Steel pipe sizes up to 12 inches have a larger OD than their nominal size; is this true?

When discussing the nominal size of steel pipes, it's crucial to understand the distinction between nominal diameter and actual dimensions. The nominal size of a steel pipe is a standardized measurement that serves as a reference point, but it does not necessarily correspond to the actual outside diameter (OD) of the pipe. For steel pipes up to 12 inches in diameter, the actual outside diameter is indeed larger than the nominal size.

For instance, a nominal 1-inch pipe will have an actual OD of 1.315 inches, illustrating this principle. This adherence to standards is important in piping systems to ensure compatibility with fittings, flanges, and joints that are likewise designed around these nominal sizes. The consistency across the industry allows for easier planning, installation, and maintenance.

Therefore, the assertion that steel pipe sizes up to 12 inches have a larger OD than their nominal size is true, reflecting the established standards in pipe manufacturing and installation practices.