What are some common faults with three-roller mills?

I. Mechanical Failures
1. Abnormal Roller Vibration
Cause: Uneven roller gap, bearing wear, or foreign matter stuck in the rollers
Action: Check roller parallelism (error ≤ 0.02mm), remove foreign matter, and replace the bearings.
2. Bearing Overheat (>60°C)
Cause: Insufficient lubrication or insufficient cooling water flow
Action: Add lithium-based grease (replace every 2000 hours) and adjust the cooling water valve opening.
3. Abnormal Gearbox Noise
Cause: Cracked planetary gear or bearing spalling.
Action: Stop the machine for inspection and replace damaged parts (such as the NU236EM1C3 bearing).
II. Process Failures
1. Fine Discharge Excessive Degree

Cause: Excessive roller gap or scraper wear
Remedy: Adjust the gap to 0.1-0.3mm and replace the scraper (blade wear >1mm requires replacement).

2. Material Leakage

Cause: Failure of the baffle seal or roller corrosion
Remedy: Replace the fluororubber seal. If corrosion is severe, repair the roller surface with a weld overlay.

3. Current Fluctuation (>10% of rated value)

Cause: Excessive material viscosity or roller overload
Remedy: Dilute the material or reduce the feed rate.

3. Hydraulic System Failure

1. Insufficient Roller Pressure

Cause: Hydraulic oil contamination or cylinder seal failure
Remedy: Replace the hydraulic oil (ISO VG46) and check the seals.
2. Hydraulic System Oscillation
Cause: Iron filings or oil line blockage
Remedy: Clean the oil line and install a magnetic filter.
IV. Typical Case Studies
Planetary Gear Crack: A cement plant's roller press experienced a vibration alarm due to a cracked planetary gear. Disassembly revealed a de-rounded inner bore in the second-stage planetary gear.
Bearing Spalling: Spalling of the bearing on the input shaft NU236EM1C3 caused abnormal noise. After replacement, the vibration level decreased by 80%.
V. Preventive Maintenance Recommendations: Check roller wear monthly (allowable value ≤ 0.5mm). Clean the lubrication system and replace the filter element quarterly. Install an online monitoring system (such as iPHM) for fault warnings.