What is a bag loader? Sounds more like a piece of manufacturing or materials processing equipment (and less like a tank)? If so, that would likely be more 'speciality' equipment, not 'mechanical' equipment, as far as Revit (and Construction Specifications) are concerned. Mechanical equipment is intended for air/water/fluid processing intended to support HVAC and related processes.
The supports themselves, I would assume would be more appropriate as structural components, unless the 'real world' equipment is one unitary assembly. However, to get Revit to behave the way desired, perhaps dissassembling the component will be necessary.
Martin Schmid
Product Line Manager
Mechanical Detailing and Electrical Design
Architecture, Engineering, and Construction
Autodesk, Inc.