NTN’s LLU: Double-Lip Seals

NTN offers a variety of shield and seal types for our ball bearings; however the best contact seal in the marketplace for excluding contamination and keeping grease inside the bearing is NTN’s LLU double-lip seal. The inner lip of a double-lip seal is pressed against the inside surface of the V-groove; the outer lip is spread open by the elastic force of rubber to create a small gap between the outer lip and the inner ring, creating a labyrinth effect (Figure 2). Should the inner lip wear, the contact pressure will decrease; however, the outer lip will get closer to the inner ring (Figure 1). In effect, a constant degree of sealing will be maintained; and, as a result, bearing service life will be noticeably lengthened.

A steel mill was experiencing bearing failures on the anti-crimping and anti-flutter rolls in its cold rolling mill that cost an estimated $33,000 per roll failure. NTN’s Engineering and Sales support team reviewed the anti-crimping and anti-flutter roll operation and NTN’s team of experts determined that, after analyzing various sealing options and considering added torsional stress on upstream drives, our LLU seal would maintain smooth operation while minimizing water ingression and optimizing added friction. NTN full-contact LLU sealed deep groove ball bearing has successfully run longer than the conventional open-type solution, as well as the competitor’s spherical roller bearing, resulting in triple the uptime and over $477,000 in annual cost savings.