Bearing overheating eliminated in a high-speed cellulose hammer mill

Some bearing applications do not present one demanding condition. They present several simultaneously. A hygiene products manufacturer operated a cellulose hammer mill with a bearing running at 3,000 rpm under a radial load of approximately 5 kN, in an environment continuously contaminated with cellulose dust. Each of those conditions alone narrows the range of suitable lubricants. In combination, they eliminate most greases from consideration. Interflon Grease HS2 was formulated precisely for this type of application: variable, multi-demand conditions where a conventional grease optimized for a single performance window will inevitably underperform. 

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The application: three demands, one bearing

The mill runs an SKF 2213 ETN9-C3 self-aligning double-row ball bearing, a C3 internal-clearance variant specified for applications with higher thermal expansion and dynamic loads. The bearing has a bore diameter of 65 mm. At 3,000 rpm, this gives a DN value of >195,000 mm·rpm, a level at which grease selection becomes critical and the range of suitable products narrows considerably. The bearing operates under a radial load of approximately 5 kN. The process environment generates a continuous stream of fine cellulose particles that penetrate bearing housings and contaminate the lubricating grease.
These three conditions interact in ways that make lubrication significantly more difficult than any one of them in isolation:

• At 3,000 rpm, the bearing generates sustained shear forces that degrade conventional grease thickener structures over time, compromising film thickness and overall surface protection.
• Especially under a radial load of 5 kN, any deterioration in the protective lubricating film leads directly to metal-to-metal contact and accelerates friction and wear.
• Cellulose is highly absorbent and fibrous, properties that directly interfere with oil film formation on bearing surfaces and break down the structure of the lubricating grease over time. Combined with the shear forces of high-speed operation and the contact stress of high load, this contamination does not simply add to the problem: it multiplies it.

Each factor accelerates the degradation caused by the others, creating conditions for exponentially worsening friction, wear and lubricant breakdown.

This is the operating profile that exposes the limits of greases formulated for steady-state conditions, and that do not take highly impactful contamination into account. A grease optimised for high speed alone may handle the rotational demands but offer insufficient protection when load and contamination reduce its effective film thickness. A grease developed for high loads may handle the load but degrade too quickly under sustained high-speed shear. Most greases require a choice. Grease HS2 does not.

Before the switch

The hammer mill runs on four bearings, all monitored continuously by the Siemens SIMATIC system. The result, before the switch to Grease HS2, was a consistent and worsening pattern: grease hardening, contamination fouling of the lubricating grease, frequent leakage at the seals, and bearing temperatures climbing above the 65°C warning threshold. On multiple occasions, bearing 4 exceeded the 75°C automatic shutdown limit, stopping the production line and requiring operators to disassemble, clean and re-lubricate before restart.
 

Why Grease HS2 works where others struggle

Interflon Grease HS2 is not a high-speed grease, or a high-load grease, or a contamination-resistant grease. It is engineered to deliver consistent protection across all three conditions simultaneously: precisely what this application requires.
Three characteristics of Grease HS2 are directly relevant here:

Its film thickness responds to operating speed across a range of -35°C to +120°C. At 3,000 rpm, it maintains a protective lubricating film designed and optimized to reduce internal friction and temperature increase. During start-stop cycles and load transitions, when metal-to-metal contact is most likely, the adaptive lubricating film thickens to ensure surface separation. This is not a trade-off between two performance states. It is consistent protection across both extremes, and everything in between. 

Its non-polar thickener system allows very high additive functionality that remains effective across the full lubrication interval, not only immediately after application. In a high-shear environment, this matters: the grease does not deplete its protective capacity within hours of relubrication, nor does it show a gradual decline in protective performance as additives are used up. With Grease HS2, the additive package protects both the oil and the surfaces at a consistently high level.

MicPol® is Interflon’s proprietary friction-reduction technology. Micronized, polarized additives bond directly to the metal surface, forming a protective barrier that remains effective between lubrication events. In this application, that surface-bonded layer also acts as a physical barrier that helps keep cellulose fibers away from the bearing’s running track and C3 clearance, preventing the absorption of base oil by cellulose debris that would otherwise accelerate grease depletion. The technology is PFAS-, microplastics- and nanotechnology-free.
The intervention

The Interflon Technical Adviser cleaned the bearing thoroughly using Interflon Eco Degreaser, removing all residue of the previous hardened lubricant. This step is critical regardless of what replacement product follows: residual degraded grease limits the performance of any new lubricant and reintroduces the contamination that caused the original failure. The bearing housing was then repacked by hand with Grease HS2 applied with a grease gun and reassembled within a single scheduled maintenance window.