本文件规定了外径符合ISO 4397的无缝和焊接精密钢管的尺寸和标称工作压力，以及符合ISO 3305的壁厚和机械性能。本文件中的标称工作压力反映了计算爆破压力的设计系数比为4:1。

This document specifies sizes and nominal working pressures for seamless and welded precision steel tubes with outside diameters in accordance with ISO 4397, and wall thicknesses and mechanical properties in accordance with ISO 3305. The nominal working pressures included in this document reflect a design factor ratio of 4 to 1 applied to the calculated burst pressures.