Dynamic Simulation with DynamicProcessHelper

Overview

NeqSim supports both steady-state and dynamic (transient) process simulation. The DynamicProcessHelper utility bridges these two modes: given a sized steady-state ProcessSystem, it automatically creates transmitters, wires PID controllers to downstream valves, and switches all equipment to dynamic mode — ready to run transient steps.

Location: neqsim.process.util.DynamicProcessHelper

Quick Start

import neqsim.process.util.DynamicProcessHelper;

// 1. Build and run the steady-state process
ProcessSystem process = new ProcessSystem();
process.add(feed);
process.add(inletValve);
process.add(separator);
process.add(gasValve);
process.add(liquidValve);
process.run();

// 2. Auto-instrument in one call
DynamicProcessHelper helper = new DynamicProcessHelper(process);
helper.setDefaultTimeStep(1.0); // seconds
helper.instrumentAndControl();

// 3. Run transient loop
for (int i = 0; i < 600; i++) {
    process.runTransient();
}

What instrumentAndControl() Creates

The method scans all equipment in the process and adds instrumentation based on equipment type:

Equipment	Transmitters Created	Controllers Created
Separator	PT (gas outlet), LT (vessel), TT (gas outlet)	PC on downstream gas valve, LC on downstream liquid valve
ThreePhaseSeparator	Same as Separator + water level	PC, LC, WLC (water level controller on water valve)
Compressor	PT (discharge), TT (discharge)	—
Heater / Cooler	TT (outlet)	—

Separator-Valve Pairing

Controllers are automatically wired to downstream valves by matching stream identity. For example, if a ThrottlingValve has its inlet stream set to separator.getGasOutStream(), the pressure controller is assigned to that valve.

PID Tuning Defaults

Each controller type has sensible default tuning parameters:

Controller Type	Kp (default)	Ti (default, s)	Action
Pressure (PC)	0.5	50	Reverse
Level (LC)	2.0	200	Direct
Flow (FC)	0.2	100	Reverse
Temperature (TC)	1.0	120	Direct

Customizing Tuning

DynamicProcessHelper helper = new DynamicProcessHelper(process);
helper.setPressureTuning(0.8, 30.0);     // Kp, Ti
helper.setLevelTuning(3.0, 150.0);
helper.setFlowTuning(0.3, 80.0);
helper.setTemperatureTuning(1.5, 100.0);
helper.instrumentAndControl();

Adding Extra Control Loops

Flow Controller

// Add flow control on any valve
ControllerDeviceInterface fc = helper.addFlowController(
    "FIC-101",          // ISA tag
    exportValve,        // valve to control
    exportStream,       // stream to measure
    50000.0,            // setpoint
    "kg/hr"             // unit
);

Temperature Controller

// Add temperature control on a heater or cooler
ControllerDeviceInterface tc = helper.addTemperatureController(
    "TIC-201",          // ISA tag
    cooler,             // heater or cooler equipment
    cooler.getOutletStream(),
    35.0                // setpoint in Celsius
);

Accessing Generated Instruments

// All transmitters as a map
Map<String, MeasurementDeviceInterface> transmitters = helper.getTransmitters();

// All controllers as a map
Map<String, ControllerDeviceInterface> controllers = helper.getControllers();

// Specific item by tag
MeasurementDeviceInterface pt = helper.getTransmitter("PT-HP sep");
ControllerDeviceInterface pc = helper.getController("PC-HP sep");

Tag naming follows ISA conventions: PT-<equipment>, LT-<equipment>, TT-<equipment>, PC-<equipment>, LC-<equipment>, WLC-<equipment>.

Complete Example

// --- Steady-state setup ---
SystemInterface gas = new SystemSrkEos(273.15 + 30.0, 65.0);
gas.addComponent("methane", 0.80);
gas.addComponent("ethane", 0.10);
gas.addComponent("propane", 0.05);
gas.addComponent("nC5", 0.05);
gas.setMixingRule("classic");

Stream feed = new Stream("feed", gas);
feed.setFlowRate(10000.0, "kg/hr");

ThrottlingValve inletValve = new ThrottlingValve("IV", feed);
inletValve.setOutletPressure(55.0);

Separator separator = new Separator("HP sep", inletValve.getOutletStream());
separator.setInternalDiameter(1.5);
separator.setLiquidLevel(0.5);

ThrottlingValve gasValve = new ThrottlingValve("GV", separator.getGasOutStream());
gasValve.setOutletPressure(40.0);

ThrottlingValve liqValve = new ThrottlingValve("LV", separator.getLiquidOutStream());
liqValve.setOutletPressure(10.0);

ProcessSystem process = new ProcessSystem();
process.add(feed);
process.add(inletValve);
process.add(separator);
process.add(gasValve);
process.add(liqValve);
process.run();

// --- Convert to dynamic ---
DynamicProcessHelper helper = new DynamicProcessHelper(process);
helper.setDefaultTimeStep(0.5);
helper.instrumentAndControl();

// --- Run 5 minutes of transient simulation ---
for (int i = 0; i < 600; i++) {
    process.runTransient();
}

// Read results
double pressure = separator.getGasOutStream().getPressure("bara");
double level = separator.getLiquidLevel();

How It Works Internally

1. Equipment scan — iterates process.getUnitOperations() to find all separators, compressors, heaters, coolers, and valves.
2. Stream identity matching — for each separator, finds downstream valves by comparing valve.getInletStream() with separator.getGasOutStream() and separator.getLiquidOutStream() (object identity, not name matching).
3. Transmitter creation — creates PressureTransmitter, LevelTransmitter, TemperatureTransmitter, or VolumeFlowTransmitter and calls process.add(device) (which uses the MeasurementDeviceInterface overload).
4. Controller wiring — creates ControllerDeviceBaseClass with the transmitter as input, sets tuning parameters, and calls valve.setController(controller).
5. Dynamic mode switch — calls unit.setCalculateSteadyState(false) on all equipment and sets process.setTimeStep(dt).

Related Documentation

• Process Controllers and Logic — Adjusters, recycles, PID controllers
• Instrument Design Framework — ISA instrument specifications and cost estimation
• Separators — Separator configuration and sizing
• Valves — Valve types and Cv calculation

DEXPI Data Exchange for Instruments

The DynamicProcessHelper supports exporting and importing instrument data using the DEXPI P&ID data exchange standard (ISO 15926-based XML).

Exporting Instruments to DEXPI XML

After calling instrumentAndControl(), export all instruments to a DEXPI file:

DynamicProcessHelper helper = new DynamicProcessHelper(process);
helper.instrumentAndControl();

// Export process + instruments to DEXPI XML
helper.exportDexpi(new File("process_pid.xml"));

The exported file contains:

• ProcessInstrumentationFunction elements for each transmitter (with ISA category, functions, and number)
• ProcessSignalGeneratingFunction elements for sensor elements
• ActuatingFunction elements for controller outputs
• SignalConveyingFunction elements linking instruments to actuators
• InstrumentationLoopFunction elements grouping each control loop

Importing Instrument Metadata from DEXPI XML

Read instrument metadata from an existing DEXPI P&ID file:

List<DexpiInstrumentInfo> instruments = helper.readDexpiInstruments(
    new File("existing_pid.xml"));

for (DexpiInstrumentInfo info : instruments) {
    System.out.println(info.getTagName()
        + " category=" + info.getCategory()
        + " functions=" + info.getFunctions()
        + " hasControl=" + info.hasControlFunction());
}

Note: Imported instruments are returned as DexpiInstrumentInfo metadata records rather than live transmitter/controller objects, because creating live instruments requires connected process streams. Use the info to identify which instruments exist in the P&ID and wire them up to the appropriate equipment.

Using the Writer/Reader Directly

For more control, use DexpiXmlWriter and DexpiXmlReader directly:

// Export with explicit transmitter/controller maps
DexpiXmlWriter.write(process, file,
    helper.getTransmitters(), helper.getControllers());

// Import instrument metadata only
List<DexpiInstrumentInfo> instruments =
    DexpiXmlReader.readInstruments(new File("pid.xml"));