Stainless steel pipe is one of the more standardized materials in the building and engineering industries. The thickness of the pipe walls, the diameter of the pipe and even the chemical composition are all written as part of the American National Standards Institute standards (abbreviated as ANSI), which is just one of multiple standards available.

#1 WALL THICKNESS

Stainless steel pipe categorized by the American National Standards Institute uses the term schedule in reference to the pipe’s wall thickness. Despite this standardization, the wall thickness is not the same for every diameter of the pipe. Instead, the schedule refers to the general strength of the pipe. Therefore, a schedule 40S stainless pipe has a wall thickness of approximately 1.73mm for a pipe with an outside diameter of 10.3mm but increases to 9.53mm for a pipe of the same schedule but 323.9mm in diameter. There are four general schedules for the stainless pipe; 5S, 10S, the 40S, and 80S.

#2 DIAMETER

Within each schedule of the pipe, there are multiple diameters of stainless steel pipe standardized by ANSI. These diameters range from 10.3mm (or .405 inches) to 323.9mm (or 12.75 inches). It is important to note that some diameters are not available in every schedule. For instance, the smallest diameters are not available in schedule 5S and many diameters are very difficult to find in some schedules, or very expensive if they are available.

#3 MATERIALS

Though ANSI standardizes stainless steel pipe, there are multiple formulas of stainless steel available. The two primary sheets of steel used in the manufacture of stainless steel pipe are ANSI 304 stainless steel and ANSI 316. Both steel has similar chemistry and differs only slightly in the amount of chromium in the steel.