Plant 3D Practical Knowledge
P&ID: symbols to DIN EN ISO 10628
The most important symbols for P&IDs at a glance: pipes, valves, pumps, vessels, heat exchangers and instruments with identification letters to DIN EN 62424.DIN – German Institute for Standardization “DIN” before a number means that the standard is published in Germany by the German Institute for Standardization. Background and sources ›EN – European Standard European Standard, developed by CEN (general) or CENELEC (electrical engineering). Background and sources › Plus the free quick reference “P&IDR&I – Piping and instrumentation diagram Flow diagram showing all pipes, valves, equipment and instrumentation of a plant (P&ID, Piping and Instrumentation Diagram). Background and sources › symbol overview” as a PDF and the route into AutoCAD P&ID.
With us you will find solutions for your tasks. The drawings on this page are our own simplified representations. The standard and the legend sheet of your project are binding.
What a P&ID shows
The P&ID (piping and instrumentation diagram) shows all pipes with their designation, the valves, equipment and machines as well as all instruments with their signal lines. It is the basic document for piping and instrumentation and electrical design.
- DIN EN ISO 10628-1: types of flow diagrams and their content
- DIN EN ISO 10628-2: graphical symbols
- DIN 28000-4: further symbols for pipes and valves
- DIN EN 62424: representation and identification of instruments
- ANSI/ISA-5ANSI – American National Standards Institute US standards institute. ASME standards are usually also ANSI standards, hence the notation “ANSI/ASME B16.5”. Background and sources ›ISA – International Society of Automation US association for automation. Its standard ISA-5.1 specifies symbols and identification letters for instrumentation. Background and sources ›.1: instrumentation in projects to US rules
Block flow diagram and process flow diagram compared: Infobase chapter Flow diagrams.
Pipes and lines
Line type and width distinguish main and secondary lines from signals. An arrow on the line shows the flow direction.
Valves
The basic form of every valve is two triangles whose tips touch. Additional marks in the middle, on the triangle or on the actuator show the type.
Pumps, compressors and drives
Machines are shown as a circle with additional lines. The lines show how conveying takes place.
Vessels and equipment
Vessels show their approximate shape and position. Proportions and elevations should remain recognizable in the P&ID.
Heat exchangers
The zigzag line stands for the heat exchange between two streams.
Instruments
An instrument (process control) is an oval with identification letters and a number. A line shows where it is operated.
Identification letters to DIN EN 62424 – the principle
The first letter names the measured variable, the succeeding letters say what the instrument does. It is followed by the loop number. Here are the most common letters – the complete list is in the standard.
| First letter | Measured variable |
|---|---|
| F | Flow |
| L | Level |
| P | Pressure |
| T | Temperature |
| Q | Quality, analysis |
| Succeeding letter | Task |
|---|---|
| I | Indication |
| R | Registration |
| C | Closed-loop control |
| A | Alarm |
| S | Switching |
| Z | Protective device |
Examples
| Identifier | Meaning |
|---|---|
| TI 101 | Temperature, local indication |
| FIC 102 | Flow, indication and control in the control room |
| LIC 103 | Level, indication and control at the local control panel |
| PIRA 104 | Pressure, indication, recording and alarm |
| PZ 105 | Pressure, protective device (safety-related) |
Quick reference “P&ID symbol overview”
All symbols on this page for printing – for training, project start and checking P&IDs.
2 A4 pages: all symbols on this page, the structure of the instrument tag and the most common identification letters.
Symbols in AutoCAD P&ID
In AutoCAD P&ID you place symbols from the tool palette. Every symbol is an object with properties and a tag and is stored in the project database – bills of materials, line lists and the comparison with the 3D model build on this.
- Select the symbol from the palette with a click and place it with a click, do not drag: why dragging bypasses grid snap
- Create your own symbols from AutoCAD blocks: Turn a block into a P&ID symbol
- Switch the symbol depending on a property, e.g. actuator with fail-safe position: field of type symbol list
- Size and representation are defined by the project configuration: why manual scaling gets lost
Ready-made symbol palettes to company standard are included in the project templates ASEING PlantConfig Pro – with a uniform tag structure and mapping between AutoCAD P&ID and AutoCAD Plant 3D.
How we support you
AutoCAD P&ID training
Live with a trainer, online or in Frankfurt: create a project, place symbols, tag, check and output.
P&ID Configuration video course
Set up symbols, properties, tag formats and annotations to company standard.
ASEING PlantConfig Pro
Project templates with ready-made symbol palettes for AutoCAD P&ID and AutoCAD Plant 3D.
Support
Quick question about a symbol or the configuration? Via Teams, billed by actual time.
Setting up a new project?
Self-test exercises
For studies, vocational training and induction – with a solution to expand.
Exercise 1 In the P&ID there is an instrument “LIC 210” with a line in the oval. What does that mean?
Show solution
L = level (measured variable), I = indication, C = control, 210 = loop number. The single line shows: the instrument is operated in the control room. So it is a level control with indication in the control room.
Exercise 2 How do you tell a globe valve from a cock in the P&ID?
Show solution
Both have the basic symbol of two triangles, tip to tip. The globe valve has a dot in the middle, the cock a circle. The legend sheet of your project is binding.
Exercise 3 Two lines meet in the flow diagram and there is a dot at that point. What does that mean – and what would a crossing without connection look like?
Show solution
The dot marks a branch with connection. At a crossing without connection, one of the two lines is interrupted at the crossing.
More exercises and a guide to the modules in your studies: For teaching and education.
Frequently asked questions
Which standard applies to symbols in the P&ID?
In Germany DIN EN ISO 10628: Part 1 covers the types and content of flow diagrams, Part 2 the graphical symbols. DIN 28000-4 contains further pipe symbols. Instruments are identified to DIN EN 62424. The legend sheet you agree with the client is decisive for your project.
What is the difference between DIN EN 62424 and ANSI/ISA-5.1 for instruments?
According to DIN EN 62424, one instrument loop with all its functions has one tag, e.g. FIC 102. According to ISA-5.1, every device with its own hardware gets its own symbol, e.g. transmitter FT 102 and controller FIC 102. In international projects, the system used therefore belongs on the legend sheet.
Are the P&ID symbols available as a PDF?
Yes. The quick reference “P&ID symbol overview” summarizes all symbols on this page and the most common identification letters on two pages. It is free of charge with a customer account. In AutoCAD P&ID the symbols are available as a tool palette.
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Standards status for this page 5 standards · researched October 2026
| Standard | Contents | Current edition | Replaced / successor |
|---|---|---|---|
| DIN EN ISO 10628-1 | Diagrams for the chemical and petrochemical industry – Part 1: Specification of diagrams | DIN EN ISO 10628-1:2015-04 | replaces DIN EN ISO 10628:2001-03 |
| DIN EN ISO 10628-2 | Diagrams for the chemical and petrochemical industry – Part 2: Graphical symbols | DIN EN ISO 10628-2:2013-04 | replaces DIN EN ISO 10628:2001-03 |
| DIN EN 62424 (VDE 0810-24) | Representation of process control engineering requests in P&I diagrams and data exchange between P&ID tools | DIN EN 62424 (VDE 0810-24):2017-12 | replaces DIN EN 62424 (VDE 0810-24):2010-01 |
| DIN 28000-4 | Chemical process equipment – Documentation in the life cycle of process plants – Part 4: Graphical symbols for valves, pipes and actuators | DIN 28000-4:2014-07 | replaces DIN 19227-1:1993-10; DIN 2429-1:1988-01; DIN 2429-2:1988-01 |
| ANSI/ISA-5.1 | Instrumentation and Control – Symbols and Identification | ANSI/ISA-5.1-2024 | replaces ANSI/ISA-5.1-2022 |
Researched at DIN Media, ISO, IECIEC – International Electrotechnical Commission International Electrotechnical Commission in Geneva: worldwide standards for electrical engineering and for instrumentation and control. Background and sources › and ASMEASME – American Society of Mechanical Engineers US engineering society. Its codes for piping, flanges and pipe dimensions apply in many plants worldwide. Background and sources ›, as of October 2026. Before binding use, please check the current edition with the standards publisher. Overview of all standards: Plant Engineering Infobase · Standards status.
Terms, background and sources 8 terms on this page
Brief explanations for reference. They do not replace the standard or code itself.
- DIN – German Institute for Standardization
“DIN” before a number means that the standard is published in Germany by the German Institute for Standardization.
DIN was founded in 1917 as the Standards Committee of German Industry. If “DIN EN” or “DIN EN ISO” precedes the number, a European or international standard has been adopted unchanged as a German standard.
- EN – European Standard
European Standard, developed by CEN (general) or CENELEC (electrical engineering).
Every member country must adopt an EN unchanged as a national standard – in Germany as “DIN EN …”. Conflicting national standards are withdrawn.
- R&I – Piping and instrumentation diagram
Flow diagram showing all pipes, valves, equipment and instrumentation of a plant (P&ID, Piping and Instrumentation Diagram).
Symbols and drawing rules: DIN EN ISO 10628-1 and -2. Identification letters for instrumentation: DIN EN 62424 or ISA-5.1.
- ISO – International Organization for Standardization
“ISO” before a number denotes a worldwide standard of the International Organization for Standardization in Geneva.
ISO was founded in 1947. Its members are the national standards bodies; for Germany, this is DIN.
- ANSI – American National Standards Institute
US standards institute. ASME standards are usually also ANSI standards, hence the notation “ANSI/ASME B16.5”.
- ISA – International Society of Automation
US association for automation. Its standard ISA-5.1 specifies symbols and identification letters for instrumentation.
- IEC – International Electrotechnical Commission
International Electrotechnical Commission in Geneva: worldwide standards for electrical engineering and for instrumentation and control.
IEC was founded in 1906. IEC standards adopted in Europe are called “EN IEC …” or “EN 6xxxx”.
- ASME – American Society of Mechanical Engineers
US engineering society. Its codes for piping, flanges and pipe dimensions apply in many plants worldwide.
ASME was founded in 1880. Well-known codes: B31.3 (process piping), B16.5 (flanges), B36.10M and B36.19M (pipe dimensions).
Sources and origins
- DIN – German Institute for Standardization (for DIN)
- CEN and CENELEC – European standardization (for EN)
- ISO – International Organization for Standardization (for R&I, ISO)
- IEC – International Electrotechnical Commission (for R&I, IEC)
- ANSI – American National Standards Institute (for ANSI)
- ISA – International Society of Automation (for ISA)
- ASME – American Society of Mechanical Engineers (for ASME)