Some Bentley AutoPLANT users also use Autodesk Navisworks as a visualization software to view Bentley AutoPLANT objects. Some of the recent releases of Autodesk Navisworks do not show Bentley AutoPLANT objects correctly. Autodesk has an Knowledge base article detailing how to view Bentley AutoPLANT objects in Autodesk Navisworks found in the following link:
Also if Bentley AutoPLANT is not installed on the computer with Autodesk Navisworks that computer will to have the Bentley AutoPLANT object enablers installed. The Bentley AutoPLANT object enablers can be downloaded using the instructions in the following Be Communities Technote: http://communities.bentley.com/Products/Plant/Design___Engineering/w/Plant_Design_and_Engineering__Wiki/autoplant-object-enabler-view-autoplant-objects-in-autocad-without-autoplant-installed.aspx.
An alternative to Autodesk Navisworks is Bentley's ProjectWise Navigator which is fully compatible with Bentley AutoPLANT. More information ProjectWise Navigator can be found here: