Whether we realize this or not, oil refineries are critical in our everyday lives. They convert crude products into diesel, gasoline, LPG, and plastics. The equipment in this plant must withstand very high temperatures, sometimes over 500°C (in the distillation unit).

The lubrication systems in these plants also must withstand very harsh environmental conditions. Quite often, the bearing temperatures in critical compressors may increase to over 100°C, threatening a trip or shutdown. Unplanned downtime reduces refinery output and may cost a refinery up to Euro 1.2 M/day. All of this can be avoided by maintaining the quality of the lubricants.

Why Varnish Threatens Refinery Operations

Varnish, lubricant-derived system deposits occur in most types of equipment. It plates out as deposits on the insides of the equipment, which will act as a thick layer of insulator, preventing heat from escaping. One of the main functions of oil is to provide cooling to the equipment by transferring heat away from the internals of the equipment. However, with the formation of varnish, this function of the oil is eliminated.

Essentially, varnish can be described as polar compounds that have been formed as a result of the degradation of oil. There are various ways in which oil can degrade to produce deposits. As such, varnish can have varying characteristics depending on the system’s conditions, the formulation of the oil, and any contaminants that may be present in the system.

Despite the way varnish was created, some aspects remain the same. The presence of varnish can cause the sticking of valves or impact the efficiency of heat exchangers. Given the small clearances for hydraulic or other precision equipment (such as turbines or in bearings), any deposits inside these components can affect oil flow.

This results in elevated temperatures, which further increase thermal stress on the oil, thereby establishing a continuous feedback loop.

Varnish buildup creates a feedback loop of rising temperatures and increased stress on oil.

According to the varnish lifecycle illustrated in Figure 1, varnish can precipitate in and out of the solution even after oxidation has occurred.

From this lifecycle, it is clear that the double arrows are used between the solubility and varnish formation stages. As such, even if varnish is formed and deposited using the right technologies, it is possible that it can be redissolved into the oil.

In compressor applications, its bearings are the most critical place for varnish to form. This occurs in the minimum film thickness zone, as seen in Figure 2.

As per (Jang, Khonsari, Soto, & Livingstone, 2024), one can predict the effect of varnish on bearing performance by solving the Reynolds equation for pressure distributions with the mass conservation algorithm coupled with the energy equation through viscosity. However, this method was not utilized at the refinery.

Based on the study by (Jang, Khonsari, Soto, & Livingstone, 2024), the maximum pressure decreases when the varnish size extends circumferentially at a given varnish thickness, but the temperature remains relatively constant.

Case Study: How TÜPRAŞ Tackled Varnish Issues

Tüpraş is Turkey’s largest oil refiner, and it is located in western Turkey. It manufactures LPG, gasoline, jet fuel, and diesel fuel. They experienced trips on their compressor in the Kırıkkale Refinery, which has a mid-level complexity by Mediterranean Standards, including hydrocracker, isomerization, diesel sulphurization, and CCR reformer units.

The Kırıkkale Refinery has an annual crude oil processing capacity of 5.4 M tonnes, and its supply is carried by the BOTAȘ’ Ceyhan Terminal and Ceyhan- Kırıkkale pipeline. It was established in 1986 to meet the petroleum demands of the Ankara, Central Anatolia, Eastern Mediterranean, and Eastern Black Sea regions.

The K1151 compressor (RB5B Thermodyne compressor) in the Kırıkkale Refinery is critical to the Crude oil processing and isomerization unit. Every time this asset trips, the facility undergoes maintenance and repairs, typically lasting seven business days. This issue may occur at least 4 times annually, and each trip costs roughly around USD274k per event.

A trip usually occurs when the bearing temperature goes above 115°C, however, based on the history of the machine, the temperatures typically see a spike to 100°C followed by a rapid increase to 115°C.

For this compressor, it was also noticed that there were sawtooth-like temperature patterns where the values fluctuated between 76-86°C, as shown in Figure 3 below. The “safe zone” of operation for the bearings is less than 89°C.

This sawtooth temperature pattern is typically seen in instances where there is varnish buildup on bearings or shafts. Usually, the varnish builds up layer by layer, acting as an insulator, which causes the temperatures to increase.

Eventually, the buildup will get to a point where the shaft wipes away the varnish, resulting in a plunge in temperature, forming this sawtooth pattern. This repeats constantly until the varnish is either removed from the system or shut down so it can be removed.

After dismantling the NDE (Non-Drive End) bearing, varnish was found along the shaft and the actual bearing, as shown in Figures 4 and 5 below.

Interestingly enough, the bearings gave different temperature readings for this component. TI 633 showed slightly different readings compared to TI 632 mainly because of where they are positioned on the bearing, as these pads had varying levels of varnish on them, as shown below in Figure 6.

The refinery elected to add Fluitec’s DECON to the system during operation to provide immediate temperature relief to the bearing. DECON enhances the solubility of the oil, which does two things:

1. It dissolves varnish throughout the system, and in this case, specifically in the bearings and shaft.
2. It prevents future varnish from forming again.

Solubility enhancers are soluble in the oil and can react with already degraded products (deposits or varnish) to make them soluble in the oil. In this way, the degraded products are not allowed to agglomerate into the layers of deposits and remain in the oil as inert, harmless products.

After Fluitec’s DECON was added to the system, the compressor saw an immediate decline in temperature from 101°C to 93°C and continued to decline afterward. Currently, this bearing is operating in the temperature range of 63°C. The highest temperature experienced by the system is 73°C, which is significantly below their “safe-zone” temperatures of 89°C.

After adding DECON, compressor bearing temperatures dropped from 101°C to 63°C.

Since adding DECON to their system, they have not had any other trips due to rapid temperature increases, and their bearings now operate below the maximum threshold temperature range.

Tüpraş is committed to sustainability and aims to be carbon-neutral by 2050. The company focuses on innovative technologies and digital transformation to enhance operational efficiency and reduce carbon emissions. DECON is consistent with their organization’s objectives as it significantly improves compressor efficiency while increasing operational reliability.

Using Fluitec’s Value Impact Calculator, it is estimated that 32 tons of CO2e will be reduced from their operation over 5 years simply by optimizing the life and performance of their lubricant.

References

Jang, J. Y., Khonsari, M. M., Soto, C., & Livingstone, G. (2024). Effect of varnish on the performance and stability of journal bearings. Tribology International, Volume 198.

In a Middle Eastern refinery, a newly commissioned fire water pump, crucial for emergency services, experienced repeated high temperatures at the non-drive end (NDE) bearing during periodic test runs. Over time, these temperature spikes eventually led to a premature bearing failure, sparking a detailed investigation that revealed a lubrication issue.

The root cause? Oil starvation, despite the constant level oiler showing a seemingly adequate oil level.

Uncovering the Lubrication Problem

The investigation raised a critical question: Why did the bearing lack lubrication even when the sight glass of the constant level oiler indicated the correct oil level? The answer pointed to a fundamental issue – incorrect orientation of the piping connected to the constant level oiler during the construction phase.

Understanding Constant Level Oilers and Installation Errors

Constant level oilers are designed to automatically maintain the correct oil level in the bearings to prevent both over and under-lubrication. Their effectiveness, however, relies entirely on precise installation. In this case, despite the oiler indicating a full level, the incorrect orientation of the piping prevented oil from reaching the bearing, ultimately causing overheating and failure.

The Importance of Proper Installation

Any failure can have catastrophic consequences for critical equipment like fire water pumps, which serve an emergency function. If this issue had gone unnoticed, the fire water pump could have failed during an actual emergency, putting the entire refinery at risk of a major fire.

The root cause investigation clearly highlighted that the construction contractor did not follow the vendor’s recommendation regarding the orientation of the constant level oiler piping. Manufacturers provide precise instructions for a reason – deviations from these instructions can result in operational issues and critical equipment failure in cases like this.

Once the constant level oiler piping was corrected and aligned per the manufacturer’s drawings, the pump operated smoothly without further bearing temperature issues. The problem was resolved, but it emphasized the importance of attention to detail during critical equipment’s construction and commissioning phases, which is often overlooked.

Lessons Learned

This incident highlighted several key lessons to improve reliability and avoid similar failures in the future:

1. Strict Adherence to Vendor Guidelines: Construction contractors must follow detailed instructions from equipment manufacturers for correctly installing equipment and associated piping. This attention to detail ensures the equipment performs as intended without introducing avoidable risks. Deviations from these guidelines can lead to operational failures and increased risks
2. Peer Review and Construction Audits: Conduct peer reviews and audits during installation to ensure all equipment and piping are installed correctly according to the vendor’s recommendations. Construction audits, focusing on equipment and piping per these vendor guidelines, can catch mistakes early and prevent costly failures later.
3. Proactive Inspections: After this incident, the refinery proactively inspected all the fire water pumps to verify the correct installation of their oilers. This proactive approach is necessary to avoid similar failures and ensure emergency equipment is ready to perform when needed.

This case is a reminder that even minor oversights in equipment installation can lead to major consequences in high-stakes environments. The incorrect piping orientation might seem like a small error, but it can seriously affect critical systems. Ensuring that every component is correctly installed is essential to maintaining reliability and safety.

The lessons learned emphasize the importance of precision, strict adherence to standards, and thorough inspections, particularly during the early phases of the project, to ensure long-term reliable operation – principles that every engineer should practice in the field of lubrication and reliability.

Lubricants are the lifeblood of machinery, and every decision, from selection, purchase, storage, dispensing, and health management, plays a critical role in ensuring the reliable operation of essential machines. A minor oversight can lead to significant downtime, production losses, and costly repairs.

Recently, a major oil and gas company in the Middle East learned a lesson when a seemingly routine task resulted in an unplanned shutdown of a critical turbo-compressor, leading to a significant loss of production for five days.

What caused this costly shutdown? A simple activity of topping up new lubricant oil.

The Incident

It all began when the maintenance staff topped up the oil reservoir of their turbo-compressor with eight drums of what was believed to be ISO VG 46 turbine oil, freshly received from a well-known and trusted lubricant supplier.

The used oil in the reservoir was of the same oil brand, so there shouldn’t be a compatibility issue. This oil is standard for turbo-compressors, designed to perform under the high-speed, low-load conditions these machines typically operate in. The new oil drums were correctly labeled, and there was no initial reason for concern.

However, almost immediately after the oil top-up, the plant operator noticed a strange and troubling issue: frequent choking of the oil filter elements in the inline oil filtration system.

The filter elements were immediately replaced. However, the problem persisted, leading to the replacement of six sets of filter elements within a short period. Despite these repeated replacements, the issue remained unresolved, and the company was at the risk of depleting its entire stock of oil filter elements.

The Investigation: Uncovering the Truth

Faced with a potentially critical situation, the company launched an urgent investigation. The clogged filter elements were sent to a lab for filter analysis for quality assurance, and oil samples were taken from the oil reservoir and new oil drums and sent to a lab for detailed analysis. The findings were both surprising and alarming.

Despite the oil drums being labeled as ISO VG 46 turbine oil, further analysis revealed that they contained ISO 460 gear oil—a completely different product with vastly different characteristics.

ISO VG 46 turbine oil is a low-viscosity oil specifically engineered for the precise needs of turbo-compressors. On the other hand, ISO 460 gear oil is a high-viscosity lubricant designed for heavy-duty, high-load applications, such as in industrial gearboxes with entirely different additive packages, including EP additives.

Significant differences exist between these two types of oils, and using them interchangeably or getting them mixed accidentally is a sure recipe for disaster.

The higher viscosity of the ISO 460 gear oil was the root cause of the filter element clogging. The inline filtration system, designed for the much thinner ISO VG 46 oil, couldn’t cope with the thicker, more viscous gear oil. The filters were overwhelmed, leading to repeated clogging and the need for constant replacements.

The Resolution: A Painful but Necessary Shutdown

Once the root cause of the problem was identified, the company had no choice but to shut down the turbo-compressor entirely to prevent any catastrophic damage to the machinery. The company then urgently involved the oil supplier that arranged a fresh batch of new turbine oil ISO VG 46, ensuring its quality met specifications.

The labor-intensive process of draining the incorrect mixture of turbine and gear oil was conducted. After thoroughly flushing the system, it was refilled with the correct ISO VG 46 turbine oil. This process was time-consuming and expensive, resulting in significant operational downtime and financial loss.

Lessons Learned: The Importance of Vigilance in Lubricant Management

This incident raised a powerful reminder of the critical importance of thorough verification and testing of lubricants before use. Since rotating machinery reliability is significant in any industry, even a small mistake in lubricant specification can have major consequences.

Onsite Testing of Lubricants

One of the most critical lessons from this incident is the necessity of onsite testing of newly received lubricants. Even when dealing with reputable suppliers, verifying that the product inside the drum matches the specifications on the label is essential.

Simple onsite tests, such as viscosity checks, moisture content, and particle count, can quickly confirm whether the lubricant is appropriate for its intended application.

Developing Robust Receiving Procedures

Companies should develop and implement robust procedures for receiving lubricants. These procedures should include steps for verifying the product specifications, conducting oil sampling and testing, and ensuring that the supplier provides all relevant documentation, such as certificates of analysis and conformity.

Supplier Communication and Accountability

Clear communication with suppliers is crucial. Companies should insist on receiving a certificate of conformity with every shipment, which confirms that the product meets the required specifications. This ensures accountability and provides a traceable record in the event of any issues.

Regular Training for Staff

Ensuring that staff are regularly trained on the importance of lubricant verification and the potential consequences of using incorrect lubricants is vital. This training should be a part of the company’s overall reliability and maintenance strategy.

The High Cost of Small Mistakes

Attention to detail is crucial in fast-paced sectors such as the oil and gas industry, where unscheduled downtime would lead to significant financial implications. The incident at this Middle Eastern oil and gas company underscores the importance of lubricant Onsite verification in maintaining operational reliability.

By implementing robust receiving procedures, onsite testing, and clear communication with suppliers, companies can prevent similar incidents and ensure that their machinery continues to operate smoothly and efficiently.

Ultimately, this costly lesson highlights a simple truth: even the tiny details matter in industrial operations. Ensuring the right lubricant is used every time is not just good practice; it’s essential for maintaining the reliability and trouble-free performance of critical machinery.

Diesel engines are the driving force powering many modern transportation and industry applications. They can be found in vehicles and machinery, from trucks to marine vessels. In the port industry, diesel engines are found in Rubber Tire Gantry (RTG), Terminal Tractors, Reach Stackers, and other heavy mobile equipment.

Efficient engine function relies heavily on the combustion process that converts fuel into mechanical energy. High-quality combustion is crucial for optimal engine performance and overall reliability.

This article will not delve into the combustion reaction but into using engine oil analysis as a robust diagnosis and prognosis tool for monitoring combustion performance.

Oil Analysis: An Effective CBM Technique for Combustion Quality Monitoring

Oil analysis, as a CBM/PdM technique, is valuable for acquiring important information about the lubricant condition, wear, and contamination. It enables early failure detection, offering an opportunity for timely intervention.

Regular in-service engine oil analysis detects most of these issues as soon as they appear, often well before they become observable to the naked eye. With oil analysis data, maintenance managers or workshop supervisors can strategically plan interventions or conduct minor corrective maintenance actions instead of triggering a major intervention on the engine.

This article specifically addresses a singular aspect of engine oil contamination – namely, the suboptimal combustion by-products. Oil analysis is a valuable tool for identifying these by-products associated with poor combustion. It provides an opportunity to proactively address or mitigate the impact of:

Oil Degradation. Due to poor-quality combustion, the oil undergoes contamination from by-products of combustion or unburned fuel in the case of fuel dilution. These contaminants alter the physical and chemical characteristics of the oil and affect its performance properties.

Consequently, the oil fails to fulfill its lubrication and cooling functions. In the case of fuel dilution, the oil is thinned to the point where it cannot support the engine load or build a sufficient film to separate the moving parts. Additionally, poor combustion by-products act as catalysts for oxidation, enhancing oil degradation.

Engine Wear. Poor-quality combustion accelerates oil degradation. Therefore, the oil’s capacity to efficiently lubricate, cool, and protect the engine is diminished, increasing component stress and accelerating wear.

Decreased Engine Performance. Efficient combustion boosts the engine’s power output, providing better acceleration and overall performance. This efficiency ensures greater fuel conversion into usable energy, enhancing fuel efficiency. Conversely, poor combustion lowers fuel efficiency, increasing fuel consumption and operational expenses.

Safety Concerns. Fuel dilution lowers the oil’s flash point. When excessive fuel infiltrates the engine oil, it reduces the oil’s viscosity and increases its susceptibility to ignition. This presents a severe hazard, especially with the high engine temperatures.

Environment Pollution. Excessive soot emissions contribute to air pollution, as they contain harmful substances that can adversely affect air quality and human health. High-quality combustion reduces atmospheric emissions, contributing to environmental sustainability.

Tests Standards for Combustion Quality Monitoring

Two common indicators of incomplete combustion are fuel dilution and soot formation. There are many standards to help measure and monitor soot content and fuel dilution in in-service engine oils. Following are some essential tests for diesel engine combustion quality monitoring:

Soot Content

Soot, comprised of unburned combustion by-products, is found in oil as carbon, causing it to become thicker and darker.

Soot from diesel combustion is expected in an engine. No engine is 100 percent efficient. That’s why engine oil is doped with detergent/dispersant additives to enhance oil dispersancy.

Dispersancy is defined in ASTM D 7899 as the property that allows oil to suspend and carry away pollutants of diverse sources, such as soot from combustion, metallic particles from wear, corrosion of mechanical parts, and insoluble products resulting from the aging of the oil [1].

Excessive soot content signals potential issues with the components involved in combustion. These can be injection problems, prolonged oil drain intervals, low compression, high fuel/air ratio, and cold air temperatures.

Sometimes, elevated soot content is due to an excessive oil drain interval or operations practices like excessive idling.

Methods for testing soot in engine lubricating oil include:

• ASTM D7686, Standard Test Method for Field-Based Condition Monitoring of Soot in In-Service Lubricants Using a Fixed-Filter Infrared (IR) Instrument). This test method pertains to field-based monitoring of soot in diesel crankcase engine oils as well as in other types of engine oils where soot may contaminate the lubricant because of a blow-by due to incomplete combustion of fuels. It applies to oils having soot levels of up to 12% by mass [2].
• ASTM D7899, Standard Test Method for Measuring the Merit of Dispersancy of In-Service Engine Oils with Blotter Spot Method). This test method provides a simple technique for condition monitoring of the dispersancy property of in-service lubricants [1].
• ASTM D5967, Standard Test Method for Evaluation of Diesel Engine Oils in T-8 Diesel Engine, is a method for soot analysis by thermal gravimetric analysis.
• ASTM D7844-2 is the standard test method for condition monitoring of soot in in-service lubricants by trend analysis using Fourier Transform Infrared (FT-IR) spectrometry. This test method pertains to field-based monitoring of soot in diesel crankcase engine oils and other engine oils where soot may contaminate the lubricant because of a blow-by due to incomplete combustion of in-service fuels. This test method uses FT-IR spectroscopy to monitor soot buildup in in-service lubricants due to normal machinery operation. It is a fast, simple spectroscopic check for monitoring of soot in in-service lubricants to help diagnose the operational condition of the machine based on measuring the level of soot in the oil [3].
• ASTM E2412, Standard Practice for Condition Monitoring of In-Service Lubricants by Trend Analysis Using Fourier Transform Infrared (FT-IR) Spectrometry. This practice covers the use of FT-IR in monitoring additive depletion, contaminant buildup, and base stock degradation in machinery lubricants, hydraulic fluids, and other fluids used in regular machinery operation. Contaminants monitored include water, soot, ethylene glycol, fuels, and incorrect oil. Base stocks’ oxidation, nitration, and sulfonation are monitored as evidence of degradation [4].

These tests could directly confirm the presence of soot in engine oil, while other oil analysis tests play a contributing role in validating this issue. In this context, viscosity measured at 100°C for multigrade oils is a secondary test, as heightened soot content increases viscosity.

Additionally, elemental analysis can substantiate this degradation by evaluating the concentrations of wear metals resulting from inadequate lubrication as the oil undergoes degradation. Furthermore, as soot serves as an oxidation catalyst, oxidation levels and viscosity increase becomes apparent.

This confirms that oil analysis parameters are mutually complementary for a comprehensive and cohesive interpretation of oil analysis results.

Fuel Dilution

Fuel dilution occurs when the amount of unburned fuel in the engine oil increases. A high fuel dilution rate indicates an abnormal fuel passage into the oil. The predominant factor leading to fuel dilution involves infiltrating surplus fuel into the crankcase, which mixes with the engine oil.

With high fuel present in the oil, the lubricant’s viscosity becomes too low, reducing overall lubricating effectiveness. This phenomenon is often associated with raw or unburned fuel mixing with the oil resulting from incomplete combustion, worn injectors, or improper fuel/air ratio.

Sometimes, elevated fuel dilution could be due to operations like excessive idling.

The international standards to measure the amount of fuel present in oil include:

• ASTM D7593, Standard Test Method for Determination of Fuel Dilution for In-Service Engine Oils by Gas Chromatography.
• ASTM D 3524, Standard Test Method for Diesel Fuel Diluent in Used Diesel Engine Oils by Gas Chromatography. This test method uses gas chromatography to determine the amount of diesel fuel in used engine lubricating oil. It is limited to SAE 30 oil. The diesel fuel diluent is analyzed at concentrations up to 12 percent by mass. This test method may apply to higher viscosity grade oils. However, such oils were not included in the program used to develop the precision statement [5].
• ASTM E2412, Standard Practice for Condition Monitoring of In-Service Lubricants by Trend Analysis Using Fourier Transform Infrared (FT-IR) Spectrometry.

These tests confirm fuel dilution. Other oil analysis tests play a significant role in validating this issue. In this case, viscosity measured at 100°C for multigrade oils is a secondary test, as fuel dilution decreases viscosity. Likewise, reducing flash point serves as an additional means of confirming fuel dilution. Furthermore, a reduction in base number (BN) may indicate a significant fuel dilution.

Elemental analysis can also confirm this degradation by evaluating the concentrations of wear metals due to inadequate lubrication as the oil degrades. This analysis also provides helpful information about additive depletion.

Countermeasures for Poor Combustion Quality

Since poor combustion quality is connected with engine oil, to mitigate it, we should start by ensuring the fulfillment of the five’ rights’ of lubrication. First, we need to satisfy the Right Lubricant and Right Change Frequency. On the other hand, countermeasures to remedy poor quality involve supplying good fuel quality, checking air intake, and adjusting injection parameters. Consider these countermeasures:

• Lubricant Selection. Oils with low oxidation resistance tend to produce a precipitate more rapidly and in greater quantities than oil with high oxidation stability. Lubricants containing detergent and dispersant additives exhibit lower susceptibility to sedimentation because these additives enhance the capacity of the oil to retain insoluble impurities and resist oxidation more effectively. Make sure to use the appropriate lubricant and adhere to recommended oil specifications.
• Oil Change. A timely oil change is highly recommended. As detailed above, changing the oil as soon as possible is crucial, even for engines where soot contamination is detected without signs of wear. Soot can lead to complications over time.
• Air Filtration. A clogged or dirty filter can restrict airflow, affecting combustion. Inspect the air filter to ensure optimal combustion conditions.
• Fuel Quality. Fuel quality influences engine combustion. The heavier the fuel by fractional composition, the more it penetrates the crankcase. Adhere to recommended fuel specifications and use high-quality, clean fuel with the proper octane rating. This helps ensure a more efficient combustion process.
• Injection System Tune-up. Evaluate the air/fuel ratio and adjust the injection system to achieve a balanced mixture. Maintaining the correct air-fuel ratio is crucial for efficient combustion.
• Exhaust Monitoring: Monitor exhaust gases for evidence of incomplete combustion or unusual exhaust smoke. The presence of black smoke or a distinctive odor can indicate incomplete combustion.
• Operation Mode: The engine is most susceptible to inefficient combustion during light operation modes. These modes include minimal loads, low speeds, frequent and extended stops, and engine idling.

Case Study: Combustion Quality Monitoring for a Terminal Tractor Diesel Engine

Let’s explore a snippet from an engine oil analysis report of a terminal tractor with a cumulative operation time exceeding 110,000 Hours. During the criticality assessment, the terminal tractor diesel engine was identified as critical equipment.

An oil sample is drawn from this diesel engine every 500 running hours. The routine analysis slate includes the following parameters: Viscosity at 100°C, Base Number (BN), Water Content, Elemental Analysis, Fuel Dilution, Oxidation, Nitration, Sulfation, Glycol Content, and Soot Content.

Two oil analysis reports have been released so far. Given the focus on engine combustion efficiency in this case study, our attention in this oil analysis report will be directed towards associated with the monitoring of combustion quality, with a primary emphasis on Fuel Dilution and soot as primary tests for the engine combustion quality monitoring.

Additionally, viscosity and wear are serving as complementary tests. The table below provides a summary of these findings:

Analyzed by Gas Chromatography in accordance with ASTM D7593, the measurement of fuel dilution in both samples confirmed acceptable values, remaining below 2% by weight.

On the other hand, soot content in the first sample exceeded the acceptable range of 2 % by weight. However, no consequential increase in wear metals was observed, as their concentrations remain within acceptable limits.

In the second sample, there is a moderate concentration of iron, elevated Soot content, and high oil viscosity. These findings suggest a rich fuel mixture, generating soot that is highly abrasive and consequently contributing to engine wear.

The maintenance team has been advised to check the control points mentioned in the Countermeasures for Poor Combustion Quality section above. The feedback received confirms the satisfactory status of the requested inspections. This leads us to conclude that the elevated soot levels are primarily due to the extensive unit service time (+100,000 hours) and prolonged use of oil (+500 Hours).

According to the OEM, the oil should be replaced every 250 Hours. A subsequent sample will be drawn for condition monitoring and trending at the next scheduled interval. We expect to observe a notable reduction in soot levels and an overall enhancement in engine health.

References

[1] ASTM D7899-13: Standard Test Method for Measuring the Merit of Dispersancy of In-Service Engine Oils with Blotter Spot Method.

[2] ASTM D7686-19, Standard Test Method for Field-Based Condition Monitoring of Soot in In-Service Lubricants Using a Fixed-Filter Infrared (IR) Instrument).

[3] ASTM D7844-21 Standard Test Method for Condition Monitoring of Soot in In-Service Lubricants by Trend Analysis using Fourier Transform Infrared (FT-IR) Spectrometry.

[4] ASTM E2412-23 Standard Practice for Condition Monitoring of In-Service Lubricants by Trend Analysis Using Fourier Transform Infrared (FT-IR) Spectrometry.

[5] ASTM D 3524-14 (2020): Standard Test Method for Diesel Fuel Diluent in Used Diesel Engine Oils by Gas Chromatography.

Fluid analysis is a powerful tool in the preventive maintenance toolbox of many equipment and maintenance managers in industries ranging from construction to aggregates to mining to marine.

Efficiently managed programs provide considerable benefits that translate directly into maintenance cost savings for industries that rely on the operation of their equipment.

Performing routine testing and analysis on the fluids circulating through components within operational equipment gleans valuable insights into the health and condition of the fluid and equipment.

It identifies potential concerns before escalating to failure and optimizes downtime schedules – ultimately resulting in what may be substantial maintenance cost savings.

Acting on the maintenance recommendations included in a fluid analysis report can lead to less costly parts replacement instead of a complete rebuild and the ability to schedule equipment downtime.

When operating equipment, it’s inevitable to see some wear as the machine operates over time. One of the most valuable advantages of fluid analysis is detecting early signs of wear within equipment by analyzing wear particles within the oil.

With a powerful scientific microscope, analysts can pinpoint unusual shapes and colors and abnormal levels of wear particles, which can indicate the asset is suffering from problems such as bearing wear, which can lead to substantial further damage and costly repairs if not caught early.

Case Study 1. Sample Report Avoids $80,000 Engine Replacement

One of POLARIS Laboratories®’ customers in the marine industry was able to save the entire replacement of an engine by performing recommended actions on a high-severity lubricant analysis sample report.

After collecting an oil sample during a break in the oil change schedule, the company’s sample report returned at a high severity. Based on the test results and interpretation, the recommended maintenance action was to borescope the cylinders, which the team observed scoring on the cylinder liners.

The maintenance team proceeded to pull the head, piston, and liner of the cylinder that had the worst signs of scoring. While continuing to investigate the concern, it was observed that the bottom of the engine piston crown showed signs of deterioration.

After discovering this, a strategic maintenance decision was made to replace all six pistons, liners, and connecting rods.

As the company shares this story with POLARIS Laboratories®, it was noted that there were no other condition monitoring indications or alarms that showed there was an engine issue – the concern was only identified based on the test results and recommendations on the lubricant analysis sample report.

Without the sample report indicating abnormal wear and the suggestion to evaluate the cylinders, the problem would not have been identified. It would have led to a total engine loss and $80,000.

Case Study 2. Avoiding Downtime, Production Loss, and $260,000+ in Engine Loss

A POLARIS Laboratories® customer in the Aggregates industry has reported back to the laboratory millions of dollars in saved maintenance costs, replacements, and total engine rebuilds throughout their fluid analysis program.

As an aggregate company, equipment downtime in this industry can harm production, customer satisfaction, labor costs, and operations.

A coolant analysis report came back at a high freeze point, which, if not addressed, would have caused the engine block to freeze, resulting in a complete engine replacement of $135,000 (this does not include the downtime if the asset was out of production for repairs).

In another instance, the company avoided a complete axle rebuild that would have cost $50,000 by addressing a simple issue and replacing the oil after a lubricant analysis report came back with results indicating a leak in the axle, resulting in dirt contamination causing wear.

A recent equipment save through oil analysis for the company involved receiving a report back indicating high lead levels. The team proactively replaced the NRS coolers before the engine could experience failure – a failure that would have cost the company $75,000 to repair, plus the additional downtime loss.

To sum it up, fluid analysis is a proactive, preventive, predictive, and cost-effective condition monitoring tool that is proven to minimize unexpected and un-budgeted maintenance costs by detecting signs of early wear and contamination.

Through interpreting test results and maintenance recommendations provided by the data analysts, maintenance and equipment managers can take action before failure has a chance.

In addition, embracing fluid analysis as part of a comprehensive preventive maintenance program with direct integration into your maintenance management software is an investment that has the potential to pay off in both the short-term and long-term.

Do you have the right tools in your toolbox today to impact your bottom line? Fluid analysis is the perfect tool!

Wear monitoring is one of the primary objectives of oil analysis for predictive maintenance. Many oil analysis tests are considered suitable for wear debris analysis, and some, like elemental analysis and Wear Particle Index, are recommended within routine analytical slates.

Others, like Analytical Ferrography, are only requested occasionally and are typically reserved for in-depth investigations whenever required.

Elemental Analysis

Elemental analysis is a part of almost all routine oil analysis test slates across many applications. It is a cornerstone of lubricant analysis and a powerful ally for wear detection at early stages.

Inductively Coupled Plasma (ICP) or Rotating Disc Electrode (RDE) are the most common analysis methods for conducting elemental analysis for used lubricants, and they are performed respectively per ASTM D5185 and ASTM D6595.

Elemental analysis is a standard method used to determine quickly and in one single measurement the concentration of various elements within an oil sample.

It identifies and quantifies at low parts per million (ppm) concentrations for at least 21 elements: Iron (Fe), Copper (Cu), Aluminum (Al), Chromium (Cr), Nickel (Ni), Lead (Pb), Silver (Ag), Tin (Sn), Silicon (Si), Sodium (Na), Potassium (K), Magnesium (Mg), Calcium (Ca), Phosphorus (P), Zinc (Zn), Boron (B), Molybdenum (Mo), Titanium (Ti), Vanadium (V), Barium (Ba), Sulfur (S).

Oil analysis professionals can monitor the levels of wear metals, additives, and some contaminants through elemental analysis. This helps assess the condition of oil and equipment and identify potential issues, such as contamination, additives depletion, or excessive wear.

However, it is essential to acknowledge the inherent limitations of elemental analysis. The ICP technique can detect elements accurately (with high repeatability) if the elements are below five microns in size, with repeatability tailing off for particles approaching and exceeding seven microns.

The RDE technique also provides confidence for detection up to a five µm size range, with detectability tailing off as particles exceed 10 microns. For RDE and ICP techniques, particle size visibility can vary by element type, such as copper and chromium.

While the accuracy of the analysis can be influenced by factors such as sample handling and instrument calibration, these techniques (ICP and RDE) are considered the preferred means for routine wear debris assessment for commercial labs.

Considering these constraints, most laboratories complement elemental analysis with additional test methods that detect particles beyond the incipient wear range (>5 µm size).

In the context of gearbox oil analysis, techniques like Particle Quantification and Ferrographic Analysis are complementary tools that provide a more holistic approach to monitoring gearbox condition.

Ferrous Density Analysis

The most prevalent and affordable method for assessing ferrous density is Particle Quantification Index (PQI), also known as Wear Particle Index (WPI).

This test directly quantifies the magnetic mass of ferrous debris in the oil sample, regardless of particle size and shape. It provides a non-dimensional value representing the total amount of the existing ferrous debris in the sample.

PQI is a powerful tool for wear detection, monitoring ferrous particles larger than the elemental analysis detection range.

In this regard, PQI is an invaluable complementary test to elemental analysis.

Performed per ASTM D8184, Particle Quantifier Index is recommended as a routine test for all types of industrial, mining, shipping, and aviation equipment.

Direct Read Ferrography (DRF) is another cost-effective technique for characterizing the wear concentrations of larger-size particles.

By leveraging the magnetic susceptibility of particles, DRF enables the calculation of the Wear Severity Index based on a direct reading of both large and small particles. Consequently, DRF can serve as a suitable alternative to PQI.

Analytical Ferrography

It is helpful to understand the underlying reason (the wear mode) whenever elemental analysis, PQ Index, or DR Ferrography indicates the presence of an elevated wear metal concentration. In these circumstances, it is helpful to ‘see’ what is occurring inside the machine.

Analytical Ferrography is a powerful and proven qualitative technique that utilizes a microscope to examine wear particle appearance, including the color, size, and shape of particles in the oil sample, to determine the different wear modes and the possible sources of wear debris.

The results are provided per ASTM D7684 and are complemented by photos, allowing the comments to be visualized. Given the time and expertise required to perform the diagnosis, its cost is relatively high.

Accordingly, it is conducted as a secondary test when other lower-cost methods have strongly indicated a problem.

With routine testing, the oil sample is drawn from the primary sampling location and represents the whole system. Secondary sampling locations close to the components should be utilized if a machine has multiple branches or subsystems.

These samples will reveal the highest concentration of wear metals and the likely source of the wear and failing components.

Given the above information, a well-designed analysis slate includes elemental analysis and Wear Particle Index as essential elements. When further investigation is needed, conduct Analytical Ferrography.

Please note that using permanently located oil sampling ports will yield the most representative results.

For a deeper investigation, oil analysts may opt for Filter Debris Analysis. This analytical technique involves examining debris and particulate matter captured within oil filters, which are explicitly designed to trap solid particles, wear debris, and sometimes even water contaminants.

Analysts can find critical clues about the types of wear occurring in the equipment by carefully scrutinizing the composition, size, shape, and quantity of particles in the oil filter.

By understanding the origins of these particles, maintenance teams can take proactive measures to rectify issues, prevent further damage, and extend the lifespan of machinery.

Case Study: Gearbox Condition Monitoring through Iron Content, Wear Particle Index, and Analytical Ferrography

The table below provides the oil analysis results of two samples drawn from a gearbox in the port industry. This case study focuses on the wear metals concentration data acquired through ICP and Particle Quantification Index.

Additionally, the Analytical Ferrography analysis was conducted only for the second sample, promptly following the release of the report of the first sample. All the other parameters are satisfactory, including Viscosity at 40°C, Total Acid Number, and Water Content.

A notably elevated PQ Index compared to the iron concentration detected by ICP has led us to deduce that there has been an accumulation of large ferrous debris within the oil sample, reaching notably high levels. This finding prompted consideration of abnormal wear phenomena inside the gearbox.

This could be attributed to various factors like the ingress of abrasive contaminants, suboptimal lubrication, misalignment issues, or excessive mechanical loading. It should be investigated further.

In this situation, maintenance personnel were asked to draw an urgent representative sample to confirm these abnormal results because this was the inaugural sampling for this gearbox.

One oil analysis report should never be used as the basis for a decision involving replacement or immobilizing equipment.

In addition to the routine analysis slate, Analytical Ferrography was requested. The lab was notified of the emergency and was asked for a quick turnaround.

Simultaneously, maintenance personnel checked the operating conditions of the gearbox, verifying the OEM-recommended parameters, the load, the speed, and the operating temperature.

They were also asked to assess alignment and vibration. Considering other non-destructive inspection techniques to confirm findings is recommended in these situations before embarking on any potentially expensive decision or action.

These combined actions are essential to promptly address and rectify any potential issues within the gearbox and provide a supporting finding. They will serve as crucial inputs for Root Cause Analysis once the lab releases the oil analysis report.

When the second sample report was received, the PQ Index result was confirmed high, and the iron content was relatively the same as the previous sample.

The Analytical Ferrography examination revealed the presence of several types of particles, including those attributed to Normal Rubbing Wear, Fatigue Chunks, Laminar Particles, Corrosive wear debris, Dark Metallo-Oxides Particles, Non-Metallic Crystals, Friction Polymers, and Fibers. Below is a compilation of potential sources of these particles:

1. Rubbing wear particles indicative of normal rubbing wear.
2. Friction polymers can be attributed to excessive mechanical load or stress on the lubricant.
3. Fatigue chunks, suggestive of abnormal periodic machine vibration.
4. Laminar particles are suggestive of a rolling contact failure.
5. Dark Metalo-Oxides, potentially resulting from high operating temperature and/or suboptimal lubrication conditions.
6. Fibers that may have entered the gearbox during maintenance or been introduced to the sample during its extraction.

These insights into the origin of the detected particles are invaluable for understanding the underlying factors contributing to the observed wear patterns. This case study is a concrete example of how combining wear debris analysis techniques is essential for gearbox condition monitoring.

By implementing this proactive approach, equipment managers can maintain high levels of equipment uptime and prevent costly breakdowns.

Oil analysis on oil reservoirs, such as a paper machine, provides much more value than most maintenance managers realize.

Regular reservoir oil sampling can provide the following:

• Reactive information, such as a spike in wear metals identifying a failed bearing or another component.
• Predictive information, such as a slight increase in wear metals indicating early stages of an impending failure.
• Or, most valuable of all, it can provide proactive information. Oil analysis can tell you when your additives are getting depleted, contamination levels are getting to a point where additional filtering may be needed, moisture levels are to the point where corrective measures are required to prevent damage, and with enough data, may even tell you if your equipment is operating outside of its intended design (too hot, too slow, cavitation).

It’s all about using facts and data to help us make better maintenance decisions and get the most out of our investments. Improving the life expectancy of equipment, extending the life of oil life, and reducing unplanned downtime (which also improves safety) are just a few reasons the value of oil analysis far outweighs the cost.

So, would continuously monitoring the oil add more value if oil analysis provides that much value? We recently decided to add a continuous oil monitoring system to the main lube on our paper machine lubricating system.

We then took that information and sent it to our historian to be trended 24/7. We are trending the oil temperature, the moisture level, and the ISO 4/6/14 particle counts.

When we started this project, we did not realize how fast it would pay for itself! Shortly after getting the system online (but before trending), the maintenance manager notified us that the paper machine dryer head had developed a steam leak.

We watched the oil condition and saw no change. A few days later, the moisture levels began to climb rapidly. Thanks to the monitoring system, we reacted to this issue by periodically draining some oil and hooking up a vacuum dehydrator.

Within 24 hours, we reduced the moisture to an acceptable level and returned to normal within 72 hours. No doubt, this quick response minimized the amount of damage the water in our system caused.

Nicholas Knott, a colleague at another paper mill, had the same experience while trending moisture levels in his paper machine. He also caught it quickly and believes this technology prevented many bearing failures. Below is the trend showing how quickly the moisture reaches unacceptable levels and how fast his team could resolve it.

The lesson from these unfortunate situations is that if we were not doing continuous monitoring, how much damage would’ve occurred? We will never know, but we know that steam leaks on a dryer head were common in the past, and oil analysis was rare.

We also know that we had to replace many bearings in the past, which is rare now. Using continuous oil monitoring systems may only be necessary for some situations. Still, in a challenging application like a paper machine, it adds way more value than it costs.

Soon we expect to have enough data to understand if situations like start-ups, shutdowns, wash-ups, and machine speeds have impacted our oil quality.

This article chronicles a reliability journey at a chemical manufacturer in the Southeastern United States.

Implementing a reliability-based maintenance program has tremendous business benefits – the kind of impact that executives get excited about. Before our plant started down the reliability path, we spent $39.1 million in maintenance. We had 200 maintenance craftspeople and, on average, 250 contractors on site.

Seven years later, we spent $17 million and had 173 maintenance craft people and six contractors. We achieved these outcomes just by making work go away. This was not just a single-plant implementation. We worked across four sites, and they all got to about the same place.

Each site was expected to develop its own business case for the reliability project. I had that responsibility for our site. Developing and presenting it taught me a valuable lesson. When you create a business case that exposes a huge opportunity for a positive impact, that message will only sometimes be received well.

I compared our spending as a percentage of replacement value versus best in class to define our maintenance cost reduction opportunity. I also did some extensive OEE calculations by looking at our best month of production in each one of the operating areas. My reasoning was that if you could do it for a month, you ought to be able to do it for a year.

I used that approach to define the business opportunity from increased production. The result was so significant that I decided to be more conservative and cut them in half. It still felt too optimistic, so I cut them in half again.

When I presented the result to the leadership team, they laughed me out of the room. They could not believe that they were mismanaging the resources of that site so badly. Just expect skeptics!

The site where I got laughed out achieved results that doubled the initial business case. We were tracking the cost of reliability events, those major reliability events that cost you a lot of production, and they were steadily declining over time.

We received significant benefits in the procurement process by reducing costs and improved service levels. Below is a chart of the four sites that tracked maintenance spending as a percentage of replacement asset value. The benchmark value for this industry is somewhere around 2%. I was at the dark blue plant.

Because the sites were somewhat different in the products produced, we did not have a universal way to measure OEE. Still, each site had some improvements, and they were significant. I recall being at one of the sites when the plant manager put up a slide that showed the break-even volume over time – the volume needed to break even versus the actual production volume.

Break-even volume was going down because costs were being reduced, and production volumes were going up because they were improving capacity through reliability improvements. The spread between the two was increasing profitability. That resonated with me.

A reliability transformation delivers steady, continuous returns.

Active leadership support must be in place to drive culture change. One of the plants had active resistance from the plant manager, and he was replaced. Corporate leadership had the courage to take the hard road when necessary.

Change management is at least as important as the technical solution. It is a challenge within one site but a much more significant challenge across a group of sites. We had an executive sponsor that walked around with his finger in the air: one solution for all sites.

It was crucial as he was a big driver of that. I will never forget when executive sponsor came to the site I was at, he said, “I have implemented four maintenance systems in my career; this is going to be the last one. We are going to dismantle the past and hardwire the future.”

Having a high level of executive sponsorship is also critical for change management.

Read the rest of this series on the PCA Consulting website.

Those who have worked in or around maintenance and reliability have probably heard about the hidden plant. This term refers to that portion of the productivity of any industry that, for some reason, is wasted and goes completely unnoticed in the eyes of the maintenance, operation, or reliability departments.

One of the advantages of having a predictive maintenance program is precisely identifying those points where this valuable opportunity is wasted. Timely identification will bring the potential defect or underutilization to light so that it can be eliminated and later improved.

The main problem in cases where the hidden plant is genuinely hidden is when everything seems to be going well, equipment does not fail, unscheduled maintenance stops are minimal, and productivity objectives are met.

When a component is replaced based on time and not on its condition, such replacement may be premature or late, and the impact of the benefit or damage may not be addressed. This is one of the clearest examples of that hidden plant.

Don’t settle for the in-service life of physical assets without asking whether they have reached their expected life cycle.

Laboratory oil analysis has a long history, dating back to the early 1940s. However, grease analysis enjoyed a different fortune, and its entry into the predictive tool hall of fame was delayed until well into two thousand’s.

Grease analysis has a comprehensive battery of tests ranging from the most straightforward, such as determining its elemental composition or knowing the type of thickener, to determining its characteristics by simulating actual operating parameters.

However, due to its short history, grease analysis still needs to be noticed by many industries. The advantages it can provide, not only for maintenance but also for the hidden plant, are relatively unknown.

Grease Analysis Case Study

Let’s look at an actual case study in an industrial plant where everything was going well, and unscheduled stops have been at a minimum for years.

For quality reasons unrelated to maintenance, it was decided to do a grease analysis on two products from different suppliers. After repairing one of the bearings, a third-party workshop added Grease 1 to the bearing. The other grease (Grease 2) has been in service for many years in this type of bearing, among others in the plant.

The results of both the technical data sheet and the lab analysis of both products in service are shown in the table below:

The bearings in these cases are a 23248EMW33 type with a life cycle of approximately ten years, a speed of 250 rpm, a maximum working temperature of 190°F, an ultrasound level that does not exceed 18dB, and a regreasing volume of 10 – 15 grams per week, a luxury for any maintenance team. However, during a visit to the plant, a couple of symptoms are observed that, to the expert eye, can be of great importance.

The lower part of the bearing has a black stain of an oily substance that reaches the ground, and when the bearing is replaced (when it has reached its life cycle), the race and the housing have a black crystalline powder in them.

These two symptoms indicate several things that are of high importance for the life cycle of the bearing and, therefore, for the availability and reliability of the plant.

1. The black stain is only oil bleeding from the grease
2. The powder in the housing is the grease thickener

In this case, we see a complete separation of the two main elements of the grease. Due to certain conditions, the oil and the thickener can separate. What are these conditions? These are mainly high temperature and EHL lubrication (elastohydrodynamic).

A simple analysis and calculations about the grease type that this bearing requires result in grease with about ~500cSt mineral oil, extreme pressure additives, and high-temperature resistance, or its equivalent with synthetic oil.

A basic calculation of the expected life reveals that the L10 bearing life is 180,000 hours, which means an expected life of almost 21 years.

However, the bearings are replaced around every ten years!

Let’s go back to the hidden plant. Of course, we want to avoid unscheduled downtime. However, sometimes the scheduled downtime may have been programmed differently or without rethinking scenarios that could cause a component to fall short of its desired useful life.

Based on some life cycle calculations, if the correct grease were in place, the bearing could stand for 18 years, and the regreasing frequency would drop to once every four weeks.

Conclusions

In maintenance and life in general, we are used to keeping things as they are without wondering if anything can be improved. In most cases, improvements are made due to a problem or failure that results in an economic issue or lost production.

Unfortunately, our reality is that we are reactive rather than proactive, and job needs mean that we often do not stop for an instant and wonder if what we have been doing for years can be improved in some way.

The economic savings, in this case, are not intended to reduce grease consumption or relubrication intervals but rather to take care of the asset used to produce a good, in this case, the bearing.

If the grease had been selected correctly, the life of this bearing would reach 20 years without problems. Still, for day-to-day reasons, it is only half that, and the maintenance personnel feel satisfied with this service time. For many, seeing a bearing reach this time in service is an achievement.

How many industrial plants today have equipment that maintains the type of grease or oil since the beginning of its commissioning?

How many bearings use a type of grease that is not the most appropriate but that, for reasons of time or lack of attention, will never see an improvement?

How many maintenance teams waste those valuable hours of work on something that, if a bit of time is spent, can directly impact improving the availability of the equipment?

How often have you considered doing a grease analysis on the most critical bearings in your plant?

How often have you gone from being reactive to being proactive in your day-to-day life?

The hidden plant is one of the market niches that can give the best performance if treated from a profit point of view. In this case study, replacing the type of grease has an impact on production of 0.06% over ten years.

This is equivalent to increasing the finished product sales by 1.3% accumulated in ten years. Of course, finding the hidden plant provides many benefits at all levels of the production and sales chain.

I have been living in Houston, Texas, for a little over three years, and to this day, when I talk to a friend, the first sentence I hear is, “Houston, we have a problem.” It’s a trendy phrase that has become an icon for the Texan city.

However, as often happens, there is a difference with the original expression. NASA launched the Apollo 13 mission on April 11, 1970, intending to make its third moon landing. Still, due to an explosion in one of the oxygen tanks, which almost caused a disaster, astronaut Jack Swigert called the base and said, “Houston, we’ve had a problem.”

There is a big difference between having a problem and having had a problem. In industrial lubrication, this can mean the difference between minimizing the effects of the problem and assuming its consequences.

Due to the global scenario, the lubricant chain supply has many problems. From the lack of raw materials to produce additives to natural disasters, such as what happened to Afton Chemical due to heavy rains in St. Louis, which on July 26, 2022, had to declare an unplanned stoppage that may affect the additives market[1]; to a global collapse in the availability of metal drums for oils/grease where China is the world’s leading exporter, to the rise in the cost of maritime transport with increases of up to four times per container and a long list of situations that had never been seen, at least not altogether in such a short period.

In this short article, I will focus only on industrial greases due to the impact on the availability of the assets that grease can generate in the plants.

The world is feeling the effect of the current conditions, which translates for the end user into an increase in the costs of greases, low or no availability of the product, and extremely long delivery times, eight months in some countries. This has forced many users to mix greases of different brands or types.

Grease Compatibility, What Do We Know So Far?

I have had my eyes on grease analysis lab results for over a decade. Due to the complexity involved in sampling, analysis, and interpretation, it is an area with much space for study and research. I have never seen anything similar to what has been happening for over 15 months, and I speak globally.

As you can imagine, the industry has been forced to mix greases for some of the above reasons. In many cases, the mixtures have had no adverse effects on the bearings, but in others, catastrophic damage or loss of bearing service life has occurred.

In a recent study on compatibility problems between greases, out of 29 cases analyzed, 76% suffered a bearing functional failure, while 24% suffered a catastrophic failure. In 52% of these cases, the bearing had to be replaced. Some plants scheduled the replacement in less than 60 days, while a minority, close to 7%, had to wait for the bearing supplier to have it available.

Of these 29 cases, only four, 14%, conducted a compatibility analysis between greases before deciding to add the new grease to the bearing. However, the worst part of all this is that in three of these four cases, there were incompatibility problems, and two resulted in a functional failure. One of them resulted in catastrophic failure.

Unfortunately, the determination of whether the grease was compatible with another was based only on the type of thickener comparison. To complete the picture, it is necessary to say that the internet is full of grease thickener compatibility tables. In many cases, the sources are unreliable, or they are analyses carried out between the 70s and 80s, where the chemistry of these products was different from the current. Compare a couple of these tables; the result will surprise you!

 You do not have to be a grease expert to know that compatibility depends on the thickener type, base oil, and the type of additives.

In addition, the ASTM D6185 standard serves as a guide to understanding the behavior of binary mixtures of greases.

However, it only partially represents what happens once the grease enters service. And, after an extensive study and developing a definition of a factor that encompasses these three grease components, I found that a global lubrication indicator (GLi) is decisive when the grease enters service in the bearing. The GLi shows how the grease lubricates.

Grease is a non-Newtonian fluid (will behave like a solid under pressure) composed:

• Oil: mineral or synthetic
• Additives: these can be dissolved in the oil or in suspension if they are solid
• Thickener: a network of material that can be soapy or non-soapy and that, in turn, can be simple or complex

They are the oil and the additives that oversee achieving the lubrication. That is the separation between the track and the rolling element through a thin film that sometimes is sacrificial. However, the three elements as a whole provide that expected quality to achieve lubrication.

The thickener acts as a sponge that retains the lubricating agents in its structure and, under mechanical stress, be it speed or load, expels these agents and then re-adsorbs them in its structure.

This intrinsic property of grease is lost over time and due to other factors specific to each operational environment. Additionally, the loss of physical properties of the grease can be due to the mixture with other(s), which results in the loss of lubrication properties and, consequently, the reduction of the service life not only of the grease but also of the bearing.

Case Study: Four of Six

In March of this year, I received one of those calls that began with, “Houston, we have a problem.” The following sentence gave clear clues to the problem “the new grease that we are using in the bearings is of an inferior quality.”

An extrusion plant had decided to replace the grease used in six bearings of one of the main lines due to the increase in price and lack of availability of the one they had in service. Both greases had a lithium-based thickener, and based on the information on the internet, it was concluded they were compatible. 

After a few weeks, one bearing suffered a catastrophic failure, and in the weekly rounds, the site found that three others had sustained a temperature increase of 18°C. For this reason, the line had to be shut down, and production ceased. 

A couple of weeks later, after analyzing the three grease samples (in service, the new one, and the mixture), the conclusions were obvious. Both greases were of good quality but with different characteristics.

The GLi of the mixture clearly showed that it was far from the minimum required and that the properties of the mix did not satisfy the bearing lubrication requirements.

This case reflects one of the biggest problems when determining grease compatibility. Compatibility does not depend solely on the type of thickener.

 The characteristics of the oil and additives also need to be analyzed and their affinity determined. In this case, the reaction mechanism was as follows:

Once the grease has lost some of the base oil (and the dissolved additives), the temperature takes care of the rest. As a result, the inside of the bearing contains a semi-solid paste with a crystallized texture, which is mainly burned thickener.

Should Greases Be Mixed or Not?

 Consider the following when trying to decide whether or not to mix grease:

 It is essential to remember that the information available on the web is not entirely reliable or does not apply to all cases. This does not only happen with the subject of greases.

 A lab should carry out the compatibility analysis with enough expertise in analyzing and interpreting the results. There is a big difference between having the results and defining the behavior of the mixture in the bearing, which requires particular knowledge.

 A compatibility test should include at least the following:

• Determination of type and concentration of additives
• Determination of the base oil
• Consistency
• Rheological determination
• Tribological tests

 Periodically evaluate the in-service grease. It is necessary to know how they behave and if they provide the lubrication the bearing needs.

 Once a new grease has been added to the bearing, increase sampling and inspection frequency (at least half of the initial frequency). 

 A grease consumption increase is usually an indicator of problems; it does not necessarily have to coincide with an increase in bearing temperature.

 Only perform a grease consolidation after first determining the pros and cons of mixing lubricants and basing your decision on lab analysis. It is very convenient to have one or two greases on site but evaluate the risk first.

 Use at least two PdM tools to determine the bearing lubrication condition.

 These recommendations can mean the difference between having a problem and having had a problem. Remember Jack, the Apollo 13 astronaut.

[1] https://www.lubesngreases.com/lubereport-americas/5_31/afton-declares-force-majeure/