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E-RAD saves precious time at the Gemini Offshore Windpark

The Gemini Offshore Windpark is being built some 85 km from shore in the Dutch part of the North Sea. With its 150 turbines it will provide green electricity to 1,5 million households once it is connected to the grid in 2017. The turbine hub height is 154 meters with a rotor diameter of 130 meters. One of the many operational challenges was to torque 15.600 M72 bolts quickly and accurately.

Figure 1: Van Oord’s installation vessel ‘AEOLUS’ installing the turbine foundations


Flange connection of the turbine foundation

Onshore wind turbines are fixed to the ground with a concrete foundation. In offshore wind the tower foundation is made of 2 large diameter steel tubes. One is hammered into the seabed and the second is bolted on top of it with 104 M72 bolts. The flange connection is pre-torqued with an E-RAD BLU electric torque wrench with a maximum torque of 8.000 Nm. Hydraulic torque wrenches are used to apply the final torque of more than 20.000 Nm.


Van Oord constructs the Gemini Offshore Wind Park

One of the Gemini project partners is Van Oord. This family-owned company operates around the world as a leading contractor for dredging, marine engineering and offshore energy projects (oil, gas and wind) offering innovative solutions to marine challenges. The company operates worldwide in more than fifty countries.


From the customer’s perspective

Van Oord’s Project Engineer Tino Kuin explains: “The E-RAD BLU made by RAD Torque had the best results in our test for pre-torqueing the bolts. The electrical drive of the tool provides a continuous rotation of the bolt whereas a hydraulic wrench only turns the bolts 20 to 30 degrees per cycle. This saves us a lot of costly time offshore. Apart from this advantage, RAD Torque supplies a number of ergonomic solutions for the tools.”


The result

The last foundation was installed by the end of 2015. The E-RAD torque wrenches accurately bolted 15.600 bolts to the desired pre-torque in a minimum amount of time. When the park connects to the grid in 2017 it will contribute to the Dutch Energy Agreement stating that 16% of power consumption should come from renewable sources.

Figure 2: E-RAD BLU 8.000 Nm with                   Figure 3: E-RAD flange roller system
ergonomic handle