The development of a concept for accurate and efficient dredging at great water depths
Type:
Presented during:
WODCON XVII: "Dredging in a Sensitive Environment" - 2004, Hamburg, Germany
Authors:
O. Verheul, P.M. Vercruijsse, S.A. Miedema
Abstract: Especially in the past decade dredging projects are being carried out at an ever increasing depth and scale. Modern Trailing Suction Hopper Dredgers (TSHD's) can now dredge up to 150 m depth. However, for certain projects, it is necessary to exceed this limit. One can think of the exploitation of certain minerals, which may be economic in the near future, or sea floor leveling to accommodate structures for the offshore oil and gas industry.
It is assumed, that at greater water depths a direct connection between the sea surface and the sea floor is not anymore possible. For this reason, the use of conventional TSHD's is not considered an option. This leads to a separation of functions. Excavating or collecting the minerals and transporting them to the sea surface is carried out by a device positioned on the sea floor, whereas the material received at the surface and its horizontal transport is carried out by a ship, which does not need to be a TSHD.
For these kinds of applications, the challenge lies in overcoming problems related to operations at such depth, e.g. stability of the vehicle at uneven sea floor, resistance to high pressure and the vulnerability of remotely controlled moving parts. These problems are minimized by keeping the design as simple as possible. This by reducing the number of moving parts and simplifying the design of the frame positioned on the sea floor, resulting in a triangular shaped frame. Once lowered from e.g. a ship to the sea floor, this triangular frame makes use of a kinematical principle that allows it to walk in all directions. The Triangular Walking Platform has been named TWP. When equipped with a dredge ladder with a wheel, the platform becomes a dredger. This dredging device carries the name "TRIPOD".
The article describes the development and operation of an Remotely Operated Vehicle (ROV), able to operate at virtually any depth. The new concept is the result of a joint study between IHC Holland NV and the Dredging Engineering Research Laboratory of the Delft University of Technology.
Keywords:, deep, sea, dredging, excavation, walking, device, ROV, TWP, TRIPOD