Pipeline Mechanical Design

Comprehensive documentation for pipeline mechanical design in NeqSim, including wall thickness calculations, stress analysis, cost estimation, and detailed design per industry standards.

📘 See Also: Related Design Documentation

Table of Contents

Overview

The pipeline mechanical design system provides:

Location: neqsim.process.mechanicaldesign.pipeline

Classes:

Architecture

Class Structure

PipelineMechanicalDesign extends MechanicalDesign
├── PipeMechanicalDesignCalculator (calculations)
├── PipelineMechanicalDesignDataSource (database)
└── MechanicalDesignResponse (JSON export)

Design Flow

1. Set design conditions (pressure, temperature)
2. Select material grade and design code
3. Load standards from database
4. Calculate wall thickness
5. Perform stress analysis
6. Calculate weights and areas
7. Estimate costs
8. Export to JSON

Design Standards

Supported Standards

Standard Application Key Features
ASME B31.3 Process Piping Allowable stress = SMYS/3
ASME B31.4 Liquid Pipelines Design factor 0.72
ASME B31.8 Gas Transmission Location classes 1-4
DNV-OS-F101 Submarine Pipelines Safety classes, resistance factors
API 5L Line Pipe Specs Material grades A-X120
ISO 13623 Petroleum Pipelines International standard
NORSOK L-002 Piping System Design Norwegian standard

Material Grades (API 5L)

Grade SMYS (MPa) SMTS (MPa) Typical Application
A25 172 310 Low-pressure utility
B 241 414 General service
X42 290 414 Low-pressure pipelines
X52 359 455 Process piping
X60 414 517 High-pressure pipelines
X65 448 531 Offshore standard
X70 483 565 High-pressure gas
X80 552 621 Very high strength
X100 690 760 Ultra high strength
X120 827 931 Extreme applications

ASME B31.8 Location Classes

Class Description Design Factor (F)
Class 1 Rural, <10 buildings 0.72
Class 2 Semi-developed, 10-46 buildings 0.60
Class 3 Developed, >46 buildings 0.50
Class 4 High-density, multi-story 0.40

DNV-OS-F101 Safety Classes

Safety Class Description γSC Factor
Low Minor environmental impact 0.96
Medium Regional impact 1.04
High Major environmental impact 1.14

Wall Thickness Calculations

ASME B31.8 (Gas Transmission)

Barlow Formula:

\[t = \frac{P \cdot D}{2 \cdot S \cdot F \cdot E \cdot T}\]

Where:

Code:

PipeMechanicalDesignCalculator calc = new PipeMechanicalDesignCalculator();
calc.setDesignPressure(15.0);  // MPa
calc.setOuterDiameter(0.508, "m");  // 20 inch
calc.setMaterialGrade("X65");
calc.setDesignCode(PipeMechanicalDesignCalculator.ASME_B31_8);
calc.setLocationClass(2);  // Design factor = 0.60

double tMin = calc.calculateMinimumWallThickness();
System.out.println("Minimum wall thickness: " + (tMin * 1000) + " mm");

ASME B31.3 (Process Piping)

\[t = \frac{P \cdot D}{2 \cdot (S \cdot E + P \cdot Y)}\]

Where:

DNV-OS-F101 (Submarine Pipelines)

\[t_1 = \frac{P_{li} - P_e}{p_b}\] \[p_b = \frac{2 \cdot t \cdot f_y \cdot \alpha_U}{\sqrt{3} \cdot (D - t) \cdot \gamma_m \cdot \gamma_{SC}}\]

Where:

Code:

calc.setDesignCode(PipeMechanicalDesignCalculator.DNV_OS_F101);
calc.setWaterDepth(350.0);  // m
double tMin = calc.calculateMinimumWallThickness();

Nominal Wall Thickness

After calculating minimum wall thickness, apply:

\[t_{nom} = \frac{t_{min} + t_{corr}}{f_{fab}}\]

Where:

Stress Analysis

Hoop Stress (Barlow)

\[\sigma_h = \frac{P \cdot D}{2 \cdot t}\]

Code:

double hoopStress = calc.calculateHoopStress(designPressure);
double ratio = hoopStress / calc.getSmys() * 100;
System.out.println("Hoop stress: " + hoopStress + " MPa (" + ratio + "% SMYS)");

Longitudinal Stress

For restrained pipe:

\[\sigma_L = \nu \cdot \sigma_h - E \cdot \alpha \cdot \Delta T + \frac{P \cdot D}{4 \cdot t}\]

Where:

For unrestrained pipe:

\[\sigma_L = \frac{P \cdot D}{4 \cdot t}\]

Code:

double deltaT = 60.0;  // Temperature rise from installation
boolean restrained = true;  // Buried or anchored
double longStress = calc.calculateLongitudinalStress(designPressure, deltaT, restrained);

Von Mises Equivalent Stress

\[\sigma_{vm} = \sqrt{\sigma_h^2 + \sigma_L^2 - \sigma_h \cdot \sigma_L + 3\tau^2}\]

For pipeline design (assuming τ ≈ 0):

\[\sigma_{vm} = \sqrt{\sigma_h^2 + \sigma_L^2 - \sigma_h \cdot \sigma_L}\]

Code:

double vonMises = calc.calculateVonMisesStress(designPressure, deltaT, true);
boolean safe = calc.isDesignSafe();  // von Mises < 0.9 × SMYS
double margin = calc.calculateSafetyMargin();  // (SMYS - σvm) / SMYS

External Pressure and Buckling

External Pressure at Seabed

\[P_e = \rho_{sw} \cdot g \cdot h\]

Where:

Code:

calc.setWaterDepth(350.0);
double Pe = calc.calculateExternalPressure();  // MPa

Collapse Pressure (DNV-OS-F101)

Elastic Collapse:

\[P_{el} = \frac{2 \cdot E \cdot (t/D)^3}{1 - \nu^2}\]

Plastic Collapse:

\[P_p = \frac{2 \cdot f_y \cdot t}{D}\]

Combined Collapse:

double Pc = calc.calculateCollapsePressure();

Propagation Buckling Pressure

\[P_{pr} = 35 \cdot f_y \cdot (t/D)^{2.5}\]

Code:

double Ppr = calc.calculatePropagationBucklingPressure();
// Buckle arrestors required if Ppr < Pe

Allowable Free Span Length

Based on vortex-induced vibration (VIV) avoidance:

\[L_{allow} = \left(\frac{\pi^2 \cdot E \cdot I}{4 \cdot m_e \cdot f_n^2}\right)^{0.25}\]

Where:

Code:

double currentVelocity = 0.5;  // m/s
double spanLength = calc.calculateAllowableSpanLength(currentVelocity);

Weight and Buoyancy

Weight Components

calc.setPipelineLength(50000.0);  // 50 km
calc.setCoatingType("3LPE");
calc.setCoatingThickness(0.003);  // 3mm
calc.setConcreteCoatingThickness(0.050);  // 50mm CWC

calc.calculateWeightsAndAreas();

// Results per meter
double steelWeight = calc.getSteelWeightPerMeter();      // kg/m
double coatingWeight = calc.getCoatingWeightPerMeter();  // kg/m
double concreteWeight = calc.getConcreteWeightPerMeter(); // kg/m
double totalDry = calc.getTotalDryWeightPerMeter();      // kg/m

Submerged Weight

\[W_{sub} = W_{dry} + W_{contents} - \rho_{sw} \cdot g \cdot V_{disp}\]

Code:

double contentDensity = 800.0;  // kg/m³ (oil)
double submerged = calc.calculateSubmergedWeight(contentDensity);
// Negative = buoyant, Positive = sinks

Concrete Coating for Stability

double targetWeight = 50.0;  // kg/m submerged weight
double thickness = calc.calculateRequiredConcreteThickness(contentDensity, targetWeight);

Detailed Design Features

Support Spacing (Above-ground)

Based on deflection limits:

\[L = \left(\frac{384 \cdot E \cdot I \cdot \delta}{5 \cdot w}\right)^{0.25}\]

Code:

double maxDeflection = 0.01;  // 10mm
double spacing = calc.calculateSupportSpacing(maxDeflection);
int numSupports = calc.getNumberOfSupports();

Expansion Loop Sizing

\[L_{loop} = \sqrt{\frac{3 \cdot E \cdot D \cdot \Delta L}{\sigma_{allow}}}\]

Where $\Delta L = \alpha \cdot \Delta T \cdot L_{anchor}$

Code:

double deltaT = 60.0;  // Temperature change
double loopLength = calc.calculateExpansionLoopLength(deltaT, "U-loop");
int numLoops = calc.getNumberOfExpansionLoops();

Minimum Bend Radius

Per API 5L:

\(R_{min} = 18 \cdot D\) (cold bends)

\(R_{min} = 5 \cdot D\) (hot bends)

Code:

double bendRadius = calc.calculateMinimumBendRadius();  // For cold bends

Flange Class Selection

Per ASME B16.5:

Class Rating at 38°C (MPa)
150 1.93
300 5.07
600 10.13
900 15.20
1500 25.33
2500 42.22

Code:

int flangeClass = calc.selectFlangeClass();  // Based on design pressure

Fatigue Life Estimation

Per DNV-RP-C203 (D-curve):

\[N = \frac{10^{11.764}}{S^3}\]

Code:

double stressRange = 50.0;  // MPa
double cyclesPerYear = 1e6;
double fatigueLife = calc.estimateFatigueLife(stressRange, cyclesPerYear);

Insulation Thickness

For temperature control:

double inletTemp = 80.0;      // °C
double minArrivalTemp = 40.0; // °C
double massFlow = 50.0;       // kg/s
double cp = 2000.0;           // J/(kg·K)

double insThickness = calc.calculateInsulationThickness(
    inletTemp, minArrivalTemp, massFlow, cp);

Cost Estimation

Cost Components

Component Basis
Steel Weight × $/kg
Coating Surface area × $/m²
Insulation Volume × $/m³
Concrete Volume × $/m³
Welding Number of welds × $/weld
Flanges Number of pairs × $/pair
Valves Number × $/valve
Supports Number × $/support
Anchors Number × $/anchor
Installation Length × $/m
Engineering % of direct cost
Testing % of direct cost
Contingency % of direct cost

Cost Calculation

// Set pipeline parameters
calc.setPipelineLength(50000.0);  // 50 km
calc.setNumberOfFlangePairs(10);
calc.setNumberOfValves(5);

// Set rates (optional - defaults available)
calc.setSteelPricePerKg(1.50);
calc.setFieldWeldCost(2500.0);
calc.setContingencyPercentage(0.15);

// Calculate costs
calc.calculateProjectCost();
calc.calculateLaborManhours();

// Get results
double totalCost = calc.getTotalProjectCost();
double directCost = calc.getTotalDirectCost();
double laborHours = calc.getTotalLaborManhours();

Installation Cost Factors

Method Base Cost ($/m) Depth Factor
Onshore 300 +50 × burial_depth
S-lay 800 +2 × water_depth
J-lay 1200 +3 × water_depth
Reel-lay 600 +1.5 × water_depth
HDD 1500 -

Bill of Materials

List<Map<String, Object>> bom = calc.generateBillOfMaterials();

for (Map<String, Object> item : bom) {
    System.out.println(item.get("item") + ": " + item.get("quantity") + " " + 
                       item.get("unit") + " - $" + item.get("totalCost_USD"));
}

JSON Reporting

Complete JSON Export

PipelineMechanicalDesign design = (PipelineMechanicalDesign) pipe.getMechanicalDesign();
design.calcDesign();
design.getCalculator().calculateProjectCost();

String json = design.toJson();

JSON Structure

{
  "equipmentType": "Pipeline",
  "designCode": "ASME_B31_8",
  "materialGrade": "X65",
  "pipelineLength_m": 50000.0,
  
  "designParameters": {
    "designPressure_MPa": 15.0,
    "designPressure_bar": 150.0,
    "designTemperature_C": 80.0,
    "outerDiameter_mm": 508.0,
    "corrosionAllowance_mm": 3.0
  },
  
  "materialProperties": {
    "smys_MPa": 448.0,
    "smts_MPa": 531.0,
    "youngsModulus_MPa": 207000.0,
    "steelDensity_kgm3": 7850.0
  },
  
  "designFactors": {
    "designFactor_F": 0.60,
    "jointFactor_E": 1.0,
    "temperatureDerating_T": 1.0,
    "locationClass": 2
  },
  
  "calculatedResults": {
    "minimumWallThickness_mm": 18.5,
    "maop_MPa": 14.2,
    "hoopStress_MPa": 287.0,
    "vonMisesStress_MPa": 265.0,
    "safetyMargin_percent": 40.8,
    "designIsSafe": true
  },
  
  "weightAndBuoyancy": {
    "steelWeight_kgm": 185.0,
    "totalDryWeight_kgm": 210.0,
    "submergedWeight_kgm": 120.0,
    "totalPipelineWeight_kg": 10500000.0
  },
  
  "detailedDesignResults": {
    "collapsePressure_MPa": 25.0,
    "propagationBucklingPressure_MPa": 8.5,
    "minimumBendRadius_m": 9.14,
    "allowableSpanLength_m": 45.0
  },
  
  "costEstimation": {
    "steelMaterialCost_USD": 15750000.0,
    "coatingCost_USD": 2000000.0,
    "weldingCost_USD": 10250000.0,
    "installationCost_USD": 40000000.0,
    "totalDirectCost_USD": 70000000.0,
    "totalProjectCost_USD": 91000000.0
  },
  
  "laborEstimation": {
    "totalLaborManhours": 125000.0
  }
}

Database Integration

Loading Design Parameters

PipelineMechanicalDesign design = new PipelineMechanicalDesign(pipe);
design.setCompanySpecificDesignStandards("Equinor");
design.setDesignStandardCode("DNV-OS-F101");
design.setMaterialGrade("X65");

// Load from database
design.readDesignSpecifications();

// This queries:
// 1. MaterialPipeProperties - SMYS/SMTS
// 2. TechnicalRequirements_Process - Company factors
// 3. dnv_iso_en_standards - DNV safety class factors
// 4. norsok_standards - Additional requirements

Database Tables

Table Content
MaterialPipeProperties API 5L grade properties
TechnicalRequirements_Process Company design parameters
TechnicalRequirements_Piping Piping code requirements
api_standards API 5L specifications
asme_standards ASME B31 requirements
dnv_iso_en_standards DNV/ISO/EN factors
norsok_standards NORSOK requirements

Examples

Example 1: Onshore Gas Pipeline (ASME B31.8)

import neqsim.process.mechanicaldesign.pipeline.*;

// Create calculator
PipeMechanicalDesignCalculator calc = new PipeMechanicalDesignCalculator();

// Set design conditions
calc.setDesignPressure(10.0, "MPa");
calc.setDesignTemperature(60.0);
calc.setOuterDiameter(0.762, "m");  // 30 inch
calc.setMaterialGrade("X65");
calc.setPipelineLength(100000.0);  // 100 km

// Set design code
calc.setDesignCode(PipeMechanicalDesignCalculator.ASME_B31_8);
calc.setLocationClass(2);  // Semi-developed area

// Calculate
double tMin = calc.calculateMinimumWallThickness();
double maop = calc.calculateMAOP();
double testP = calc.calculateTestPressure();

System.out.println("=== ASME B31.8 Design ===");
System.out.println("Minimum wall thickness: " + (tMin * 1000) + " mm");
System.out.println("MAOP: " + (maop * 10) + " bar");
System.out.println("Test pressure: " + (testP * 10) + " bar");

// Stress analysis
double hoop = calc.calculateHoopStress(calc.getDesignPressure());
double vonMises = calc.calculateVonMisesStress(calc.getDesignPressure(), 40.0, true);

System.out.println("Hoop stress: " + hoop + " MPa (" + (100*hoop/calc.getSmys()) + "% SMYS)");
System.out.println("Von Mises stress: " + vonMises + " MPa");
System.out.println("Design is safe: " + calc.isDesignSafe());

Example 2: Subsea Pipeline (DNV-OS-F101)

// Create calculator
PipeMechanicalDesignCalculator calc = new PipeMechanicalDesignCalculator();

// Set design conditions
calc.setDesignPressure(20.0, "MPa");
calc.setDesignTemperature(80.0);
calc.setOuterDiameter(0.508, "m");  // 20 inch
calc.setMaterialGrade("X65");
calc.setPipelineLength(50000.0);  // 50 km

// DNV design code
calc.setDesignCode(PipeMechanicalDesignCalculator.DNV_OS_F101);
calc.setWaterDepth(350.0);
calc.setInstallationMethod("S-lay");

// Coating and concrete
calc.setCoatingType("3LPE");
calc.setCoatingThickness(0.003);  // 3mm
calc.setConcreteCoatingThickness(0.050);  // 50mm CWC

// Calculate
double tMin = calc.calculateMinimumWallThickness();
calc.setNominalWallThickness(Math.ceil(tMin * 1000) / 1000.0 + 0.002);  // Round up + 2mm

// External pressure and buckling
double Pe = calc.calculateExternalPressure();
double Pc = calc.calculateCollapsePressure();
double Ppr = calc.calculatePropagationBucklingPressure();

System.out.println("=== DNV-OS-F101 Design ===");
System.out.println("Minimum wall thickness: " + (tMin * 1000) + " mm");
System.out.println("External pressure: " + Pe + " MPa");
System.out.println("Collapse pressure: " + Pc + " MPa");
System.out.println("Propagation pressure: " + Ppr + " MPa");

// Weight and buoyancy
calc.calculateWeightsAndAreas();
double submerged = calc.calculateSubmergedWeight(800.0);  // Oil @ 800 kg/m³

System.out.println("Steel weight: " + calc.getSteelWeightPerMeter() + " kg/m");
System.out.println("Total dry weight: " + calc.getTotalDryWeightPerMeter() + " kg/m");
System.out.println("Submerged weight: " + submerged + " kg/m");

// Free span analysis
double spanLength = calc.calculateAllowableSpanLength(0.5);  // 0.5 m/s current
System.out.println("Allowable span length: " + spanLength + " m");

Example 3: Complete Cost Estimation

// Create calculator with full specifications
PipeMechanicalDesignCalculator calc = new PipeMechanicalDesignCalculator();
calc.setDesignPressure(15.0, "MPa");
calc.setOuterDiameter(0.508, "m");
calc.setMaterialGrade("X65");
calc.setDesignCode(PipeMechanicalDesignCalculator.DNV_OS_F101);
calc.setPipelineLength(50000.0);

// Installation parameters
calc.setInstallationMethod("S-lay");
calc.setWaterDepth(350.0);
calc.setNumberOfFlangePairs(10);
calc.setNumberOfValves(5);

// Coatings
calc.setCoatingType("3LPE");
calc.setCoatingThickness(0.003);
calc.setConcreteCoatingThickness(0.050);

// Calculate everything
calc.calculateMinimumWallThickness();
calc.calculateWeightsAndAreas();
calc.calculateJointsAndWelds();
calc.selectFlangeClass();
calc.calculateProjectCost();
calc.calculateLaborManhours();

// Print cost summary
System.out.println("=== COST ESTIMATION ===");
System.out.println("Total pipeline weight: " + calc.getTotalPipelineWeight()/1000 + " tonnes");
System.out.println("Number of joints: " + calc.getNumberOfJoints());
System.out.println("Number of welds: " + calc.getNumberOfFieldWelds());
System.out.println();
System.out.println("Direct Costs:");
System.out.println("  Steel: $" + String.format("%,.0f", calc.getSteelMaterialCost()));
System.out.println("  Coating: $" + String.format("%,.0f", calc.getCoatingCost()));
System.out.println("  Installation: $" + String.format("%,.0f", calc.getInstallationCost()));
System.out.println("  Total Direct: $" + String.format("%,.0f", calc.getTotalDirectCost()));
System.out.println();
System.out.println("Total Project Cost: $" + String.format("%,.0f", calc.getTotalProjectCost()));
System.out.println("Labor manhours: " + String.format("%,.0f", calc.getTotalLaborManhours()));

// Generate BOM
System.out.println("\n=== BILL OF MATERIALS ===");
List<Map<String, Object>> bom = calc.generateBillOfMaterials();
for (Map<String, Object> item : bom) {
    System.out.printf("%-25s %8s %-10s $%,15.0f%n",
        item.get("item"),
        item.get("quantity"),
        item.get("unit"),
        item.get("totalCost_USD"));
}

Example 4: Integration with Process Simulation

import neqsim.thermo.system.SystemSrkEos;
import neqsim.process.equipment.stream.Stream;
import neqsim.process.equipment.pipeline.AdiabaticPipe;
import neqsim.process.mechanicaldesign.pipeline.PipelineMechanicalDesign;

// Create fluid
SystemSrkEos gas = new SystemSrkEos(303.15, 150.0);
gas.addComponent("methane", 0.92);
gas.addComponent("ethane", 0.05);
gas.addComponent("propane", 0.03);
gas.setMixingRule("classic");

// Create stream
Stream inlet = new Stream("Inlet", gas);
inlet.setFlowRate(20.0, "MSm3/day");
inlet.run();

// Create pipeline
AdiabaticPipe pipeline = new AdiabaticPipe("Export Pipeline", inlet);
pipeline.setLength(100000.0, "m");
pipeline.setDiameter(0.762, "m");
pipeline.run();

// Initialize mechanical design
pipeline.initMechanicalDesign();
PipelineMechanicalDesign design = (PipelineMechanicalDesign) pipeline.getMechanicalDesign();

// Configure design
design.setMaxOperationPressure(150.0);  // bara
design.setMaxOperationTemperature(60.0);  // °C
design.setMaterialGrade("X65");
design.setLocationClass("Class 2");
design.setDesignStandardCode("ASME-B31.8");
design.setCompanySpecificDesignStandards("Equinor");

// Run design
design.readDesignSpecifications();
design.calcDesign();

// Get complete report
String jsonReport = design.toJson();
System.out.println(jsonReport);