A way of starting a model is to use the existing diagrams (such as P&ID's) as background images and then overlay objects.
For example, you can put a P&ID into the background of a diagram (using Paste Special) and then place objects on the diagram.
This has the advantage that you do not have to connect the objects. (This is a mixed blessing however since the connections between objects can be used to add value to the model and for simulation.)
Typically, the P&ID is used temporarily and subsequently the symbols are moved into other diagrams with a better structure that the P&ID has - as P&ID's are flat and rarely S88 based for example with one for each Unit
If you also have an Instrument index (some P&ID CAD packages provide this) then you can copy from that and paste the onto the diagram using Paste Special.
Once it has served it's purpose the P&ID background can be deleted.
Tip if you want to keep your original P&ID based diagram but have the objects shown in a different structure (for example a page for each Equipment Module) you can use clones of the symbols on the P&ID overlay. (Copy and Paste Special as Clones) You can then make those in other page the masters (Right Click Make this clone the Master) so then P&ID overlay has the clones.
This can provide a graphical cross reference from the P&ID to the System Modules. It can also be used as a means of defining the Graphics in the target control syste,.
Linking to P&ID data
You can use External tag so that the tags on the P&ID can be related to the instances in the model.
ControlDraw provides a variety of methods to generate an External Tag that matches the P&ID tags
If you have a Tag Database such as an Instrument List or IO List you can use this tag to link between a CD Model and Tag Database.
An Import Export tool is available from ControlDraw Ltd that allows you to import, export or compare the data in the two.