(April 11, 2011)
Trelleborg Offshore has developed an elastomeric spring bearing to improve the stability of the 90-monopole wind turbine foundations at Sheringham Shoal Wind Farm, being installed near Norfolk, UK.
The manufacturer of polymer and syntactic foam-based solutions for the offshore industry supplied project owners, Scira Offshore Energy, with 600 of the bespoke steel and rubber bearings, designed to reduce stress on the grouted connection in the wind turbine foundation.
Trelleborg Offshore delivered the spring bearings in six months.
Sigmund Lunde, Scira's company representative for the elastomeric contract with Trelleborg, said: 'The gap between the inner foundation pipe and outer transition piece of the wind turbine is filled with cement grouting, which must withstand the vertical weight of the tower and the lateral wind loading forces.
'Following reports of grout failure on various wind farm projects, DNV, the certifying authority for the Sheringham Shoal project, radically reduced the acceptable loads on the grouted connections, which threatened project completion.
'However, the Trelleborg Offshore bearings enabled us to reduce the load on the grouted connection and keep the project on schedule,' he added.
Each wind turbine foundation comprises a 50m-long, 5m-diameter steel monopile pipe, which is piled 30m into the seabed.
Below water level, a larger-diameter transition-piece pipe is fitted over the foundation for 7-8m and extends above water to a flange to attach the wind turbine tower.
The bearings had to be totally compatible with the existing design of the wind turbines, which were already under construction and required urgently.
By designing, manufacturing and delivering the bearings within six months, Trelleborg allowed installation to be carried out before the onset of winter.
The bearings developed for Sheringham can also be retrofitted to existing wind turbine schemes where failing grout connections have since become problematic.
Product Model | Inside Diameter | Outside Diameter | Thickness |
NN3084K KOYO | 420 | 620 | 150 |
NNU4940K KOYO | 200 | 280 | 80 |