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From A-Frames to Z: Full-scope engineering for offshore lifting systems

When operational demands evolve and heavier equipment comes into play, existing lifting solutions must be reconsidered to ensure they remain fit for purpose. For Geoquip Marine, this meant taking a fresh look at their A-frames. Both an already modified system on the Saentis and a new installation on board of their Silvretta.

What was required, where did the challenges lie, and how were they addressed from an engineering perspective? For these projects, Geoquip contacted Saltwater Engineering to develop a well-considered and future-proof solution. Building on Geoquip’s extensive operational experience, we worked in close collaboration throughout the process.

Evolving lifting requirements for the Saentis

The original A-frame of the Saentis was once modified by adding an extension piece between the legs, increasing the available lifting height. At that time, the Working Load Limit (WLL) was determined based on the equipment required for that specific operation.

However, significantly heavier equipment now had to be lifted. This raised the key question: Is the modified A-frame still structurally sufficient?

That’s where Saltwater Engineering came in.

Structural re‑evaluation of the modified A‑frame

The scope involves lifting a Roson and a Vibrocorer. Our structural assessment with the use of FEM showed that the existing A-frame was not capable of safely handling these loads in its current configuration. Therefore, modifications were required and the A-frame was fitted with two new lifting padeyes:

One on the centerline for the Roson
One offset from the centerline for the Vibrocorer

Finally, the proof load procedures were defined, followed by successful testing of the A-frame.

Designing a new 30‑tonne A‑frame for the Silvretta

In the meantime, Geoquip also asked us to design a new A-frame for the Silvretta. It was positioned at the stern, where part of the shelter deck and bulwark were removed to accommodate the installation. The system has a Safe Working Load (SWL) of 30 tonnes.

The installation of the A-frame was reviewed and approved by DNV, with particular focus on its integration with the existing vessel structure, including the foundation and deck connections. The A-frame itself is designed and constructed in accordance with the applicable DNV rules and standards.

Full engineering scope and project support

Within this project, Saltwater Engineering carried out a broad scope of work. We performed FEM analyses to verify the structural strength of both the A-frame and the deck. In addition, we developed construction drawings, along with all required outfitting drawings for items such as stairs, platforms, and railings.

We also prepared demolition drawings, as well as drawings for reinstating the structure after removing existing components. This included modifications such as relocating doors, bollards, and stairs.

Based on a 3D scan, we verified whether the deck is sufficiently level for the installation of the foundation. In addition, we developed a load test arrangement and the corresponding test protocol in close collaboration with Geoquip.

During the construction phase, Saltwater Engineering also provided construction support, working closely with the yard to address questions and to effectively implement any changes arising during execution.

Supporting safe and reliable offshore operations

These projects demonstrate how Saltwater Engineering supports offshore operations throughout the full lifecycle of complex lifting systems. Our work focuses on ensuring that structural integrity, operational requirements, and safety margins are aligned. By combining detailed structural analysis, practical engineering solutions, and close collaboration with all stakeholders, we help our clients adapt their equipment to changing demands with confidence.

Whether it concerns upgrading existing structures or developing new designs from the ground up, Saltwater Engineering delivers engineering solutions that are robust, transparent, and ready for operation. If your project involves lifting equipment, structural modifications, or complex marine integrations, we would be pleased to support you. Contact our team to explore how we can add value to your offshore operations.