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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 pioneering 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
As pioneers of S-lay technology, known for its fast installation speed in all water depths, our dynamically positioned pipelay vessels have transformed the offshore pipelay industry. Continuously pushing offshore boundaries, these vessels have completed over 300 projects and laid more than 28,000 kilometers of pipeline worldwide.
Specialist construction and offshore support
Our advanced offshore construction and survey vessels perform deepwater installation, pipelay and heavy-lift operations. With high-capacity lifting equipment and expansive deck space, these versatile vessels handle a wide range of specialised tasks, from transporting heavy materials to installing large subsea structures with precision and efficiency.
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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 offshore pipelaying to installing and removing 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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