Rotary Shaft Seals in Wind Energy Applications
by Sara McCaslin, PhD Sara McCaslin, PhD No Comments

Rotary Shaft Seals in Wind Energy Applications

Wind turbines are becoming an increasingly common sight in many parts of the world, including both on-shore and off-shore wind farms. Each of these wind turbines includes complex electrical and mechanical systems that convert wind energy into electrical power. A key aspect of achieving this conversion in a reliable, consistent manner is the numerous seals involved–including rotary shaft seals. This post will discuss the use of rotary shaft seals in wind energy applications.

Global Look at Installed Wind Energy Capacity

According to data from Statista, the global installed wind energy capacity continues to grow, reaching a record 743 GW in 2020. Furthermore, the cumulative capacity of wind energy is expected to reach 840.9 GW by 2022. To be able to provide energy efficiency and predictability, every aspect of generation and transfer must be designed for reliability, from the massive propeller blades to the energy transfer systems. 

Wind Turbines and Seals

When propellers are often 120 ft long, it is extremely important that the rotors function effectively. Of particular interest are rotary shaft seals which are usually tasked with keeping lubricants in and contamination outside. In a wind turbine, there are two specific areas where rotary shaft seals are critical: the main shaft bearings and gearbox shafts. These seals are directly involved with the main turbine shaft, and a failure in these rotary shaft seals means the wind turbine is quickly rendered useless. 

Challenges of Seals for the Wind Energy Market

Rotary shaft seals for wind turbines are not only critical to the functionality of a wind turbine but also face some of the most difficult operating environments. 

All rotary shaft seals for wind turbines must deal with high speeds. While the tip of the propeller may seem to move slowly, the length of these propellers means that the shaft speeds are incredibly high. Extremely high speeds mean that friction between the shaft and the seals can lead to significant heat generation, which means energy losses. These high speeds also lead to faster wear. Low friction and excellent wear resistance are extremely important.

There are also extreme temperature changes involved which can drop to cryogenic levels. The seal material used must be dimensionally stable despite these temperature changes and maintain performance at extremes (e.g., not becoming brittle when temperatures drop below freezing). Temperatures can also impact the type of lubricant that can be used with the seal.

Another challenge faced by the rotary shaft seals for the main shaft bearings is UV exposure, which can cause certain materials to rapidly degrade. Add to that potential exposure to water, ice, snow, rain, sand, dust, and winds and the choice of a good seal material becomes even more critical. In addition, exposure to moisture can also cause problems for wind turbine seals. Some materials will absorb water which will deform their shape.

The fact that these turbines are often located in remote locations and that changing out the seals is not a simple task means that repair costs just for labor are expensive. Because many of the seals are large in diameter and are considered custom seal designs means that the seals themselves are far from inexpensive. 

Turbines for off-shore wind farms face an extra set of challenges with exposure to saltwater and extreme weather events such as tropical storms and hurricanes. In addition, they are usually even more remote than their on-shore counterparts, making maintenance and repair much more challenging and expensive.

PTFE Rotary Shaft Seals in Wind Energy Applications

The type and geometry of rotary shaft seals are extremely important when selecting a seal for a wind turbine, but so is the seal lip material. One of the materials that are extremely well-adapted for facing the challenges just outlined is PTFE, polytetrafluoroethylene.

PTFE has the lowest coefficient of friction of any polymer. Furthermore, with a wise choice of additives, it can exhibit excellent wear resistance. Because of its low friction, self-lubrication, dry running capabilities, and very low breakout friction, PTFE works extremely well in high-speed applications.

PTFE also has an extensive operating temperature range of -328°F and 500°F with a melting point of  620°F. This allows it to maintain performance at the high speeds involved with wind turbines as well as the extreme temperatures involved with their operating environment. In addition, PTFE has a low coefficient of thermal expansion compared to many other polymers which means it changes geometry very little when temperature changes occur.

PTFE also has very good UV resistance, which means that it maintains its properties even during extended exposure to sunlight. In addition, PTFE performs well even in the presence of saltwater and other potential environmental issues. Saltwater can, of course, lead to problems but PTFE is not significantly affected in terms of wear and friction. In addition, PTFE also has a very low moisture absorption rate which means that it can remain dimensionally stable in the presence of water.

Conclusion

Rotary shaft seals for wind turbines, whether installed on the main shaft bearings or the gearbox shafts, must be able to function in extremely adverse conditions. One of the best materials for wind energy seal applications, both onshore and offshore, is PTFE. If you are looking for a reliable, robust wind energy sealing solution, contact the experts here at Advanced EMC. Our sealing team can recommend the best PTFE blend, seal type, and seal geometry for your rotary shaft seal needs.

US Plastics Pact Roadmap and the Plastics Industry | Advanced EMC Technologies
by Jackie Johnson Jackie Johnson No Comments

U.S. Plastics Pact and the Plastics Industry

In September of 2020, the United States launched the US Plastics Pact, a consortium of industry leaders whose goal is to work collectively towards a circular economy for plastics in the United States. Around 100 companies, including big brand names such as Coca-Cola and Target, as well as organizations geared towards sustainability such as the Ocean Conservancy, have agreed to be a part of the program, with the end goal being all plastic packaging be recyclable by 2025. In June of this year, the U.S. Plastics Pact released their roadmap, providing their plan for hitting the ambitious 2025 target.

The goals set in the road-map seem lofty, and not everyone in the plastics industry agrees with the timeline and language used.

In this week’s blog post, we will go over the goals set by the U.S. Plastics Pact Roadmap, the industry leaders who are on board, and the ones who are not.

Roadmap to Sustainability

On June 15th, the US Plastics Pact, with the help of WRAP UK, released a 36-page road-map detailing their plan to make plastic waste a thing of the past. The plan targeted four specific areas to address said plastic waste, through, according to their website, “specific actions, responsibilities, and interim timeframes in order to realize meaningful, target outcomes for a circular economy for plastic packaging.”

These target areas are:

  • Defining a list of packaging to be designated as problematic or unnecessary by 2021.
  • Ensuring 100% of new plastic packaging is reusable, recyclable or compostable by 2025.
  • Undertaking actions to effectively recycle or compost 50% of plastic packing (including PET and PP thermoformed and injected molded containers) by 2025.
  • Ensuring the average recycled content or responsibly sourced bio-based content in plastic packaging (such as PE films) is at 30% by 2025.

The roadmap also calls to boost recycling rate of packaging made from PET, polypropylene and high-density polyethylene to 70% by 2025.

It’s goal by the end of 2022 is for all of its members to make public commitments to use recycled content in most of their packaging.

Lofty goals, but goals they say are obtainable. Not everyone agrees, however.

Realistic Goals or Pipe Dream?

The American Chemistry Council, the trade association for chemical companies and plastics manufacturers, says it welcomes the goals of the pact. In fact, many plastic firms have also signed on to the pact, including Amcor, Eastman Chemical and the National Association for PET Container Resources.

The issue, according to the ACC, is the timeline, and the language regarding phasing out “problematic plastic products”. In a statement issued by Joshua Baca, ACC’s vice president of plastics, said they want the Pact to be “transparent, data-driven and make recommendations based on science and engineering, rather than ideology” and to have “an inclusive and open process” that will “generate more informed and reliable outcomes and minimize risks of unintended consequences that can result from material substitution.”

The ACC had announced its own plans to create a circular plastics economy in 2018. Their plan was slightly less aggressive, with goal of 100% recyclable plastic packaging by 2030, and 100% of plastic packaging being either re-used, recycled or recovered by 2040. In 2020, the ACC announced their own “Roadmap to Reuse”, which outlined the ACC’s vision to achieve the previously listed goals.

Some in the plastics industry agree with the Pact.

Many plastic firms and trade groups have also signed on to the pact, including Amcor, Eastman Chemical and the National Association for PET Container Resources.

Amcor’s VP of Sustainability, David Clark, went on record saying “…we are proud to support the rollout of the US Plastics Pact Roadmap – which shows how cooperation across the value chain can help us solve the problem of waste in the environment.”

The National Association for PET Container Resources, or NAPCOR, even worked with the Pact to help launch the Roadmap, with NAPCOR Executive Director Darrel Collier saying that the U.S. Plastics Pact recycling goal of 50% is “ambitious, but not impossible.”

In Conclusion

While not everyone is keen on the US Plastics Pact Roadmap’s ambitious plans to create a circular plastics economy and reduce waste, many companies are more on board.

With more and more manufacturing companies agreeing to do their part to reduce plastic waste, The US Plastics Pact believes it can pave the way forward to a more sustainable plastics industry. The ACC also believes their plan can achieve those goals, while giving a more realistic timeline.

The important thing is, according to Collier, to do something.

“The timeframe is short, and the workload is immense, but if we choose to do nothing, the visions of a circular economy across the U.S. will give way to the status quo.”

With help from plastics manufacturers, companies can help make sure plastics remain both in the US economy, but out of the environment, for years to come.