Simulation has become an established technique to support the design of complex, mechatronic or cyber-physical systems. Ideally, simulations should already be performed at an early design phase before high-cost design commitments are made, and the recent advances in the digitalization of design information open possibilities for automatic generation of simulation models. However, high-fidelity simulation model building depends on accurate data. In particular, first-principles models are desirable source information for simulations, but such models generally are not available at an early design stage. This paper investigates the automatic generation of first-principles 3-D models for piping intensive systems based on design information that is available at an early design stage, namely piping & instrumentation diagrams (P&ID). An algorithm is presented for the generation of such 3-D models based on machine-readable P&ID information. The main focus of the algorithm is the automatic generation of feasible pipelines into the 3-D models, so that the model has sufficient information, which can be exploited in further work to automatically generate high fidelity first-principles thermo-hydraulic simulations.