P&ID Editor — Process & Instrumentation Diagrams with ISA 5.1 and ISO 10628-2 Symbols

ANSI/ISA-5.1-2009 (Instrumentation Symbols and Identification) defines the graphical symbols and alphanumeric tag notation used on P&IDs throughout the process industries. The standard divides symbols into four categories: primary elements and sensors (flow, level, pressure, temperature, analytical, multi-variable), final control elements (control valves, on/off valves, regulators), general instruments and controllers (indicators, transmitters, controllers, recorders), and process equipment (vessels, heat exchangers, pumps, compressors, columns, tanks).

The editor's equipment and instrument symbols are drawn in the ISA 5.1 style, so they are recognisable to any process engineer trained under the standard; they are modelled on ISA 5.1, not a certified or compliant reproduction of it. The instrument bubble is the cornerstone of ISA 5.1: the tag code encodes the measured variable (first letter) and the function class (subsequent letters), e.g. FIC for Flow Indicating Controller or PT for Pressure Transmitter. The editor supplies dedicated FT, PT, LT, TT and AT bubbles alongside generic indicator, transmitter, controller, recorder and analyser bubbles, and every placed symbol carries an editable tag rendered beside it on the drawing.

P&IDs distinguish each class of interconnection by line style, so a reviewer can trace whether a path carries process fluid, measurement signal, control signal, electrical power, or pneumatic supply without reading every label. The MechanixCalc editor uses its own colour-coded dash patterns in that spirit — they are conventions in the ISA style, not ISA 5.1's own line glyphs: process lines are solid and the heaviest weight; instrument signal lines are dashed fine-weight; electrical lines use a dot-dash pattern; signal lines a fine dash; pneumatic supply lines a fine dotted pattern. Four more line types (solids / pneumatic conveying, compressed air, dust / extraction duct, by others / existing) are drawing conventions for bulk-solids plants, not ISA or ISO line symbols.

Connections between nodes are drawn as orthogonal (right-angled) runs that snap to the named port positions on each symbol — suction, discharge, top nozzle, drain, signal connection and so on — so the topology of the P&ID is encoded in the graph structure, not just its appearance. Selecting a line opens the Line Spec panel, where its line number, size, service / medium, design pressure, design temperature and insulation are recorded (the size and line number also form an automatic, overridable label on the drawing); those fields fill the line list, giving downstream document-control and HAZOP teams a machine-readable inventory.

Process plants are documented on multiple indexed P&ID sheets: one for each process section or unit operation (feed preparation, reactor, separation, utilities). The editor supports any number of named sheets within a single project file. A symbol placed on Sheet 1 (e.g. a pressure transmitter PT-201) can reference the corresponding control loop shown on Sheet 2, using free-text annotation nodes to carry the cross-reference. The editor has no dedicated off-page connector symbol, so the cross-reference is a note you write, not a linked object.

The bill of materials is generated from the placed node inventory across every sheet: one row per placed component, carrying its sheet, class (equipment, valve or instrument), tag, type, service and description, plus Reg. no. and Verification columns for ISO symbols. Separate equipment, valve, instrument and line lists export the same inventory split the way a P&ID document set expects. All five serialise as RFC 4180 CSV (fields quoted and escaped) or as tabs of one Excel workbook, suitable for import into CMMS, document-management, or HAZOP-study spreadsheets. The PDF drawing carries a zoned frame and a title block with project number, revision, drawn-by, date and sheet name; whether it satisfies a given company's management-of-change procedure is for that company to decide.