When talking about pipe classes, what does 'nominal pipe size' refer to?

Nominal pipe size refers to the size designation used for classification, which is a standardized system used to identify and categorize pipes. It does not represent the actual physical dimensions of the pipe, but rather a rough sizing framework that helps in the standardization of pipe fittings and systems.

For example, a nominal pipe size of 2 inches does not mean that the actual outer diameter of the pipe is exactly 2 inches; it is simply a classification tool. This designation allows engineers and technicians to communicate effectively about pipe sizes without needing to specify the exact dimensions, which can vary depending on the type of pipe material and thickness.

Understanding nominal pipe size is critical when designing, specifying, or working with piping systems because the correct identification ensures compatibility with fittings, valves, and other components in the system. This classification simplifies construction, maintenance, and installation in various engineering contexts.