Control Valves

Comprehensive documentation for control valves in NeqSim process simulation.

Table of Contents

Overview

Location: neqsim.process.equipment.valve

NeqSim provides specialized control valves for process automation and safety systems:

Class Description Typical Application
CheckValve Non-return valve Pump/compressor protection
LevelControlValve Level regulation Separator liquid discharge
PressureControlValve Pressure regulation Gas pressure letdown
ESDValve Emergency shutdown Process isolation
PSDValve Process shutdown Overpressure protection

All control valves extend ThrottlingValve and inherit Cv sizing, JT effects, and dynamic capabilities.

Check Valve

A check valve (non-return valve) prevents reverse flow automatically based on differential pressure.

Features

Applications

Java Example

import neqsim.process.equipment.valve.CheckValve;

// Create check valve on pump discharge
CheckValve checkValve = new CheckValve("CV-101", pumpDischargeStream);
checkValve.setCrackingPressure(0.2);  // Opens at 0.2 bar differential
checkValve.setCv(250.0);              // Flow coefficient when fully open
checkValve.run();

// Check valve state
if (checkValve.isOpen()) {
    System.out.println("Forward flow - valve open");
    double flowRate = checkValve.getOutletStream().getFlowRate("kg/hr");
} else {
    System.out.println("Reverse flow blocked - valve closed");
}

Python Example

from neqsim import jneqsim

CheckValve = jneqsim.process.equipment.valve.CheckValve

# Create check valve
check_valve = CheckValve("CV-101", pump_discharge)
check_valve.setCrackingPressure(0.2)  # 0.2 bar
check_valve.setCv(250.0)
check_valve.run()

print(f"Valve open: {check_valve.isOpen()}")
print(f"Cracking pressure: {check_valve.getCrackingPressure()} bar")

Key Methods

Method Description
setCrackingPressure(double) Set minimum ΔP to open valve (bar)
getCrackingPressure() Get cracking pressure
isOpen() Check if valve is currently open

Level Control Valve

A level control valve (LCV) modulates opening to maintain vessel level at setpoint.

Features

Control Actions

Action Description Use Case
DIRECT Increase opening → increase outflow → decrease level Liquid discharge (most common)
REVERSE Increase opening → decrease outflow → increase level Rare configurations

Java Example

import neqsim.process.equipment.valve.LevelControlValve;
import neqsim.process.equipment.valve.LevelControlValve.ControlAction;

// Create separator with liquid outlet
Separator separator = new Separator("V-101", feedStream);
Stream liquidOut = separator.getLiquidOutStream();

// Create level control valve
LevelControlValve lcv = new LevelControlValve("LCV-101", liquidOut);
lcv.setLevelSetpoint(50.0);          // Control to 50% level
lcv.setControllerGain(3.0);          // Proportional gain
lcv.setControlAction(ControlAction.DIRECT);
lcv.setMeasuredLevel(45.0);          // Current level from transmitter
lcv.setCv(150.0);
lcv.run();

System.out.println("Valve opening: " + lcv.getPercentValveOpening() + "%");
System.out.println("Level error: " + lcv.getControlError() + "%");

Python Example

from neqsim import jneqsim

LevelControlValve = jneqsim.process.equipment.valve.LevelControlValve

# Create level control valve on separator liquid outlet
lcv = LevelControlValve("LCV-101", separator.getLiquidOutStream())
lcv.setLevelSetpoint(50.0)       # 50% level setpoint
lcv.setControllerGain(3.0)       # Proportional gain
lcv.setMeasuredLevel(45.0)       # Current measured level
lcv.setCv(150.0)
lcv.run()

print(f"Valve opening: {lcv.getPercentValveOpening()}%")
print(f"Control error: {lcv.getControlError()}%")

Key Methods

Method Description
setLevelSetpoint(double) Set target level (0-100%)
setMeasuredLevel(double) Update measured level from transmitter
setControllerGain(double) Set proportional gain (1-10 typical)
setControlAction(ControlAction) DIRECT or REVERSE
getControlError() Get setpoint - measured level
setFailSafePosition(double) Position on loss of signal (%)

Pressure Control Valve

A pressure control valve (PCV) modulates opening to maintain pressure at setpoint.

Features

Control Modes

Mode Description Application
DOWNSTREAM Control outlet pressure Gas letdown stations
UPSTREAM Control inlet pressure Back-pressure control
DIFFERENTIAL Control ΔP across valve Flow control

Java Example

import neqsim.process.equipment.valve.PressureControlValve;
import neqsim.process.equipment.valve.PressureControlValve.ControlMode;

// Create pressure control valve
PressureControlValve pcv = new PressureControlValve("PCV-101", hpGasStream);
pcv.setPressureSetpoint(25.0);       // Control to 25 bara downstream
pcv.setControlMode(ControlMode.DOWNSTREAM);
pcv.setControllerGain(5.0);          // Proportional gain
pcv.setCv(300.0);
pcv.run();

System.out.println("Valve opening: " + pcv.getPercentValveOpening() + "%");
System.out.println("Outlet pressure: " + pcv.getOutletStream().getPressure("bara") + " bara");
System.out.println("Control error: " + pcv.getControlError() + " bar");

Python Example

from neqsim import jneqsim

PressureControlValve = jneqsim.process.equipment.valve.PressureControlValve

# Create pressure control valve for gas letdown
pcv = PressureControlValve("PCV-101", hp_gas_stream)
pcv.setPressureSetpoint(25.0)  # 25 bara target
pcv.setControllerGain(5.0)
pcv.setCv(300.0)
pcv.run()

print(f"Outlet pressure: {pcv.getOutletStream().getPressure('bara'):.1f} bara")

Key Methods

Method Description
setPressureSetpoint(double) Set target pressure (bara)
setControlMode(ControlMode) DOWNSTREAM, UPSTREAM, DIFFERENTIAL
setControllerGain(double) Proportional gain (1-10 typical)
getProcessVariable() Get measured pressure
getControlError() Get setpoint - PV
setAutoMode(boolean) Enable/disable automatic control

ESD Valve

An ESD valve (Emergency Shutdown Valve / Isolation Valve XV) is a fail-closed valve for emergency isolation.

Features

Design Philosophy

State Description
Energized Valve is open (normal operation)
De-energized Valve closes (emergency or loss of power)

Java Example

import neqsim.process.equipment.valve.ESDValve;
import java.util.UUID;

// Create ESD inlet valve (normally open)
ESDValve esdValve = new ESDValve("ESD-XV-101", feedStream);
esdValve.setStrokeTime(10.0);  // 10 seconds to close
esdValve.setCv(500.0);         // Large Cv for minimal ΔP when open

// Normal operation - valve open
esdValve.energize();
esdValve.run();
System.out.println("Normal: Valve " + (esdValve.isEnergized() ? "OPEN" : "CLOSED"));

// Emergency shutdown
esdValve.deEnergize();  // Triggers closure

// Dynamic simulation of closure
double dt = 0.5;  // 0.5 second time steps
for (double t = 0; t <= 12.0; t += dt) {
    esdValve.runTransient(dt, UUID.randomUUID());
    System.out.printf("t=%.1f s: Opening = %.1f%%%n", 
        t, esdValve.getPercentValveOpening());
}

Integration with ESD Controller

// ESD controller monitors process conditions
if (pressure > highPressureSetpoint || fireDetected || manualESDActivated) {
    esdValve.deEnergize();  // Initiate emergency closure
}

Python Example

from neqsim import jneqsim
import uuid

ESDValve = jneqsim.process.equipment.valve.ESDValve

# Create ESD valve
esd_valve = ESDValve("ESD-XV-101", feed_stream)
esd_valve.setStrokeTime(10.0)  # 10 seconds closure
esd_valve.setCv(500.0)

# Normal operation
esd_valve.energize()
esd_valve.run()

# Emergency shutdown
esd_valve.deEnergize()

# Simulate closure
dt = 0.5
for i in range(25):
    esd_valve.runTransient(dt, uuid.uuid4())
    print(f"Opening: {esd_valve.getPercentValveOpening():.1f}%")

Key Methods

Method Description
energize() Power actuator - allows valve to open
deEnergize() Remove power - initiates closure
isEnergized() Check energization state
setStrokeTime(double) Set closure time (seconds)
getStrokeTime() Get closure time
setFailSafePosition(double) Position on de-energize (0=closed)
startPartialStrokeTest() Initiate PST
hasTripCompleted() Check if closure is complete

PSD Valve

A PSD valve (Process Shutdown Valve) automatically closes on high-high (HIHI) pressure alarm.

Features

Java Example

import neqsim.process.equipment.valve.PSDValve;
import neqsim.process.measurementdevice.PressureTransmitter;
import neqsim.process.alarm.AlarmConfig;

// Create pressure transmitter with alarm configuration
PressureTransmitter PT = new PressureTransmitter("PT-101", separatorInlet);
PT.setAlarmConfig(AlarmConfig.builder()
    .highHighLimit(55.0)
    .deadband(1.0)
    .delay(0.5)
    .unit("bara")
    .build());

// Create PSD valve linked to transmitter
PSDValve psdValve = new PSDValve("PSD-101", feedStream);
psdValve.linkToPressureTransmitter(PT);
psdValve.setClosureTime(2.0);  // 2 seconds fast closure

// In dynamic simulation loop
for (int i = 0; i < 100; i++) {
    process.runTransient(0.1, UUID.randomUUID());
    
    if (psdValve.hasTripped()) {
        System.out.println("PSD valve tripped on HIHI alarm!");
        break;
    }
}

// Reset after alarm clears (operator action)
psdValve.reset();

Python Example

from neqsim import jneqsim

PSDValve = jneqsim.process.equipment.valve.PSDValve

# Create PSD valve
psd_valve = PSDValve("PSD-101", feed_stream)
psd_valve.linkToPressureTransmitter(pressure_transmitter)
psd_valve.setClosureTime(2.0)  # Fast closure

# Check trip status
if psd_valve.hasTripped():
    print("Valve tripped on HIHI!")
    # After condition clears
    psd_valve.reset()

Key Methods

Method Description
linkToPressureTransmitter(MeasurementDeviceInterface) Connect to PT
setClosureTime(double) Set closure time (seconds)
hasTripped() Check if valve has tripped
reset() Reset trip state (requires operator action)
setTripEnabled(boolean) Enable/disable automatic trip
getPressureTransmitter() Get linked transmitter

Dynamic Simulation

All control valves support dynamic simulation with runTransient().

Valve Travel Dynamics

// Configure valve travel times
valve.setOpeningTravelTime(5.0);   // 5 seconds to fully open
valve.setClosingTravelTime(3.0);   // 3 seconds to fully close

// Simulate opening
valve.setPercentValveOpening(100.0);  // Command full open
for (double t = 0; t <= 6.0; t += 0.1) {
    valve.runTransient(0.1, UUID.randomUUID());
    System.out.printf("t=%.1f: Actual opening = %.1f%%%n", 
        t, valve.getActualValveOpening());
}

Level Control Dynamic Response

// Simulate level disturbance
double level = 50.0;
double dt = 1.0;

for (int i = 0; i < 100; i++) {
    // Disturbance at t=20s
    if (i == 20) level = 70.0;
    
    lcv.setMeasuredLevel(level);
    lcv.runTransient(dt, UUID.randomUUID());
    
    // Level responds to valve opening
    double flowOut = lcv.getOutletStream().getFlowRate("kg/hr");
    level = level - (flowOut - inflow) * dt / vesselVolume;
    
    System.out.printf("t=%d: Level=%.1f%%, Opening=%.1f%%%n", 
        i, level, lcv.getPercentValveOpening());
}

API Reference

Common Base Methods (from ThrottlingValve)

Method Description
setCv(double, String) Set flow coefficient (“US” or “SI”)
getCv(String) Get flow coefficient
setOutletPressure(double, String) Set outlet pressure
setPercentValveOpening(double) Set valve position (0-100%)
getPercentValveOpening() Get commanded position
run() Execute steady-state calculation
runTransient(double dt, UUID id) Execute dynamic step

Valve Sizing

// Size valve for service
valve.setCv(calculateRequiredCv(flow, dP, fluid));
valve.setValveCharacteristic("equal_percentage");

// Check valve selection
double maxCv = valve.getCv("US");
double actualCv = valve.getActualCv();  // At current opening
double rangeability = maxCv / actualCv;