07/27/2006
Bauer Flydrill BFD 5500 drilling monopile foundations at Barrow Offshore Wind Farm in the East Irish Sea, UK
Construction of the largest offshore wind farm in UK coastal waters is currently underway at the Barrow Offshore Wind Farm site in the East Irish Sea approximately 7 km south west of Walney Island, near Barrow-in-Furness. When completed the wind farm, which comprises 30 Vestas V90-3.0 MW wind turbines and an offshore sub-station and covers an overall area of around 10 square kilometers, will feed clean renewable energy into the UK’s National Grid at Heysham at an anticipated annual rate of production of 305 GWh and provide green electricity to around 65,000 homes. The Barrow Offshore Wind Farm project is an important building block in the UK Government’s plan to increase the share of electricity generation from renewable sources to 10% by 2010 in an effort to combat the effects of global warming.
With the installation of up to 61.2 m long 4.75 m diameter tubular steel monopile foundations weighing up to 452 tonnes in water depths ranging between 21 and 23 m, the Barrow Offshore Wind Farm is clearly at the cutting edge of offshore wind developments.
All offshore construction work including installation of the monopile foundations for the wind turbines and offshore sub-station, erection of the turbine towers and installation of the nacelles and rotor blades is carried out by Marine Projects International Ltd. (MPI) based in Middlesbrough, Cleveland, from their purpose-built jack-up turbine installation vessel TIV Resolution.
Specialist foundation equipment manufacturer BAUER Maschinen GmbH of Schrobenhausen, Germany was awarded the contract for supplying its innovative Flydrill System BFD 5500 together with full technical and operational support for drilling out the soil and, in particular, the weak to moderately weak sedimentary rocks from inside monopiles that refused above their final elevations to assist driving them to their terminal set. Drilling out the inside of a pile eliminates the skin friction acting on the internal surface of the steel tube over the drilled length. Although this will reduce the total combined frictional resistance, it is generally unlikely to reduce the pile’s driving resistance sufficiently to achieve terminal penetration. The pile bore must, therefore, be advanced a sufficient distance ahead of the pile toe to enable stress release to occur enabling the annulus under the base of the pile to be displaced during subsequent driving.
The BFD 5500 Flydrill System is a completely new concept for drilling large diameter boreholes for a wide range of applications both on land and offshore. In contrast to fixed pile-top drilling systems, such as the Bauer BA 3000 top drill RC -reverse circulation or air-lift - drilling system, the Bauer Flydrill System BFD 5500 is a highly versatile ’mobile’ pile-top drilling system of unpresidented dimensions for applications in kelly mode in all types of soil and weak rock or RC mode for drilling rock sockets in hard rock. Integrating the power packs fully into the setup by mounting them on a platform immediately adjacent to the rotary drive and eliminating the need for an ’umbilical cord’ was an essential part of the design concept which aimed at a truly ’mobile’ top drill capable of being suspended from a crane, placed on top of an isolated monopile in the sea and operating fully independently from any other power source on deck of the support vessel. This concept also requires a fully integrated remote control system that enables the Flydrill to be operated purely via a radio-controlled link. The operation is supported by Bauer’s B-Tronic® electronic monitoring, control and recording system.
The Bauer Flydrill BFD 5500 comprises Bauer’s most powerfull rotary drive KDK 480 which produces a torque of 462 kNm at 320 bar; two hydraulic crowd cylinders each producing a crowd pressure of 40 tonnes; two heavy-duty hydraulic power packs HD 460 each with an installed power of 260 kW and an hydraulic output of 450 l/min at 320 bar; a clamping device consisting of three hydraulically operated heavy-duty clamping units delivering a clamping force of 32 tonnes each; a specially designed triple telescopic kelly bar with an overall extended length of 63.9 m, a nominal drilling depth of 65 m and an outer diameter of 559 mm; a 3 m diameter pre-drilling bucket c/w centralizer; and a 4.4 m diameter reaming bucket for reaming the prebore to the full internal diameter of the monopile.
After lifting the fully assembled unit weighing 74 tonnes off the deck of TIV Resolution, the Flydrill is mounted on top of the partially driven monopile and clamped to the top of the steel tube by way of three hydraulic clamps which transfer not only the torque produced by the rotary drive into the pile, but also the crowd force generated by the crowd cylinders. Finally, kelly and drilling bucket are lowered onto the seabed inside the monopile.
In contrast to the RC air-lift drilling system which uses water for conveying the drill spoil to the surface and dumping it in a generally uncontrolled manner into the sea with the potential of widespread pollution, the deployment of the Bauer Flydrill System BFD 5500 in kelly mode with drilling bucket offers an environmentally friendly method of controlled spoil disposal.
A total of nine monopiles have been drilled and subsequently driven to their terminal set.
With the installation of up to 61.2 m long 4.75 m diameter tubular steel monopile foundations weighing up to 452 tonnes in water depths ranging between 21 and 23 m, the Barrow Offshore Wind Farm is clearly at the cutting edge of offshore wind developments.
All offshore construction work including installation of the monopile foundations for the wind turbines and offshore sub-station, erection of the turbine towers and installation of the nacelles and rotor blades is carried out by Marine Projects International Ltd. (MPI) based in Middlesbrough, Cleveland, from their purpose-built jack-up turbine installation vessel TIV Resolution.
Specialist foundation equipment manufacturer BAUER Maschinen GmbH of Schrobenhausen, Germany was awarded the contract for supplying its innovative Flydrill System BFD 5500 together with full technical and operational support for drilling out the soil and, in particular, the weak to moderately weak sedimentary rocks from inside monopiles that refused above their final elevations to assist driving them to their terminal set. Drilling out the inside of a pile eliminates the skin friction acting on the internal surface of the steel tube over the drilled length. Although this will reduce the total combined frictional resistance, it is generally unlikely to reduce the pile’s driving resistance sufficiently to achieve terminal penetration. The pile bore must, therefore, be advanced a sufficient distance ahead of the pile toe to enable stress release to occur enabling the annulus under the base of the pile to be displaced during subsequent driving.
The BFD 5500 Flydrill System is a completely new concept for drilling large diameter boreholes for a wide range of applications both on land and offshore. In contrast to fixed pile-top drilling systems, such as the Bauer BA 3000 top drill RC -reverse circulation or air-lift - drilling system, the Bauer Flydrill System BFD 5500 is a highly versatile ’mobile’ pile-top drilling system of unpresidented dimensions for applications in kelly mode in all types of soil and weak rock or RC mode for drilling rock sockets in hard rock. Integrating the power packs fully into the setup by mounting them on a platform immediately adjacent to the rotary drive and eliminating the need for an ’umbilical cord’ was an essential part of the design concept which aimed at a truly ’mobile’ top drill capable of being suspended from a crane, placed on top of an isolated monopile in the sea and operating fully independently from any other power source on deck of the support vessel. This concept also requires a fully integrated remote control system that enables the Flydrill to be operated purely via a radio-controlled link. The operation is supported by Bauer’s B-Tronic® electronic monitoring, control and recording system.
The Bauer Flydrill BFD 5500 comprises Bauer’s most powerfull rotary drive KDK 480 which produces a torque of 462 kNm at 320 bar; two hydraulic crowd cylinders each producing a crowd pressure of 40 tonnes; two heavy-duty hydraulic power packs HD 460 each with an installed power of 260 kW and an hydraulic output of 450 l/min at 320 bar; a clamping device consisting of three hydraulically operated heavy-duty clamping units delivering a clamping force of 32 tonnes each; a specially designed triple telescopic kelly bar with an overall extended length of 63.9 m, a nominal drilling depth of 65 m and an outer diameter of 559 mm; a 3 m diameter pre-drilling bucket c/w centralizer; and a 4.4 m diameter reaming bucket for reaming the prebore to the full internal diameter of the monopile.
After lifting the fully assembled unit weighing 74 tonnes off the deck of TIV Resolution, the Flydrill is mounted on top of the partially driven monopile and clamped to the top of the steel tube by way of three hydraulic clamps which transfer not only the torque produced by the rotary drive into the pile, but also the crowd force generated by the crowd cylinders. Finally, kelly and drilling bucket are lowered onto the seabed inside the monopile.
In contrast to the RC air-lift drilling system which uses water for conveying the drill spoil to the surface and dumping it in a generally uncontrolled manner into the sea with the potential of widespread pollution, the deployment of the Bauer Flydrill System BFD 5500 in kelly mode with drilling bucket offers an environmentally friendly method of controlled spoil disposal.
A total of nine monopiles have been drilled and subsequently driven to their terminal set.
- Source:
- Bauer Maschinen GmbH
- Author:
- Wolfgang Brunner
- Email:
- wolfgang.brunner@bauer.de
