Eager.one has, on behalf of Van Oord, designed and constructed a tool for the installation of anode cages from a floating vessel.
The Anode Cage Installation Aid (ACIA) has now completed a factory acceptance test and will now be prepared for transport to the onshore harbour for commissioning and training of the Van Oord operational crew, the Dutch independent consultancy said.
The tool will be used by Van Oord’s heavy lift vessel Svanen on an unnamed offshore wind project.
The challenge presented to the Eager.one team was to design an installation aid that can install the anode cage over the monopile while preventing collision between the two. This was to be carried out from a floating vessel by means of a service crane with limited capacity.
Weight restrictions, precise handling, and monitoring were the main operational challenges, starting with how to position the anode cage over the monopile. Due to the weight restrictions lightweight materials such as aluminium were used to construct the tool.
Installing the AC directly over the MP is not possible due to the motions of the vessel and marginal tolerances. Therefore the ACIA, with the anode cage connected to it, will first be lifted onto the monopile, Eager.one said.
Once positioned according to the required heading, the three synchronized winches will lower the anode cage over the ACIA towards the monopile flange.
By means of eye-to-eye slings, the anode cage is connected to a lowering ring, which is an aluminium circular truss frame that will guide the cages towards the installation position.
Spring-loaded wheels are connected to the lowering ring. These wheels follow the ACIA structure down to the monopile and make sure that the anode cage will stay exactly centred and will not collide with the MP. The hydraulics and electrical and instrumentation fitted onto the lowering ring are powered via the umbilical winch fitted onto the ACIA.
The lowering of the anode cage into the installation position will be monitored by means of cameras, supported by lighting for visual confirmation of the cage’s position. In addition, the exact position can be determined by a pay-out measuring system in the winches, the company said.
As soon as the anode cage has reached the installation position, the pin-pushers will release the eye-to-eye sling on one side. In case the sling is stuck the secondary pin-pushers can release the other side of the sling as a mitigation.
Once installed, the aluminium ring will be lifted back to the ACIA base which is still positioned on top of the monopile.