NTN success reports

NTN’s LLU Seals Expected to Triple Uptime at Cold Rolling Mill

Success Report: LLU Sealed Deep Groove Ball Bearings

AnnualizedCostSavings$, LLUSeals

A major North American based steel mill was experiencing bearing failures on the anti-crimping and anti-flutter rolls in its cold rolling mill. These failures would force the mill to stop running in order to change out the roll. It is estimated that it cost the mill about $33,000 per roll failure.

The mill previously had another bearing company evaluate its operation. This bearing company changed the design of the bearing from an open type deep groove ball bearing to a spherical roller bearing and while this did provide a slight increase in bearing life, constant failure still occurred.

NTN’s Engineering and Sales support team reviewed the anti-crimping and anti-flutter roll operation and assessed the failed bearings. The bearings were only lasting 4 months but should have been seeing significantly longer life.

The NTN Solution

NTN’s team of experts determined that the competitor’s spherical roller bearing would never achieve its expected life for this application due to light loads and water ingression. After analyzing various sealing options and considering added torsional stress on upstream drives, NTN’s metal mill experts selected our LLU seal in an effort to maintain smooth operation while minimizing water ingression and optimizing added friction.

The Result

The NTN solution is still running with no end in sight! Our 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, and is estimated to triple the uptime!

The increased bearing life, decreased downtime and reduced acquisition cost have all added to over $477,000 in annual cost savings. The mill has maintained its satisfaction with NTN products and service and continue to break production records with NTN products supporting the load.

Value added breakdown



Sealed Deep Groove Ball Bearing

Grooved Type Sealing Figure for Excellent Performance (All Models)

A v-shaped groove is cut around the inner ring. Under centrifugal force, the outer surface of the ‘v’ acts to keep out dirt; the inner surface of the ‘v’ acts to seal in the grease.

Double-Lip Seal Adjusts to Wear (LLU Spec)

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. Should the inner lip wear, the contact pressure will decrease; however, the outer lip will get closer to the inner ring. In effect, a constant degree of sealing will be maintained; and, as a result, bearing service life will be noticeably lengthened.

Give downtime the cold shoulder.

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