Moving Beyond Detection to Deliver Reliability

For maintenance managers and reliability professionals, identifying a problem is only the beginning. The real objective is preventing it from happening again.

In demanding industries with processing and manufacturing equipment that operate under high loads, harsh environments, and tight production schedules, when a gearbox, hydraulic system, or bearing fails, the cost extends far beyond replacement parts. Uptime, safety, and production are on the line.

Oil analysis plays a critical role in early detection. But when advanced diagnostics are applied, it becomes a powerful tool for root cause investigation.

Routine Testing Identifies the Symptom

Standard oil analysis parameters like wear metals, contamination levels, viscosity, oxidation, and particle counts are essential for trending and early warning. They answer important questions like: Is wear increasing? Is contamination entering the system? Is the lubricant degrading prematurely?

However, for reliability engineers tasked with eliminating repeat failures, elevated iron levels or rising particle counts just aren’t enough. Those results identify the symptom – not the failure mechanism.

Understanding the mechanism is what drives corrective action to prevent future problems.

Filter Debris Analysis: Examining What the Filter Captures

In high-load applications common in production and manufacturing operations, significant wear debris is often captured by the filter before it can be detected in a standard oil sample.

Filter Debris Analysis retrieves and evaluates that trapped material, providing a clearer picture of active damage. Using Analytical Ferrography and Micropatch testing to examine particle size, morphology, and composition, analysts can determine whether the debris originates from rolling element fatigue, gear tooth spalling, severe sliding wear and even break-in conditions versus progressive failure.

For a maintenance manager, this level of detail supports informed, smarter decisions; to continue operating under monitoring, schedule a controlled shutdown, or take immediate action. It replaces guesswork with evidence.

Define the Wear Mode

Analytical Ferrography testing uses magnetic separation and microscopic examination to characterize wear particles in detail. This method distinguishes between wear modes and can answer these questions:

Are wear particles caused by rubbing wear during normal operation?
Is it cutting wear caused by abrasive contamination?
Is lubrication film failure causing severe sliding wear?
Is it fatigue wear caused by surface distress?
Are chemicals causing corrosive wear?

For facilities where contamination control and lubricant performance are critical, identifying the wear mode is often the turning point in a root cause investigation.

For example, severe sliding wear may indicate inadequate viscosity selection or excessive load. Cutting wear often traces back to contamination control deficiencies in breathers, seals, or overall maintenance practices. Fatigue wear may reveal misalignment or load distribution problems.

Without microscopic confirmation, these distinctions are difficult to make. With it, corrective actions become targeted and sustainable.

Microscopic Contaminant Identification: Finding the Entry Pathway

Contamination remains one of the leading root causes of equipment failure across all industries. Advanced microscopic analysis can identify:

• Silica from environmental dirt
• Process materials unique to processing and manufacturing facilities
• Fibers from filters or cleaning materials

Reliability managers can use this information to address ingress points, refine storage and handling practices, or adjust filtration strategies. Instead of repeatedly changing oil, facilities can eliminate the source.

Turning Data Into Reliability Strategy

For reliability engineers, the goal is not simply monitoring machine health – it is building a no-surprises culture around asset performance.

Advanced oil analysis techniques such as Filter Debris Analysis and Analytical Ferrography transform a condition monitoring program into a diagnostic partnership. They provide evidence-based insight that supports root cause analysis, justifies maintenance planning decisions, and reduces repeat failures.

In high-demand production environments, that distinction matters.

Oil carries the story of what is happening inside your equipment. When you look beyond the numbers and examine the evidence, you move from reacting to failures to preventing them. And that is where real reliability gains are made.

One of the goals of Root Cause Analysis (RCA) is to identify the factors leading to an event that resulted in an undesired outcome and to develop corrective actions to prevent such results from recurring.

In maintenance, recognizing patterns during analysis can provide insights into severe outcomes, such as increased wear, which can be detected through ICP elemental analysis, elevated ferrous values by Particle Quantifier, or Ferrous Density.

It is crucial to differentiate the appropriate measures when conducting RCA. This can shift the analysis method entirely from immediately shutting down the equipment, using additional conditional monitoring technologies, or allowing other processes to assist in determining the root cause.

Technologies and Impact on the RCA Process

• Vibration Analysis can confirm a defect in the rolling element but, in some instances, only confirms the wear seen in your fluid report and can lead to a diagnosis to disassemble and replace
• Ultrasonic Analysis is more suitable for mobile equipment and offers higher advantages for slow-rotating equipment
• Thermography can indicate elevated temperatures of the running equipment

Despite these technologies providing dependable results, these tools cannot determine the amount or type of wear being presented. Fortunately, those familiar with the Analytical Ferrogram already have access to a tool to assist.

Since the fluid analysis should already be completed, the next step is to request that the Analytical Ferrogram test be performed. Tests should be requested within a reasonable time frame and recommended as soon as you get the fluid analysis results or within 30 days, depending on your fluid analysis laboratory.

This is due to how the wear metals in the fluid analysis report relate to the wear metals observed on the ferrogram. You could also submit a new sample to verify the elevated wear and request an analytical ferrogram on that sample.

A Picture is Worth a Thousand Words

Over the years, customers have used this process to determine whether disassembly is warranted. However, the average size of particles observed falls well below the visual size of what the eye can see, meaning the damage typically cannot be observed as easily once torn apart.

There needs to be more than just a visual inspection when determining wear, for example, within the United States Navy, where they implemented a Planned Maintenance System (PMS) involving scheduled intervals to disassemble equipment, inspect for wear (sometimes measuring it), and reassemble the components In many cases, the U.S. Navy observed no significant findings and repeated this process over time, eventually leading to the practice known as “gun decking” or “pencil whipping.”

During Analytical Ferrography, the laboratory analyst reviews the ferrogram under a microscope and interprets the results. This helps apply severity to the amount and type of wear observed, and depending on the analysts’ experience, the observation can assist in providing the needed interpretation to the customer.

Regarding microscope analysis, training on the microscope is needed to observe the debris and truly understand how the contaminants and wear debris were generated within the system. A few critical observations considered while analyzing include:

• The purpose of the requested ferrogram
• The customers (understanding) with control
• The equipment’s environment (clean, dirty, hot, cold, etc.)
• The equipment manufacturer and model
• The lubricant type and grade
• The additives used and their purpose

Most of these items can be found in any article on the web. Sometimes, the missing element in fluid analysis is the equipment’s duty cycle, which is more in the realm of the customer’s understanding than the laboratory analysis.

Most often, fluid time and unit time are the hallmarks of determining the relation of wear occurring. However, understanding the unit’s duty cycle is essential when analyzing wear under a microscope.

Analyzing the Duty Cycle

The duty cycle is called the run time versus rest time, on-off-on cycle. Depending on the equipment, the duty cycle can occasionally have more inputs.

Information like cycle time and the material being moved or loaded must be included. For an excavator, the duty cycle is defined as pre-digging, digging, lifting, unloading, and swinging. See Figure 1.

Figure 1 demonstrates an example of the swing portion of the excavator and wear that commonly occurs. Rubbing wear (2 body wear) is normal as the gears will come into contact; the EP additive prevents welding when contact happens.

Next, the viscosity under load will react, slowing the contact and transmit power. However, when the slew bearing wears, it increases loading for the gear box. Excessive backlash will also increase wear and overload the lubricant’s protection ability.

This can create three-body wear, usually in the form of fatigue particles or an elevated number of laminar particles formed by flattening larger particles between surfaces.

In the example seen in Figure 2, a wheel loader duty cycle, which is the time it takes to drive forward into the mound, scoop, reverse, swing loaded dump, and repeat.

Figure 2 illustrates that the lubricant facilitates power transmission and offers protection against wear and loading when necessary. However, due to usage, wear can still occur if the load capacity exceeds the lubricant’s limits.

By studying the relationship between wear and lubricant protection and incorporating the duty cycle process, one can better understand the wear patterns observed in the report.

Example Guide for Analyzing Ferrogram Results

A customer submitted a sample of a crane wheel, which was lubricated and on a routine maintenance schedule, and the laboratory performed an analytical ferrogram on the sample. A ferrogram identified why wear was occurring.

The results showed the equipment was experiencing rubbing wear, fatigue wear, and laminar wear. The crane wheel was a grease bearing with NGLI 2 with a 220 cSt base oil with an average air temperature for the crane of 110 to 125 degrees F.

The amount of rubbing wear and three body wear indicated the possibility that the base oil was not providing the necessary fluid film thickness at elevated temperatures and loading capacity.

In this case, the customer was recommended to contact the manufacturer about using a higher-viscosity base oil to provide more protection.

Fluid analysis laboratories offer a wealth of helpful information for interpreting the results of an analytical ferrogram. These valuable resources enable customers to take necessary maintenance actions to address current wear conditions and prevent them in the affected unit and other units within the fleet in the future.

References:

https://www.epa.gov/moves/epa-nonregulatory-nonroad-duty-cycles

What Is Microdieseling?

Microdieseling occurs when entrained air moves from low-pressure zones to high-pressure in a lubrication system, reaching localized temperatures above 1000°C and carbonizing the oil.

The term microdieseling got its name from the diesel engine. In a diesel engine, there is usually a rapid compression of air, which leads to an explosion. Similarly, during the degradation of an oil, there is firstly the introduction of entrained air into the oil. Typically, this entrained air moves from a low-pressure zone to a high-pressure zone.

During this transition, the entrained air produces localized temperatures above 1,000°C. While the trapped air is at this temperature, its outer surface is in contact with the lubricant.

As the lubricant around the bubble is exposed to this temperature, it becomes carbonized. The oil quickly darkens and produces carbon deposits since many entrained air bubbles undergo this process.

Eventually, the bubble will implode (or cause a small explosion). This is where the term “microdieseling effect” comes from, as the bubble undergoes a similar process to that of the diesel engine.

During microdieseling, the air will compress rapidly and eventually produce an explosion similar to the compression of air to create an explosion in a diesel engine. However, microdieseling has one more step, which heavily influences the type of deposits created.

 The Effects of Microdieseling

When microdieseling occurs, its final results can differ depending on the conditions experienced in the system. The entrained air will typically experience a low flash point (there is no need to worry about a fire risk here).

However, the bubble can either undergo a high or low implosion pressure. The type of implosion pressure makes a significant difference in the kind of deposit that is formed.

When the bubble undergoes a low flash point with a high implosion pressure, this is similar to a quick explosion. We can compare this to a bomb exploding.

In this case, ignition products of incomplete combustion form, such as soot, tars, and sludge. If we have an explosion, we will also have incomplete combustion of the items in the area, such as items that did not fully explode.

On the other hand, if the bubble undergoes a low flashpoint with a low implosion pressure, it experiences adiabatic compressive thermal heating. This will result in varnish insolubles such as coke, tars, and resins. Unlike a quick explosion, these products fully degrade to form these deposits.

Confirming The Presence of Microdieseling

Based on the types of deposits that form after microdieseling, it may be challenging to determine whether these are related to this mechanism. However, there is one tell-tale sign which usually takes place during microdieseling. This is cavitation.

Although cavitation is a mechanism experienced by pumps, it can also be seen in lubrication systems.

During microdieseling, there are small explosions of trapped air, which can significantly impact the internal surface of the equipment. As such, operators usually notice some form of cavitation in systems experiencing microdieseling.

Some laboratory tests can be employed to confirm the presence of the types of deposits. The FTIR (Fourier Transform Infrared) and QSA® (Quantitative Spectrophotometric Analysis) are helpful tools for confirming the presence of sludge, soot, tars, or resins in the oil.

Getting To the Root Cause

Now that the basics of microdieseling are covered, we need to identify if it is occurring in our system. The best way to figure this out is by using a logic tree and asking the right questions. We can start to build the logic tree by asking “How could?” instead of “Why?”. This is the beginning of the tree, as shown in Figure 1 below.

In this first part, we assume we are investigating an unplanned shutdown where a critical pump failure was the failure mode. We ask the question, “How could a critical pump have a failure?“. In this case, we are following the lubrication failure path (in a real investigation, there may be more than one failure mode).

As such, we hypothesize that there was a critical bearing failure due to lubrication degradation. This is where the question of “How could a critical bearing failure occur due to lubricant degradation?” is critical.

In a real investigation, several different degradation mechanisms can be investigated. However, for this example, we will investigate the degradation mechanism of microdieseling.

We ask the famous question, “How could microdieseling occur?“. Based on the information we gathered earlier in this article, we know that the main reason for microdieseling is the presence of entrained air moving through different pressure zones.

Hence, this becomes our next hypothesis, and we must again ask the question, “How could entrained air that moves through different pressure ones exist in our system?” which is investigated in Figure 2 below.

The second way occurs if air is introduced within the closed system. On the other hand, the third way involves having air leaks into the system. These will now be investigated by asking our famous “How could?” question.

We must investigate “How could air be introduced into a closed system?“. The first hypothesis which comes to mind is if we have air trapped in the system. As such, the air is already in the system, so it has not entered the closed system.

“How could air be trapped in the system?”. When thinking about a closed system, there are two main ways in which air can be trapped. If the lines were not bled before being used, any air in the lines can become trapped and result in entrained air in the system, or if the intake lines were positioned too high in relation to the adequate sump level to introduce air into the system.

At this time, a decision had to be made on whether to bleed the lines; this is where the line of questioning changes from “How could?” to “Why?”. In this step, we move from a physical root to a human or systemic root.

When asked, “Why were the lines not bled?” there are two general answers. The personnel carrying out this task lacked the experience or training for the proper procedure. In this case, we can drill down even further to explore why they did not have the proper expertise, but we will stop here as this is part of the investigation.

Or, there were inadequate (Less Than Adequate – LTA) procedures for bleeding the lines. This can be related to a systemic root where questions such as “Do the employees have access to the manuals?” or “Were these procedures detailed in the scope of works?” will be asked.

Another way air can be trapped in a closed system and lead to microdieseling is if air is being introduced into the system due to the positioning of the intake lines. If the sump levels are not properly aligned with the intake lines, air can enter the system. In this case, the system may have a design error, or the lines were not installed correctly during the initial setup.

These are just some of how air can be trapped in the system. Another hypothesis explores how air could be introduced into a closed system, as shown below in Figure 4.

Another way in which air can be introduced into the system is if the lubricant churns when it is re-entering the sump. There are a couple of ways in which this can happen.

The first way this can occur is if the lubricant creates a splash upon re-entering and introduces air into the system. Typically, this can happen if the lubricant viscosity is too high, causing a splash in a system that was not designed for it to splash or if the system was not adequately designed.

If we further investigate the hypothesis that the lubricant’s viscosity was too high, we can decipher the following in Figure 5.

The “How could?” question can lead us to two hypotheses when investigating whether the viscosity was too high and causing microdieseling. Either the OEM guidelines regarding viscosity were not followed, or the required viscosity was unavailable, and a heavier oil viscosity was substituted.

If we follow the hypothesis of the OEM guidelines not being followed, clearly, a decision was being made here. As such, the line of questioning changes from “How could?” to “Why?”.

There are two general reasons why the OEM guidelines would not be followed. The first reason is that the OEM guidelines do not exist. This is sometimes the case as OEMs may not always publish the required viscosity for the equipment and may say a general statement such as, “Use hydraulic oil.”

In these cases, it would be wise to contact the OEM directly and ask for guidance on choosing the most appropriate viscosity based on your system’s operating and environmental conditions.

The second reason for not following the OEM guidelines (which are more common in the industry) is that the site’s best practices were used instead. For instance, if only ISO 46 hydraulic oil is used on all the pumps, then it may be assumed that this pump should utilize that viscosity when that may not be true.

On the other hand, if the required viscosity was not available and a higher viscosity was substituted, another decision was also made here. Thus, the line of questioning changes again from “How could?” to “Why?”.

Not having the required viscosity is another common occurrence in the industry, and this may span three reasons. Either the supplier was unable to supply the correct viscosity, so the supplier should conduct their own root cause analysis to determine where their challenges lie.

Or, Warehousing dispatched the wrong viscosity, which can occur if there is an inadequate procedure for dispatching lubricants or an inadequate procedure for ensuring the correct lubricant is received by operations or maintenance. In these cases, the errors are more systematic as there are no proper checks to ensure the product is dispatched or received correctly.

Another reason the required viscosity is unavailable is if the site did not have the required viscosity at its location. This can be a result of inadequate ordering procedures or inventory checks such that they are not aware of the quantity of lubricants they physically have or how much they need.

Two other hypotheses should be investigated regarding the churning of the lubricant as it re-enters the sump, as seen in Figure 6.

There are three main reasons for a lubricant to churn as it re-enters the sump. The first reason with the viscosity being too high was covered above. The second reason involves the placement of the return line to the sump.

If this is too high or at a steep angle, it can allow the lubricant to flow at an accelerated rate back into the sump, resulting in churning. This can result from a poorly designed system, which is a systemic cause.

On the other hand, if the actual return flow rate of the lubricant has been set to a higher value, this can also cause churning in the sump. No decisions have yet been made, so the line of questioning remains at “How could?”.

This leads to three new hypotheses: the first can be an inadequate system design. This aspect of the system may have been overlooked by the designers initially, and they were unaware of the results of this increased flow rate back to the sump.

Another hypothesis can suggest that the lubricant flow rate was adjusted to compensate for some other issue in the system. Typically, this is done to allow for faster cooling in certain areas, which can help maintain the system temperatures and avoid overheating. In this case, there may not have been an adequate procedure for adjusting the lubricant flow rates, which reverts to a systemic microdieseling cause.

The last hypothesis centers on the OEM guidelines about the lubricant flow rate not being followed. In this instance, a decision was made, so the question becomes, “Why?” instead of “How could?”.

Two main reasons exist why the OEM guidelines weren’t followed. The first is that the OEM guidelines do not exist. This can be very common as not all OEMs may have designed the entire system.

The other reason is that the site’s best practices were followed. Usually, this is the case when these site’s practices were used in the past without any challenges to the equipment. This is another systemic cause that can be noted in this logic tree.

Reverting to the top of the tree again, one hypothesis investigated whether “Air leaks into the system” could result from entrained air in the system. This was the last hypothesis under the main hypothesis, as seen below and in Figure 7:

Entrained air moving through different pressure zones can lead to the introduction of air within the closed system, varying pressure zones, air leaks into the system

When we think about air leaks into the system, there is one main way this can occur. There must be an opening along the lubrication system, which allows air to enter the system. Now, we ask, “How could there be an opening?”.

One of the main ways for an opening to occur along a closed system is that there is a damaged component, such as a seal or some other component. Again, “How could we have a damaged component?” arises.

The first hypothesis is that the component has been damaged during its lifetime. The investigation has veered away from the lubricant aspect and dived heavily into the mechanical area. A component can be physically damaged in four main ways: wear, fatigue, corrosion, or overload.

These will not be investigated further in this example, but in the actual microdieseling investigation, an expert should assess which failures occurred and how. This will give more depth to the tree and provide more root causes.

The second way we can have a damaged component is if it was defective in the first place; this is shown in Figure 8 below.

If the OEM supplied it, they need to perform quality inspections before any components leave their facility. This is something that a lot of the larger OEMs may enforce, so it would be a good idea to contact them and look at their past inspections during your investigation.

On the other hand, the component can also become damaged while on the customer’s site. There may be inadequate inspections to verify the integrity of the components before they are installed into the equipment. This is yet another systemic root cause that we have uncovered.

The Final Root Causes

From the above exercise, we can determine many root causes when microdieseling is involved. The essential factor to remember is to investigate why the air gets entrained into the system, which has varying pressures.

The line of questioning is critical in uncovering exactly “How could?” this happen, based on the facts of the system and not opinions. Some oil analysis tests can help determine the presence of microdieseling, but we need to get to the root causes before the issue is solved.

This is a list of the suggested root causes for this investigation, which will differ based on varying equipment (where LTA – Less Than Adequate):

• Defective components
  • LTA quality inspections at OEM facility
  • LTA inspections for the integrity of components
• Viscosity too high, causing a splash in the designed system
  • OEM guidelines regarding viscosity did not exist
  • The site’s best practices were used, replacing OEM-recommended guidelines
  • Supplier unable to supply correct viscosity
  • Warehousing dispatched the wrong viscosity
    • LTA procedure for dispatching lubricants by warehouse
    • LTA procedure for ensuring correct lubricants received by operations/maintenance
  • The site did not have the available viscosity
    • LTA ordering procedure & Inventory Checks
  • Lubricant return flow rate is too high
    • Lubricant flow rate adjusted to compensate for another issue
      • LTA procedure for adjusting lubricant flow rate
    • OEM guidelines were not followed regarding lubricant flow rate
      • No OEM guidelines existed
      • The site’s guidelines were used successfully on similar types of equipment in the past
    • LTA system design
  • Air trapped in the system
    • Lines have not been bled before use
      • Lack of experience/training in the proper procedure for this equipment
      • LTA procedures for bleeding lines
    • Intake lines positioned too high in relation to the adequate sump level and introduces air into the system
      • LTA Intake line/system design

Here’s a handy Guideline RCA Tree for Microdieseling.

References:

Latino, Bob, Sanya Mathura. 2021. Lubrication Degradation – Getting into the Root Causes. CRC Press, Taylor & Francis.

Typically, when an oil undergoes degradation, the first culprit to be blamed is oxidation. We often hear that the oil has oxidized, producing varnish, leading to its degradation. While this simple statement may seem plausible, it is not the only way oil can degrade.

If an oil has undergone oxidation, the real question we should be asking is not how much varnish has been produced but what caused the oxidation in the first place?

In this article, we will explore the various ways in which an oil can degrade via oxidation. However, as you know from previous articles, other degradation methods exist.

How Can Oxidation Occur?

Before diving further into the root cause of oxidation, one must first fully understand how oxidation occurs. When truly investigating a root cause for a failure, we should start with the question “How could?” rather than “Why?”.

This line of questioning heavily influences the answers. The “How could?” responses stem from a more evidence-based approach.

On the contrary, if we question “Why?” this is more opinionated and can mislead the investigation towards a biased opinion rather than the facts.

This leads us to the main question, “How can oxidation occur?”.

According to Ameye, Wooton, and Livingstone, 2015, oxidation occurs when there is any reaction in which electrons are transferred from one molecule. Ideally, in oxidation, during the initiation phase, free radicals are formed, which in turn produce more free radicals.

A free radical is a molecular fragment with one or more unpaired electrons which are accessible and can easily react with other hydrocarbons, as explained by Ameye, Wooton, and Livingstone, 2015.

After the initiation phase, which has the free radicals, the propagation phase follows, in which the antioxidants react with these free radicals to make them more stable. This is part of the reaction in which there is usually a drastic depletion of antioxidants or where the oil becomes sacrificial.

The antioxidants act as a barrier to protect the base oil from oxidizing. However, they can no longer protect the base oil once they become depleted. This leads to the termination phase, where the remaining free radicals attack the base oil.

As a result, this gives rise to the condensation phase, where we begin to physically notice the changes in the oil’s viscosity and the presence of insoluble by-products. These are the deposits that are known are lube oil varnish to some but can further be defined by their chemical composition.

Understanding how oxidation occurs can assist us in determining the root cause when an oil degrades. It allows us to identify the different stages to further help us determine if it is indeed oxidation that is occurring or not.

What Evidence Is Needed?

However, understanding the oxidation process is just one part of the puzzle. When performing an investigation, we also need to know what factors or characteristics should be present. Additionally, we need to prove that their presence confirms our hypothesis of whether or not oxidation is occurring. This is where the line of evidence-based questioning plays a significant role.

When oxidation occurs, it is usual to see the presence of aldehydes, ketones, hydroperoxides, and even carboxylic acids. These can be confirmed using the FTIR (Fourier Transform Infrared test).

Typically, one will also find some deposits in the system. These deposits can be further characterized and tested to determine their nature using FTIR. Their presence, however, may be confirmed using the MPC (Membrane Path Colorimetry, ASTMD7843) test.

Identifying the presence of the deposits and/or the compounds listed above can lead to the conclusion that oxidation has occurred.

Another critical characteristic of oxidation is the depletion of antioxidants. This can be easily identified by utilizing the RULER® (Remaining Useful Life Evaluation Routine) test. This test quantifies the remaining antioxidants in the oil and gives the value for the amines and phenols (which is very important, especially in synergistic mixtures).

As such, one can detect the trend in the depletion of antioxidants and implement measures to prevent this before they become depleted.

The main tests to assist in determining the presence of Oxidation include:

RULER (Remaining Useful Life Evaluation Routine) levels less than 25% compared to new oil. This value represents the level of antioxidants in the oil. Hence, low levels indicate that the antioxidants are decreasing, possibly due to oxidation. This test can accurately give information on whether oxidation is currently occurring in the oil before deposits are formed.

An increase in acid number indicates the presence of acids resulting from oxidation. However, it must be noted that this change in acid number only occurs after oxidation has taken place. Hence this test is not a good indicator to determine if oxidation is occurring; instead, it is more definitive in letting us know that oxidation has already occurred.

Rapid color changes – darkening of the oil due to the deposits being present. While color is not the best indicator, in some instances, the darkening of the oil can provide a bystander to ask whether something is occurring in the oil. It is not a definitive test for the presence of oxidation.

FTIR test (Fourier Transform Infrared) for the presence of insolubles formed during the oxidation reaction. This can accurately determine the presence of any compound to assist us in determining whether oxidation is occurring.

MPC (Membrane Patch Colorimetry) levels outside the normal range (above 20). This lets us know that insoluble deposits are present in the oil. One must note that there may be instances where the deposits might not appear in the MPC test. As such, this should not be a standalone test to determine the presence of deposits.

RPVOT (Rotating Pressure Vessel Oxidation Test) levels are less than 25% compared to new oil (this is the warning limit). This is the industry standard, but this test does not have a high repeatability value in that if the same test were performed on identical samples, the values would be different. Additionally, the value (reported in minutes) is not easily translated into the environment of the components.

These tests provide us with the evidence we need to determine the presence of oxidation when performing the root cause analysis on the component’s failure.

Determining the Root Causes

Finally, we’ve arrived at the point where we can effectively determine the root cause. It is critical that the analyst understands oxidation and has knowledge of the evidence needed before embarking on the root cause journey. As noted in the first part of this article, the question we should ask is, “How could?”.

We hypothesize that oxidation is occurring. In a complete root cause analysis, we should hypothesize the occurrence of all the degradation mechanisms and eliminate them with evidence-based data.

There are two main ways in which oxidation can occur either through the presence of oxygen and temperature over the normal operating temperature of the system or if there is a less-than-adequate presence of antioxidants.

If we follow our line of questioning with the presence of oxygen and temperature and again ask, “How could?” we can get two primary responses. Either there was an air leak in the system, or the system was being pushed beyond its operating limits.

If we further investigate the air leak into the system, we ask, “How could it?” again. There are two main ways: either there are damaged components, or a less-than-adequate system design allows air to enter the system.

If we follow the pathway of investigating “how could” the system be pushed beyond its operating limits, then we can come up with two hypotheses. Either an increase in production was required, or there was a malfunction of the components, which caused strain on the other components.

Both of these hypotheses are physical and can be investigated further, but we will focus on the lubricant aspect of this article. Hence, we will follow the questioning surrounding the less-than-adequate presence of antioxidants.

We begin with the question, “How could we have a less-than-adequate presence of antioxidants?”. From the information gathered in this article, we know this can result from free radicals or less than adequate lubricant specifications.

We will investigate the “Presence of free radicals” first.

“How could we have the presence of free radicals?” Free radicals can emerge as a result of chemical reactions.

“How could these chemical reactions produce free radicals?” There are two main ways in which this can occur. Either the lubricant got contaminated, which introduced catalysts for these chemical reactions, or adverse operating conditions gave rise to these chemical reactions.

Then, we must ask again, “How could we have contamination?” Contamination can occur if leaks are getting into a closed lubrication system or if there is ingress of foreign material from the environment.

Our line of questioning continues when we ask, “How could we have leaks in a closed lubrication system?”. These can result from damaged components or seals allowing leaks into the system or if the system is less than adequately designed.

These are physical attributes of the system, so we will go back to investigating the lubricant aspect.

This is where we get to ask our famous question, “How could we have ingress of foreign material from the environment?”. Ideally, this can be classified in three ways;

1. There are openings which are allowing materials to enter the system or
2. Wrong lubricant was placed in the system or
3. Contaminated lubricant was placed in the system

Let’s investigate all three aspects, starting with the openings allowing foreign material to enter the system. There are two main ways in which this can occur. Either the openings were not closed after use, or the safety latches malfunctioned.

Suppose the openings were not closed after use. In that case, there is a possibility that there were less than adequate inspections to verify that these were closed after use or a less than adequate procedure for the task being completed which required the opening of the hatch.

On the other hand, if the safety latches malfunctioned, this could result from less than adequate checks to verify the functioning of the safety latches.

In these cases, the root causes are not the physical elements but rather the systemic reasons for these procedures not being adequately performed.

Now we investigate the second central hypothesis, “How could the wrong lubricant be placed in the system?” While there are many ways in which this can occur, we have narrowed it down to two main areas.

Either there were less than adequate checks to verify that the technician received the correct lubricant, or there were less than adequate procedures to dispatch the correct lubricant from the warehouse. We will not go further into these two as they are now systemic causes that must be addressed.

Onto the third hypothesis of “How could a contaminated lubricant be placed in the system?”. There are two main avenues for this to occur. Either there were improper storage and handling procedures, or there needed to be more adequate procedures to verify the cleanliness of the lubricant before entering the system.

The other hypothesis stemming from the “less than the adequate presence of antioxidants” is having “less than adequate lubricant specifications.” Let’s investigate this one a bit further.

“How could we have a less than adequate lubricant specification?” Typically, this can result from the lubricant not being blended properly or less than adequate antioxidant levels, which were inappropriate to protect the lubricant.

Now, the line of questioning changes to “Why?” as we have gone past the physical element and some decision-making was involved in this hypothesis. We must ask, “Why wasn’t the lubricant blended properly?”

This can result from less than adequate procedures to ensure the quality of the lubricant by the supplier or less than sufficient checks for the proper blending mix being processed.

These are factors one should consider when receiving any lubricant from their supplier.

On the other hand, if we follow the line of questioning of “How could there be a less than adequate antioxidant level to protect the lubricant?” we can come up with the following.

Either the operating environment caused the antioxidants to be depleted at a higher rate. This would be as a result of a harsh but normal operating environment. In this case, we may be unable to make those environmental changes (without the OEM’s consent).

Or the antioxidants used were not suited to the operating conditions. This is where the line of questioning again shifts to “Why were they not suited?”. This could result from inadequate information in choosing the right lubricant suited for the system.

What Is the Real Root Cause of Oxidation?

From the logic tree that we have created, we can see that there is no sole root cause for oxidation. It can stem from various causes, including physical, human, and even systemic roots. The main takeaway from this exercise is to acknowledge that root causes are not limited to physical causes, such as leaks in the system.

Instead, the actual root causes can be linked to systemic areas of concern where there may not have been enough information to guide the analyst in choosing the most ideally suited lubricant for the application. There are also root causes related to the lubricant not being appropriately blended.

It is critical to thoroughly investigate the real root causes when the lubricant becomes degraded to avoid being stuck in the loop of constantly experiencing degradation.

For more info on other methods, check out the book Bob Latino, and I authored called “Lubrication Degradation – Getting Into the Root Causes,” published by CRC Press.

References:

Ameye, Jo, Dave Wooton, and Greg Livingstone. 2015. Antioxidant Monitoring as Part of a Lubricant Diagnostics – A Luxury or Necessity. Rosenheim, Germany. February 2015.

Latino, Bob, Sanya Mathura. 2021. Lubrication Degradation – Getting into the Root Causes. CRC Press, Taylor & Francis.