The international application standard of metal pipe water supply system was formulated by the British Empire in the heyday of history, and the size of this standard is in inches. The pipe thread (thread) and faucet standards in the relevant standards are still in use today, and four pipes, six pipes and one-inch pipes are also used in spoken language.
British pipeline standard is based on that the water supply plane diameter of a quarter faucet is 1 1.5 mm, and the standard pipeline sizes are 12.7 mm, 19.05 mm, 25.4 mm, 3 1.75 mm, 50.8 mm, etc. The advantage of this standard system is that it saves money and does not affect the water supply function.
Extended data:
Generally speaking, the diameter of a pipe can be divided into outer diameter, inner diameter and nominal diameter. The outer diameter of the 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, with a wall thickness of 5MM, is represented by D 108*5, and a plastic pipe is also represented by an outer diameter, such as De63.
Others such as reinforced concrete pipes, cast iron pipes, galvanized steel pipes, etc. , represented by DN, and generally represented by nominal diameter in design drawings. Nominal diameter is an artificially specified standard for the convenience of design, manufacture and maintenance, and it is also a nominal diameter, which is the specification name of a pipe (or pipe fitting).
The nominal diameter of a pipeline is not equal to its inner diameter and outer diameter. For example, seamless steel pipes with a nominal diameter of 100MM include 102*5 and 108*5. 108 is the outside diameter of the pipeline, and 5 represents the wall thickness of the pipeline. Therefore, the inner diameter of the steel pipe is (65438+).
However, the specification name of pipe diameter is not equal to the inner diameter. Therefore, the nominal diameter should be used in the design drawings to determine the structural dimensions and connection dimensions of pipes, fittings, valves, flanges, gaskets, etc. According to the nominal diameter, the nominal diameter is indicated by the symbol DN. If the outer diameter is used in the design drawings, a pipeline specification comparison table shall be made to indicate the nominal diameter and wall thickness of a pipeline.
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