181 Process Flow Diagram (PFD) Symbols for Engineers

Welcome to our process flow diagram symbols list. Scroll down and use the table of contents on the left to navigate this page and see the different symbol types most commonly used by engineers.

But first, let’s review the purpose and benefits of a PFD.

The Purpose and Benefits of a Process Flow Diagram

The use of different types of flowcharts and diagrams provide a number of benefits and purposes including:

An easy to understand structure, for high-quality control and in-depth training
Being able to standardize a process for optimal efficiency, repetition, and use
To aid the study of efficiency and improvement in a process, highlight areas of inefficiency, bottlenecks, and unnecessary steps in a diagram
To model a new or improved process
To communicate and collaborate on a number of projects

Much like with P&ID symbols, knowing important engineering symbology can help to improve document collaboration.

Process Flow Diagram Equipment Symbols

Flow chart symbols use different shapes to represent different components, such as equipment, valves, instruments, and piping flow. There is a standardized set of flowchart symbols.

Process Flow Diagram equipment symbols include centrifuges and heat exchangers.

Centrifuges

Centrifuges are devices that use centrifugal force/ acceleration to separate components of a mixture on the bases of their density, size, viscosity, and rotor speed. The more dense molecules move to the outside of the centrifuge and the less dense molecules move towards the centre.

CENTRIFUGAL COMPRESSOR 1

CENTRIFUGAL COMPRESSOR 2

CENTRIFUGAL COMPRESSOR 3

CENTRIFUGAL FAN

CENTRIFUGAL PUMP 0

CENTRIFUGAL PUMP 2

CENTRIFUGAL PUMP 3

CENTRIFUGAL PUMP 4

CENTRIFUGAL PUMP 5

CENTRIFUGAL PUMP

CENTRIFUGAL PUMPCENTRIFUGAL PUMP

CENTRIFUGE BLOWER

CENTRIFUGE SCREW, PERFORATED SHELL

CENTRIFUGE SCREW

CENTRIFUGE, PERFORATED SHELL

CENTRIFUGE BLOWER

CENTRIFUGE, PUSHER

CENTRIFUGE, SEPARATOR DISC

CENTRIFUGE, SKIMMER

CENTRIFUGE, SOLID SHELL

Heat Exchangers

Heat exchangers are a system that transfers heat between 2 or more fluids, separated by a solid wall. Heat exchangers can be used for both cooling and heating processes.

AIR-BLOWN COOLER

BOILER

BRIQUETTING MACHINE

COIL TUBES HEAT EXCHANGER

COMBUSTING CHAMBER

CONDENSER

CONDENSER 1

COOLER

COOLER TOWER 1

COOLING TOWER 2

COOLING TOWER 3

DOUBLE PIPE HEAT EXCHANGER

ELECTRIC HEATER

EXCHANGER

EXTRACTOR HOOD

FAN-FAN COOLER

FINNED TUBES HEAT EXCHANGER

FIRED HEATER

FLOATING HEAD HEAT EXCHANGER

FORCED-DRAFT COOLING TOWER

HEAT EXCHANGER

HEAT EXCHANGER 3

HEATER

HOSE REEL

INDUCED FLOW AIR COOLER

INDUCED-DRAFT COOLING TOWER

KETTLE HEAT EXCHANGER

LIGHT WATER STATION

OIL BUMER

PLATE HEAT EXCHANGER

REBOILER

REBOILER HEAT EXCHANGER

SHELL AND TUBE HEAT 1

SHELL AND TUBE HEAT 2

SHELL AND TUBE HEAT 3

SINGLE PASS HEAT EXCHANGER

SPIRAL HEAT EXCHANGER 1

SPIRAL HEAT EXCHANGER 2

SPRAY COOLER

STRAIGHT TUBES HEAT EXCHANGER

THIN-FILM EVAPORATOR

U-TUBE HEAT EXCHANGER

U-TUBE HEAT EXCHANGER 2

VENT

VERTICAL TURBINE

Miscellaneous PFD Symbols

Miscellaneous PFD symbols include crushers, dryers, general, mixers, and peripherals.

Crushers

Crushers are used to reduce the size of or change the form of materials, often for waste, to be deposited or recycled. They reduce the size of a solid mix of raw material.

COARSE CRUSHER

CONE CRUSHER

CRUSHERS

HAMMER CRUSHER

HAMMER CRUSHERS

IMPACT CRUSHER

JAW CRUSHER

MEDIUM CRUSHERS

ROLLER CRUSHER

VARIOUS CRUSHERS

JAW CRUSHER

Dryers

Dryers are components used to dry fluids through different processes.

DRYER

DRYING OVEN

FLUIDIZED BED DRYER

HEAT CONSUMER

MOTOR GENERATOR

MOVING SELF DRYER

ROLLER CONVEYOR BELT DRYER

SPRAY DRYER

General PFD Symbols

There are a number of other standard symbols included in PFD diagrams with a multitude of functions, as shown below.

ALKYATION

AUTOMATIC STOKER

BOOM LOADER

CHIMNEY TOWER HYPERBOLIC

COUNTERFLOW FORCED DRAFT

CROSSFLOW INDUCTED DRAFT

ELECTRIC MOTOR

FLUID CATALYTIC CRACKING

FLUID CRACKING

FLUIDIZED REACTOR

FURNACE

FURNACE 1

HYDROCRACKING

HYDROCRACKING 1

HYDROSULFURIZATION

PACKED TOWER

PLATE TOWER

SCREEN

TRANSPORT

TUBULAR

Mixers Symbols

There are a number of other standard symbols included in PFD diagrams with a multitude of functions, as shown below.

ANCHOR AGITATOR

CROSS-BEAM AGITATOR

DISC AGITATOR

GAT PADDLE AGITATOR

HELICAL AGITATOR

IMPELLER AGITATOR

IN-LINE MIXER

MIXER

PROPELLER AGITATOR

STIRRER AGITATOR

TURBINE AGITATOR

VARIOUS MIXER

VARIOUS MIXER 2

VARIOUS MIXERS

Peripheral PFD Symbols

Peripheral PFD symbols represent devices that are not core components used in the flow diagram.

AERATOR WITH SPARGER

BACKDRAFT DAMPER

BAG FILLING MACHINE

BELT SKIMMER

BOX TRUCK

BUCKET ELEVATOR

CHIMNEY

CONVEYOR

CONVEYOR 1

CONVEYOR, CHAIN, CLOSED

CONVEYOR, SCREW, CLOSED

CONVEYOR, VIBRATING, CLOSED

CRANE

CYCLONE

CYCLONE SEPARATOR

CYLINDER PISTON

ELECTROMAGNETIC PRECIPITATOR SEPARATOR

ELECTROMAGNETIC SEPARATOR

ELEVATOR

ELEVATOR 1

ELEVATOR 2

FIRING SYSTEM

FLAME ARRESTOR

GAS FLARE

GRAVITY SEPARATOR

HOISTS

HORIZONTAL SHAPING MACHINE

IMPACT SEPARATOR

INDUSTRIAL TRUCK

INJECTOR

LIFT

MANUAL FORKLIFT

OVERHEAD CONVEYOR

PALLETIZER

PELLETIZING DISC

PERMANENT MAGNET

PISTON EXTRUDER SHAPING MACHINES

PROPORTIONAL FEEDER

REDUCER

ROLLER CONVEYOR

ROLLER PRESS

ROLLING BIN TRUCK

ROTARY TABLE FEEDER

ROTARY VALVE FEEDER

RUPTURE DISC

SCRAPER CONVEYOR

SCREENING

SCREW CONVEYOR

SCREW EXTRUDER SHAPING MACHINES

SHIP

SKIP HOIST

SOLIDIFIER

SPRAY NOZZLE

TRUCK FORKLIFT

VIEWING GLASS WITH LIGHTING

VIEWING GLASS

Z-FORM ELEVATOR

Piping Fittings

Piping fittings are adaptors used to connect straight sections of pipe or tube in a pipe system to create the required geometry.

EXHAUST HEAD

STRAINER

TRIANGLE SEPARATOR

TRIANGLE SEPARATOR 2

FAQ - System Integration

What is a Process Flow Diagram?

A process flow diagram is a flowchart that depicts the relationships between major components in a process or circuit. The concept originated in 1921 – it was designed by industrial engineer Frank Gilbreth. Today the concept is often used in industrial plants for chemical and process engineering but the concepts can also be applied to a number of other applications.

Process flow diagrams consist of a series of flowchart symbols and notations to illustrate a process. The different types of flowcharts can vary hugely from hand-drawn flowcharts to complex software flowcharts.

What's Included in a Process Flow Diagram?

For a single unit process, the flowchart diagram includes:

Process piping
Major equipment items
Operational data (pressure, temperature, etc.)
Major bypass
Process stream names

To reduce over-annotating a process flow diagram, there are a number of aspects that aren’t included:

Pipe classes and line numbers
Minor bypass lines
Instrumental details
Instrumentation
Isolation and shut off valves
Controllers (such as a flow controller)
Maintenance vents and drains
Flanges
Relief and safety valves

What is a Process Flow Diagram Used for?

Process flow diagrams can be used to document a predefined process, improve an existing process, or model a new process. Process flow diagrams can also be known as:

Process Flow Chart
Flowsheet
Plumbing & Instrumental Diagram
Macro Flowchart
Top-Down Flowchart
Block Flow Diagram
Schematic Flow Diagram
System Flow Diagram
System Diagram

What is the Process Symbol in a Flowchart?

Process symbols represent an action, process, or function. They are also referred to as an ‘action symbol’ and are the most commonly used symbols in flowcharting. These types of symbols are often used in software.

How to Create a Process Flow Diagram

Here are 6 steps to create a process flow diagram:

Define the scope of the system, what will it achieve?
Determine the process boundaries, what causes it to start? Where does it end? What are the boundaries of the process?
Identify the process outputs, what is the final goal?
Identify the inputs, are there any manual inputs? What is required at each step?
Use this data to create a model, add necessary detail such as control points and measurements. Think methodically how do components interact with one another.
Add process symbols to describe the component/ equipment.
Create a data dictionary, outlining data omitted from the flowchart.
Review, revise, and test when necessary.

What are Process Flow Diagram Standards?

There are a number of standards related to process flow diagrams in industry, to ensure adequate representation of engineering systems. The most common standards are:

ISO 15519-1:2010(en): Specification for diagrams for the process industry — Part 1: General rules
ISO 15519-2:2015(en): Specifications for diagrams for the 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

What Are Basic Flowchart Symbols?

For software-based process flow diagrams, there are a number of basic symbols to identify. These include:

Oval – input/ output of the system
Rectangle – a step in the process
Arrows/ lines – indicate directional flow
Diamond – represents a decision

These symbols are not commonly used in engineering diagrams such as mechanical, chemical, and electrical process flow diagrams. These symbols, however, can be found in computer software.