I enjoyed the course very much,thanks for creating it! I changed a few things among the way, not everything worked out, but learned a lot; procedual materials are very nice! I have one strange thing when rendering. The red pipes had stands to the downside but there aren't there in the object. I know its though without the .blend but can you think of any possibility what can cause this?
You are right, very hard w/o the .blend (you can post a link to your file, when you upload it to Dropbox, GoolgeDrive or so).
When there is a difference betwen what you see and the render, look in the Outliner for clues (enable some extra icons!):
Also, you might have a Modifier that is disabled in the Viewport, but still renders (for instance a Mirror...).
Thanks, It was just as easy as an disabled mirror Modifier. I have a lot to learn...