Inside the piping input panel is an option referred to as Nozzle Lmt Check, this allows the user to provide CAESAR II with user defined Force and Moment limits, or to read those limits from provided files, such as the limit values for API-610.
One of the more complicated concepts to grasp is the idea of the "Ref Vector" in this dialog. Here is an attempt to explain how the reference vector should be provided. For CAESAR II, the "Ref Vector" is the "equipment central axis" meaning for vessels, this is the longitudinal direction of the vessel, and for pumps, this is the pump shaft direction.
By defining this reference vector, which is also the B vector - CAESAR II can then associate the "A" vector, which is the vector of the pipe bearing down on the equipment, as well as the cross product of these two vectors, the C vector.
The C vector is established by the right hand rule. Here’s how it works. Imagine an axis going through the tails of A and B, perpendicular to the plane containing them. Grab the axis with your right hand so that your fingers sweep A into B. Your outstretched thumb points in the direction of AxB. This is the C vector direction.
The B vector is always perpendicular to the pipe direction, and for CAESAR II this simplifies the reference vector to two main possibilities.
- If your pipe is Vertical - that is, oriented along the global Y axis, then the reference vector is horizontal, and aligned along either the vessel centerline, or the pump's major axis.
- If your pipe is horizontal, that is, oriented along the global X or Z axis, then the reference vector is set in the global Y axis.