Specification table of flanges commonly used in pipelines

Generally speaking, the diameter of the tube can be divided into outer diameter, inner diameter and nominal diameter. The outer diameter of a pipe made of seamless steel pipe is indicated by the letter D, followed by the size and wall thickness of the outer diameter. For example, a seamless steel pipe with an outer diameter of 108, a wall thickness of 5 mm, is represented by D108 * 5. Plastic pipe It is also expressed by the outer diameter, such as De63. Others such as reinforced concrete pipes, cast iron pipes, galvanized steel pipes, etc. are indicated by DN. In the design drawings, the nominal diameter is generally used to indicate the nominal diameter for the convenience of design, manufacture and maintenance. A standard, more nominal diameter, is the specification name of the pipe (or fitting). The nominal diameter of the pipe is not equal to its inner diameter and outer diameter. For example: seamless steel pipes with a nominal diameter of 100mm are 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 * 5-5) = 98mm, but it is not exactly equal to the difference between the outer diameter of the steel pipe minus twice the wall thickness. It can also be said that the nominal diameter is close to the inner diameter, but it is not equal to the inner diameter. The specification name of a pipe diameter, so the nominal diameter is used in the design drawings, in order to determine the structural dimensions and connection dimensions of pipes, fittings, valves, flanges, gaskets, etc. according to the nominal diameter. It indicates that if the outer diameter is used in the design drawing, a comparison table of pipe specifications should also be made, indicating the nominal diameter and wall thickness of a certain pipe.

Plumbing workers often say that the pipe specifications 4 points, 6 points, 1 inch, etc. refer to what units, and how to convert mm

4 minutes, 6 minutes, and 1 inch are inch system, 1 inch = 25.4mm.

1 inch = 8 cents

A few minutes and a few inches are inch units, 1 inch = 25.4mm, 1 inch = 8 inches.

The corresponding relationship between a few minutes, a few inches and the nominal diameter is as follows: 1 inch = DN25, 1 point = 1/8 inch = DN6, 2 points = 1/4 inch = DN8, 3 points = 3/8 inch = DN10 , 4 points = 1/2 inch = DN15, 6 points = 3/4 inch = DN20.