Eccentric shaft bearing failure maintenance of jaw crusher

Eccentric shaft bearing failure maintenance of jaw crusher

1. Overview

The eccentric shaft bearing is one of the core load-bearing components of a jaw crusher. It bears huge impact load, alternating stress and friction heat during operation. Once it fails, the crusher will stop immediately. Common failure types include bearing heating, abnormal noise, raceway pitting, roller cracking, cage damage, shaft seizure and bearing clearance out of tolerance.

2. Main Causes of Eccentric Shaft Bearing Failure

  1. Lubrication failure
    • Insufficient grease/oil supply, oil cut-off;
    • Lubricant deterioration, mixed with dust, ore powder and water;
    • Wrong lubricant grade, poor high-temperature resistance;
    • Over-lubrication (too much grease causes heat accumulation).
  2. Assembly and clearance problem
    • Bearing installation offset, eccentric shaft bending;
    • Internal clearance too small → easy heating and seizure; clearance too large → impact vibration, raceway damage;
    • Bearing housing deformation, loose bearing cap bolts.
  3. Overload and impact load
    • Unbreakable foreign matter enters the crushing cavity, instant overload;
    • Long-term full-load or over-feed operation; uneven feeding causes frequent shock load.
  4. Sealing failure
    • Oil seal, labyrinth seal worn or damaged; dust and slurry invade the bearing chamber, abrasive wear occurs.
  5. Bearing quality & fatigue aging
    • Substandard bearing material, poor heat treatment;
    • Long service time, metal fatigue spalling on raceway and rolling elements.
  6. Other factors
    • Eccentric shaft journal wear, journal out of round;
    • Misalignment between eccentric shaft and pulley.

3. On-site Fault Judgment Method

  • Temperature check: Normal bearing temperature ≤70℃. Continuous temperature rise above 75℃ is an early warning; over 85℃ must stop the machine.
  • Sound check: Uniform low hum is normal; sharp squeaking, clattering, knocking sound indicates bearing damage.
  • Vibration check: Obvious abnormal vibration increases with speed.
  • Lubricant inspection: Check oil/grease for black powder, metal chips and moisture. Metal debris means bearing has worn.

4. Step-by-Step Maintenance & Replacement Procedure

⚠️ Safety precondition: Lockout-tagout (LOTO), cut off power, clean materials in crushing cavity.

Step 1: Dismantle auxiliary parts

Remove the flywheel, pulley, tension device, bearing end cover and sealing assembly on both sides of the eccentric shaft. Drain old lubricant completely.

Step 2: Take out the eccentric shaft assembly

Hoist the eccentric shaft steadily, avoid collision to prevent journal scratch.

Step 3: Remove old bearings

Use hydraulic puller to dismount bearings. Do not directly knock bearing race with hammer to avoid journal damage.

Step 4: Inspect matching parts

  • Check eccentric shaft journal: If there is scratch, pitting, out-of-roundness, repair by grinding or surfacing;
  • Check bearing housing: Check inner hole deformation, crack, thread damage;
  • Check oil seal, labyrinth ring, spacer sleeve: Replace all worn sealing parts.

Step 5: Select and preheat new bearing

Use matched heavy-duty spherical roller bearings (the mainstream type for jaw crusher eccentric shaft). Preheat bearing uniformly to 80–100℃ by oil bath or induction heater. Do not use open fire heating.

Step 6: Bearing installation and clearance adjustment

  • Install bearing onto journal smoothly; install spacer, inner retaining ring;
  • Adjust axial and radial clearance strictly according to equipment manual. Too small clearance is the most common reason for burning bearing;
  • Tighten bearing cap bolts diagonally and evenly.

Step 7: Restore sealing system

Install new oil seal and labyrinth seal, fill the sealing groove with clean grease to block dust.

Step 8: Refill lubricant

Fill the bearing chamber with specified grease. Generally fill 1/2 ~ 2/3 of the cavity space, not full.

Step 9: No-load test run

After assembly, run without load for 30–60 min. Monitor temperature, noise and vibration. If stable, then carry out load feeding.

5. Daily Preventive Maintenance Points

  1. Strictly follow lubrication cycle: Check grease supply every shift; replace lubricant regularly.
  2. Inspect sealing parts frequently, replace oil seal in advance once leakage is found.
  3. Avoid iron, drill bits and other hard foreign objects entering the crushing chamber.
  4. Regularly detect bearing temperature with infrared thermometer.
  5. Check bearing cap fastening bolts regularly to prevent loosening under vibration.
  6. Record bearing working hours and arrange planned replacement before fatigue failure.

6. Common Troubleshooting Quick Table

表格

Fault Phenomenon Possible Cause Solution
Bearing continuous overheating Too small clearance / Too much grease / Oil cut-off Adjust clearance, discharge excess grease, refill qualified lubricant
Abnormal knocking noise Bearing roller/cage broken, large clearance Stop immediately, replace bearing
Grease quickly turns black with metal powder Seal invalid, dust invasion, abrasive wear Replace seal and bearing, clean bearing chamber
Bearing seizes up Serious lack of lubrication, long time overheat Replace bearing and repair journal

7. Safety Notes

  • It is forbidden to inspect and maintain the bearing when the crusher is powered on;
  • Hot bearing and preheated parts may cause scald;
  • Waste lubricant should be collected for environmental treatment, not discharged randomly;
  • Use lifting tools with rated load to prevent eccentric shaft falling.