You just received your latest oil analysis report for your engine. For months, there hasn’t been significant contamination and overall numbers have been stable. This last test now shows a sudden spike in wear metals. What do you do?
There are a few things you could do at this point. Review if there are any current environmental or maintenance circumstances that may have impacted on this result. Alternatively, you could request a retest on the current sample to confirm there weren’t any anomalies in the testing process. However, if it’s a critical component, it may require taking an immediate resample from the same component and resubmit for rush testing.
Same result coming back? This should then trigger advanced testing to find the root cause.
What is Triggered Testing?
Triggered testing is a common practice in an oil analysis program where additional tests are activated to run in exceptional circumstances. If you have set alarms and flagging limits for your components and oils, this can then prompt a secondary, more diagnostic, test to be done if the results fall outside of the set limits.
Triggered Testing for Wear
Basic Testing
A basic oil analysis program may include Spectrometry (ICP), FTIR analysis, viscosity, a particle count, a test for magnetic iron (Total magnetic iron or PQ index), and tests for specific contaminants such as glycol and water.
Inductively-Coupled Plasma (ICP) Spectrometry is a common test found in most of our industry test packages and is used to detect wear and contamination. ICP Spectrometry can only detect particles larger than 10um and cannot 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. This is often coupled with an ISO Particle Count which can quantify the number of large particles and provide a means to implement cleanliness and filtration targets.
Because of these limitations, ICP Spectrometry test is generally used as a “trigger test” for more advanced testing to analyze particles with diameters larger than 10um and to get greater depth analysis to determine the causes and sources of abnormal wear and contamination.
Advanced Tests
Using Spectrometry alone (ICP, RDE, XRF), 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.
An Analytical Ferrography can be performed to provide information regarding the approximate size of particles and morphological information about the wear mode. The interpretation of an Analytical Ferrography is subjective and dependent on the skill of the analyst. In most cases it is not possible to determine or differentiate specific alloys or sources using an Analytical Ferrography.
SEM-EDS Wear Debris Analysis can determine the size, shape, and composition of hundreds of particles per sample. SEM-EDS takes analysis even deeper and can differentiate between wear, contamination and additives overcoming the limitations of traditional oil analysis. From this data the source, size and severity can be determined quantitively and enables informed decision making.
The chart below outlines the various tests that can be used to identify wear and contamination.
Triggered Test Example
When conducting a review of engine oil test results for a client, we noticed that there was a higher than normal incidence of titanium (Ti) wear metal present.
Sources of Titanium
Titanium is a wear metal commonly found alloyed with other metals. Proportional increases in titanium (Ti) and iron (Fe) are indicative of ferrotitanium, which is typically used in the manufacture of shafts. Connecting rods, wrist pins are alloys of titanium, aluminum, and vanadium and wear from these parts is often disproportional with iron levels. Without knowing the age of the engines in play initially, the results could have been simple “break-in” wear. Alternatively, a form of a harmless increase in titanium may be seen from the use of paints (e.g. recent repainting of a casing exterior using aerosols). Most bright or reflective paints contain titanium dioxide as a brightener; however, the titanium from worn or dissolved paint is typically not near clearance size and therefore not likely to lead to wear.
A common misconception about titanium is the attribution of wear from titanium parts that are not oil-wetted, such as turbo manifolds or turbine blades. While these parts made be made from titanium, they are not in contact with the lubricant, nor is their wear debris expected to migrate to the engine oil.
Also, some oil manufactures may utilize Ti as an additive. The main purpose of using Ti as an additive is that it provides enhanced oxidation resistance and protection against engine wear. However, based on the bulk oil this customer listed, it wouldn’t have suggested that a Ti additive was used.
Triggered SEM-EDS Test
Based on these elevated results, we triggered an SEM-EDS analysis to determine the source of the titanium and high lead values. What the analysis found was that the lead appeared to have been leached, as no lead bearing material was present. The titanium was confirmed to be the result of additive carryover. The vast majority of particles present were additive related – ashed and degraded anti-wear add-pack. Upon investigation we found that the customer had recently switched away from an oil which had titanium as an additive. The new oil only appeared to still be the initial fill as it only had 600 hours on it, but what was likely happening was small top ups were being done with the previous engine oil leading to the heightened titanium values. In short, there wasn’t anything for the customer to be significantly worried about. This potentially saved hundreds of dollars in maintenance costs as an oil change was not required.
As this example shows, these are the types of situations where automatic triggered testing, like SEM-EDS analysis, can definitively answer questions related to elevated wear and contamination. If you would like to review your current oil analysis flagging limits and set up automated trigger testing, contact us. We will work with you to determine the best balance of alerts and triggers to suit your needs.