Fugro’s QuickVision® Technology supports installation of Arcadis OST 1 Wind Farm from a heavy lift vessel

The Challenge

Heerema is a leader in heavy lifting for offshore construction, owning a fleet of the largest crane vessels in the world. Safe to say, its project teams understand exactly what it takes to manoeuvre valuable structures exposed to the volatile forces of the sea and offshore elements.

Heerema’s most recent project required the installation of 27 wind farm towers and RNAs for Parkwind’s Arcadis Ost 1 wind farm located in the Baltic Sea off the German coast. Pooling expertise with its partners, Heerema not only devised an improved method of installation but a game-changer for offshore wind.

The first floating installation of a wind farm

Heerema set its sights on a world first - the construction of a wind turbine using a semi-submersible (floating) crane vessel instead of a wind turbine installation vessel (WTIV) supported on the seafloor.

The concept involved the two floating cranes on Heerema’s Thialf, a heavy lift vessel, working at the same time. While one lifted the wind turbine generator (WTG) tower into the seabed foundation, the other would use a support plinth to pre-assemble the RNA swiftly and securely before placing it on top of the turbine.

This novel approach is paving the way for installations in areas where seabed conditions or water depths make jack-up barges less feasible.

But the biggest challenge of floating installation is managing the relative motion between the vessel crane lifting the RNA and the fixed foundation tower installed on the seabed.

Typical practice relies on personnel present on the tower to watch the lifting of the RNA and guide the crane operator via walkie-talkie and a simple video streaming camera looking down on the tower. This lacks the accurate input for fine control to assure precise handling of the RNA with its expensive blade components and poses safety risks to crew in proximity to handling operations communicating the position of the lifted load.

Solution

Spot on with real-time machine vision technology

An answer was at hand that would help turbo-drive progress. Our specialists were already working closely with Heerema under a contract to provide real-time machine vision technologies and remote services to optimise their offshore installation and decommissioning campaigns.

We adapted and scaled our QuickVision® camera technology to achieve precise installation control of the new novel RNA assembly on Heerema’s heavy lift vessel – Thialf.

During subsea operation this patented solution accurately tracks and measures the position, heading and attitude of an adhesive coded target (dotted patterns) attached to subsea structures, removing the need to install expensive and bulky peripheral sensors on subsea structures.

During eight months of intensive preparation work, we adjusted the pattern tracking technology to work with battery powered cameras that could be mounted in a downward looking position and stream wireless positioning data to the survey computer on the vessel. We also devised a special circular tracking pattern to fit the turbine tower with a focus on easy installation and removal.

Precise positioning

Our established working relationship with Heerema surveyors and engineers proved crucial at every point of development and testing, including dry fitting the systems on the RNA to establish effective reporting of data. This reduced mobilisation time when it came to installing the first turbine and ensured operations ran as expected. The turbine supplier, Vestas, provided tools to enable assembly of RNA components using the floating set-up.

As a result, QuickVision® provided real-time information from the camera system ensuring precise monitoring of the lifting, positioning, and lowering phases of the installation process. On its debut use, Heerema engineers were able to position the RNA with an accuracy of 2 cm.

Innovative Highlight

The use of QuickVision® for offshore installations advances on our existing tracking technology by enabling a fully remote solution. The camera system is battery powered and transmits data wirelessly for users on the vessel to view it in real time. This makes it easy to mobilise and delivers real time, high accuracy data for RNA/Nacelle positioning. It also removes the need to have engineers on the tower during lifting, and minimises the risk of damage to the RNA.

Impact

The QuickVision® solution delivered 2 cm accurate positioning data in all directions starting at a height of 10 m above the turbine tower. The camera was combined with a motion reference unit (MRU) to measure tilt of the RNA within 0.1° of accuracy. This allowed Heerema to move personnel to a safer location during positioning of the RNA whilst still having highly accurate real-time data to install the RNA. Not only is HSSE risk reduced, but having full control and reliable data during lifting operations also reduces the risk of damage from unwanted or unexpected movement of the RNA/Nacelle.

Benefits at a glance:

• Allows RNA to be installed remotely and efficiently within strict tolerances

• Reduces personnel and equipment risks traditionally associated with offshore installation operations.

• Reduces project complexity

• Speeds up turnaround times