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Redefining offshore pipelay and subsea construction
Allseas has set new standards in offshore pipelay and subsea construction with decades of industry-defining engineering and installation solutions. Our S-lay process, enhanced through 40 years of deepwater expertise, enables fast, precise pipeline installation in all water depths.
Designed and optimised in-house, our versatile fleet of record-breaking pipelay and construction vessels exceed the limit of what is possible above and below the water surface. From ultra-deepwater installations and intricate tie-ins to shore pull-ins, each vessel is equipped with custom in-house automated technology to safely handle even the most challenging offshore environments.
Allseas stands for reliability, efficiency and unparalleled deepwater capability, enabling us to tailor each solution to our client’s needs.
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Leaders in pipeline construction
For more than four decades, Allseas has been at the forefront of offshore pipeline construction. As pioneers of deepwater S‑lay technology, we transformed the industry and have since installed over 30,000 kilometres of subsea pipelines worldwide.
Specialist construction and offshore support
Our specialised offshore construction and support vessels deliver the flexibility demanded by today’s offshore energy projects. Featuring high-capacity lifting systems and expansive deck space, these versatile assets execute a broad spectrum of activities, from subsea structure installation and pipelay support to heavy-lift operations.
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S-lay
Allseas’ S-lay method revolutionised offshore pipelay with its fast installation speed and versatility across all water depths. Named for the “S” shape the pipe takes between vessel and seabed, this process starts as single steel pipe joints are welded, inspected and coated in a horizontal work plane – the firing line – on board our pipelay vessels.
As the vessel moves forward, the welded pipeline gradually exits the firing line, curving downward through the water until it reaches the seabed. The pipeline assumes the “S” shaped curve under its own weight as more pipe is paid out.
The curvature of the upper section of the pipeline (overbend) is controlled by a stinger, a steel structure with rollers protruding from the end of the firing line to prevent buckling of the pipe. The curvature in the lower section of the pipeline (sagbend) is controlled by pipe tensioners, caterpillar tracks that grip the pipe. The amount of tension is one of the most important factors in the capabilities of an S-lay vessel.
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Offshore pipelay projects
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Other activities
From subsea pipelay to the installation and removal of offshore structures, Allseas excels in the design and execution of large and complex offshore projects worldwide. Activities include design, engineering, procurement, fabrication and project management.
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