All components are dimensioned from the reference line. For a vertical vessel, the reference line is the tangent line of the bottom head, while for a horizontal vessel, it is the tangent line of the left side head.
The reference line serves as the starting point for all components, such as nozzle locations, saddle positions, and lifting lug locations. The center of gravity is also referenced from the reference line, except for vertical vessels on a skirt. Please refer to the images below for further clarification.
Lug Support (Bracket):
Leg Support:
Skirt Support:
Saddle Support:
See Also