Jessica Schulz | 02/02/2021
Mandatory inspection meets lack of resources
Regular maintenance of wind turbines is essential for both safety and efficiency. The wind turbine is regardless of the location permanently exposed to a wide variety of weather conditions – especially the circumstances of offshore turbines are extreme. The technical manager is responsible for the regular maintenance of wind turbines.
Furthermore, the maintenance of wind turbines is not a decision of the operator, but mandatory. The legislator, but also insurance and even the employers’ liability insurance association prescribe a recurring inspection of the turbines.
But the pain for the operators is huge: maintenance means long downtimes and thus a loss of production. In addition, the availability of industrial climbers is more than limited. Operators have to take what they can get – the worst case is that the plant may have to be shut down for maintenance on a day with very good wind conditions.
However, there is no choice, the risk of skipping the maintenance is simply too high – on worst case the operator may lose the permit for his wind turbine.
Range of wind turbine maintenance
Regular inspections must be performed by experts on the machine, blades and tower. The inspection intervals result from the expert statements on the machine and amount to a maximum of two years, but with certain circumstances may be extended to four years.
Finally, the specific intervals of the regular inspections result from the type test performed by Germanischer Lloyd or TÜV (Expert Companies).
The inspection intervals are thus based on the installed capacity of the wind turbine and are determined as follows:
- WTG smaller than 300 kW: every 4 years
- WTG from and including 300 to less than 1500 kW: every 2 years
- WTG from and including 1500 kW: annually
In addition, insurance companies sometimes require further inspection intervals, which can vary. For example, they usually require the inspection of the lightning protection in a 2-year cycle. In principle, the maintenance intervals correspond to those mentioned above, although it should be noted that if the prescribed intervals are exceeded by more than 3 months, the insurance cover for the relevant components may lapse.
In case of offshore plants, operators should also consider the specified intervals. Plants on the open sea are exposed to extreme conditions and are therefore particularly susceptible to damage. Just the CMS technology does not guarantee complete monitoring, especially in non-electronic areas such as blades and base. For the construction and operation of offshore turbines, the German Federal Maritime and Hydrographic Agency (FMHA) specifies technical standards that must be met in order to guarantee safe operation. The specified FMHA standards must be checked regularly. For example, regular visual maintenance (visual inspection) on site is mandatory. In such “recurring inspections”, at least 25% of a plant must be visually inspected on site every year. Otherwise, maintenance is recommended approximately every 6 months.
Since a very high number of wind turbines have been built in Germany for the last years, the Employer’s Liability Insurance Association has also become aware of the need to comply with occupational health and safety regulations when working on or in wind turbines. Operators or the management of WEAs are thus obliged to carry out regular inspections with regard to occupational health and safety regulations.
- Maintenance of the fire extinguisher: at least every 2 years
- Inspection of ladders and personal protective equipment: annually
Even though most maintenance and service technicians bring their own harnesses and restraints, wind turbine licensing regulations require that a certain amount of personal protective equipment is available for emergencies.
Components of wind turbine maintenance
The maintenance of a wind turbine includes the inspection of all important mechanical as well as electrical parts:
- Inspection of all components including blades and tower
- Visual inspection of the turbine with regard to corrosion, mold, cracks, scouring, or the like
- Torque check of all bolts
- Leakage and function test
- Check of laser alignment
- Check of oil levels (refilling if necessary) incl. functional check of the oil circuit by means of oil analysis
- Change of all existing filters
- Check of the entire drive train incl. frequency-selective vibration analysis
- Cleaning and adjustment of the brakes
- Lightning protection measurement
- Video endoscopy
Problems of regular maintenance
Although the rules and regulations regarding regular maintenance of wind turbines are clear, operators sometimes fail to comply with them. The reason for this is the aforementioned lack of industrial climber capacity. Maintenance companies simply don’t have enough staff for the volume of wind turbines. This problem exists in the market for several years and creates enormous difficulties. The regular maintenance is for operators a thorn in the flesh because they depend on the resources of the maintenance company which sometimes results in long downtimes, even on days that might have been very productive. If the regular maintenance intervals are not adhered to, the operators get a problem of liability – who bears the risk if a plant is damaged? This is exactly the reason why experts and also insurance companies demand regular maintenance including lightning protection measurement. The dichotomy becomes clear – regular maintenance is required, but the capacity is not sufficient. Thus the market needs a solution and better yesterday than today. There are already some alternatives to industrial climbers, such as climbing robots or drone-based inspections, which can solve the capacity problem in the long run.
Note: this article is about the German maintenance standards