Spring-Energized Seals for the Wind Industry
There is little doubt that global interest in renewable energy sources remains high, and that includes wind-based energy sources. According to the World Wind Energy Association (WWEA), the overall capacity of wind turbines installed worldwide reached 650.8 gigawatts in 2019, representing a 10.1% increase from 2018. However, for increased growth in the wind industry, the design of wind turbines must become even more efficient and reliable — and wind turbine seals are one area where there is potential for improvement.
Wind Turbine Seals
Among over 5,000 components in a typical wind turbine, there are six places where you will always find seals:
- Main bearing
- Main gear
- Pitch cylinder
- Lock cylinder
- Main and yaw brakes
- Hydraulic accumulator
Another way of looking at wind turbine seals is by their location:
- Rotor
- Blades
- Tower
- Alternator
- Gear Box
The importance of reliable seals in the wind industry cannot be overstated. They enhance the performance and efficiency of the wind turbines, extend their useful life, and minimize the costs and downtime associated with maintenance. Investing in the right type of seals for wind applications are critical, and traditional seals may not offer the sealing power and expected life that is needed.
Sealing Challenges in the Wind Industry
There are a host of challenges faced by engineers selecting seals for wind turbine applications beyond just vibration and high stresses caused by wind gusts and rotor speed variations. Because they are outdoors year-round, wind turbines are constantly exposed to UV and ozone which can cause seals to degrade more rapidly than normal. Then there are the extreme operating temperatures, from an icy -40°F in Arctic regions to 140°F as a maximum standard operating temperature which can make it challenging to find a seal material that can maintain reliable performance.
Then there are issues with abrasive substances such as sand, grit, and salt from seawater that can cause the lip of the seal to wear away. Then there are the inevitable changes in pressure that come from normal weather variations. The use of polymeric spring-energized seals, however, can address many of these challenges.
Spring-Energized Seals
In a spring-energized seal, a metal spring is used to maintain the seal lip in place to achieve a far more reliable seal for both keeping contaminants out and critical lubricants within. Spring-energized seals can maintain contact even in the presence of misalignments and uneven mating surfaces, dimensional changes resulting from temperature fluctuations or water absorption, premature wear from contact with abrasive substances, and vibration.
Various geometric configurations for the spring element are available, including coil, canted coil, helical, and cantilever springs. Each of these spring types has conditions for which they work best (e.g., cantilever springs work very well for static sealing). When the right spring geometry is coupled with an appropriate polymer, the result is a durable, rugged, reliable seal.
Conclusion
One of the key aspects of wind turbine design involves selecting the right kind of seals — seals that will maintain consistent, secure contact even in the harshest of operating conditions. Spring-energized seals are an excellent way to contribute to efficient performance, reliability, and reduced maintenance requirements for modern wind turbines.
