CS WIND Offshore Integrates CNC Onsite’s Machine for Processing Flanges Up to 10 Meters in Diameter

- CS WIND Offshore integrates solution in transition piece manufacturing
- 1mm tolerance after machining; meets requirements for large flanges
- Machined flanges reduce maintenance costs and enhance wind turbine reliability and lifespan
CNC Onsite, a Danish specialist in mobile machining solutions, has developed a flange machining system that meets the stringent tolerances required for the increasingly large flanges used in transition pieces for offshore wind turbines. By using this technology, CS WIND Offshore can deliver flanges with a global flatness tolerance of just 1 millimeter, ensuring an optimal interface for flange assemblies.
This innovation, developed by CNC Onsite, helps reduce maintenance costs and increases the reliability and lifespan of wind turbines. Two years ago, CS WIND Offshore, a leading supplier of transition pieces for offshore wind farms, commissioned CNC Onsite to design a precision machine for milling large-diameter flanges used in their manufacturing facility in Aalborg.
"The one-millimeter tolerance achieved with our machine as part of CS WIND Offshore’s production line ensures the end customer can achieve nearly perfect surface contact in large bolted flange connections," says Søren Kellenberger, Sales Director at CNC Onsite.
The precision machine, aptly named "Goliath," was designed and manufactured at CNC Onsite’s headquarters in Vejle. It is used to mill flanges after the welding process.
"CNC Onsite’s machine has been fully integrated into our production of large-diameter Transition Pieces, ensuring precise flange tolerances. We’ve been highly impressed by the fact that the tolerances achieved are even better than specified," says Ole Springby, Manager of Measurement & Handover at CS WIND Offshore.
CS WIND Offshore produces transition pieces at its 450,000-square-meter factory in Aalborg, supplying wind farms worldwide.
"Achieving global flatness within a few millimeters on a flange with a diameter of four meters is already challenging. Achieving the same result on today’s flanges, which exceed eight meters in diameter, is simply impossible with traditional methods," Søren explains.
Large flanges are critical mechanical connections within the structure of wind turbines. The two surfaces must fit precisely to ensure reliable assembly. Since these flanges are bolted together, they must meet flatness tolerances of 1–2 millimeters to achieve the required structural strength, fatigue resistance, and proper bolt tensioning.
Loose bolts can lead to significant repair costs and turbine downtime. Accurate flange connections will play an increasingly important role in wind turbine reliability. Better tolerance in flange assemblies reduces the need for regular bolt re-tightening, saving labor costs and minimizing downtime. Ultimately, improved flange connections can extend the turbine's operational lifespan.
"If the flange surface is uneven – even by just a few millimeters – after welding, CNC Onsite’s machine mills it to restore optimal flatness," Søren explains.
With global flatness tolerances of 1 millimeter and local flatness tolerances of 0.3 millimeters on flanges with an 8-meter diameter, Goliath exceeds current industry standards for both offshore and onshore applications, opening new engineering possibilities.
Goliath was developed by CNC Onsite, leveraging over a decade of experience in flange machining for the onshore and offshore wind industries. CNC Onsite will showcase its flange machining expertise at WindEnergy Hamburg from September 24 to 27 in Hall B1.EG, Stand 508.
About CNC Onsite
Headquartered in Vejle, Denmark, CNC Onsite designs, builds, and delivers high-precision mobile machining solutions for wind turbines, including offshore foundations. The machines are adaptable for a wide range of tasks. CNC Onsite serves the wind energy sector onshore and offshore, offering solutions such as: large-diameter steel flange and blade root end machining, specialized repair services for slewing bearings, rotor locks, generator shafts, bearing housings, broken bolt removal and thread hole repair.
The press release has been translated by Energy Cluster Denmark.
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