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P&ID symbols
The complete legend: 92 symbols for valves, pumps, vessels, heat exchangers, instruments, line types and fittings, as US legends draw them (ISA 5.1, PIP PIC001) and as ISO 10628-2, DIN and IEC 62424 draw them. Free to download as SVG and PNG, or as one printable chart.
P&ID symbols by standard
- ISA 5.1 symbolsBubbles, letters, lines and actuators
- ISO 10628 P&ID symbols52 symbols with registration numbers
- PIP P&ID symbols (PIC001)The US legend and documentation criteria
- DIN P&ID symbols (R&I-Fließschema)R&I-Fließschema, with German names
- IEC 62424 P&ID symbols9 PCE request ovals and the letter tables
- ISA vs ISO P&ID symbolsSide by side, symbol by symbol
- Field-mounted instrument
- Panel-mounted instrument
- Behind-panel instrument
- Local panel instrument
- DCS shared display
- PLC function
- Computer function
- Interlock
- Pressure gauge
- Pressure transmitter
- Level transmitter
- Flow transmitter
- Temperature transmitter
- Level gauge
- Orifice plate
- Venturi
- Rotameter
- Magnetic flow meter
- Thermowell
How to read P&ID symbols
Most P&ID symbols are built from a small set of base shapes, with a mark added to show the type. Learn the bases and you can read almost any legend:
- Valves start from two triangles meeting at their points. A dot makes a globe valve, a circle a ball valve, a filled half a check valve. See valve symbols.
- Actuators sit on the valve stem: a dome for a diaphragm, M for a motor, S for a solenoid. See control valve symbols.
- Rotating equipment is drawn around a circle. See pump and compressor symbols.
- Instruments are bubbles with a tag inside. See instrument symbols.
- Lines tell you what connects what: thick for process piping, marked lines for signals. See P&ID line types.
For a step-by-step walk through a real sheet, see how to read a P&ID.
Instrument bubbles at a glance
| Bubble | Meaning (ISA 5.1) |
|---|---|
| Circle, no line | Field-mounted, at the process |
| Circle, solid line | Main control room, on the panel |
| Circle, dashed line | Main control room, behind the panel |
| Circle, double line | Local panel in the plant |
| Circle in a square | Shared display, for example the DCS |
| Diamond in a square | PLC function |
| Hexagon | Computer function |
The letters inside follow ISA 5.1: the first letter is the measured variable (P pressure, T temperature, F flow, L level, A analysis), the next letters are the function (I indicate, T transmit, C control, E element, G gauge, V valve). PIC 101 is a pressure indicating controller in loop 101.
Which standards P&ID symbols follow
- ISA 5.1: instrument symbols, bubbles, signal lines and identification letters (ANSI/ISA-5.1-2024).
- ISO 10628-2: graphical symbols for equipment, valves and piping on process diagrams, each with a registration number.
- PIP PIC001: the P&ID documentation criteria used on many US projects, with ISA 5.1 for instruments.
- IEC 62424: process control functions drawn as ovals, the European counterpart to ISA bubbles.
- DIN EN ISO 10628 and DIN EN 62424: the German editions, used on the R&I-Fließschema.
Use the standard switch in the legend above to see each symbol as ISO 10628-2 or IEC 62424 draw it, or compare them all on ISA vs ISO P&ID symbols. Symbols also differ slightly between companies and projects. The legend sheets at the front of every P&ID set are the final word.
Using these symbols
Every symbol on this page was drawn by Deskely. You are free to use them in your own drawings, documents and training material. Each symbol page has its SVG and PNG, and the full set is in the PDF chart and the SVG download above.
Frequently asked questions
What are P&ID symbols?
P&ID symbols are the standard shapes used on piping and instrumentation diagrams to show equipment, valves, instruments, piping and the signals between them. Each symbol stands for a real item that is tagged in the plant.
Which standard defines P&ID symbols?
Instrument symbols and identification letters come from ISA 5.1 in US practice and IEC 62424 in European practice. Equipment, valve and piping symbols follow ISO 10628-2 internationally (DIN EN ISO 10628-2 in Germany) or PIP PIC001 on US projects. Every project still issues its own legend sheet, which takes precedence.
What is the difference between ISA and ISO P&ID symbols?
Most symbols match, but ISO 10628-2 draws a bar in the gate valve, a dot on the check valve, an arrow through the control valve and pumps as a circle with a chevron, and IEC 62424 draws instruments as ovals. See the side by side comparison.
Where do I find the legend for a P&ID?
On the legend sheets at the front of the P&ID set, usually the first two to four drawings. They show every symbol, line type, abbreviation and tag format used on that project.
Is there a P&ID symbols PDF?
Yes. The full legend on this page is free to download as a printable PDF chart, and every symbol is available as an SVG and PNG file.
Can I use these symbols in my own drawings?
Yes. The symbols on this page were drawn by Deskely and are free to use in your own drawings, documents and training material.
What is the difference between a P&ID and a PFD?
A process flow diagram (PFD) shows the main process flow and conditions. A P&ID shows every pipe, valve, instrument and control loop needed to build and operate the plant. See P&ID vs PFD.
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