Why Pellet Mill Press Roller Bearings Get Hotter After Greasing

When pellet mill press roller bearings get hot, operators often suspect insufficient lubrication. If press roller bearings get hotter after greasing, operators may add more grease. However, excess grease also increases resistance inside the press roller bearing. Adding more grease can therefore make the overheating worse.

This article covers press roller bearings designed for periodic grease replenishment. Flat die pellet machines e vertical ring die pellet machines may deliver grease differently. Do not apply the same grease replenishment quantity to every pellet mill. These procedures do not cover gearbox oil changes or circulating oil lubrication. These greasing procedures do not apply to maintenance-free sealed bearings.

Check the Temperature Trend Instead of Relying on One Reading

Fresh grease needs to redistribute inside the press roller bearing. Bearing rolling elements, such as balls or rollers, push and churn the grease. Grease churning consumes energy and generates heat. Press roller bearing temperature may therefore rise temporarily after greasing. Persistent excess grease can maintain churning resistance and keep bearing temperatures elevated.

Use the pellet mill’s existing temperature monitoring equipment. Alternatively, measure the same temperature point each time from a safe position. Compare readings with normal operating records taken under similar pellet mill loads. Readings from different measurement points are not directly comparable. Never touch a press roller to judge whether the bearing is overheating.

Temporary bearing heating does not justify running the pellet mill indefinitely. Stop the pellet mill if bearing temperature keeps rising rapidly. Stop the pellet mill when its temperature alarm limit is reached. Unusual noise or vibration accompanying the temperature rise also requires shutdown. Follow the pellet mill’s shutdown procedure.

Before opening pellet mill covers, isolate and lock out energy sources. Grease line inspections and component removal also require energy isolation and lockout. Release stored pressure and verify that the pellet mill cannot move unexpectedly.

Check for Excess Grease and Blocked Grease Discharge Passages

Grease must lubricate contact between the bearing’s rolling elements and raceways. Raceways are the tracks where the bearing’s balls or rollers run. Filling every surrounding space with grease does not improve lubrication. The permitted grease fill depends on bearing speed, internal space and housing design. Grease appearing near a grease fitting does not confirm the correct fill. The correct grease quantity depends on the specific press roller assembly.

Check how much grease was added and when the previous replenishment occurred. Confirm whether anyone added grease manually alongside the automatic lubrication system. When changing grease guns, do not simply reuse the previous stroke count. Different grease guns may deliver different amounts with each stroke.

Some press roller assemblies have passages designed to discharge old grease. After shutdown and energy isolation, check those existing passages for blockages. If overgreasing is confirmed, maintenance technicians should remove excess grease as instructed. Follow the maintenance procedure for the specific pellet mill. Never remove seals on your own to release grease. Do not keep the pellet mill running with persistently high bearing temperatures.

Check Grease Delivery and Compatibility

Grease gun pressure alone does not confirm adequate lubrication of press roller bearings. A running lubrication pump does not prove adequate grease delivery either. Blocked grease fittings, supply lines or distribution components can prevent grease delivery. Grease may therefore fail to reach the bearing contacts requiring lubrication. Increasing lubrication pump cycles does not necessarily resolve a grease delivery fault.

Press roller bearings may already be overheating before grease is added. If bearing heating persists after greasing, technicians should trace the grease delivery path. Do not keep increasing grease quantities without checking actual delivery. Relieve pressure before inspecting greasing tools, connectors or supply lines. Never use your hands to search for leaks from pressurized grease equipment.

Check whether the grease brand or product has changed. Similar colors do not prove that two greases are compatible. Labels describing both products as high-temperature greases do not establish compatibility either. Mixing incompatible greases can cause excessive softening, hardening or abnormal oil separation. Abnormal grease consistency or oil separation can reduce bearing lubrication. Confirm the specified grease grade, base oil viscosity, and operating temperature range.

Do not keep adding new grease over unidentified old grease. Confirm grease compatibility with both the equipment supplier and lubricant supplier. After confirming compatibility, agree on cleaning, replacement or grease displacement methods with suppliers. Keep grease fittings clean and use dedicated tools for each grease product. Retain complete product labels to help prevent contamination and accidental grease mix-ups.

How TCPEL Checks Whether Heating Started Before or After Greasing

At TCPEL, we first establish when the press roller bearing started heating. If previously stable bearings heat up after greasing, we first check grease quantity. We also check whether the grease product changed before bearing temperatures rose. If bearings overheated before greasing, adding grease was a response to existing trouble. Adding grease does not rule out insufficient grease delivery, contamination or mechanical damage.

Assembly reference only. Follow the model-specific maintenance procedure for grease quantities.

One press roller may run much hotter than others in the same system. Comparing press roller temperatures helps identify which press roller assembly needs inspection. However, a hotter press roller does not prove a blocked grease line. Compare the corresponding grease supply branches, seal condition and bearing installation.

Insufficient bearing internal clearance can also cause abnormal heating. Bearing internal clearance is the free movement between the bearing’s inner and outer rings. Incorrect bearing installation or excessive seal friction can also raise bearing temperatures. Adding grease cannot correct improper installation, insufficient bearing clearance or excessive seal friction.

After corrective work, restore the pellet mill guards and confirm safe operating conditions. Restart according to the procedure for the specific pellet mill. Recheck bearing temperature trends and operating sounds under comparable pellet mill loads. A lower bearing temperature after shutdown cooling does not confirm a successful repair.

Record the grease product, actual quantity added, replenishment time and temperature measurement location. These maintenance records help reveal whether future heating problems relate to lubrication work.

If press roller bearing heating remains unexplained, Entre em contato com a TCPEL for troubleshooting support. Provide the pellet mill model, temperature records and details of recent maintenance.