by Sara McCaslin, PhD Sara McCaslin, PhD No Comments

Spring-Energized Seals for the Wind Industry

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.

Arkansas Spring Energized Seal Company

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.

by Sara McCaslin, PhD Sara McCaslin, PhD No Comments

Spring Energized Seals for Use in Food Processing, Pharmaceutical, and Medical Applications

Spring-energized seals are a popular choice for applications that involve food, dairy, and medicinal applications, as well as medical devices. However, not just any polymer can be used for these seals because of the risk of contamination. In this blog post, we are going to review why FDA approved materials are so important, and then talk about the three most common engineering polymers that are used with spring-energized seals.

FDA Approved Materials

The FDA CFR 177 is contained in Title 21 of the Code of Federal Regulations and deals with indirect food additives in the form of polymers. The term indirect additive refers to something that inadvertently makes its way into food, pharmaceuticals, or inhaled substances (i.e., via an inhaler or oxygen machine).

Real-world applications where FDA approved materials are of concern include filling and mixing equipment for food and beverages as well as pharmaceutical products that can include pills, powders, caplets, tablets, liquids, oral suspensions, and inhalers. In the context of medical equipment, FDA approved materials are key to the design of devices that must be free of contamination.  For analytical equipment it is vital that samples are not contaminated; machines and devices for treatment, such as blood dialysis machines or ventilators, must not have any contaminants that can harm the patient.

Spring Energized Seals with FDA Approved Materials

When spring-energized seals are combined with FDA approved materials, the result is a durable, reliable seal that is safe for use in food processing, pharmaceutical, and medical applications. Three of the most common materials used are UHMW PE, Virgin PTFE, and mineral-filled PTE

UMHW PE

UHMW PE (Ultra High Molecular Weight Polyethylene) is an FDA and USDA engineering polymer with an extremely low coefficient of friction, low moisture absorption, and good chemical compatibility. In addition, it can withstand rigorous sterilization requirements that may involve hot water, steam, or aggressive chemicals. One of its key characteristics is its self-lubrication, which eliminates the need for lubricants that could cause contamination issues.

Virgin PTFE

PTFE (Polytetrafluoroethylene) often goes by the trade name Teflon. Virgin PTFE, which has no fillers added, has the lowest coefficient of friction of any material in existence. It is also one of the most chemically inert engineering polymers and handles extreme temperatures (both cold and hot) and is both thermally and dimensionally stable. Like UHMW PE, it is also FDA and USDA approved as well as self-lubricating.

Mineral-Filled PTFE

Mineral-filled PTFE takes the outstanding properties of PTFE and enhances them for improved wear performance and strength. It, too, is FDA and USDA approved, self-lubricating, a wide range of operating temperature, chemical inertness, and compatibility with even the most aggressive cleaning and sterilization regimens.

Conclusion

Spring-energized seals provide the often mission-critical reliability that is demanded in industries involving food, medicine, and medical treatment. However, they must be matched with an FDA approved polymers such as UHMW PE, virgin PTFE, or mineral-filled PTFE.