Flow Diagrams and Types

Flow diagrams describe in a schematic drawing format the flow of fluids and gases through a unit or an entire plant. By using symbols to represent various pieces of equipment, the flow diagram provides the piping designer with an overall view of the operation of a facility.

Process engineers are responsible for developing flow diagrams. In many large engineering firms, an entire department is dedicated to the development of flow diagrams. Today almost all flow diagrams are laid out with CAD, using third-party piping packages such as ProFlow or individually developed company packages. The flow diagram should be laid out in a very simplistic and logical order and be read from left to right. It guides the drafter and designer in the same manner a road map guides a traveler.


  • Process Flow Diagram

 The process flow diagram is the first flow diagram developed by the flow diagram department. It includes major equipment, main piping, direction of flow, operating pressure and temperature, major instrumentation.

  • Mechanical Flow Diagram

 From the process flow diagram, the mechanical group develops the mechanical flow diagram. The mechanical flow diagram provides much more detailed data than the process flow diagram. Mechanical flow diagrams includes pipe line numbers and direction of flow, pipe specifications and line sizes, all equipment , all valves, all instrumentation with controlling devices.

  • The Utility Flow Diagram The utility flow diagram shows the piping, valves, and instrumentation for the basic plant utilities. Utilities are services that are essential to the proper function of the plant. These utilities correspond to some of the same utilities used in a typical house, such as water, gas, and sewer drains.

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