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Figure 1 Vessel Mobilisations & Deck Modifications

Deck Modifications & Seafastening – Structural Design & Installation Engineering

Poseidon Offshore Energy’s engineers led multiple vessel mobilisations, deck modification, and seafastening projects supporting subsea and cable-lay operations for various clients and vessels.

These scopes involved detailed structural design, finite element analysis, and mobilisation engineering for temporary deck structures, grillage systems, seafastening arrangements, and installation aids, all tailored to meet different operational configurations.

The engineering campaigns covered a variety of vessel types and scopes, including:

  • Design and installation of elevated decks for ROV mobilisation on offshore support vessels.
  • Design and construction of temporary cable tanks for subsea cable transportation and spooling operations.
  • Deck strengthening and modification of barges for cable lay operations, including crane seafastening, RDS track installation, reel cradles, and winch base integrations.

Task

The engineering scope covered the complete detailed design and installation engineering of the CSU module, including:

Poseidon’s engineering team was responsible for the complete detailed design and installation engineering scope, including:

Structural analysis and verification using SACS and ANSYS for decks, supports, and interface points.
Grillage and seafastening design for reels, RDS systems, and auxiliary equipment.
Loadout and lifting engineering, including centre-of-gravity checks and rigging arrangements.
Fabrication and construction drawings in AutoCAD.
Onsite mobilisation supervision and final as-built verification.

Challenges

Adapting deck modifications to multiple vessel layouts and equipment configurations.
Ensuring structural integrity for heavy dynamic loads during cable-lay and ROV operations.
Maintaining centre of gravity and alignment accuracy during installation.
Meeting aggressive project timelines for design, fabrication, and mobilisation.

The Solution

The engineering workflow began with detailed FEA modelling of the vessel decks and support structures in SACS and/or ANSYS to evaluate load paths and local stress concentrations. Grillage layouts were optimised for structural adequacy, while allowing rapid installation and removal offshore.

For the elevated ROV deck, a lightweight yet robust steel frame was designed to distribute loads uniformly across the existing deck plating, ensuring adequate clearance and stability during operation.

For cable transportation, Poseidon developed cable tank designs capable of supporting full cable loads under dynamic sea conditions. The designs included cable tank, wooden cladding, and internal netting systems to prevent cable shifting during transit.

For barge modification and cable lay mobilisation, the engineering team produced a complete structural and seafastening package including:

  • Crane pedestal design and seafastening.
  • RDS track systems and reel cradle supports.
  • Winch base foundations and auxiliary seafastening.
Figure 2 - Structural modeling & Deck Strength Checks

All structures were verified for combined static and dynamic load conditions and checked against DNV-ST-N001, AISC, and GL Noble Denton requirements.

Figure 3 – Deck Layout and Seafastening Drawings

Comprehensive documentation, including design reports, fabrication drawings, and method statements, ensured constructability, traceability, and compliance with offshore lifting and seafastening standards.

Summary

These projects demonstrate Poseidon Offshore Energy’s capability to deliver fit-for-purpose structural design, installation engineering, and mobilisation solutions across multiple offshore vessel and barge configurations.

Each mobilisation was completed safely, efficiently, and in accordance with international design and lifting standards.

Engineering Tools:

ANSYS, SACS, MathCAD, and AutoCAD

Key Deliverables:

Key Deliverables: Structural Analysis Reports, Deck Layout Drawings, Grillage & Seafastening Design, Fabrication Drawings, Installation Method Statements.

Project Information

Completely synergize resource taxing relationships via premier.

Client Name

Various Offshore Operators

Category

Showcase