Centrifugal pumps can fail due to mechanical wear, improper operation, or fluid-related issues. This guide covers common failures, diagnostics, and repair steps to restore pump performance.
| Symptom | Possible Causes | Diagnostic Checks |
|---|---|---|
| No Flow/Low Flow | - Clogged impeller/suction - Air leakage (cavitation) - Wrong rotation | - Inspect suction strainer - Check NPSHₐ vs. NPSHᵣ - Verify motor rotation |
| Low Pressure | - Worn impeller - Speed too low - Air in system | - Measure impeller clearance - Check motor RPM - Bleed air from casing |
| Excessive Vibration | - Misalignment - Unbalanced impeller - Bearing failure | - Laser alignment check - Dynamic balancing - Inspect bearings |
| Leakage at Seal | - Mechanical seal failure - Gland packing worn out | - Check seal faces for wear - Tighten/replace packing |
| Overheating | - Running dry - Low flow (recirculation) - Bearing lubrication failure | - Verify liquid supply - Ensure min. flow bypass - Grease/oil bearings |
✔ Shut off power & lockout/tagout (LOTO).
✔ Drain the pump and relieve pressure.
✔ Disconnect piping if necessary.
Remove coupling (check alignment before full disassembly).
Unbolt casing (volute or diffuser).
Extract impeller (may need a puller if corroded).
Inspect shaft & bearings (check for scoring/wear).
| Part | Inspection | Repair Action |
|---|---|---|
| Impeller | - Cracks/wear - Erosion/corrosion | - Replace if worn >5% - Clean or coat if corroded |
| Mechanical Seal | - Cracked faces - Worn O-rings | - Replace entire seal - Use correct material (SiC, carbon) |
| Bearings | - Noise/roughness - Overheating | - Replace if damaged - Re-grease (NLGI #2) |
| Shaft | - Bent/scratched - Runout >0.05mm | - Straighten or replace - Polish if minor damage |
| Casing | - Cracks/wear - Corrosion | - Weld repair (if cast iron) - Replace if severely damaged |
Reinstall impeller (ensure proper clearance).
Align pump & motor (laser/shims for <0.05mm misalignment).
Prime the pump (fill casing with liquid).
Test run (check vibration, leakage, amp draw).
✅ Always replace seals in pairs (stationary + rotating face).
✅ Use OEM parts for impellers & bearings to avoid imbalance.
✅ Check NPSH—cavitation damage often looks like pitting on the impeller.
✅ Document clearances (impeller gap, shaft deflection) for future reference.
| Condition | Action |
|---|---|
| Minor wear (seals, bearings) | Repair |
| Cracked casing or shaft | Replace pump |
| Severe impeller erosion | Replace impeller (if >10% efficiency loss) |
| Frequent failures | Redesign system (wrong pump type?) |
✔ Monthly: Check vibration, lubrication, leaks.
✔ Quarterly: Inspect bearings, alignment, and seals.
✔ Annually: Full tear-down, impeller clearance check.
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