In the Merchant Fleet a distinction is made between pipe and tubing.
This distinction is based on the way the tubular product is identified
as to size.
There are three important dimensions of any tubular product: outside diameter (OD), inside diameter (ID), and wall thickness.
A tubular product is called PIPE if size is identified by a nominal dimension called iron pipe size or IPS Iron Pipe Size and by reference to a wall thickness schedule designation. Pipe over 12 inches the nominal pipe size and the actual outside diameter are the same. For example a 14 inch pipe will have measured outside diameter of 14 inches.
Pipe can also be identified as STANDARD (STD), EXTRA STRONG (XS), and DOUBLE EXTRA STRONG (XXS). These designations still in use today refer to wall thickness. Standard and schedule 40 are the same.
The figure shows the relative wall thickness of pipes having the same nominal OD. Note that the inside diameter is reduced as the wall thickness is increased. Pipe is manufactured in a number of different wall thicknesses, and some pipe does not fit into the standard, extra strong, and double extra strong classifications. The wall thickness schedules are used increasingly to identify wall thickness of pipe as they provide for the identification of more wall thicknesses.
In the Merchant Fleet a distinction is made between pipe and tubing. This distinction is based on the way the tubular product is identified as to size.
There are three important dimensions of any tubular product: outside diameter (OD), inside diameter (ID), and wall thickness.
A tubular product is called TUBING if its size is identified by actual measured outside diameter (OD)