The Three Types Of Process Diagrams

July 6, 2016 by admin

Process Diagrams are fundamental requirements for project design and engineering.  There are three types of process diagrams:

  1. Block Flow Diagram (BFD)
  2. Process Flow Diagram (PFD)
  3. Process and Instrumentation Diagram (P&ID)

Block Flow Diagram (BFD)

The Block Flow Diagram is the simplest form of Flow Diagram which provides an overall view of a process.  The diagram usually resembles an organized chart composed of text enclosed boxes, process commodities and flow arrows.


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Process Flow Diagram (PFD)

The Process Flow Diagram goes a little further than the Block Flow Diagram in that it provides more detail about major equipment, sub systems and flow path.  The PFD can also include the pressure and temperature information as well as main points of control.


Process & Instrumentation Diagram (P&ID)

A process and instrumentation diagram, also known as a P&ID, is a technical drawing of a process.  It uses graphical symbols for equipment and piping together with graphical symbols for process measurement and control functions.  A P&ID’s information typically spans multiple engineering disciplines and is a pictorial representation of piping and instrument details, safety and regulatory requirements, start-up and operational information, as well as control and shutdown schemes.

P&ID’s include the following information:

  • Permanent start-up and flush lines
  • Flow directions and interconnection references
  • Control inputs, outputs, interlocks and control system input
  • Interfaces for class changes
  • Identification of components and subsystems
  • Instrumentation and designations
  • Mechanical equipment with names and numbers
  • All valves and identifications
  • Process piping, sizes and identifications


If you require help reading or specifying valves located on a Process and Instrumentation Diagram, please contact your local LowFlow Valve representative for assistance.  Your local representative can be found using this link.

Next week, we will discuss the different types of process diagram symbols.

Mike Theobald
Mike Theobald, LowFlow Valve Product Manager

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