Rotary kiln support roller bearing overheating is rarely caused by a single component. The most reliable correction is a system-level adjustment that restores lubrication and cooling, stabilizes hydraulic thrust roller movement, verifies bearing clearances, realigns tyre-to-roller contact, and confirms performance during a monitored low-speed trial. All settings must follow the kiln manufacturer's drawings and site safety procedures.
In the documented case, increasing tyre-to-roller contact from 40% to 65%, reducing the hydraulic thrust roller's downward speed from 0.5 to 0.2 mm/min, and increasing oil-entry clearance from 0.001D to 0.003D reduced bearing temperature from 82 to 55-60 °C. The kiln then operated continuously for more than 180 days.
Because support rollers carry the kiln load under high-temperature, heavy-duty conditions, a hot bearing should be treated as evidence of a wider mechanical, lubrication, hydraulic, or alignment problem. Diagnosis should focus on oil-film stability, cooling, load distribution, axial movement, and post-adjustment performance.
1.Lubrication Loss or Oil Deterioration
2.Abnormal Axial Thrust
3.Restricted Cooling
4.Incorrect Clearance or Poor Bearing Scraping
5.Uneven Tyre-to-Roller Contact or Installation Error
Before moving any rotary kiln support roller, record bearing temperatures, vibration, oil level and condition, cooling-water flow and temperature, hydraulic thrust roller speed and pressure, kiln axial movement, tyre-to-roller contact pattern, and the dimensional data from the kiln drawings. Trend data is more useful than a single temperature reading because it reveals whether the fault is stable, cyclical, or worsening.
As a practical reference, the source project treated bearing temperatures up to 65 °C as normal and temperatures above 75 °C as requiring urgent action. These thresholds must be checked against the bearing design, lubricant specification, alarm logic, and OEM limits for the specific kiln.
Use a lubricant with the viscosity, oxidation resistance, demulsibility, corrosion protection, and temperature capability specified for the support roller bearing. Replace degraded oil and clean the reservoir and oil circuit. Repair leaking seals, secure or replace the oil scoop, and verify its immersion depth. For water-cooled assemblies, remove restrictions and replace corroded pipework where necessary. The source project used at least 90% of design flow, an inlet temperature no higher than 30 °C, and an outlet temperature below 45 °C as operating checks.
Inspect and adjust the flow-control and throttle valves so that upward and downward movement is smooth and consistent. The original engineering study used a movement rate within 0.3 mm/min, or the equipment manufacturer's specified value. The correct setting must suit the kiln slope, speed, load, tyre condition, and hydraulic design.
Measure oil-entry and end clearances with calibrated gauges and compare them with the bearing drawing. Do not apply a single clearance formula to every kiln: shaft diameter, bearing material, lubrication method, thermal expansion, and prior re-metalling all matter. The case described below restored the oil-entry clearance from 0.001D to 0.003D, where D is the support roller shaft diameter. Bearing scraping should also produce an even, continuous contact band and allow the spherical seat to articulate without binding.
Use marking compound during slow kiln rotation to evaluate contact. The study targeted uniform contact over more than 60% of the roller face, without pronounced bright or dark bands. Survey the support roller positions with a laser alignment instrument or equivalent method. For the installation examined in the study, roller-to-kiln centerline parallelism was held within 0.5 mm/m, while the two roller centers and tyre center formed the intended 60-degree support geometry within plus or minus 1 degree. Always use the approved kiln drawings as the final acceptance standard.
After adjustment, run the kiln at low speed for approximately two to four hours while continuously monitoring bearing temperature, oil delivery, axial movement, hydraulic pressure, cooling-water performance, vibration, and contact pattern. If the readings stabilize, return the kiln to service in controlled stages and continue trending the same parameters. Record the final position and measurements as a baseline for future inspections.
A 4.8 m x 74 m rotary kiln repeatedly experienced support roller bearing temperatures of up to 82 °C. Inspection identified three interacting problems: only about 40% tyre-to-roller contact with visible banding, hydraulic thrust roller downward movement of 0.5 mm/min, and an oil-entry clearance of just 0.001D.
| Adjustment | Before | After |
| Tyre-to-roller contact | 40% with banding | 65%, more uniform |
| Thrust roller downward speed | 0.5 mm/min | 0.2 mm/min |
| Oil-entry clearance | 0.001D | 0.003D |
After the roller position, hydraulic setting, and bearing clearance were corrected, the bearing temperature stabilized between 55 and 60 °C. The kiln then operated continuously for more than 180 days. The result demonstrates why treating only the hot bearing - without correcting contact, thrust, and clearance - is unlikely to deliver a lasting solution.
Support roller maintenance is moving from experience-based intervention toward condition monitoring. Temperature probes, vibration sensors, hydraulic pressure data, oil-condition monitoring, and axial-position measurements can be combined in a single trend platform. With reliable baseline data, plants can detect changes in load distribution or lubrication before a hot bearing forces an unplanned shutdown.
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