Offshore Wind Tower Flange Repair

Client: Saipem
Project: Neart na Gaoithe (NNG) Offshore Wind Farm
Location: 15.5 km off the Fife coast, Scotland

The Challenge

During the installation phase at the Neart na Gaoithe offshore wind farm, dimensional surveys identified non-conforming tower flange bolt holes. Ovalisation of the flanges meant the pre-machined Ø68 mm holes no longer aligned with mating flanges, preventing bolt installation and placing critical project milestones at risk.

With the arrival of the heavy lift installation vessel imminent, repairs had to be completed offshore on newly installed monopiles—without permanent services or habitat. The scale and urgency of the scope presented a significant technical and logistical challenge.

The Scope

• Approx. 124 bolt holes per platform

• Around 50 platforms

• Holes enlarged from Ø68 mm to Ø74 mm

• Tolerance of ±0.5 mm

• Machining through 220 mm flange thickness

• Target of one platform completed within 24 hours, with work on up to two turbines per day

The Solution

Reekie Machining worked closely with Saipem to develop a precision in-situ machining solution aligned with the project schedule.

The works were carried out using Reekie’s DR50 precision drilling and boring machines, fitted with 110V electric drives powered by portable generators. A bespoke drilling tool, designed and manufactured in-house, enabled each hole to be completed in a single operation, minimising setup time and maximising consistency.

All equipment and tooling were packaged into dedicated offshore kits, allowing rapid mobilisation via Crew Transfer Vessels (CTV) or Walk-to-Work (W2W) systems.

Delivery

To meet production demands, Reekie mobilised:

• 12 experienced machinists on rotation

• 12 full equipment and tooling kits

Teams were led by Reekie in-situ machining supervisors and supported by Reekie personnel and trusted contractors from Reekie’s established network. As an equipment manufacturer, Reekie was able to increase its DR50 machine fleet to meet project requirements.

Despite a two-week mobilisation window, all documentation—including quality plans, ITPs, method statements, and dimensional control records—was prepared, approved, and implemented on time.

The Result

Reekie Machining successfully mobilised on schedule and completed the offshore machining works within the required tolerances and timeframes. The solution restored flange compliance, avoided delays to installation milestones, and eliminated the need for component removal or replacement.

The Reekie Advantage

• Proven offshore wind experience

• Precision in-situ machining at scale

• Rapid mobilisation and flexible resourcing

• In-house equipment and bespoke tooling capability