The relationship between OD (outside diameter), ID (inside diameter), and WT (wall thickness) of tubing or piping can be described by the following equation:
OD = ID + 2 x WT
This means that the outside diameter of the tubing or piping is equal to the sum of the inside diameter and twice the wall thickness.
Alternatively, this equation can be rearranged to calculate the ID or WT given the OD and one of the other dimensions:
ID = OD – 2 x WT
WT = (OD – ID) / 2
These equations are important because they allow you to calculate the dimensions of the tubing or piping you need for your specific application, or to verify that the dimensions of the tubing or piping you have received are within the required tolerances.
It is important to note that the actual dimensions of the tubing or piping may vary slightly due to manufacturing tolerances or other factors, so it is important to also specify any required tolerances or other requirements that must be met by the tubing or piping to ensure that it will work properly in your application.