100ZJ-48 Slurry Pump Bearing Housing Oil Seal Leakage: Diagnosis of Return Hole Blockage and Breather Failure

Subtitle: Repeated oil seal replacement still leaks? – Blocked return hole or breather causes internal pressure buildup, clearing them stops leakage

Introduction

The 100ZJ-48 is a high‑efficiency ZJ series slurry pump (100mm discharge, 480mm impeller diameter), widely used in coal preparation and fine tailings transport. Its bearing housing uses oil bath lubrication, relying on oil seals (lip seals or labyrinth seals) to prevent leakage. Field reports of oil seal leakage are common; even after replacement, leakage soon returns. Some users replace seals monthly with no improvement.

Hebei Xingou Machinery Equipment Co., Ltd. has found that the root cause of frequent oil seal leakage is often not seal quality, but blocked return holes or blocked breathers that raise internal pressure, forcing oil out past the seal. This article describes diagnosis, field remedies, and preventive measures.

1. Common Causes of Bearing Housing Oil Leakage

The last two causes are most often overlooked but account for >60% of repeat leakage cases.

2. Diagnosing and Clearing Blocked Return Holes

2.1 Function of Return Holes

Return holes (or channels) guide oil flung from bearings back to the sump, maintaining stable oil level. If blocked by sludge or debris, oil accumulates at the seal, pressure builds, and leakage occurs.

2.2 How to Detect Blockage

2.3 Clearing Procedure

3. Diagnosing and Fixing Blocked Breathers

3.1 Function of the Breather

The breather equalizes pressure inside the bearing housing as temperature changes. If blocked, internal pressure rises during operation, forcing oil out past the seal.

3.2 How to Detect Breather Failure

3.3 Fixing Procedure

3.4 Breather Upgrade Recommendations

Hebei Xingou Machinery recommends sintered metal breathers – resistant to clogging, good airflow, long life.

4. Fast Troubleshooting Flowchart

5. Field Case

Background: A 100ZJ-48 at a coal preparation plant had severe bearing housing oil leakage, requiring seal replacement every 2-3 weeks. Inspection showed the seal was not worn, and the shaft surface was smooth.

Diagnosis:

• Breather was a plastic type, completely clogged with sludge.

• Return hole was partially blocked.

Actions:

• Cleared the return hole by flushing with kerosene.

• Replaced the breather with a sintered metal type.

• Replaced the oil seal and filled with fresh oil to correct level.

Results: No oil leakage for 6 months; seal remains in good condition.

6. Daily Maintenance and Prevention

Conclusion

Frequent oil seal leakage on 100ZJ-48 bearing housings is often not a seal quality issue, but rather blocked return holes or blocked breathers causing internal pressure buildup. Clearing the return hole and cleaning or upgrading the breather can permanently stop leakage and significantly extend seal life. Hebei Xingou Machinery Equipment Co., Ltd. offers bearing housing leakage diagnosis and sintered metal breather supplies. Please contact us.