I'm new to CAESAR II and just built my first model.

I constructed it with the Z-axis as vertical but now I'm not sure if this is correct. All other example files I've seen show the Y-axis as vertical.

What is the default direction for gravity loads? Can gravity orientation be altered?

What is the default orientation for hangers? Can hanger orientation be altered?

Gravity and Hanger loads act in the vertical direction, which by default is "Y". If you set the vertical axis to "Z", then gravity and hangers act in "Z".

How should look like a "Gravity" combination to check a displacements in system without work temperature and pressure ??? (only ambient) without fluid.
It is in the default pack of combination ???

I would look up how to correctly define your load cases. However, when you specify W in the load case editor, gravity is included, with the weight of the operating fluid inside the pipe (where you defined fluid density). WW is with water. WNC is with the pipe empty.

So I suppose in the event we work on building a refinery in outer space, we ignore these values altogether when we define load cases.