While CAESAR II compares entered thickness to the base Code minimum thickness for straight and bent pipe, the program does not qualify the design pressure for the piping system. (The program does not reference "design pressure".)
CAESAR II does not directly address the criteria found in Chapter IX. Off the top of my head, you will have a different pressure wall thickness calculation, the "non-liberal" allowable stress for displacement stress range, a temperature limit on allowable stress and a more detailed consideration of fatigue in this thick wall piping.
_________________________
Dave Diehl