by Dennis Collin
One of the benefits of working with BIM software is having the ability to perform geometry inference checks from models from other disciplines. Native Revit files are generally preferred for this task, but what about models from other AutoCAD based products like Plant 3D?
Despite the clash detection function not working with vanilla AutoCAD DWG data, there is a workflow that can be used to achieve this. The drawings need to be a vanilla DWG format as at the time of writing Revit does not support Object enablers to be able to read in enhanced object enabled DWG files like Plant produces.
Fig 1. Use the Export to AutoCAD command to create a vanilla 3D solid model elements drawing file.
To bring a plant model into Revit, the data needs to be exported to a vanilla AutoCAD DWG format, that will convert Plant elements and pipework etc. to AutoCAD based solids. This drawing should also contain reference elements such as a structural grid or other registration reference to enable the Plant model drawing to be positioned correctly in the Revit model.
Fig 2. Creating an in-place family for the Plant model.
In Revit, start a new model and create an In-place family, call it Plant Model or similar and categorise it as Mechanical Equipment or similar. I have found some category classifications such as ‘site’ elements do not seem to register on the inference check tool at a later stage.
Fig 3. Classify the model as Mechanical Equipment seems to work well for this task.
The geometry should import and display as the original AutoCAD drawing. Save the family and then save and name the Revit project containing the plant family as Plant Model or similar.
Within the Infrastructure model, link in the Plant Model project and locate the element using reference planes and other coordination tools. If shared coordinates are desired, then publish the shared coordinate system from the current model to the Plant Model project. This means when connecting the two files in future, the shared positioning method of referencing projects can be used.
Fig 4. When linking models initially use centre to centre but ultimately shared positioning is the best workflow.
To conduct the clash detection tool, access the collaborate tab and choose Interference Check.
Fig 5. The Interference check is just one of Revit’s many collaboration tools!
Select the Linked file on the left-hand side (containing the ‘Mechanical Equipment’) and the appropriate categories in the current project, e.g. Walls, slabs etc. If no categories are visible check the category type of the in-place family of the plant model. Certain categories such as ‘Site’ do not seem to be valid candidates for clash detection purposes at the time of writing for this version of Revit (2025.x)
Fig 6. Clashing the blue Plant model against retaining wall elements.
If clashes do register, the elements can be inspected via their category and element ID and highlighted and discussed at coordination review meetings. The report itself can be exported as a generic XML file that can be viewed in any Office type application or web browser.
Fig 7. Revit’s Clash report is a lot more basic than Navisworks but it is useful as certain stages.
A more comprehensive clash detection tool can be found in Autodesk Navisworks. Navis supports soft clashing (clearances) and future clashes for renovation projects, but for interim checks and internal working Revit’s interference check tool can be sufficient in many cases.
Creating families, working with other disciplines, and accessing work-around solutions are some of the topics covered on our follow-on Revit training courses. Visit the Arkance UK site to get an overview of the courses on offer and talk to one of the team for dates and availability or if you have more bespoke requirements, just ask, we are here to help!