TL;DR
Rotor bearing overheating indicates lubrication failure, contamination, or bearing wear. Check bearing temperature and regrease before condemning the bearing.
What you might see
- bearing housing temperature above 80 C measured with IR thermometer
- grinding or rumbling noise from the rotor bearing location
- grease discoloration or leakage at the bearing cap
- elevated motor current without load change
Likely causes
Bearing under-lubricated or over-lubricated causing grease churning heat
Bearing contaminated with regrind dust entering through a worn seal
Bearing wear from extended service beyond replacement interval
Misalignment between the rotor shaft and the driven pulley from belt tension
Required tools
- IR thermometer
- Grease gun with machine-specified grease
- Bearing puller and installer set (if replacing)
- LOTO kit
Safety first
- Lock out the granulator and allow the bearing housing to cool before touching it.
- Do not over-pressurize the grease fitting. Excess grease can blow the bearing seal and contaminate the regrind stream.
Procedure
- 1
Measure the bearing housing temperature with an IR thermometer during operation. Record the reading and compare to the 80 C threshold.[1]
- 2
Stop the granulator and lock it out. Do not touch the bearing housing immediately. Allow it to cool.
- 3
Inspect the bearing cap seal for grease leakage or regrind dust ingress.
- 4
Clean the grease fitting and apply fresh grease of the grade specified on the granulator nameplate. Do not over-grease, which causes churning heat.[1]
- 5
After greasing, restart and re-measure bearing temperature after 30 minutes of operation. Temperature should decrease.
- 6
If temperature does not decrease after lubrication, lock out and plan a bearing replacement at the next planned outage.
- 7
When replacing bearings, check the rotor shaft for scoring at the bearing seat and inspect the drive belt tension, which should not be tight enough to cause radial load on the bearing.
Sources
Cumberland (ACS Group) Cumberland 3600 / 5800 / 6800 Granulator / Shredder general technical documentation, Cumberland (ACS Group)
Cumberland granulator maintenance manual, rotor bearing lubrication and inspection schedule (general)
More guides for Cumberland (ACS Group) Cumberland 3600 / 5800 / 6800
How to restore regrind quality on a Cumberland 3600 / 5800 / 6800 granulator
Poor regrind quality with fines, dust, or uneven particle size almost always means dull or improperly gapped rotor blades. Inspect the blade edge and gap setting before running more material.
How to diagnose motor overload trips on a Cumberland 3600 / 5800 / 6800 granulator
Granulator motor overload trips are usually from large or thick feed pieces jamming the rotor, or from dull blades increasing cutting force. Clear the jam, check the blade gap, then reset the overload.
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