For any steel pipe size, how does the OD compare with the ID?

The correct answer indicates that the outside diameter (OD) of steel pipe is a constant measurement for a given nominal size, while the inside diameter (ID) can vary depending on the wall thickness of the pipe. This relationship arises from the design and manufacturing processes of pipe.

For instance, if you look at standard pipe sizes, a nominal pipe size gives a standard OD that manufacturers adhere to for consistency across materials and applications. However, the ID changes based on the pipe's wall thickness. Different pressure ratings or grades of the same nominal pipe size may have different wall thicknesses, thus affecting the ID even though the OD remains the same.

In terms of context, some options suggest that OD can change with pipe sizes, which is not accurate for standardized sizes. Others propose that both OD and ID are constant, which would overlook the variability based on wall thickness and pipe specifications. Understanding this relationship is crucial for ensuring compatibility in piping systems, especially in applications requiring precise flow characteristics.