The available dimensional standards, such as the ASME B36.10 for pipe and B16.9 for fittings, do not always provide the pipe or fitting suitable for the design requirements. For example the pressure can be too high for the strongest component in the standards. In that case a custom build component will be the solution.
The Tee in this case was a custom build component, large diameter and large wall thickness. Red-Bag provided the detail calculation as per the code requirements. (Fluor)