Process Flow Diagram (PFD) Export

NeqSim can generate professional oil & gas style process flow diagrams (PFDs) that follow industry conventions, comparable to UniSim, Aspen, and HYSYS.

Quick Start

// Create and run your process
ProcessSystem process = new ProcessSystem("Gas Processing Plant");
// ... add equipment ...
process.run();

// Export to DOT format (text)
String dot = process.toDOT();

// Or use the diagram exporter for more control
process.createDiagramExporter()
    .setTitle("Gas Processing Plant")
    .setDetailLevel(DiagramDetailLevel.STANDARD)
    .exportAsSVG(Path.of("diagram.svg"));

Features

Gravity-Based Layout

The diagram layout follows oil & gas conventions with left-to-right flow:

Phase-Aware Stream Styling

Streams are automatically colored based on phase composition:

Separator Outlet Semantics

For two-phase separators, outlets are positioned:

For three-phase separators (gas, oil, aqueous), outlets follow gravity:

Comprehensive Equipment Support

The diagram system supports all NeqSim equipment types with industry-standard shapes:

Separators & Vessels

Equipment Shape Color
Separator Cylinder Green
ThreePhaseSeparator Cylinder Green
Scrubber Cylinder Light Green
GasScrubber Cylinder Light Green
KnockOutDrum Cylinder Light Green
Flash Cylinder Light Green

Columns

Equipment Shape Color
DistillationColumn Tall Cylinder Green
Absorber Rectangle Light Green
Stripper Rectangle Light Green
WaterStripperColumn Rectangle Light Green

Compressors & Expanders

Equipment Shape Symbol
Compressor Trapezoid Standard P&ID trapezoid
CompressorModule Trapezoid Standard P&ID trapezoid
Expander Inverted Trapezium Inverted trapezoid
TurbineExpander Inverted Trapezium Inverted trapezoid

Pumps

Equipment Shape Symbol
Pump Circle with impeller Circle on triangle base
PumpModule Circle with impeller Circle on triangle base
ESP (Electrical Submersible Pump) Circle with impeller Circle on triangle base

Heat Exchangers

Equipment Shape Symbol
HeatExchanger Circle Simple circle
Cooler Circle Simple circle
Heater Circle Simple circle
Condenser Circle Simple circle
Reboiler Circle Simple circle
MultiStreamHeatExchanger Circle Simple circle
DirectContactHeater Circle Simple circle

Valves

Equipment Shape Symbol
ThrottlingValve Bowtie (▶◀) Two triangles tip-to-tip
ValveMoV Bowtie (▶◀) Two triangles tip-to-tip
ControlValve Bowtie (▶◀) Two triangles tip-to-tip
SafetyValve Bowtie (▶◀) Two triangles tip-to-tip
PressureReliefValve Bowtie (▶◀) Two triangles tip-to-tip
ESDValve Bowtie (▶◀) Two triangles tip-to-tip
HIPPSValve Bowtie (▶◀) Two triangles tip-to-tip

Reactors

Equipment Shape Color
Reactor Hexagon Orange
GibbsReactor Hexagon Orange
EquilibriumReactor Hexagon Orange
ElectrolyzerCell Hexagon Light Blue

Other Equipment

Equipment Shape Color
Mixer Triangle Light Gray
Splitter Inverted Triangle Light Gray
Stream Ellipse Light Green
Ejector Pentagon Light Gray
Flare Diamond Orange
Filter Rectangle Tan
Membrane Rectangle Light Blue
Tank Cylinder Gray
Pipeline Rectangle Gray
Well House Brown
GasGenerator/GasTurbine Octagon Steel Blue

Control Equipment

Equipment Shape Color
Recycle Rectangle (dashed) Gray
Adjuster Rectangle (dashed) Gray
Calculator Rectangle (dashed) Light Blue
Controller Rectangle (dashed) Light Yellow
SetPoint Rectangle (dashed) Light Gray

Diagram Styles

Four diagram styles are available to match different simulator conventions:

import neqsim.process.processmodel.diagram.DiagramStyle;

ProcessDiagramExporter exporter = new ProcessDiagramExporter(process);
exporter.setDiagramStyle(DiagramStyle.HYSYS);
Style Description Stream Color Background
NEQSIM Default NeqSim style with phase-based coloring Phase-dependent White
HYSYS HYSYS/UniSim style Blue (#0066CC) Light Cyan
PROII PRO/II style Dark Blue (#003366) White
ASPEN_PLUS Aspen Plus style Blue (#0066FF) Light Gray

Equipment Symbols (PFD Standard)

Equipment symbols follow oil & gas PFD conventions:

Equipment Symbol Description
Valve ▶◀ Bowtie - two triangles tip-to-tip
Heater/Cooler ○ Simple circle
Pump ○ on ▽ Circle with impeller on triangle
Compressor ⌂ Trapezoid shape
Mixer ▶ Right-pointing triangle
Splitter ◀ Left-pointing triangle
Separator ▭ Vertical cylinder

Recycle Stream Highlighting

Anti-surge loops and recycle streams are automatically detected and highlighted:

Stream Value Display

Two display modes for process values:

Simple Text Labels

exporter.setShowStreamValues(true)
        .setUseStreamTables(false);

Shows: Stream Name\n25.0°C, 50.0 bar\n1000 kg/hr

HTML Table Labels (Professional)

exporter.setShowStreamValues(true)
        .setUseStreamTables(true);

Generates HTML tables with:

Control Equipment Filtering

Control equipment (Recycle, Adjuster, Calculator, etc.) can be hidden for cleaner diagrams:

exporter.setShowControlEquipment(false);

Detail Levels

Three detail levels are available:

CONCEPTUAL

ENGINEERING

DEBUG

API Reference

ProcessSystem Methods

// Quick DOT export
String dot = process.toDOT();

// DOT export with specific detail level
String dot = process.toDOT(DiagramDetailLevel.CONCEPTUAL);

// Full-featured exporter
ProcessDiagramExporter exporter = process.createDiagramExporter();

// Direct SVG/PNG export (requires Graphviz)
process.exportDiagramSVG(Path.of("diagram.svg"));
process.exportDiagramPNG(Path.of("diagram.png"));

ProcessDiagramExporter Configuration

ProcessDiagramExporter exporter = new ProcessDiagramExporter(process)
    .setTitle("My Process")
    .setDiagramStyle(DiagramStyle.HYSYS)  // NEQSIM, HYSYS, PROII, ASPEN_PLUS
    .setDetailLevel(DiagramDetailLevel.ENGINEERING)
    .setVerticalLayout(false)   // LR layout (left-to-right flow) - default
    .setUseClusters(true)       // Group equipment by role
    .setShowLegend(true)        // Include legend
    .setShowStreamValues(true)  // Show T/P/F on streams
    .setUseStreamTables(false)  // Use HTML tables (true) or text (false)
    .setHighlightRecycles(true) // Highlight recycle streams
    .setShowControlEquipment(true)  // Show/hide control equipment
    .setShowDexpiMetadata(true);    // Show DEXPI line numbers/fluid codes

// Export options
String dot = exporter.toDOT();
exporter.exportDOT(Path.of("diagram.dot"));
exporter.exportSVG(Path.of("diagram.svg"));  // Requires Graphviz
exporter.exportPNG(Path.of("diagram.png"));  // Requires Graphviz
exporter.exportPDF(Path.of("diagram.pdf"));  // Requires Graphviz

Rendering DOT Files

The DOT format can be rendered using Graphviz:

# Install Graphviz (if needed)
# Windows: choco install graphviz
# macOS: brew install graphviz
# Linux: apt-get install graphviz

# Render to SVG
dot -Tsvg process.dot -o process.svg

# Render to PNG
dot -Tpng process.dot -o process.png

# Render to PDF
dot -Tpdf process.dot -o process.pdf

Example: Gas Separation Process

// Create fluid
SystemInterface fluid = new SystemSrkEos(298.0, 50.0);
fluid.addComponent("methane", 0.7);
fluid.addComponent("ethane", 0.15);
fluid.addComponent("propane", 0.1);
fluid.addComponent("n-butane", 0.05);
fluid.setMixingRule("classic");

// Build process
ProcessSystem process = new ProcessSystem("Gas Separation");

Stream feed = new Stream("Well Fluid", fluid);
feed.setFlowRate(5000.0, "kg/hr");
feed.setTemperature(60.0, "C");
feed.setPressure(80.0, "bara");
process.add(feed);

Separator hpSep = new Separator("HP Separator", feed);
process.add(hpSep);

Compressor comp = new Compressor("Export Compressor", hpSep.getGasOutStream());
comp.setOutletPressure(120.0, "bara");
process.add(comp);

Cooler cooler = new Cooler("Gas Cooler", comp.getOutletStream());
cooler.setOutTemperature(40.0, "C");
process.add(cooler);

Pump pump = new Pump("Oil Pump", hpSep.getLiquidOutStream());
pump.setOutletPressure(60.0, "bara");
process.add(pump);

process.run();

// Export diagram
process.createDiagramExporter()
    .setTitle("Gas Separation Process")
    .setDetailLevel(DiagramDetailLevel.ENGINEERING)
    .exportSVG(Path.of("gas_separation.svg"));

This generates a professional PFD with:

Example: Three-Phase Separation

// Create three-phase fluid (gas, oil, water)
SystemInterface fluid = new SystemSrkEos(298.0, 50.0);
fluid.addComponent("methane", 0.5);
fluid.addComponent("n-heptane", 0.3);
fluid.addComponent("water", 0.2);
fluid.setMixingRule("classic");
fluid.setMultiPhaseCheck(true);

// Build process
ProcessSystem process = new ProcessSystem("Production Separation");

Stream feed = new Stream("Well Fluid", fluid);
feed.setFlowRate(5000.0, "kg/hr");
feed.setTemperature(60.0, "C");
feed.setPressure(80.0, "bara");
process.add(feed);

// Three-phase separator
ThreePhaseSeparator separator = new ThreePhaseSeparator("Production Separator", feed);
process.add(separator);

// Gas compression
Compressor gasCompressor = new Compressor("Gas Compressor", separator.getGasOutStream());
gasCompressor.setOutletPressure(120.0, "bara");
process.add(gasCompressor);

// Oil export pump
Pump oilPump = new Pump("Oil Pump", separator.getOilOutStream());
oilPump.setOutletPressure(60.0, "bara");
process.add(oilPump);

// Produced water handling
Pump waterPump = new Pump("Water Pump", separator.getWaterOutStream());
waterPump.setOutletPressure(10.0, "bara");
process.add(waterPump);

process.run();

// Export diagram
process.createDiagramExporter()
    .setTitle("Production Separation")
    .setDetailLevel(DiagramDetailLevel.ENGINEERING)
    .exportSVG(Path.of("production_separation.svg"));

This generates a PFD where the three-phase separator shows:

Each stream is color-coded by phase type for easy identification.

Example: Compressor Anti-Surge System

// Create gas fluid
SystemInterface gas = new SystemSrkEos(298.0, 50.0);
gas.addComponent("methane", 0.9);
gas.addComponent("ethane", 0.1);
gas.setMixingRule("classic");

// Build process with recycle
ProcessSystem process = new ProcessSystem("Compressor Station");

Stream feed = new Stream("Feed Gas", gas);
feed.setFlowRate(1000.0, "kg/hr");
feed.setTemperature(25.0, "C");
feed.setPressure(50.0, "bara");
process.add(feed);

// Mixer for recycle
Mixer suctionMixer = new Mixer("Suction Mixer");
suctionMixer.addStream(feed);
process.add(suctionMixer);

// Main compressor
Compressor compressor = new Compressor("Main Compressor", suctionMixer.getOutletStream());
compressor.setOutletPressure(100.0, "bara");
process.add(compressor);

// Anti-surge splitter
Splitter splitter = new Splitter("Discharge Splitter", compressor.getOutletStream(), 2);
splitter.setSplitFactors(new double[] {0.9, 0.1});
process.add(splitter);

// Anti-surge recycle
Recycle recycle = new Recycle("Anti-Surge Recycle");
recycle.addStream(splitter.getSplitStream(1));
recycle.setOutletStream(suctionMixer.getOutletStream());
process.add(recycle);

process.run();

// Export with recycle highlighting
process.createDiagramExporter()
    .setTitle("Compressor Anti-Surge System")
    .setDetailLevel(DiagramDetailLevel.ENGINEERING)
    .setHighlightRecycles(true)    // Purple dashed lines for recycles
    .setShowStreamValues(true)
    .exportSVG(Path.of("anti_surge.svg"));

This generates a PFD with:

DEXPI Integration

The diagram system integrates with DEXPI (Data Exchange in the Process Industry) for importing P&ID data and generating PFD diagrams from industry-standard data exchange files.

One-Step Import and Diagram

// Import DEXPI XML and create pre-configured diagram exporter
ProcessDiagramExporter exporter = DexpiDiagramBridge.importAndCreateExporter(
    Paths.get("plant.xml"));

// DEXPI metadata (line numbers, fluid codes) shown in labels by default
exporter.exportDOT(Paths.get("diagram.dot"));
exporter.exportSVG(Paths.get("diagram.svg"));  // Requires Graphviz

Full Round-Trip Workflow

// Import DEXPI → run simulation → generate diagram → export enriched DEXPI
ProcessSystem system = DexpiDiagramBridge.roundTrip(
    Paths.get("input.xml"),     // Input DEXPI P&ID file
    Paths.get("diagram.dot"),   // Output diagram
    Paths.get("output.xml"));   // Re-exported DEXPI with simulation results

DEXPI Metadata in Labels

Equipment imported from DEXPI files displays P&ID reference information:

// Enable/disable DEXPI metadata display
exporter.setShowDexpiMetadata(true);

Creating Exporters for DEXPI-Imported Processes

// Standard exporter with DEXPI features enabled
ProcessDiagramExporter exporter = DexpiDiagramBridge.createExporter(system);

// Detailed exporter with full operating conditions
ProcessDiagramExporter detailed = DexpiDiagramBridge.createDetailedExporter(system);

See DEXPI XML Reader for complete DEXPI import/export documentation.

Customization

Custom Layout Policy

PFDLayoutPolicy customPolicy = new PFDLayoutPolicy();
// Policy automatically classifies equipment by type

ProcessDiagramExporter exporter = new ProcessDiagramExporter(process, customPolicy);

Equipment Visual Styles

Visual styles are defined in EquipmentVisualStyle with defaults for all common equipment types. The style includes:

Architecture

The diagram export system consists of:

  1. ProcessDiagramExporter - Main entry point for diagram generation
  2. PFDLayoutPolicy - Layout intelligence layer with gravity logic
  3. EquipmentRole - Classification of equipment by function
  4. DiagramDetailLevel - Control over information density
  5. EquipmentVisualStyle - Visual styling for equipment types (unified with EquipmentEnum)
  6. DexpiDiagramBridge - Integration bridge for DEXPI P&ID data exchange

Design Philosophy

Professional PFDs are not drawn — they are computed using rules.

The layout intelligence layer applies engineering conventions:

  1. Gravity logic (gas up, liquid down)
  2. Functional zoning (separation center, gas upper, liquid lower)
  3. Equipment semantics (separator outlets positioned correctly)
  4. Stable layout (same model → same diagram)

This approach produces diagrams that are: