International System of Units and kgf/cm2 in the Engineering System of Units

Generally speaking, the diameter of pipes in flange type electric heating pipes can be divided into outer diameter, inner diameter, and nominal diameter. The outer diameter of seamless steel pipes is represented by the letter D, followed by the size and wall thickness of the outer diameter. For example, for seamless steel pipes with an outer diameter of 108, the wall thickness is 5MM, represented by D108 * 5, plastic pipes are also represented by the outer diameter, such as De63, and other pipes such as reinforced concrete pipes, cast iron pipes, galvanized steel pipes, etc. are represented by DN. In design drawings, the nominal diameter is generally used, The nominal diameter is a standard that is artificially specified for the convenience of design, manufacturing, and maintenance. It is also a specification name for pipes (or fittings) compared to the nominal diameter. The nominal diameter, inner diameter, and outer diameter of the pipe in the flange type electric heating pipe are not equal. For example, there are several types of seamless steel pipes with a nominal diameter of 100MM, such as 102 * 5, 108 * 5, etc., where 108 represents the outer diameter of the pipe and 5 represents the wall thickness of the pipe. Therefore, the inner diameter of the steel pipe is (108 * 5-5)=98MM, but it is not completely equal to the difference between the outer diameter of the steel pipe and twice the wall thickness. It can be said that the nominal diameter is close to the inner diameter, However, the specification name for a pipe diameter that is not equal to the inner diameter should be used in the design drawings. The purpose is to determine the structural dimensions and connection dimensions of pipes, fittings, valves, flanges, gaskets, etc. in flange type electric heating pipes based on the nominal diameter. The nominal diameter is represented by the symbol DN. If the outer diameter is used in the design drawings, a comparison table for the pipe specifications should also be made, Indicates the nominal diameter and wall thickness of the pipeline in a flange type electric heating pipe.

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