Burial Sledge System III
Subsea cables are typically installed using cable-laying vessels that carry the cables on board. Dedicated tools are utilized to excavate a trench in the seabed and bury the cable within it. Boskalis engaged TME to design and engineer a burial sledge system specifically for this purpose.
The BSS III comprises a towed sledge vehicle that moves on skids over the seabed. It incorporates a telescopically adjustable jetting lance to fluidize soft sands and clays using water jets ahead of the lance. In situations with harder clays, a mechanical chain cutter is employed, enabling burial depths of up to eight meters – a remarkable advancement in cable burial technology.
When the lance negotiates curves in hard soil, significant forces are exerted. To avoid mechanical overload, a flexible, hinge-like construction supports the lance on the sledge, acting as a mechanical buffer. Moreover, an improved load measuring system, employing tensile-compressive load cells, is integrated into the lance design to accurately measure critical loads and facilitate timely intervention.
Addressing the weight challenge was pivotal in the design process. Given the limited bearing capacity of the seabed, a lightweight structure was essential. To achieve this, the skids were intentionally detached from the primary lance support system. While the primary support system endures substantial loads, it necessitates a design with ample strength. The detachment of the skids from the primary support system enables a compact, lightweight skid design.
In pursuit of meeting the weight target and ensuring predictable mechanical behavior, welding connections were replaced by pin-hole connections, which exhibit pure tensile-compressive behavior. These precise connections contribute to a reliable lightweight construction.
The demanding requirements and the high-risk nature of this project necessitated close collaboration with our customer and a comprehensive engineering approach.