Fluid leaks pose a significant threat to turbine operations and the environment, particularly in remote natural environments or offshore settings. Whether it's hydraulic oils, lubricants, or gear oil, effectively preventing leaks demands adhesives and sealants with outstanding resilience and proven chemical resistance.
The Challenge of Oil Leakage
Operating in extreme conditions, wind turbines demand precise monitoring and maintenance. Among the various challenges, contamination with hydraulic oils stands out, posing threats to groundwater, marine life, and turbine functionality due to accessibility issues. Although eliminating hydraulic oil leakage entirely may prove challenging, it's essential to seal potential leakage points effectively. Understanding the vulnerable areas within turbines is crucial. And when it comes to lubrication, hydraulic fluid and gear oil, the primary cause of concern is the gearbox. The main gearbox’s task is to speed up the slow high-torque rotation for the generator.
A complex assembly of gears, it relies on oil for smooth rotation and temperature stabilization. In case of an emergency (e.g. overheating of components), hydraulic disk brakes are required to stop the rotating turbine. Furthermore, to optimize performance, wind turbines can rotate in two ways to improve wind capture. First, the yaw drive keeps the nacelle pointed to the wind. Next, the pitch drive rotates all the blades to the right angle. Both can be tuned to either maximize wind capture or minimize it if wind conditions become too harsh. These drives are often powered using hydraulics, and their intricate components necessitate robust seals to prevent leakages.
A complex assembly of gears, the main gearbox relies on oil for seamless rotation and temperature regulation. In emergency situations, such as component overheating, hydraulic disk brakes are essential for halting the turbine's rotation. Moreover, to enhance performance, wind turbines can rotate in two ways to optimize wind capture. Firstly, the yaw drive maintains the nacelle's alignment with the wind direction. Secondly, the pitch drive adjusts all blades to the optimal angle. Both systems can be calibrated to maximize wind capture or minimize it during harsh wind conditions. These drives are often powered using hydraulics, and their intricate components require robust seals to prevent leakages.
The Alternatives
Sika conducts project-based testing of materials to evaluate their resiliance to chemical contamination, providing extensive technical information on numerous products. In the case of wind turbines, hydraulic oil resistance is a common concern addressed by Sika's technical team through thorough investigations. They assess the performance of various adhesives and sealants against hydraulic oils. The tested materials encompass threeprimary chemistries: polyurethane (PUR), silane-terminated polymers (STP), and silicone-based adhesives. Adhesion performance is evaluated alongside specific mechanical properties after 8 weeks of immersion at room temperature (yellow) and at an elevated temperature of 60°C (grey).
A Chemical-Resistant Solution
Among the various elastic adhesives tested, Sikaflex®-554 PowerCure has proven to have exceptional resilience, standing out in comparison to the widely used solutions available in the market. These conventional options experienced significant deterioration, losing most of their elasticity with up to 350% higher modulus. Sikaflex®-554 PowerCure, however, maintained a high level of elongation (>440%). Most importantly, it exhibited minimal changes in both strength (-8%) and modulus (-9%) over the complete aging cycle, all while maintaining a high level of adhesion performance.
Therefore, we can conclude that hydraulic oil resistance can be achieved through engineered adhesive design to prolong the service life and improve the protection of assembled parts.
Here are some of the benefits of Sikaflex®-554 PowerCure
- Outstanding resilience to hydraulic oils
- Increased cure speed compared to one-component adhesives
- Free from diisocyanates
- 60% less waste and up to 82% reduction of global warming potential compared to plastic cartridges
A Fast-Curing, Scalable Process
During maintenance procedures, it is crucial to minimize turbine downtime and associated costs. Rapid-curing systems like Sikaflex®-554 PowerCure address this challenge effectively. Sikaflex®-554 PowerCure is a one-component adhesive, accelerated with 2% water-based paste to speed up curing and ensure consistently fast through-curing.
The accelerated curing does not change the final material properties and enables engineers to quickly scale an adhesive bonding process without re-engineering the joint design. PowerCure refers to the packaging and dispensing system in small pack size, while Sikaflex® Booster is used for the same materials for bulk dispensing.
More diisocyanate-free adhesives and sealants
In addition to the above options, the silane terminated polymer (STP) adhesives and sealants from the Sikaflex®-5xx and -95x series are free from diisocyanates and therefore do not require the REACH safety training for safe use.(To learn more about safe handling of diisocyanate-containing adhesives, take a look at the 1st issue of INSIDE WIND magazine).