Process and instrumentation symbols drawn to P&ID convention: ball, check and gate valves, centrifugal pump, tank or vessel, flange, reducer and instrument bubble. Valves share a common body so a type change on the diagram does not move the line.
8 blocks in 2 families. DXF R2018, drawn in inches.
A piping and instrumentation diagram is a schematic, not a scaled plan, and the eight symbols here are the starting set for one: ball, gate and check valves, a centrifugal pump, a tank or vessel, a flange, a reducer and an instrument bubble. Process and chemical engineers draw P&IDs to show every line, valve and control loop in a system, and the instrumentation conventions come from ISA-5.1. NCS assigns the D designator to process, so layers like D-PIPE for lines and D-INST for instruments keep a P&ID organized alongside the rest of a drawing set.
Every symbol is built on a unit u, 12 by default and adjustable from 6 to 24, so the valves are 24 x 12 units, the pump 21.6 units square and the bubble 14.4 units across. Those are drawing units, not pipe sizes; pick one u for a whole diagram so valve bodies match. The line sizes and specifications belong in the line number tag, not the symbol size.
The valves share one body geometry. That is deliberate: change a gate valve to a ball valve during a revision and the pipe endpoints stay where they were. Each valve inserts at its center on a horizontal pipe axis, so trim the line, insert on the gap midpoint, and rotate for vertical runs. The check valve points in the flow direction, +X by default, and the reducer's large end is at -X; rotate 180 degrees rather than mirroring so the flow arrow stays true.
The instrument bubble carries a tag attribute, FT-101 by default. Under ISA-5.1 the first letter is the measured variable and the following letters the function, so FT is a flow transmitter and 101 is the loop number. A plain circle is a field-mounted instrument; a solid horizontal line through it means a primary location such as the control room. Keep loop numbers unique across the diagram.
The set is free to download as DXF, DWG or PNG. In the CADdillo editor at app.caddillo.com you can place them in a browser and edit the tag text without a desktop CAD package.
Plan-view footprint in inches. Each name opens the block's section on its family page, with DXF, DWG and PNG downloads.
| Block | Footprint (in) | Family |
|---|---|---|
| P&ID Flange | 21.6 x 12 | P&ID Equipment and Symbol CAD Blocks |
| P&ID Instrument Bubble | 14.4 x 14.4 | P&ID Equipment and Symbol CAD Blocks |
| P&ID Centrifugal Pump | 21.6 x 21.6 | P&ID Equipment and Symbol CAD Blocks |
| P&ID Reducer | 14.4 x 12 | P&ID Equipment and Symbol CAD Blocks |
| P&ID Tank / Vessel | 12 x 19.2 | P&ID Equipment and Symbol CAD Blocks |
| P&ID Ball Valve | 24 x 12 | P&ID Valve CAD Blocks |
| P&ID Check Valve | 24 x 12 | P&ID Valve CAD Blocks |
| P&ID Gate Valve | 24 x 12 | P&ID Valve CAD Blocks |
ISA-5.1, Instrumentation and Control Symbols and Identification, defines the tag letters and bubble conventions. The first letter is the measured variable, such as F for flow or P for pressure, and succeeding letters give the function, such as T for transmitter. The bubble block ships with the tag FT-101, a flow transmitter in loop 101.
They are not, because a P&ID is a schematic; symbols are sized for legibility and consistency. Each block here is built on a unit u, default 12 and adjustable from 6 to 24; valves are 2u long and u high. Use one u across a diagram and record pipe size in the line tag instead of the symbol.
Break the line, then insert the valve at the gap's midpoint: every valve block's origin is its center on the pipe axis, which runs along X. Rotate 90 degrees for vertical lines. The ball, gate and check valves share the same body length, so swapping one type for another does not move the line ends.
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