Manifold Mechanical Design Guide

This guide documents the manifold mechanical design capabilities in NeqSim, covering topside, onshore, and subsea applications.

Overview

Manifolds are critical process equipment used for stream distribution and collection. In NeqSim, manifolds are modeled as a combination of a mixer and splitter, with comprehensive mechanical design capabilities added for:

Topside manifolds - Offshore platform applications
Onshore manifolds - Process facility applications
Subsea manifolds - Seabed production and injection systems

Design Standards

The manifold mechanical design implementation follows these industry standards:

Standard	Application	Scope
ASME B31.3	Topside/Onshore	Wall thickness, stress analysis, reinforcement
DNV-ST-F101	Subsea	Pressure containment, collapse, safety factors
API RP 14E	All	Erosional velocity limits
NORSOK L-002	Topside/Onshore	Support spacing requirements
API RP 17A	Subsea	Subsea production system design
DNV-RP-F112	Subsea	Duplex stainless steel design
ASME B16.5	All	Flange pressure-temperature ratings

Quick Start Example

Basic Topside Manifold

import neqsim.process.equipment.manifold.Manifold;
import neqsim.process.equipment.stream.Stream;
import neqsim.process.mechanicaldesign.manifold.ManifoldMechanicalDesign;
import neqsim.process.mechanicaldesign.manifold.ManifoldMechanicalDesignCalculator.ManifoldLocation;
import neqsim.thermo.system.SystemSrkEos;

// Create fluid
SystemInterface fluid = new SystemSrkEos(298.0, 50.0);
fluid.addComponent("methane", 0.9);
fluid.addComponent("ethane", 0.1);
fluid.setMixingRule("classic");
fluid.init(0);

// Create feed stream
Stream feed = new Stream("Feed", fluid);
feed.setFlowRate(5000.0, "kg/hr");
feed.run();

// Create manifold with 2-way split
Manifold manifold = new Manifold("Production Manifold");
manifold.addStream(feed);
manifold.setSplitFactors(new double[] {0.5, 0.5});
manifold.run();

// Initialize mechanical design
manifold.initMechanicalDesign();
ManifoldMechanicalDesign design = manifold.getMechanicalDesign();

// Configure design parameters
design.setMaxOperationPressure(50.0);  // bar
design.setMaxOperationTemperature(298.0);  // K
design.setLocation(ManifoldLocation.TOPSIDE);
design.setMaterialGrade("A106-B");
design.setHeaderDiameter(0.2032);  // 8 inch
design.setBranchDiameter(0.1016);  // 4 inch
design.setNumberOfInlets(1);
design.setNumberOfOutlets(2);

// Run design calculations
design.calcDesign();

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

Subsea Manifold Design

import neqsim.process.mechanicaldesign.manifold.ManifoldMechanicalDesignCalculator.ManifoldLocation;
import neqsim.process.mechanicaldesign.manifold.ManifoldMechanicalDesignCalculator.ManifoldType;

// Create subsea manifold
Manifold subseaManifold = new Manifold("Subsea Production Manifold");
subseaManifold.addStream(wellStream1);
subseaManifold.addStream(wellStream2);
subseaManifold.addStream(wellStream3);
subseaManifold.addStream(wellStream4);
subseaManifold.setSplitFactors(new double[] {1.0});  // Single output to flowline
subseaManifold.run();

// Configure for subsea design
subseaManifold.initMechanicalDesign();
ManifoldMechanicalDesign design = subseaManifold.getMechanicalDesign();

design.setMaxOperationPressure(150.0);  // bar
design.setMaxOperationTemperature(280.0);  // K (7°C)
design.setLocation(ManifoldLocation.SUBSEA);
design.setDesignStandardCode("DNV-ST-F101");
design.setMaterialGrade("X65");  // Subsea line pipe grade
design.setWaterDepth(350.0);  // meters
design.setHeaderDiameter(0.4064);  // 16 inch
design.setBranchDiameter(0.1524);  // 6 inch
design.setNumberOfInlets(4);  // 4 well connections
design.setNumberOfOutlets(1);  // 1 flowline outlet

design.calcDesign();

// Access detailed calculations
ManifoldMechanicalDesignCalculator calc = design.getCalculator();
System.out.println("Required wall thickness: " + calc.getMinHeaderWallThickness() * 1000 + " mm");
System.out.println("Submerged weight: " + calc.getSubmergedWeight() + " kg");

Manifold Locations

The ManifoldLocation enum defines the installation context:

Location	Description	Design Code
`TOPSIDE`	Offshore platform manifold	ASME B31.3
`ONSHORE`	Land-based facility manifold	ASME B31.3
`SUBSEA`	Seabed manifold	DNV-ST-F101

Manifold Types

The ManifoldType enum categorizes manifolds by function:

Type	Description
`PRODUCTION`	Gathering produced fluids from wells
`INJECTION`	Distributing injection fluids (water, gas)
`TEST`	Test separator feed manifold
`PIGGING`	Pig launcher/receiver manifold
`DISTRIBUTION`	General distribution manifold

Design Calculations

Wall Thickness

ASME B31.3 (Topside/Onshore)

Wall thickness is calculated per ASME B31.3 Equation 3a:

t_m = P × D / (2 × (S × E + P × Y))
t_min = t_m / (1 - tolerance) + corrosion_allowance

Where:

P = Design pressure (MPa)
D = Outside diameter (m)
S = Allowable stress (MPa) from ASME B31.3 Table A-1
E = Joint efficiency factor
Y = Coefficient (0.4 for ferritic steel < 482°C)

DNV-ST-F101 (Subsea)

Wall thickness for subsea includes safety class factors:

t_1 = P × D / (2 × f_y × α_U / (γ_M × γ_SC))
t_min = t_1 / (1 - tolerance) + corrosion_allowance
t_min = max(t_min, 6.35mm)  // Minimum handling thickness

Where:

γ_M = Material resistance factor (1.15)
γ_SC = Safety class factor (1.046 low, 1.138 medium, 1.308 high)
f_y = SMYS (Specified Minimum Yield Strength)

Velocity Limits

Erosional velocity is calculated per API RP 14E:

V_e = C / √ρ_m

Where:

C = Erosional constant (100-150)
ρ_m = Mixture density (kg/m³)

Recommended velocity limits:

Service	Maximum Velocity
Gas	20-30 m/s
Liquid	3-5 m/s
Multiphase	15-20 m/s
Erosional limit	0.8 × V_e

Branch Reinforcement

Branch connections are analyzed per ASME B31.3 area replacement method:

Calculate area removed by branch opening
Calculate excess area in header wall
Calculate excess area in branch wall
If total excess < area removed, reinforcement pad required

// Check reinforcement requirement
design.calcDesign();
ManifoldMechanicalDesignCalculator calc = design.getCalculator();

if (calc.isReinforcementRequired()) {
    double padThickness = calc.getReinforcementPadThickness();
    System.out.println("Reinforcement pad required: " + padThickness * 1000 + " mm");
}

Support Spacing

Support spacing follows NORSOK L-002 guidelines:

Pipe Size	Support Spacing
≤ NPS 4	2.7 m
NPS 4-8	3.7 m
NPS 8-12	4.3 m
> NPS 12	5.0 m

For subsea manifolds, the structure itself provides support.

Material Properties

Carbon Steel (Topside/Onshore)

Grade	Allowable Stress at 20°C (MPa)
A106-B	138
A312-TP316	138
A312-TP316L	115
A790-S31803 (Duplex)	207
A790-S32750 (Super Duplex)	241

Subsea Line Pipe Grades

Grade	SMYS (MPa)	SMTS (MPa)
X52	359	455
X60	414	517
X65	448	531
X70	483	565
22Cr Duplex	450	620
25Cr Super Duplex	550	750
6Mo	300	650
Inconel 625	414	827

Weight Calculations

Dry Weight

Dry weight includes:

Header pipe weight
Branch pipe weights
Valve weights (estimated from size)
Structure weight (10% topside, 20% subsea)
Reinforcement pads (if required)

double dryWeight = calc.calculateDryWeight();
System.out.println("Total dry weight: " + dryWeight + " kg");

Submerged Weight (Subsea)

For subsea manifolds, submerged weight accounts for buoyancy:

if (design.getLocation() == ManifoldLocation.SUBSEA) {
    double submergedWeight = calc.calculateSubmergedWeight();
    System.out.println("Submerged weight: " + submergedWeight + " kg");
}

Design Verification

The design verification checks:

Wall thickness - Actual ≥ required
Velocity limits - Header and branch velocities within limits
Reinforcement - Branch connections properly reinforced
Support - Adequate support spacing

// Perform complete design verification
design.calcDesign();
ManifoldMechanicalDesignCalculator calc = design.getCalculator();

boolean allPassed = calc.performDesignVerification();

System.out.println("Wall thickness check: " + 
    (calc.isWallThicknessCheckPassed() ? "PASSED" : "FAILED"));
System.out.println("Velocity check: " + 
    (calc.isVelocityCheckPassed() ? "PASSED" : "FAILED"));
System.out.println("Reinforcement check: " + 
    (calc.isReinforcementCheckPassed() ? "PASSED" : "FAILED"));

JSON Output

The design produces comprehensive JSON output:

{
  "designStandardCode": "ASME-B31.3",
  "materialGrade": "A106-B",
  "manifoldLocation": "TOPSIDE",
  "manifoldType": "PRODUCTION",
  "numberOfInlets": 1,
  "numberOfOutlets": 2,
  "headerDiameter_m": 0.2032,
  "branchDiameter_m": 0.1016,
  "designCalculations": {
    "configuration": {
      "location": "TOPSIDE",
      "manifoldType": "PRODUCTION",
      "numberOfInlets": 1,
      "numberOfOutlets": 2,
      "numberOfValves": 4
    },
    "geometry": {
      "headerOuterDiameter_m": 0.2032,
      "headerWallThickness_m": 0.0087,
      "branchOuterDiameter_m": 0.1016,
      "branchWallThickness_m": 0.00602
    },
    "wallThicknessAnalysis": {
      "minHeaderWallThickness_m": 0.0075,
      "wallThicknessCheckPassed": true
    },
    "velocityAnalysis": {
      "headerVelocity_m_s": 8.5,
      "branchVelocity_m_s": 12.3,
      "erosionalVelocity_m_s": 14.14,
      "velocityCheckPassed": true
    },
    "reinforcementAnalysis": {
      "reinforcementRequired": false,
      "reinforcementCheckPassed": true
    },
    "weightAnalysis": {
      "totalDryWeight_kg": 850.5
    },
    "appliedStandards": [
      "ASME B31.3 - Wall Thickness",
      "API RP 14E - Erosional Velocity",
      "ASME B31.3 - Branch Reinforcement",
      "NORSOK L-002 - Support Spacing"
    ]
  }
}

Database Integration

Design parameters are loaded from database tables:

TechnicalRequirements_Process

Company-specific parameters for manifolds:

Parameter	Default	Equinor	Unit
designFactor	0.72	0.67-0.72	-
jointEfficiency	0.85-1.0	-	-
corrosionAllowance	1.5-3.0	3.0	mm
erosionalCFactor	100-150	100-125	-
safetyClassFactor	1.046-1.138	-	-

asme_standards

ASME B31.3 and B16.5 parameters for manifolds.

dnv_iso_en_standards

DNV-ST-F101 and API RP 17A parameters for subsea manifolds.

Best Practices

Sizing Recommendations

Header sizing: Size for total combined flow with velocity < 15 m/s
Branch sizing: Size for individual well/outlet flow with velocity < 20 m/s
Corrosion allowance: Use 3mm for sour service, 1.5mm for sweet service

Subsea Design Considerations

Always specify water depth for external pressure calculation
Use appropriate safety class factor based on consequence of failure
Consider minimum 6.35mm wall thickness for handling
Use corrosion resistant alloys for long-term subsea service

Material Selection

Application	Recommended Materials
Topside sweet service	A106-B, A333 Gr 6
Topside sour service	NACE compliant A106-B
Subsea standard	X65 with FBE coating
Subsea corrosive	22Cr Duplex, 25Cr Super Duplex
High temperature	A335 Gr P11, P22

Manifold Mechanical Design Guide

Comprehensive Java library for thermodynamic, physical property, and process simulation. NeqSim provides tools for PVT analysis, phase equilibria, transport properties, and full process simulation.

Manifold Mechanical Design Guide

Overview

Design Standards

Quick Start Example

Basic Topside Manifold

Subsea Manifold Design

Manifold Locations

Manifold Types

Design Calculations

Wall Thickness

ASME B31.3 (Topside/Onshore)

DNV-ST-F101 (Subsea)

Velocity Limits

Branch Reinforcement

Support Spacing

Material Properties

Carbon Steel (Topside/Onshore)

Subsea Line Pipe Grades

Weight Calculations

Dry Weight

Submerged Weight (Subsea)

Design Verification

JSON Output

Database Integration

TechnicalRequirements_Process

asme_standards

dnv_iso_en_standards

Best Practices

Sizing Recommendations

Subsea Design Considerations

Material Selection

See Also

API Reference