KCI has launched an innovative new joint method for the renewables market: the Double Slip Joint concept. KCI’s Double Slip Joint (DSJ) is a smart alternative to grouted or bolted connections between transition pieces and monopile foundations for offshore wind turbines.
In the Double Slip Joint concept, two sets of steel rings with matching conical surfaces are integrated into the standard cylindrical tubes of the monopile and the transition piece.
The transition piece is installed by lifting it over the monopile. The Double Slip Joint involves two sets of rings, which have a small taper angle of about 2⁰ and are an exact fit, providing a self-locking steel-on-steel connection.
The tower, nacelle and blades can then be installed immediately. The transition piece will automatically settle under the gravity and the operational turbine loads within a short period of time, locking rigidly to the monopile, as if ’welded’ together.
The DSJ has impressive advantages. One of the most appealing benefits to the industry will probably be the short installation time, resulting in a sharp cut in installation costs. There is no need to inject grouting material and wait for it to cure or to install bolts to be tightened. This saves an immense amount of time and the use of expensive installation ships at sea. Safety is also improved because there are fewer (manual) handling activities offshore during the installation process and no maintenance is required on the connection. A last cost-saving factor is the ease of manufacture because cylindrical rolled plates are used instead of cones or expensive flange connections.