A process flow diagram is a diagram commonly used in chemical and process engineering to
indicate the general flow of plant processes and equipment.
The PFD displays the relationship between major equipment of a plant facility and does
not show minor details such as piping details and designations.
Another commonly used term for a PFD is a flowsheet.
Typical content of a process flow diagram
Typically, process flow diagrams of a single unit process will include the following:
Process piping Major equipment items
Control valves and other major valves Connections with other systems
Major bypass and recirculation streams Operational data, often by stream references
to a mass balance.
Process stream names Process flow diagrams generally do not include:
Pipe classes or piping line numbers Process control instrumentation
Minor bypass lines Isolation and shutoff valves
Maintenance vents and drains Relief and safety valves
Flanges Process flow diagrams of multiple process
units within a large industrial plant will usually contain less detail and may be called
block flow diagrams or schematic flow diagrams.
Process flow diagram examples ≠ The process flow diagram below depicts
a single chemical engineering unit process known as an amine treating plant:
Multiple process units within an industrial plant
The process flow diagram below is an example of a schematic or block flow diagram and depicts
the various unit processes within a typical oil refinery:
Other items of interest A PFD can be computer generated from process
simulators, CAD packages, or flow chart software using a library of chemical engineering symbols.
Rules and symbols are available from standardization organizations such as DIN, ISO or ANSI.
Often PFDs are produced on large sheets of paper.
PFDs of many commercial processes can be found in the literature, specifically in encyclopedias
of chemical technology, although some might be outdated.
To find recent ones, patent databases such as those available from the United States
Patent and Trademark Office can be useful.
Standards ISO 10628: Flow Diagrams For Process Plants
- General Rules ANSI Y32.11: Graphical Symbols For Process
Flow Diagrams SAA AS 1109: Graphical Symbols For Process
Flow Diagrams For The Food Industry See also
Piping and Instrumentation Diagram Hazop Studies
Further reading Raymond E. Kirk and Donald F. Othmer.
Kirk-Othmer Encyclopedia of Chemical Technology.
Wiley-Interscience.
ISBN 0471419613.
M.S.
Ray and M.G.
Sneesby.
Chemical Engineering Design Project: A Case Study Approach.
Gordan and Breach Science Publishers.
ISBN 9056991361.
R. Turton, R.C.
Bailie, W.B.
Whiting and J.S.
Shaeiwitz.
Analysis, Synthesis, and Design of Chemical Processes.
Prentice Hall.
ISBN 0-13-064792-6.
Fritz Ullmann.
Ullman’s Encyclopedia of Industrial Chemistry.
Wiley-VCH.
ISBN 3-527-30385-5.
Srikumar Koyikkal.
Chemical Process Technology and Simulation.
Prentice Hall India.
ISBN 978-81-203-4709-0.
External links The PFD at The Engineering Tool Box
Simplified process flowsheets and flow diagrams of process industries.
Development of new integration methods and model flow diagrams.