Why Lubricating Oil Failure Analysis Was Needed
A lamp manufacturing plant in Southeast Asia experienced recurring problems in a large hydraulic system before the oil reached 3,000 operating hours.
The main symptoms included:
- severe oil foaming
- frequent filter blockage caused by sticky deposits
- unstable hydraulic valve operation
- repeated recurrence even after replacing the hydraulic oil and cleaning the oil circuit
The customer could not determine whether the problem came from equipment wear, external contamination, or the lubricant itself.
A Lubricating Oil Failure Analysis was therefore performed on three types of samples:
- used hydraulic oil from the failed system
- deposits collected from the blocked filter
- fresh hydraulic oil from the original supplier
The objective was to identify the actual failure mechanism rather than simply replace the oil again.
Lubricating Oil Failure Analysis Methods
The investigation combined chemical analysis of the oil and deposits with comparative testing of fresh and used samples.
Analytical methods included:
- FTIR for oxidation products and major organic components
- LC-MS for organic additives and contaminant identification
- ICP-OES for metals and inorganic elements
- water content analysis
- acid number testing
- solid-phase extraction for component separation
- iron spectrum / wear debris analysis
- comparative analysis of fresh oil, used oil and filter deposits
This multi-sample approach was important because the failure could not be explained by the used oil alone.
What the Lubricating Oil Analysis Revealed
The first important finding was that the used oil contained significantly elevated water.
FTIR also showed increased oxidation-related signals, while some antioxidant and corrosion-inhibitor components had been heavily depleted.
However, the blocked filter deposit did not mainly consist of metallic wear particles.
Instead, the deposit contained:
- acidic products associated with lubricant degradation
- organic salt-like contamination
- sticky polymeric or gum-like material
This immediately suggested that the filter blockage was not simply a mechanical wear problem.
External Contamination Was Identified as the Root Cause
LC-MS analysis detected surfactant-related components and a small amount of strongly alkaline cleaning-agent residues in the hydraulic oil.
The investigation indicated that cleaning fluid had entered the hydraulic oil system during equipment maintenance.
These contaminants interacted chemically with lubricant additives, including corrosion-inhibiting components, and accelerated lubricant oxidation.
The result was a chain of problems:
cleaning-agent contamination → additive disruption → oxidation → sticky deposits → foaming and filter blockage
The failure was therefore not caused by an inherently defective batch of hydraulic oil.
The true root cause was external chemical contamination introduced during maintenance.
Why Replacing the Hydraulic Oil Did Not Solve the Problem
Before the laboratory investigation, the customer suspected poor oil quality and repeatedly replaced the hydraulic oil.
But the same symptoms continued.
The reason was that the contamination source remained inside the hydraulic system.
If residual cleaning chemicals remain in pipes, seals or system cavities, fresh oil can become contaminated again shortly after replacement.
This is why Lubricating Oil Failure Analysis should not focus only on whether the oil meets basic specifications. The surrounding process history, maintenance chemicals and deposit composition may be equally important.
Corrective Actions After Lubricating Oil Failure Analysis
Based on the analytical findings, several corrective actions were recommended:
- improve equipment sealing and maintenance procedures
- prevent cleaning-agent residues from entering the oil circuit
- flush the hydraulic system before refilling
- replace contaminated oil from the bottom of the system
- establish routine monitoring of water content and additive condition
After corrective action, the hydraulic system returned to stable operation.
The recurring filter blockage and foaming problems did not reappear, and the lubricant service interval returned toward the intended operating range.
What Lubricating Oil Failure Analysis Can Help Identify
Lubricant-related equipment failures may result from:
- lubricant oxidation
- additive depletion
- water contamination
- cleaning-agent contamination
- external chemical contamination
- abnormal wear debris
- sludge or varnish formation
- formulation changes
- supplier variation
- incompatible maintenance chemicals
The key is to distinguish whether the problem originates from the lubricant, equipment, contamination source, or their interaction.
Lubricating Oil Failure Analysis at Xinbodi
Xinbodi Laboratories provides Lubricating Oil Failure Analysis services for hydraulic oils, gear oils and other industrial lubricants. For cases involving composition changes, contamination or additive depletion, our chemical analysis services can help identify the underlying chemical differences.
Projects may combine oil composition analysis, deposit identification and fresh-versus-used oil comparison to determine whether failures are related to lubricant degradation, additive changes, contamination or equipment-related factors.
For recurring failures, submitting the failed oil, fresh reference oil and deposits or filter residues together can significantly improve root-cause interpretation.