Common Lubrication System Failures and How to Prevent Them
A centralized lubrication system is only as effective as its maintenance. When the system fails — silently, without triggering an alarm — the machine continues running while its bearings, guideways, and friction surfaces run dry. The damage accumulates over hours or days before it manifests as a breakdown. Understanding the most common failure modes, how to detect them, and how to prevent them is essential for any maintenance engineer responsible for lubrication systems.
1. Empty Reservoir
What happens: The pump runs dry, drawing air instead of lubricant. The system delivers no lubrication. All bearing points are starved simultaneously.
Why it happens: No one refilled the reservoir. The low-level alarm was ignored or was not fitted. Reservoir capacity was undersized for the lubrication interval.
Prevention:
- Install a float switch on the reservoir — it triggers an alarm (and optionally stops the machine) when oil level drops below a safe minimum.
- Set a calendar reminder for reservoir top-up based on actual consumption, not an arbitrary schedule.
- Upgrade to a larger reservoir if topping up is required more than once per week.
2. Blocked Distribution Line or Metering Device
What happens: One or more lubrication points receive no lubricant. In a progressive system, the entire block stalls. In a manifold system, only the blocked point is affected — and the fault may go undetected.
Why it happens: Contamination in the oil clogs a metering cartridge or progressive distributor block piston. A kinked or crushed tube blocks flow. A fitting corrodes shut.
Prevention:
- Install and replace the in-line filter on schedule — contaminated oil is the primary cause of blocked metering devices.
- Use a pressure switch to detect when the system fails to reach operating pressure, indicating a blockage or pump fault.
- Check the cycle indicator pin on progressive blocks regularly — a stationary pin means the block has stalled.
- Inspect tubing for kinks, especially after machine maintenance or relocation.
3. Pump Failure
What happens: The pump runs but delivers no pressure, or does not run at all. All lubrication points are starved.
Why it happens: Worn pump elements (plunger and barrel wear from contaminated oil). Motor failure. Controller or timer fault — pump never receives the run signal. Electrical supply failure.
Prevention:
- Keep the oil clean — particulate contamination is the primary cause of pump wear. A good suction strainer and in-line filter extend pump life significantly.
- Use a pressure switch to confirm that the pump is actually building pressure each cycle, not just running.
- Verify the timer or controller is functioning by observing a complete lubrication cycle periodically.
- Keep spare pump elements and motor components for critical machinery.
4. Wrong Lubrication Interval or Dose
What happens: Bearings are either under-lubricated (wearing prematurely) or over-lubricated (excess lubricant attracts contamination, overheats, or causes seal failure).
Why it happens: Timer settings were never correctly commissioned. Someone changed the interval without understanding the implications. Metering devices were replaced with the wrong size. Machine duty cycle changed but lubrication settings were not updated.
Prevention:
- Commission the system properly — document the correct timer interval, pump run time, and dose per point for each machine.
- Label the controller or timer with the correct settings so they can be restored if changed.
- Review lubrication settings when machine duty cycle changes significantly (e.g., shift pattern changes, new materials, higher production rates).
5. Wrong Lubricant Grade in the Reservoir
What happens: Incompatible lubricant damages seals, reacts with residual lubricant in the system, or fails to provide adequate film strength at operating temperature.
Why it happens: Someone refilled with the wrong oil. Two different oil types were mixed. Grease of the wrong NLGI grade was used in a grease system.
Prevention:
- Label every reservoir clearly with the specified lubricant type, grade, and viscosity.
- Keep only the correct lubricant in the maintenance area for each machine — eliminate the possibility of using the wrong product.
- If the wrong lubricant was added, drain and flush the system before restarting.
6. Air in the System
What happens: The pump draws air instead of lubricant (or in addition to it), delivering inconsistent or zero lubrication. Progressive blocks cycle erratically.
Why it happens: Reservoir ran dry at some point. Suction line fittings are loose. Suction strainer is partially blocked, causing cavitation.
Prevention:
- Never allow the reservoir to run empty — fit a float switch alarm.
- Inspect suction line fittings periodically for looseness.
- Clean the suction strainer regularly — a blocked strainer causes partial vacuum at the pump inlet.
- After refilling an empty reservoir, bleed air from the system by running the pump until consistent flow is seen at each outlet.
Preventive Maintenance Checklist
| Check | Frequency |
|---|---|
| Check reservoir oil level | Daily |
| Verify cycle indicator pin is moving (progressive systems) | Daily |
| Check pressure gauge reading is within normal range | Weekly |
| Inspect tubing for kinks, leaks, or damage | Monthly |
| Clean suction strainer | Monthly |
| Replace in-line filter element | Every 3 months or as specified |
| Test float switch alarm function | Every 3 months |
| Verify timer/controller settings against documentation | Every 6 months |
| Full system inspection including pump elements | Annually |
SP Engineers supplies spare parts, replacement metering cartridges, filters, float switches, pressure switches, and pump elements for centralized lubrication systems. Contact us for technical support or spare parts enquiries.