Preparing a Wind Farm for the Season: Inspection, Cleaning, and Tower Anti-Corrosion Protection

The winter season is not kind to wind farm infrastructure. Several or even several dozen weeks of low temperatures, freeze–thaw cycles, snow, icing, and salty air, especially at coastal locations or near roads, leave their mark on every element, from blades to welds at the base of the tower. When spring brings higher temperatures and longer weather windows, it is the optimal moment for professional wind turbine inspection and servicing, which will determine the technical condition of the turbine for the coming months of intensive operation.

The question is not whether to carry out inspection and preparatory work after winter. The question is how to plan it so that it fits within the weather window and does not conflict with the wind farm’s production schedule.

Why Spring Tower Inspection Is Crucial After the Winter Season

A wind turbine tower is a steel structure covered with an anti-corrosion coating system, designed for decades of operation. With proper maintenance, this service life is achievable. The problem is that anti-corrosion coatings degrade unevenly: faster in areas exposed to particular stresses, chips, and moisture conditions, and more slowly on open, well-exposed surfaces. Winter climate conditions accelerate this process.

The freeze–thaw cycle acts like a mechanical wedge. Water penetrates microcracks in the coating, freezes, and expands, widening the damage. The next cycle penetrates deeper. After several months, what was a barely visible microcrack in spring of the previous year has become a place with detached coating and exposed steel: an entry point for rust.

A spring tower inspection makes it possible to detect these changes before corrosion penetrates deep into the material and before extensive, costly repair becomes necessary. This is preventive inspection in the full sense of the term. Every detected defect that is currently still at the stage of local coating damage can be repaired quickly and inexpensively. The same areas, after two more winters without intervention, may require blasting and full coating reconstruction over a significant surface area.

What to Assess: Weld Corrosion, Seals, and the Condition of Tower Paint Coatings

Inspection of a wind turbine tower after the winter season includes several key areas.

Welds and Tower Segment Joints

A tower consists of steel segments joined by circumferential welds. It is around the welds, where residual welding stresses overlap with variable operational loads, that coating damage appears most quickly. Every welded joint requires close inspection for blisters, flaking, discolouration, and signs of underfilm corrosion, where rust creeps beneath the coating from the edge of the damaged area.

Particular attention should be paid to the lower tower segments. Areas close to the base are exposed to moisture from the ground, rainwater running down the tower, and splashes from cleaning machines or service vehicles. Corrosion in the lower segments is therefore systematically more common than at mid-levels.

Seals Around Openings and Penetrations

The tower has openings and penetrations: access doors, cable and installation passages, and vents. In each of these locations, seals are exposed to thermal and mechanical degradation. A cracked or shrunken access door seal allows water and moisture to enter the tower interior, which translates into corrosion of internal components and a risk of electrical cabling problems.

Condition of Paint Coatings: Assessment Criteria

Assessing the condition of an anti-corrosion coating is not simply a matter of “paint present” or “paint absent.” An experienced inspector assesses:

•adhesion, meaning whether the coating adheres well to the substrate or can be detached during a cross-cut or cross-hatch adhesion test;

•presence of blisters, as blisters beneath the coating indicate moisture penetration to the coating–steel interface and an active corrosion process underneath;

•discolouration, because brown or rust-coloured stains, even across the coating, may indicate the beginning of underfilm corrosion;

•brittleness and cracking, as an old coating may become brittle and develop a network of cracks, known as “alligatoring,” which means it has lost its elastic properties and requires renovation;

•thickness, measured with a magnetic or ultrasonic thickness gauge. A coating that is too thin, below the minimum system thickness, does not provide the required protection even if it appears visually undamaged.

Cleaning the Nacelle and Blades: The Impact of Cleanliness on Aerodynamics and Production

During the winter season, a wind turbine collects contamination on every exposed surface. Blades, both on the leading edges and across their entire surface, become covered with insect deposits, salt, dust, lichen in lower rotational speed zones, and the remains of dead insects. The nacelle collects the same contaminants on its external surface.

What matters is what happens to airflow over a contaminated blade. A smooth, clean blade surface allows laminar flow in the boundary layer. A layer of biological deposits, insect residues, or salt changes this geometry microscopically but along the entire blade length. It makes the flow more turbulent, reduces lift, and lowers the efficiency of torque generation.

Cleaning blades before the spring season is an action with a measurable return. Wind farms that clean blades regularly observe an improvement in turbine power curves after cleaning compared with the pre-cleaning condition. The effect is difficult to separate from other factors, such as coating condition and air temperature, but the mechanism is well described in industry literature.

Nacelle cleaning has a different justification: hygiene and operational reliability. Contaminants on nacelle fans, filters, and coolers reduce their throughput and may lead to component overheating. Cleaning accessible nacelle surfaces and verifying the condition of ventilation filters are part of a proper seasonal inspection.

Planning Seasonal Work: Weather Windows and the Wind Farm Schedule

Work at height on wind turbines is highly dependent on weather conditions. This is a limitation that must be managed. It cannot be eliminated, but it can be taken into account during planning, thereby avoiding a situation in which the lack of an available contractor date or unfavourable weather pushes the work into the next season.

Weather Windows for Rope Access Work

Rope access work on blades and towers requires:

•wind speed below the technical limit for rope work, usually 10–12 m/s at blade level. At higher speeds, work becomes unsafe, and the quality of resin-based repairs cannot be ensured;

•no precipitation during repair work using composite materials, as epoxy resins should not be applied in rain or on a wet surface;

•temperature above the minimum required for the resins used, usually above 5–10°C, which rules out work in early spring or late autumn during frosty nights.

Spring, especially the period from mid-April to the end of June at most locations in Poland, is the optimal time for preventive work. The temperature is favourable for work with resins, weather windows are statistically longer than in summer, with fewer storm fronts and strong gusts, and there is still time before turbines enter the peak production season.

Schedule for a Multi-Turbine Wind Farm

A wind farm with a dozen or several dozen turbines cannot be serviced all at once, both for organizational reasons, such as the limited number of technicians and equipment, and production reasons, because too many turbines out of operation at the same time affects the farm’s output. Seasonal planning should include:

•prioritization of turbines based on the results of previous inspections, with turbines where damage was detected serviced first;

•division into groups, for example servicing three to five turbines per week by one crew, which allows work continuity without excessive production downtime;

•weather reserve, meaning the schedule should include buffer days, because work must be suspended in strong winds;

•synchronization with O&M inspections, as many tasks can be aligned with the service contract inspection schedule, optimizing the total turbine downtime.

Booking Date: Why a Time Margin Matters

Experienced wind farm operators know that a good contractor with the proper qualifications and equipment for rope access work on turbines is a limited resource. Spring season dates are booked during the first quarter of the year. Contacting a contractor in March or early April gives a real chance to schedule work in the optimal window. Contacting one in May or June, when the season is in full swing, often results in postponement until late summer or autumn, when weather windows are shorter and working conditions are more difficult.

Book Your Spring Inspection Date in Advance

If your turbines have not undergone tower and blade inspection after the previous season, or if the next inspection cycle is approaching, it is worth booking a date before the season schedule fills up.

Contact us to discuss the scope of seasonal work, available dates, and how to optimize the schedule for your wind farm. Arrange a site visit or ask for a quotation for a spring inspection.