1.1 Block Flow Diagram (BFD) Process Flow Diagram (PFD) Piping and Instrument Diagrams (P&ID) (a) PFD (b) BFD (c) PFD or P&ID (d) P&ID (e) P&ID 1.2 P&ID 1.3 It is important for a process engineer to be able to review a 3-dimensional model prior to the construction phase to check for clearance, accessibility, and layout of equipment, piping, and instrumentation. 1.4 (1) Clearance for tube bundle removal on a heat exchanger. (2) NPSH on a pump – affects the vertical separation of feed vessel and pump inlet. (3) Accessibility of an instrument for an operator – must be able to read a PI or change/move a valve. (4) Separation between equipment for safety reasons – reactors and compressors. (5) Crane access for removing equipment. (6) Vertical positioning of equipment to allow for gravity flow of liquid. (7) Hydrostatic head for thermosiphon reboiler – affects height of column skirt. 1.5 Plastic models are no longer made because they are too expensive and difficult to change/revise. These models have been replaced with virtual/E-model using 3-D CAD. Both types of model allow revision of critical equipment and instrument placement to ensure access, operability, and safety. 1.6 Another reason to elevate the bottom of a t