Function
The pre-installation and testing of anchors and mooring lines at site. Completing as much pre-installation as possible ahead of the installation critical path allows the hook-up of the floating offshore wind turbine to be completed faster.
Who is involved
Anchor and mooring installation services are conducted by specialist suppliers contracted by the developer.
Key facts
The pre-installation begins by installing an anchor on the seabed. The process depends on the anchor type:
- Drag embedment anchors are installed by placing the anchor on the seabed and using the pulling force of the anchor-handling vessel (AHV) to obtain the necessary embedment.
- Suction embedment anchors are installed by lowering a suction pile to the seabed which self-penetrates part-way into the seabed under its own weight. The piles are then embedded to their full depth by evacuating seawater from inside the pile using a pump on the anchor operated by a specialised remote operated vehicle (ROV).
- A piled anchor is installed by lowering a pile to the seabed which penetrates the seabed under its own weight. A pile hammer is then used from the AHV to obtain the required penetration depth. Piled anchors can also be drilled and grouted into place, depending on ground conditions.
Anchors are proof loaded for 15 to 30 minutes, according to the standard used, using the pulling force of the AHV to ensure sufficient holding capacity.
The lower section of the mooring line, often anchor chain, is connected to the anchor during installation:
- For drag embedment anchors it is attached before the anchor is embedded, as the attachment point is below the seabed once it is embedded.
- For suction and piled anchors, it is attached after the anchor is installed.
A submersible marker buoy is connected to the end of the mooring line to support retrieval for later hook-up operations.
