The topside connection connects the upper section of the mooring line to the floating substructure.

What it costs

About £3 million for a 450 MW floating offshore wind farm.

Who supplies them

First Subsea, Hydrosphere, InterMoor, Macgregor and The Crosby Group.

Key facts

The major items may include:

  • A chain stopper which stops the chain and which is normally be used with a fairlead, which provides a “fair”, or good, “lead-in” for the anchor chain onto the substructure which helps reduce chafe and damage during connection and disconnection.
  • A pull-through connector that fits around a chain and can be readily made and unmade. An example is Macgregor’s pull-through connector.
  • A ball and taper connection that is easy to make and unmake. An example is First Subsea’s Ballgrab® connector.
  • A fixed padeye is the simplest type of topside connection. It is a plate welded to the floating substructure with a hole, or “eye”, through which a shackle can be fitted.

The topside connector must either allow for the continuous dynamic motion of the floating substructure for a safe lifetime of at least 30 years or be subject to planned replacement.

The topside connection sees greater loads than any other part of the mooring line as it carries the weight of the mooring line and jewellery in addition to the dynamic loads from the substructure.

The detailed design of the topside connector is vital to ensure that it does not introduce stress concentrations that could add to the fatigue loading of the chain that is expected to be used in the upper section of the mooring line.

The topside connector must allow the connection and disconnection of the mooring lines.

Winches have been used on early demonstration projects, but they are not expected to be used on commercial-scale projects.

What’s in it

Guide to a Floating Offshore Wind Farm