Internal Pipe Surface

Im not too sure this is the right forum to post this in, but i need to
export only the internal surface of a small length of pipe.

Does anyone
know if this is possible in UG?

We want to run some CFD on a piping
system and the CFD guys only want the interior walls of the pipe. I
have tried exporting a .step of only surfaces but that didnt work too
well. Any suggestions? (Using UG NX6)

Thanks for the help.

You could extract the internal faces and then export them, or un-sew the bodies and export the internal faces.