by Craig Winterfield, Vice President – Laboratory Services
The sudden appearance of copper and lead in engine oil can be a cause for concern and lead to unnecessary maintenance, downtime and equipment failure if the root cause is not determined.
A rise in copper and lead can be related to bearing wear, cooler core pacification or corrosion, or a combination of other wear and contamination sources. If the problem is related to bearing wear, routine oil analysis may not be sufficient to differentiate normal wear from abnormal or severe wear.
The initial steps to take when there’s a rise in copper and lead are to investigate the:
- Historical oil analysis results to determine if the copper and lead concentrations are increasing or decreasing and if the rate of change has increased.
- Maintenance records including the oil and equipment hours, recent maintenance, oil change history and cooler core history.
Based on the outcomes of the initial investigation, one course of action would be to request a re-sample to determine if the trend continues upward. You may also want to trigger advanced sample testing to determine the source of the copper and lead.
Determining the Source of Copper and Lead in Oil
Routine Oil Testing
ICP Spectrometry is often included as a part of routine oil analysis test packages. This test can monitor for copper and lead wear, however, there are limitations if this test is used as a stand-alone indicator.
- ICP Spectrometry has a well-known loss of sensitivity to particles larger than 10µm and is unable detect particles or contamination composed of carbon or other organics.
- Interpreting the results of an ICP Spectrometry-based oil analysis report can be difficult because the method does not differentiate between sources of the same element, particle sizes or severity. As a result, accurate wear rate and trending is impractical or impossible to implement using ICP analysis alone.
- Using Spectrometry alone, it is not possible to pinpoint the specific source of most elements such as copper, which may include material from bearings, brass, bronze, cooler core pacification, paints, anti-seize, mine dust and other sources. Some modes of copper generation can hide or obscure abnormal wear. For example, an engine with a new cooler core may see a rise in copper concentrations in the oil because of cooler core pacification. This generally harmless source of copper may obscure a serious bearing failure generating copper wear debris and requiring action.
Spectrometry based oil analysis cannot differentiate between steel housings and steel bearings, gears, and shafts or between outside contamination such as iron containing process dust and wear of steel components.
To combat these limitations, elevated copper and lead wear found in Spectrometry results can be used to trigger more advanced testing to determine the source and composition of wear.
Advanced Testing
Spectrometry-based oil analysis leaves a gap in how to monitor for large particles. Particles with diameters larger than 10µm provide key information regarding component wear and contamination. These larger particles may provide early warning of abnormal wear and can themselves be abrasive and cause secondary wear.
A Scanning Electron Microscopy (SEM) uses electrons instead of light (photons) to analyze and visualize the surface features of a material. SEM can be combined with Energy Dispersive X-Ray Spectrometry (EDS) to provide compositional microanalysis of particles and surfaces. EDS is used to determine the chemical composition of a sample including what elements are present along with their distribution and concentration in Mass% and Atomic%.
SEM-EDS Wear Debris Analysis can determine the size, shape, and composition of hundreds of particles per sample. This test methodology can also differentiate between wear, contamination, and additives. From this data the source, size and severity can be determined quantitively and enables informed decision making.
Best Practices
To get the most out of your oil analysis program, we recommend that you:
- Submit the oil filter and spinner filter (if applicable) for SEM-EDS analysis to follow up on routine oil analysis results.
- Include the component and oil service hours when submitting samples.
- Investigate other maintenance information and warning signs when following up on alerts.
- Work with your Account Manager or Reliability Specialist to set reasonable alarm limits and implement automatic follow-up testing triggers for critical components and conditions.
Contact us to learn more about triggered testing and using SEM-EDS for advanced oil and filter analysis.
Case Study: Bearing Wear
A large Canadian Mine is using SEM analysis of Engine oil and Spinner filter debris to provide early warning of abnormal wear of main engine and connecting bearings for their fleet of Komatsu 830E Haul trucks (with QSK60 diesel engines). SEM-EDS analysis is used to identify abnormal wear of the multi-layer bearings and differentiate it from cooler core leaching which does not require intervention.
As the mine site is remote, it is difficult and expensive to bring in parts. The maintenance teams use SEM to make informed decisions and provide justification for pulling a unit for unscheduled maintenance.
Unit History
One unit had a new engine changed out and the oil analysis was normal until the component passed 1,000 hours of service when routine analysis showed increasing levels of copper (>600ppm) and lead (~2-6ppm). The source of the copper and lead could not be determined by routine oil analysis; therefore a sample of the spinner filter was submitted for SEM-EDS analysis.
| Component Service | Oil Service | Aluminum (AI) | Iron (Fe) | Copper (CU) | Lead (Pb) | Tin (Sn) | Chromium (Cr) |
|---|---|---|---|---|---|---|---|
| 2027 | 1937 | 3 | 20 | 671 | 4 | 0 | 3 |
| 1884 | 1794 | 4 | 17 | 639 | 2 | 0 | 0 |
| 1542 | 1452 | 2 | 15 | 402 | 2 | 0 | 0 |
| 988 | 898 | 2 | 11 | 3 | 1 | 0 | 0 |
SEM Analysis of Spinner Filter Debris
The SEM analysis revealed that the presence of copper was due to wear of the top and intermediate layer of the main bearings and not related to cooler core leaching.
The multi layer bearings in this engine had a 20-30µm thick Lead/indium (Pb/In) top layer, followed by a thin Indium/Tin (In/Sn) barrier layer and a ~270-280µm copper/lead intermediate layer with a steel (Fe) backing.
The SEM analysis of the spinner filter debris (~1000hours) showed significant quantities of copper/lead/tin as well as lead/indium consistent with the composition of the top layer and intermediate layer of the bearing.
Outcome
Routine oil analysis was successful at identifying the presence of copper and lead in the oil but could not identify the source of these metals. Based on the ICP results, the reliability and maintenance team at this mine initially suspected that the copper was due to cooler core leaching, or the wear of a copper bushing found on the spinner filter assembly.
Fluid Life’s Reliability Specialists suggested that the customer submit a sample for SEM-EDS analysis to positively identify the sources of the metals. SEM-EDS pinpointed abnormal bearing wear and provided justification for maintenance to pull the unit out of service for an inspection.
