This free tool lets you sketch a Piping & Instrumentation Diagram (P&ID) the way a process engineer would rough one out on a whiteboard — drag standard ISA equipment, valve, and instrument symbols onto a canvas, connect them with process piping or instrument signal lines, and label each one with a real ISA tag. It's built to teach P&ID conventions, not to replace CAD software: there's no import/export of industry file formats, just a clean, fast way to understand how the symbols and tagging system fit together before you open AutoCAD P&ID or a DCS configuration tool.
The left palette has three groups. Equipment (pump, vessel/tank, heat exchanger) represents the physical hardware process fluid flows through. Valves (control valve, block/gate valve, check valve) represent flow-control elements — note the control valve's extra stem and actuator circle on top, which is what distinguishes an automated valve from a manually-operated block valve on a real P&ID. Instruments (pressure, level, flow, temperature) are drawn as circles — the "bubble" symbol ISA uses for any field-mounted or panel-mounted instrument, split by a line with the tag letters on top and the loop number below, exactly as it appears on a real drawing.
Drag any palette item onto the canvas to drop a new symbol (on touch devices, tap the palette item instead — it drops near the center of your current view). Drag a placed symbol to reposition it. To connect two symbols, click the first one, then click the second — the tool automatically draws a solid process line with an arrowhead for equipment-to-equipment or equipment-to-valve connections, and a dashed blue line for any connection touching an instrument, representing an instrument signal rather than a physical pipe. Click any line to delete it, or select a symbol and use the "Delete" button in the side panel to remove it and its connections.
Every instrument on a real P&ID carries a tag built from a letter code plus a loop number, defined by ISA-5.1. The first letter identifies the measured variable (P = pressure, F = flow, L = level, T = temperature); the second (and sometimes third) letter identifies the function performed (I = indicator, T = transmitter, C = controller). So PT-101 is a pressure transmitter on loop 101, and FIC-204 is a flow indicating controller on loop 204 — a single instrument that both displays and controls flow. Click any symbol on the canvas and edit its tag in the side panel to practice building tags for different loop scenarios.
The canvas loads with a simple, complete loop already built: a centrifugal pump (P-101) feeds a control valve (FV-103), which discharges into a tank (TK-104) — the process path, drawn as solid lines. A flow transmitter (FT-102) sits on the line between the pump and the valve, sending a dashed instrument signal to the control valve — this is the classic flow-control loop pattern: measure flow, then throttle a valve to hold it at setpoint. Click "Clear" to start from a blank canvas, or "Load Example" any time to bring this loop back.
The second letter is the primary function: I (indicator), T (transmitter), C (controller), R (recorder), S (switch), A (alarm), among others. A third letter often modifies that function — for example FIC combines Indicator and Controller on one flow instrument, meaning a single field device or DCS point both displays the flow value and actively controls it, rather than just reporting it.
On a real P&ID, only automated final control elements get the extra actuator symbol on top of the valve body — a circle (diaphragm/pneumatic actuator) connected by a stem, matching what this tool draws for the control valve. A block (gate) valve is manually operated, so it's drawn as the same bowtie-shaped valve body with just a handwheel bar, no actuator — that visual difference is exactly how an engineer scanning a drawing tells "this valve is controlled by the DCS" from "this valve is only touched by an operator in the field."
Solid lines represent process piping — the actual pipe the fluid flows through, drawn between equipment and valves. Dashed lines represent instrument signals — the electronic or pneumatic connection carrying a measurement or control command between a field instrument (like a flow transmitter) and a controller or final control element (like a control valve). This tool draws that distinction automatically based on which symbol types you connect.
Not in this version — this tool is intentionally scoped as a learning and quick-sketch aid for understanding ISA symbols and tagging, not a substitute for professional P&ID software like AutoCAD Plant 3D or SmartPlant P&ID, which support full document control, revision tracking, and DCS/instrument database tie-ins required for real engineering deliverables.