What does ductile iron pipe "ND200" mean?
Generally speaking, the diameter of the pipe can be divided into outer diameter, inner diameter and nominal diameter. The pipe is a seamless steel pipe pipe diameter by the letter D to represent, then additional outer diameter size and thickness, such as diameter of seamless steel pipe 108, a wall thickness of 5MM, denoted by D108*5, is also used outside said, such as De63 plastic pipe, such as reinforced concrete pipe, cast iron pipe, galvanized steel pipe, said the DN, in the design drawings is generally used to represent the nominal diameter, nominal diameter is a standard in order to design and manufacture and maintenance convenient set artificially, with nominal diameter, tube (or pipe) specification name.
The nominal pipe diameter and the inner diameter and the outer diameter were not equal, for example: the nominal diameter of 100MM seamless steel pipe 102*5, 108*5 several, 108 for the outer diameter of pipes, 5 said that the wall thickness of the tube, therefore, the pipe diameter (108-5-5 = 98MM), but it is not completely equal to pipe diameter minus two times the wall thickness difference, it can be said that the nominal diameter is close to the diameter, but not equal to the diameter of a pipe diameter specifications on the design drawings, so we use the nominal diameter, the purpose is to determine according to the nominal diameter pipe, flange and gasket structure and size connecting dimensions, nominal diameter is represented by the symbol DN, if the diameter of said in the design drawings, piping specifications should also make the table, show that the nominal diameter of a pipe wall thickness.
The tube is thin from the metal tube, and the outer diameter of the tube is almost the same as the inner diameter of the tube, so the average value of the outer diameter of the tube and the inner diameter of the pipe is called the diameter.
