New Mexico Pipe Fitter Journeyman (JPF) Practice Exam

True or False: Steel pipe sizes up to 12 inches have larger ODs than their nominal size.

1. True

2. False

3. Only for galvanized pipes

4. Only for cast iron pipes

The correct answer is: True

The statement that steel pipe sizes up to 12 inches have larger outside diameters (ODs) than their nominal sizes is true. In piping terminology, the nominal size refers to a standard measurement which does not equate to the actual physical dimensions of the pipe. For example, a nominal 1-inch steel pipe typically has an outside diameter of approximately 1.315 inches. This difference arises because the nominal size is a standardized way to reference the pipe, not an accurate measurement of its dimensions. The actual measurements of the outside diameter can vary slightly based on the wall thickness and the type of pipe, but the general understanding is that for steel pipes up to 12 inches, the outside diameter exceeds the nominal size. Understanding this distinction is crucial for scenarios involving fitting, joining, or estimating the flow capacity of pipes, as it significantly affects the projects involving plumbing or mechanical systems.