In 2023, Flender and Freudenberg Sealing Technologies (FST) – longstanding partners – came together to address the evolving demands of large industrial gearboxes. FST has now enhanced its Simmerrings for Flender’s gearboxes, achieving remarkable progress validated by extensive bench testing. These product improvements extend the service life of oil seals by up to 50 percent.
In Brief
Advanced Development: Through collaboration, Flender and FST have modified oil seals for large gearboxes, increasing their service life by up to 50 percent.
Competitive Edge: The new solution reduces the risk of failure and lowers maintenance and repair costs, giving both companies a clear advantage in mechanical engineering.
Technical Progress: FST’s specially engineered spring keeps temperatures lower and reduces wear in the tribological system, significantly boosting both efficiency and seal longevity.
Sustainability & Efficiency: Optimized sealing technology helps save energy and improves operational reliability – critical as energy prices rise and sustainability requirements grow.
Meeting New Demands
As shaft diameters and speeds increase in large gearboxes, the tribological system -comprising the rotating shaft, seal, and lubricant – must operate reliably for longer periods. Efficiency is now more important than ever, with lower energy consumption becoming a key priority.
During a 2023 technology exchange, Flender and FST then recognized that traditional solutions were reaching their limits. FST took on the challenge to systematically improve sealing technology, and the results are evident.
Reducing Friction
In tribological systems, friction is the main factor limiting service life and energy efficiency. Solutions include advanced lubricants and improvements in seal materials and design. For radial shaft seals like Simmerrings, the steel spring pressing the sealing lip onto the shaft is a key area for innovation. FST manufactures these springs in-house, tailoring them to specific requirements.
The Spring Makes the Difference
FST’s large-scale testing has shown that a specially designed spring can dramatically improve the service life of Simmerrings in Flender gear units – up to 50 percent – without changing the seal design, material, or lubricant. In short: a small change, a big impact.
Trials at FST’s state-of-the-art test facility compared conventional oil seals with the new spring-equipped seals. Each seal ran continuously on a 120 mm shaft for 504 hours at speeds ranging from 1,000 to 3,000 rpm (6.28 to 18.8 m/s).
15 Degrees less
Results showed that conventional springs led to significant wear and high temperatures, even at moderate speeds. These conditions increase the risk of leakage and reduce seal life. Notably, every 10 °C reduction in temperature can double the service life of a tribological system.
With the new spring, temperatures dropped by at least 15 °C at speeds of 1,500 rpm and above, and wear was significantly reduced.
Ready for Series Production
The tests clearly proved the superiority of the new spring design: longer service life, less wear, and higher energy efficiency. FST recommends equipping all Simmerrings in large Flender gearboxes with this spring as standard. The switch offers a major performance boost and competitive advantage, with minimal effort and moderate cost.
More Solutions Ahead
FST is committed to developing even more advanced sealing solutions for large gearboxes, pushing the boundaries of what’s technically feasible.
Optimizing FST’s Premium Sine Seal (PSS) for large gearboxes looks promising. The PSS, an evolution of the successful MSS1 Modular Sealing Solution, delivers higher performance in a compact design, 100% sealing with less friction, and a long, maintenance-free service life. While it’s popular in demanding robotics and automation, it’s only been used in smaller gearboxes so far.
Switching from mineral to synthetic oils could further improve efficiency and service life. FST’s sealing materials are compatible, and the company can test seal-lubricant combinations in-house to find the ideal match.
Project managers Benjamin Kohl (Head of Product Development – Oil Seals Industry), Erich Prem (Design Engineer – Senior Expert Product Engineering Industry), and Daniel Schlick (Key Account Manager – Sales General Industry Sector Power) are convinced: “When premium partners work together, they can set trends and gain competitive advantages as innovation leaders. We are ready to provide the technology.”
