Torpedo anchors

Anchors formed like torpedoes can become the next cost-effective and robust anchor solution for floating structures in deep water down to 3000 metres depth.

As an alternative to traditional anchoring methods, which can be quite time-consuming to install, a new anchoring concept has been developed. These new anchors are designed such that after release from a specified height above the seabed they are installed down into the seabed by penetration after reaching velocities up to 100 km/h during 'free-fall' through the water. 'Deep Penetrating Anchor' may typically have a dry weight of 50 - 100 ton and a height of 10-15 m.

NGI developed instrumentation for the testing of the new anchor in the Trondheimfjord and at the Troll field in the North Sea. Acceleration, pressure, pitch and yaw during the free-fall and penetration into the seabed are logged. NGI also carried out a research project where anchor penetration into the seabed clay soil and the stress distribution around the anchor have been modelled by a large deformation finite element analysis.

The Norwegian company DSA (Deep Sea Anchors) in Trondheim has developed the anchor with research funding from Statoil and The Research Council of Norway.

Two "Deep Penetrating Anchors"on board ship before installation. Photo: Deep Sea Anchors AS.