Monopiles &
Transition Pieces
Precision milling of large-diameter on- and offshore flanges to ensure structural fit, bolt integrity, and long-term reliability.
Support Structures & Flange Solutions
Monopiles &
Trusted by wind operators and OEMs across Europe and North America
- Vestas
- Siemens Energy
- NextEra Energy
- GE Vernova
- Enercon
- Nordex
- EDF Renewables
- Welcon
- RWE
- CS Wind
- EEW
- Muehlhan
- Nicon Industries
- Orsted
- Cadeler
- Vattenfall
- Smulders
- Windar
- Titan Wind
- SubC Partner
- Semco Maritime
- LM Wind Power
- Iberdrola
How It Works Precision For Large Diameter
Precision For Large Diameter
Monopiles & TPs
Welding heat input during manufacturing can twist and bend large flanges, sometimes pushing flatness outside tolerance. Our proprietary Goliath flange milling system machines monopile and transition piece flanges flat before installation. Fully CNC-controlled. Sub-millimetre flatness. In most cases faster than heat straightening, with much better achievable tolerances.
Milled flat, not bent back
After welding, Goliath mills the flange face in a controlled, repeatable CNC process - replacing manual correction methods. On an 8-metre flange it delivers global flatness of 1 millimetre and local flatness of 0.5 millimetre, meeting the required structural fit.
Built for offshore scale
- Mills flanges up to 10 metres in standard configuration, configurable up to 12 metres
- Machining happens at the manufacturer's factory - or we train your own technicians to operate the machine
- Made for the next generation of offshore wind structures, where flanges keep growing while tolerances tighten
12 mmaximum flange diameter
0.5 mmlocal flatness on an 8-metre flange
2-7days on site, typical project
Why it beats heat straightening
Machining is in most cases faster than traditional methods like heat straightening, and the achievable tolerances are much better. That precision lets designers specify smaller flanges and opens the potential for maintenance-free bolt connections - ultimately reducing both CapEx and OpEx.
Technical Specifications
Typical duration 2–7 days on site
Diameter range Up to Ø10,000 mm
Flatness Customer/OEM specification
Certification ISO 9001
Equipment Mobile flange milling system
Structures Monopiles, TPs
Expected lifetime Design lifetime equivalent
ISO 9001OFFSHORE READYLARGE DIAMETERSCNC CONTROLLED
Reduced Lifecycle Costs Improved flange flatness helps reduce bolt-related maintenance, corrective actions, and long-term operational costs.
HSE Advantages If combined with precise bolt tensioning methods, the precise flange tolerances achieved with Goliath can help reduce the need to retighten bolts and eventually lead to maintenance free connections – reducing OpEx and improving Health, Safety and Environment (HSE).
Repeatable Manufacturing Quality Fully CNC-controlled machining replaces manual correction methods with a predictable and repeatable production process.
Built For Offshore Scale Goliath machines monopile and transition piece flanges up to 12 metres in diameter, supporting the increasing size and complexity of offshore wind structures.
How It Works
Our Process
01
Quotation Request
The manufacturer contacts CNC Onsite to discuss specifications for the monopile flanges. Our technical sales team will analyse the project and customer schedule. We will issue the quote based on the customers need and timeline. The customer issues the purchasing order.
02
Planning
We plan the technical part of the project, which includes preparation and programming of Goliath, the precision machine that will perform the milling. We plan staff availability and timing, including flexibility to accommodate potential changes to the schedule.
03
Implementation
Our technicians will conduct the precision milling of the flanges at the customer’s factory. Alternatively, CNC Onsite will train the customer’s own technicians for the operation of the machine. The team will use the Goliath machine to mill the flange faces, leaving them flat to within one millimeter.
04
Handover
After machining measurements are made, a measurement report is issued to the customer. Alternatively, the customer or a customer-contracted third party conduct the measurements. Once the measurement are complete, the customer signs off the work.
05
Follow-up
We offer follow-up meetings with the customer. CNC Onsite’s follow-up program is part of our high quality standards.
Talk to our team Let Us Find
Let Us Find
The Right Solution
Whether it's a repair, machining project, or custom machine solution, our engineers are ready to help you find the most efficient way forward.
Request received.
An engineer will get back to you within one working day.
“Goliath, which can work both horizontally and vertically, can cope with features on large flanges such as double-tilted flanges and requirements for parallelism of the flange surfaces. Our Goliath machine can manage the many new complex flange designs, making it probably the most advanced and precise flange milling tool on the market”
Søren Kellenberger CEO, CNC Onsite
Global reach
Wherever your turbines stand
On site within days Worldwide call-out, 24/7. Technicians mobilize within days of a purchase order.
Onshore & offshore The same in-nacelle method works at sea - no offshore crane deployment needed.
Five continents A proven repair track record on wind turbines across five continents.
FAQ
Frequently asked questions
How large a flange can be machined on a monopile or transition piece?
Our fully automatic CNC-controlled Goliath machine mills flanges up to 10 metres in diameter in standard configuration and can be configured for diameters up to 12 metres.
What flatness tolerance can be achieved on monopile flanges?
For an 8-metre flange, Goliath achieves global flatness of 1 millimetre and local flatness of 0.5 millimetre. Final tolerances are machined to the customer or OEM specification.
How long does monopile flange machining take?
A typical project takes 2 to 7 days on site. Machining is in most cases faster than traditional methods like heat straightening, and the achievable tolerances are much better.
Where does the flange machining take place?
Our technicians perform the precision milling at the manufacturer's factory, before the structure is installed. Alternatively, CNC Onsite can train the customer's own technicians to operate the machine.
Why do monopile and transition piece flanges need machining?
When flanges are welded to the structure during manufacturing, the heat input can cause twisting and bending, sometimes leaving flatness outside tolerance. Post-weld milling restores flatness to ensure structural fit, bolt integrity, and reliable bolted connections.
