How is the size of a pipe typically measured?

• A. By its outer diameter
• B. By its nominal pipe size (NPS)
• C. By its wall thickness
• D. By its weight per foot

Answer: (B)

The size of a pipe is typically measured by its nominal pipe size (NPS). The NPS is a standardized designation that reflects the approximate internal diameter of the pipe, which is useful for identifying the pipe size in a consistent manner across various materials and manufacturing processes. While the NPS does not directly represent a precise measurement of the internal diameter (due to different wall thicknesses among pipe schedules), it provides a reliable reference point for sizing fittings, valves, and other connections, making it essential for proper pipe fitting and installation.

Understanding NPS is critical for pipefitting as it ensures compatibility between different piping systems and fittings, ultimately leading to more effective and efficient installations. This measurement system is ingrained in industry standards, making it a universal point of reference among pipefitting professionals.