Spiral steel pipe size

Spiral steel pipe size can be divided into outer diameter, inner diameter, nominal diameter. The outer diameter of the pipe of the seamless pipe is denoted by the letter D, and the diameter and wall thickness of the outer diameter are added, for example, a seamless steel pipe having an outer diameter of 108 mm, with a wall thickness of 5MM, expressed by D108 * 5 Nominal diameter, is the pipe (or pipe) the name of the specification. The nominal diameter of the pipe and its inner diameter, outer diameter are not equal