Hi Holly! :-)
As you see on the picture below, the 3D-line (marked) is in the top of the pipe:
I'm using SUE with Power Rail Track SS4. I have attached a file (SUE_Test.dgn) in which is places the 3D line on top of the pipe. I'm looking forward to your answer, and thank you for you help :-)
(Please visit the site to view this file)