A process flow diagram (PFD) 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 ''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 *Connections with other systems * Major bypass and recirculation (recycle) streams * Operational data (

temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied on ...

pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country a ...

, mass flow rate,

density Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' can also be used. Mathematicall ...

, etc.), often by stream references to a mass balance. * Process stream names Process flow diagrams generally do not include: *

Pipe class Pipe(s), PIPE(S) or piping may refer to: Objects * Pipe (fluid conveyance), a hollow cylinder following certain dimension rules ** Piping, the use of pipes in industry * Smoking pipe ** Tobacco pipe * Half-pipe and quarter pipe, semi-circula ...

es or piping line numbers * Instrumentation details * Minor bypass lines * Instrumentation * Controllers like Level Control or Flow Control * Isolation and shutoff valves * Maintenance vents and drains *

Relief Relief is a sculptural method in which the sculpted pieces are bonded to a solid background of the same material. The term '' relief'' is from the Latin verb ''relevo'', to raise. To create a sculpture in relief is to give the impression that th ...

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: AmineTreating

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 An oil refinery or petroleum refinery is an industrial processes, industrial process Factory, plant where petroleum (crude oil) is transformed and refining, refined into useful products such as gasoline (petrol), diesel fuel, asphalt, asphalt ...

Other items of interest

A PFD can be computer generated from process simulators (see List of Chemical 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 DIN or Din or din may refer to: People and language * Din (name), people with the name * Dīn, an Arabic word with three general senses: judgment, custom, and religion from which the name originates * Dinka language (ISO 639 code: din), spoken by ...

, 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 15519-1:2010(en): Specification for diagrams for process industry — Part 1: General rules * ISO 15519-2:2015(en): Specifications for diagrams for process industry — Part 2: Measurement and control * ISO 10628-1:2014(en): Diagrams for the chemical and petrochemical industry — Part 1: Specification of diagrams * ISO 10628-2:2012(en): Diagrams for the chemical and petrochemical industry — Part 2: Graphical symbols * ANSI Y32.11: Graphical Symbols For Process Flow Diagrams (withdrawn 2003) * SAA AS 1109: Graphical Symbols For Process Flow Diagrams For The Food Industry

External links

{{commons category, Process flow diagrams
The PFD at The Engineering Tool Box

Kolmetz Handbook of Process Equipment Design engineering design guidelines for process flow sheets
Chemical process engineering Piping Diagrams Process engineering