Which factor is used to determine the wall thickness in ANSI pipe schedules?

• A. Outer Diameter
• B. Design Pressure
• C. Wall Thickness
• D. Material Grade

Answer: (C)

In ANSI pipe schedules, the wall thickness is not something you derive from a single calculation for a given pipe size; it is fixed by the schedule that you select for that nominal size. Each schedule provides a standard, tabulated wall thickness for every NPS, so once you choose a schedule to meet the service’s design requirements, the corresponding wall thickness is determined by that schedule. The outer diameter is set by the nominal size, while the material grade affects the allowable stress and helps you decide which schedule is appropriate, and the design pressure helps drive the need to use a particular schedule. But the actual thickness you use comes from the schedule’s predefined thickness for that size.