To make a 3D pipe from a polyline with CadTools you use the “Create 3D solids from 3D polylines” command. This command use AutoCAD’s “Extrude object along path”.
If your polyline is a simple 2D polyline you first need to convert it to a 3Dpolyline, to do that you use the CadTools convert command. You can also use CadTools “Chord Height” setting to change the accuracy of the converted arc part of the polyline.
Hope this will help!
/Lars