---

name: orcaflex-installation-analysis description: Create and analyze OrcaFlex models for offshore installation sequences including subsea structure lowering, pipeline installation, and crane operations. Generate models at multiple water depths and orientations for installation feasibility studies. version: 1.0.0 updated: 2026-01-17 category: offshore-engineering triggers:

• installation analysis
• subsea installation
• structure lowering
• crane operation
• installation sequence
• depth variation
• installation feasibility
• heavy lift
• payload handling

---

OrcaFlex Installation Analysis Skill

Generate and analyze OrcaFlex models for offshore installation sequences with automated depth variation and orientation studies.

Version Metadata

Copyversion: 1.0.0
python_min_version: '3.10'
dependencies:
  orcaflex-modeling: '>=2.0.0,<3.0.0'
orcaflex_version: '>=11.0'
compatibility:
  tested_python:
  - '3.10'
  - '3.11'
  - '3.12'
  - '3.13'
  os:
  - Windows
  - Linux
  - macOS

Changelog

[1.0.0] - 2026-01-17

Added:

• Initial release with installation sequence capabilities
• Multi-depth model generation
• Orientation variation support
• Crane wire length adjustment

When to Use

• Subsea structure installation analysis
• Pipeline/umbilical installation sequences
• Heavy lift crane operations
• Installation depth variation studies
• Lowering phase analysis
• Splash zone analysis
• Installation feasibility assessment
• Crane wire and sling configuration

Prerequisites

• OrcaFlex license (for simulation)
• Python environment with digitalmodel package installed
• Reference model files (.yml format recommended)
• Reference elevation configuration

Installation Sequence Workflow

Copy[Reference Model] → [Define Delta Elevations] → [Generate Depth Models]
        ↓                    ↓                           ↓
   Base geometry      [-10m, -20m, -30m, ...]    Model per depth:
   at datum                                       - Update structure Z
                                                  - Update buoy Z
                                                  - Extend crane wire
                                                  - Update sling connections
                                                           ↓
                                               [Orientation Variants]
                                                           ↓
                                               [Batch Simulation]

Configuration

Basic Installation Depth Study

Copy# configs/installation_config.yml

structure:
  BaseFile: "reference_model.yml"
  reference_model_file: "models/installation_reference.yml"
  reference_elevation_file: "models/elevation_reference.yml"

  # Objects to update
  6DBuoys:
    - "Subsea_Structure"
  3DBuoys:
    - "Masterlink"

  # Lines to extend
  Lines:
    - name: "Crane_Wire"
      EndBZ: true           # Update end B Z coordinate
      length_index: 2       # Section index to extend
      TargetSegmentLength: 5.0
    - name: "Intermediate_Sling"
      EndBZ: true

  # Depth increments from reference
  delta_elevations:
    - 0      # Reference position
    - -10    # 10m below reference
    - -20    # 20m below reference
    - -30    # 30m below reference
    - -50    # 50m below reference
    - -75    # 75m below reference
    - -100   # 100m below reference

Analysis:
  analysis_root_folder: "results/installation/"

Heavy Lift Configuration

Copy# configs/heavy_lift_config.yml

reference_elevation_file: "models/heavy_lift_reference.yml"

# Key components
structure: "Topside_Module"
masterlink: "Lifting_Padeye"
crane_wire: "Main_Crane_Wire"
intermediate_sling: "Spreader_Sling"

# Output naming
output_basefile: "topside_installation"

# Installation depths (negative = below reference)
delta_elevations:
  - 0      # At deck level
  - -5     # Splash zone entry
  - -10    # Through splash zone
  - -15    # Below splash zone
  - -20    # Mid-water
  - -30    # Approaching seabed
  - -40    # Near seabed
  - -45    # Final position

Python API

Generate Installation Depth Models

Copyfrom digitalmodel.modules.orcaflex.orcaflex_installation import OrcInstallation

# Initialize
installer = OrcInstallation()

# Configuration for depth variation
cfg = {
    "structure": {
        "BaseFile": "reference.yml",
        "reference_model_file": "models/reference_model.yml",
        "reference_elevation_file": "models/elevations.yml",
        "6DBuoys": ["Structure"],
        "3DBuoys": ["Masterlink"],
        "Lines": [
            {
                "name": "Crane_Wire",
                "EndBZ": True,
                "length_index": 1,
                "TargetSegmentLength": 5.0
            }
        ],
        "delta_elevations": [0, -10, -20, -30, -50, -75, -100]
    },
    "Analysis": {
        "analysis_root_folder": "results/"
    }
}

# Generate models for all depths
installer.create_model_for_water_depth(cfg)

Simple Depth Model Generation

Copyfrom digitalmodel.modules.orcaflex.orcaflex_installation import OrcInstallation

installer = OrcInstallation()

# Simpler configuration
cfg = {
    "reference_elevation_file": "models/reference.yml",
    "structure": "Subsea_Template",
    "masterlink": "Lifting_Point",
    "crane_wire": "Main_Wire",
    "intermediate_sling": None,  # Optional
    "output_basefile": "template_installation",
    "delta_elevations": [0, -10, -20, -30, -40, -50]
}

# Generate depth models
installer.create_installation_depth_model(cfg)

With Structure Orientation

Copyfrom digitalmodel.modules.orcaflex.orcaflex_installation import OrcInstallation

installer = OrcInstallation()

# This generates:
# 1. Base model at each depth
# 2. Orientation variant (rotation about Z)
cfg = {
    "structure": {
        "BaseFile": "reference.yml",
        "reference_model_file": "models/reference.yml",
        "reference_elevation_file": "models/elevations.yml",
        "6DBuoys": ["Mudmat"],
        "3DBuoys": [],
        "Lines": [
            {"name": "Wire1", "EndBZ": True, "length_index": 0}
        ],
        "delta_elevations": [0, -5, -10, -15, -20]
    },
    "Analysis": {
        "analysis_root_folder": "results/mudmat/"
    }
}

# Generates files:
# - _el_00000m.yml (reference)
# - _el_00000m_str_orientation.yml (with Rotation3 = 0)
# - el_00000m.yml (final model)
# - _el_-0010m.yml
# - ... etc for each depth

installer.create_model_for_water_depth(cfg)

Output File Structure

Copyresults/installation/
├── _el_00000m.yml              # Reference depth, base orientation
├── _el_00000m_str_orentation.yml   # Reference depth, zero rotation
├── el_00000m.yml               # Final reference model
├── _el_-0010m.yml              # 10m below reference
├── _el_-0010m_str_orentation.yml
├── el_-0010m.yml
├── _el_-0020m.yml              # 20m below reference
├── _el_-0020m_str_orentation.yml
├── el_-0020m.yml
└── ...

Key Concepts

Reference Elevation File

Contains the initial Z positions for all objects:

Copy# models/elevation_reference.yml

6DBuoys:
  Subsea_Structure:
    InitialZ: -50.0      # Initial elevation
    InitialRotation3: 45  # Initial rotation (deg)

3DBuoys:
  Masterlink:
    InitialZ: -45.0

Lines:
  Crane_Wire:
    EndBZ: -45.0
    Sections:
      - Length: 10.0
      - Length: 50.0      # Section to extend
      - Length: 5.0

Delta Elevation Application

For each delta_elevation:

1. 6DBuoys: NewZ = ReferenceZ + delta_elevation
2. 3DBuoys: NewZ = ReferenceZ + delta_elevation
3. Line EndBZ: NewEndBZ = ReferenceEndBZ + delta_elevation
4. Line Length: NewLength = ReferenceLength + |delta_elevation|

Crane Wire Extension

As structure lowers, crane wire extends:

Copy# For each delta_elevation
new_wire_length = reference_length + abs(delta_elevation)

Integration with Universal Runner

After generating installation models, run batch simulations:

Copyfrom digitalmodel.modules.orcaflex.universal import UniversalOrcaFlexRunner

# Initialize runner
runner = UniversalOrcaFlexRunner(
    input_directory="results/installation/",
    output_directory="results/installation/.sim/",
    mock_mode=False
)

# Run all installation models
results = runner.run_batch(
    pattern="el_*.yml",
    parallel=True,
    max_workers=4
)

# Check results
for file_name, status in results.items():
    print(f"{file_name}: {'SUCCESS' if status['success'] else 'FAILED'}")

Analysis Types

1. Splash Zone Analysis

Focus on depths around waterline:

Copydelta_elevations:
  - 5     # Above water
  - 2     # Near waterline
  - 0     # At waterline
  - -2    # Just below
  - -5    # Submerged
  - -10   # Below splash zone

2. Full Lowering Sequence

Complete installation from deck to seabed:

Copydelta_elevations:
  - 0     # At deck
  - -5    # Clear of vessel
  - -10   # Splash zone entry
  - -15   # Through splash zone
  - -20   # Mid-water (upper)
  - -30   # Mid-water
  - -50   # Mid-water (lower)
  - -75   # Approaching seabed
  - -95   # Near seabed
  - -100  # At seabed

3. Landing Sequence

Fine resolution near seabed:

Copy# Reference at 5m above seabed
delta_elevations:
  - 0     # 5m above seabed
  - -1    # 4m above
  - -2    # 3m above
  - -3    # 2m above
  - -4    # 1m above
  - -4.5  # 0.5m above (touchdown)
  - -5    # On seabed

Post-Processing Installation Results

Copyfrom digitalmodel.modules.orcaflex.opp import OrcaFlexPostProcess

opp = OrcaFlexPostProcess()

# Extract crane wire tensions at each depth
cfg = {
    "orcaflex": {
        "postprocess": {
            "summary": {
                "flag": True,
                "variables": [
                    {"object": "Crane_Wire", "variable_name": "Effective Tension"},
                    {"object": "Structure", "variable_name": "Z"}
                ]
            }
        }
    }
}

# Process all simulation files
sim_files = list(Path("results/installation/.sim/").glob("*.sim"))
for sim_file in sim_files:
    results = opp.process_single_file(sim_file, cfg)
    depth = extract_depth_from_filename(sim_file.stem)
    print(f"Depth {depth}m: Max tension = {results['max_tension']:.1f} kN")

Best Practices

Model Preparation

1. Reference model at datum - Start with well-converged static model
2. Appropriate segment lengths - Finer segments for crane wire
3. Buoyancy and mass - Verify structure properties
4. Crane capacity - Check against maximum tensions

Depth Increments

1. Fine resolution at splash zone - Wave loading peaks here
2. Coarse mid-water - Quasi-static behavior
3. Fine at seabed - Landing dynamics critical

Output Validation

1. Check crane wire tensions - Must be within capacity
2. Verify structure orientation - No unexpected rotations
3. Validate connections - All links maintained
4. Review static convergence - Each depth should converge

Error Handling

Common Issues

Copy# File not found
try:
    installer.create_model_for_water_depth(cfg)
except FileNotFoundError as e:
    print(f"Reference file not found: {e}")
    print("Check: reference_model_file and reference_elevation_file paths")

# Invalid line section index
# Error: "Key not found in line item"
# Fix: Verify length_index matches actual line sections

# Convergence failure at depth
# Check: Environmental loads, line lengths, tensions

Related Skills

• orcaflex-modeling - Run OrcaFlex simulations
• orcaflex-post-processing - Extract results
• orcaflex-static-debug - Debug convergence issues
• orcaflex-line-wizard - Configure line properties

References

• OrcaFlex Installation Analysis: Orcina Documentation
• DNV-RP-H103: Modelling and Analysis of Marine Operations
• API RP 2A: Planning, Designing and Constructing Fixed Offshore Platforms
• Source: src/digitalmodel/modules/orcaflex/orcaflex_installation.py