Tagged: lubricants

The Influence of Lubricant Selection on Degradation

Guidelines should always be followed when selecting a lubricant for a particular application. OEMs will have specific criteria ranges for specialty applications that must be satisfied. Some general guidelines which should be considered can be summarized in the table below based on the listed mechanisms above.

Based on the three listed mechanisms above, one can identify that choosing a lubricant can impact the type of degradation which occurs during its lifetime. As such, when selecting lubricants, it is critical to note their applications and the conditions they will endure.

Having a history of lubricant failures for particular equipment can also assist in this regard by informing users of past failure trends. Therefore, when selecting a lubricant, operators can be more mindful of the properties which should not be compromised during the selection process.

The process of troubleshooting degradation in lubricants has been covered in detail in the book, “Lubrication Degradation – Getting Into the Root Causes” by Bob Latino and myself, published by CRC Press, Taylor and Francis.

Want to read the entire article? Find it here in Precision Lubrication Magazine!

Which Degradation Mechanism Is Affected?

My previous article published in Precision Lubrication covered six degradation mechanisms: oxidation, thermal degradation, microdieseling, electrostatic spark discharge, additive depletion, and contamination.

Upon further investigation, there are only three mechanisms where selecting the correct lubricant will impact the degradation mode. These are; oxidation, microdieseling, and electrostatic spark discharge. The properties of the lubricant can easily influence each of these degradation mechanisms.

When selecting a lubricant, especially for rotating equipment, one of the critical areas of importance is the performance of the antioxidants. When formulated, oils must be balanced to protect the components in various aspects.

Thus, some oils that boast a high level of antioxidants may suffer from low levels of antiwear, or these increased levels can react with other components to reduce the performance of the oil. During oxidation, antioxidants are depleted at an accelerated rate which can lead to lube oil varnish. Hence, the choice of lubricant can influence this degradation mechanism.

A good trending test, in this case, would be the RULER test to accurately quantify and trend the remaining useful antioxidants for the oil. This test can easily distinguish and quantify the type of antioxidant rather than providing an estimate of the oxidation, as with the RPVOT test.

It has been noted that oils with an RPVOT of more than 1000 mins have a low reproducibility value which can mislead users during trending of lubricant degradation. Corrosion inhibitors, not just antioxidants, have also influenced the RPVOT values. Thus, there are better tests for monitoring the presence of antioxidants and helping operators to detect the onset of possible lube oil varnish.

On the other hand, during microdieseling, entrained air can lead to pitting the equipment’s internals and eventually the production of sludge or tars depending on whether the entrained air experiences a high or low implosion pressure.

If bubbles become entrained in the lubricant and do not rise to the surface, this can directly result from the lubricant’s antifoaming property. The antifoaming property is essential when selecting an oil, especially for gearboxes. Typically, OEMs will have recommendations for their components that should be followed.

Another degradation mechanism that can be influenced by lubricant selection is electrostatic spark discharge. This mechanism occurs when the lubricant accumulates static electricity after passing through tight clearances. These then discharge at the filters or other components inside the equipment, providing sharp points or ideal areas to allow static discharge.

This is frequently seen in hydraulic oils due to the very tight clearances within the equipment. If fluid conductivity is above 100 pS/m, the risk of static being produced is reduced. Some OEMs also provide particular values the lubricant should meet for this property.

 

Want to read the entire article? Find it here in Precision Lubrication Magazine!

Has the Lubricant Failed the Equipment, or Has the Equipment Failed the Lubricant?

Many lubrication engineers are faced with finding the most appropriate lubricant for an application. Therefore, they are tasked with selecting the “right” lubricant; subsequently, their decision can influence several outcomes.

A lot of the positive results are in the realm of extending the life of the oil, providing better energy efficiency, and even saving costs associated with downtime. However, can the choice of an “incorrect” lubricant impact its degradation process or lead to the presence of lube oil varnish?

Has the Lubricant Failed the Equipment, or Has the Equipment Failed the Lubricant?

Lubricants provide many different functions. These can range from moving heat or contaminants away from the components, minimizing wear and friction, improving efficiency, providing information about the status of the lubricant, or even transmitting power, as is the case with hydraulic oils.

There has been the time aged question of whether a lubricant fails the equipment or the equipment has failed the lubricant. If a deeper dive is performed into this question, one can deduce that lubricants are engineered to withstand particular conditions.

Once those conditions are met, lubricants can perform their intended functions. However, if the conditions exceed the tolerances of the lubricant, then one will notice a faster degradation. In this case, the environment and its conditions have failed the lubricant.

On the other hand, lubricants are designed to be sacrificial and are used up while in service. Hence, it is normal to see additives’ values deplete when trending oil analysis values, especially for turbine oils. Quite notably, additives responsible for antiwear or extreme pressure will decrease over time as they protect the components.

For this instance, the lubricant would have been performing its function until it could no longer do so or has reached its end of life. The conditions in the environment cannot be blamed for the lubricant failing. This is the nature of the lubricant.

Lubricant condition monitoring lets analysts detect whether a lubricant is undergoing degradation and can even help determine some areas where it has begun to fail. For instance, if the RULER® test can quantify the remaining antioxidants in an oil. Analysts can easily interpret its results to determine if the process of oxidation is occurring within that lubricant.

Similarly, an FTIR test can detect whether contaminants are present in the lubricant or if the additive packages have become severely depleted. These tests all aid in allowing analysts to successfully determine whether or not a lubricant is performing at its full functional capacity.

 

Want to read the entire article? Find it here in Precision Lubrication Magazine!

Why Do We Need Lubricant Additives?

Lubricants keep the world turning. Once something moves, a lubricant should be present to reduce friction or wear between the surfaces. But what makes lubricants so unique in our industry? Is it just the base oil?

No, this is where the power of lubricant additives truly shines, an area many overlook.

Why Do We Need Lubricant Additives?

Before getting into the world of additives, let’s step back to the basics: why are they needed? A lubricant is composed of base oil and additives. Depending on the type of oil, different ratios of additives will be used for the various applications. Additionally, each Lubricant OEM will have its unique formula for its lubricant.

To simplify this, we can think of making a cup of tea. The first thing we need is some hot water in a cup. This can be our base oil. It can be used on its own (some people drink hot water or use it for other purposes), but if we want to make a cup of tea, we must add stuff.

Depending on the purpose for which you’re drinking the tea, you may choose a particular flavor. Perhaps peppermint for improved digestion or to help improve your concentration or chamomile to keep you calm.

These flavors can represent the various types of oils: gear oils, turbine oils, or motor oils. Different blends are suited for different applications.

Now, while we’ve added the tea bag to the hot water (and some people can drink tea like this), others need to add sweetener or milk. These are the additives to the base oil (hot water).

Depending on the preference of the person drinking the tea, there will be varying amounts of sweetener (honey, stevia, or sugar) and varying amounts of milk (regular, low-fat, oat, dairy-free). The combinations are endless!

The same can be said of additives in finished lubricants. Depending on the type of oil (tea flavor, think gear or turbine oil) and its application (the person drinking the tea, with dietary preferences of being dairy-free or sugar-free), the combination of lubricant additives and their ratios will differ. The percentage of additives can vary from 0.001 to 30% based on the type of oil.

Additives have three main functions in a finished lubricant. They can;

  • Enhance – improve some of the properties of the base oil
  • Suppress – reduce some of the characteristics of the base oil
  • Add new properties – introduce new features to the base oil

The finished lubricant will have properties from the base oil and additives combined.

Want to read the entire article? Find it here in Precision Lubrication Magazine!

The Difference Between Antiwear and Extreme Pressure Additives

The terms antiwear additives and extreme pressure additives are often used interchangeably, suggesting that they provide the same functions in a lubricant. This is not exactly true. While there are many similarities in how they function, both additives have distinct functions in protecting lubricants.

Both are film-forming additives (Bruce, 2012). Their functions are to reduce wear between two contacting surfaces or reduce friction to lower the heat produced between the two rubbing surfaces.

They can also be classified as boundary additives that can be temperature-dependent (EP additives) or non-temperature-dependent (Antiwear additives). They both function to mitigate against wear, which is usually caused during boundary lubrication where higher speeds, loads, or temperatures can cause contact with the asperities.

One of the significant differences, as noted by Mang & Dresel, 2007 is that antiwear additives are designed to reduce wear when the system is exposed to moderate stress. On the other hand, EP additives are much more reactive. These are used when the system’s stress is very high to prevent the welding of moving parts.

According to (Bruce, 2012), there are four main groups of commercially available EP additives based on the structures containing phosphorus, sulphur, chlorine, and overbased sulfonates. He explains that the phosphorus, sulphur, and chlorine-containing EP additives are activated by heat over a range of temperatures.

For instance, chlorine-containing EP additives are usually activated between 180-240°C, phosphorus-containing additives are activated at higher temperatures, and sulphur-containing additives operate at 600-1,000°C.

On the other hand, overbased sulfonates contain a colloidal carbonate that reacts with iron to form a thin-film barrier layer between tribocontacts. This protects the surface from direct contact and welding.

As we can see, antiwear and EP additives protect the surfaces between which the lubricant exists. However, they are activated differently and subsequently perform two different functions.

Antiwear additives protect against wear and are not temperature dependent, while EP additives are activated by high stress to prevent the welding of moving parts.

Both functions are essential to protecting the system from additional wear and ensuring it remains operational.

 

Want to read the entire article? Find it here in Precision Lubrication Magazine!

 

References

Bloch, H. (2009). Practical lubrication for industrial facilities, Second edition. Lilburn: Fairmont Press Inc.

Bruce, R. W. (2012). Handbook of Lubrication and Tribology, Volume II, Theory and Design, Second Edition. Boca Raton: CRC Press Taylor and Francis Group.

Coyle, C. L., Greaney, M. A., Stiefel, E. I., Francis, J. N., & Beltzer, M. (1991, Feb 26). United States of America Patent No. 4,995,996.

Mang, T., & Dresel, W. (2007). Lubricants and Lubrication, Second, Completely Revised and Extended Edition. Weinheim: WILEY-VCH Verlag GmbH & Co. KGaA.

Mortier, R. M., Fox, M. F., & Orszulik, S. T. (2010). Chemistry and Technology of Lubricants, Third Edition. (C. Bovington, Ed.) Dordrecht Heidelberg: Springer Science+Business Media B.V. doi:10.1023/b105569_3

Pirro, D. M., Webster, M., & Daschner, E. (2016). ExxonMobil, Lubrication Fundamentals, Third Edition, Revised and Explained. USA: CRC Press Taylor and Francis Group.

Zhang, J., & Spikes, H. (2016). On the Mechanism of ZDDP Antiwear Film Formation. Tribol Lett, pp. 1–2.

Measuring Oil Viscosity

The viscosity of oil is one of its most essential characteristics. Thus, it is important to understand how this is measured and quantified. There are two main types of viscosity, dynamic (or absolute) and kinematic viscosity.

The dynamic viscosity measures the force required to overcome fluid friction in a film and is reported in centipoise (cP) or in SI units Pascal Seconds (Pa s) where 1 Pa s = 10 P (Poise). It can also be considered the internal friction of a fluid. This is usually used for calculating elastohydrodynamic lubrication related to rolling element bearings and gears.

On the other hand, the kinematic viscosity of a fluid is the relative flow of a fluid under the influence of gravity. Its unit of measure is centistokes (cSt) which in SI units is mm2/s, 1cSt = 1 mm2/s. (Mang & Dresel, 2007).

Kinematic Viscosity = Dynamic Viscosity / Density

Other units of measure for viscosity include; Saybolt, Redwood, and Engler, but these are less widely used than the cSt or cP, especially for lubricants.

Oil Viscosity Grades and Standards

One of the best-kept secrets about viscosity is that a particular grade often represents a range. When oils are classified, one may see an ISO 32 or ISO 220 and believe that the oil will have this exact viscosity (32 cSt or 220 cSt). However, this is not the case.

There are three general classifications where viscosity grades have particular ranges based on the fluid type. The fluid may behave differently in each application, hence the need for these three scales. However, there is a chart that allows users to convert the various scales into the one needed.

Engine Oil Classification (SAE J300)

As per the Society of Automotive Engineers (SAE), the SAE J300 standard classifies oils for use in automotive engines by viscosities determined at low shear rates and high temperature (100°C), high shear rate and high temperature (150°C) and both low and high shear rates at low temperature (-5°C to -40°C) (Pirro, Webster, & Daschner, 2016).

Engine manufacturers have widely used this system to aid in designing lubricants suited for these applications. As such, oil formulators also adhere to these classifications when engineering lubricants.

One will note the use of the suffix letter “W” in some of the grades below. These oils are intended for low ambient conditions, whereas those without the “W” are intended for oils that will not encounter low ambient conditions.

These are commonly described as multigrade (where the “W” is found between two numbers) and monograde oils (where the “W” is at the end or the grade is identified by a number only) in the table below.

The table shows that the viscosities must fall within a particular range to be classified. For instance, a 5W30 oil should meet the specifications of:

  • Low temperature, Cranking viscosity of 6600 cP at -30°C
  • Low temperature, Pumping Viscosity Max with No Yield Stress of 60,000 cP at -35°C
  • Low shear rate Kinematic viscosity at 100°C should be between 9.3 -12.5 cSt
  • High Shear rate viscosity at 150°C Max at 2.9 cP

One will notice the range of 9.3 to 12.5 cSt (at 100°C). This is where oils can be blended to either end of this scale but still achieve the classification of a 5w30 oil.

Axle and Manual Transmission Lubricant Viscosity Classification (SAE J306)

As per the SAE recommended practice J306, automotive manual transmissions and drive axles are classified by viscosity, measured at 100°C (212°F), and by the maximum temperature at which they reach the viscosity of 150,000 cP (150 Pa s) when cooled and measured in accordance to ASTM D2983 (Method of Test for Apparent Viscosity at Low Temperature Using Brookfield Viscometer). (Pirro, Webster, & Daschner, 2016).

The table below shows that for an SAE grade of 190, the kinematic viscosity must fall within the range of 13.5 to 18.5 cSt at 100°C. While most viscosities tend to fall mid-range of these values, it also indicates that if the lubricant achieves 18 cSt at 100°C, it can still be classified at an SAE grade 90.

The most common multigrade lubricants within this grade fall within the 80w90 or 75w140 classifications.

Another factor for these types of lubricants is API GL4 or GL5 ratings. It must be noted that a GL5 lubricant is recommended for hypoid gears operating under high-speed, high-load conditions.

On the other hand, a GL4 lubricant is usually recommended for the helical and spur gears in manual transmissions and transaxles operating under moderate speeds or loads. These should not be used interchangeably as the GL5 lubricants tend to adhere to the surfaces and may cause more damage in a GL4 application.

Figure 5: Automotive Gear Lubricant Viscosity Classification. Source: Lubrication Fundamentals, Third Edition Revised and Expanded by Pirro D. M., Webster M., and Daschner E. pg 52

Viscosity System for Industrial Fluid Lubricants

This classification was jointly developed by the ASTM and STLE (Society for Tribologists and Lubrication Engineers). Initially, the system was based on viscosities measured at 100°F but converted to viscosities measured at 40°C.

ASTM D2422 and ISO 3448 are the references for this system. In this system, it is clearer to see the variances in the ranges of viscosities. In this case, the mid-point of the range is used as the ISO viscosity. To determine the range of any ISO viscosity, one can calculate ±10% of the mid-point value to get the minimum and maximum values of the range.

Figure 6: Viscosity System for Industrial Fluid Lubricants. Source: Lubrication Fundamentals, Third Edition Revised and Expanded by Pirro D. M., Webster M., and Daschner E. pg 52

All of these systems can be represented in the figure below, where it is easy to calculate the oil viscosity using another system:

Figure 7: Various viscosity systems in one chart.

Factors That Affect Oil Viscosity

Similar to the molasses and water examples above, different factors can affect the viscosity of a liquid. For instance, water can assume other states depending on the temperature.

If water is at its freezing point (0°C), it can turn to ice but remains liquid at room temperature (around 20-30°C). Then, at 100°C, it can turn into a vapor. Its viscosity can change depending on the influencing factors.

Four factors affect oil viscosity:

  • Temperature
  • Pressure
  • Shear rate
  • Oil type, composition, and additives

Temperature

As seen with the example of the water above, when the temperature decreases, the water can turn to ice. Similarly, for lubricants, as the temperature drops, the viscosity increases. This means the oil will get thicker or more resistant to flow at lower temperatures. Likewise, as the oil heats up, it can become thinner.

This is similar to a block of ice melting as temperatures increase. Its viscosity will decrease, and the ice will turn to water. In this case, the internal molecules gain more energy with the increase in temperature, lowering the internal friction within the fluid. As such, the viscosity also decreases.

Since the oil’s viscosity will change with temperature, most OEMs will supply a temperature–viscosity chart for their equipment to help ensure the correct viscosity is used depending on the operating temperature.

In the figure below, gear oils of varying viscosities are plotted against the temperature for a particular piece of equipment. OEMs will typically specify the optimum operational viscosity range for their equipment.

It is then up to the lubrication engineers to determine the ideal viscosity based on the conditions of their equipment (this can vary depending on the application).

Figure 1: Temperature – Viscosity chart for Shell Omala S2 G (Source: Shell Lubricants TDS)
Figure 1: Temperature – Viscosity chart for Shell Omala S2 G (Source: Shell Lubricants TDS)

From the figure above, one can see that at 40°C, most of the gear oil grades correspond with their viscosities (ISO 68 corresponds with a 68 viscosity). However, at 0°C, an ISO 68 gear oil can become 1000 cSt, while at 90°C, this same grade of oil is around 11cSt.

Interestingly, all of the oils listed here can achieve a viscosity of 100cSt but at different temperatures, as shown below:

  • 32°C – ISO 68
  • 40°C – ISO 100
  • 47°C – ISO 150
  • 55°C – ISO 220
  • 63°C – ISO 320
  • 68°C – ISO 460
  • 75°C – ISO 680

Temperature is a significant influencing factor of viscosity, but it is not the only factor.

Pressure

The effects of pressure on a lubricant’s viscosity are often overlooked. However, the viscosity-pressure behavior has become part of the calculation for elastohydrodynamic films. In these cases, oil viscosity can rapidly increase with pressure.

One such instance occurs with metal-forming lubricants, which are subjected to high pressures such that the oil’s viscosity can increase tenfold (Mang & Dresel, 2007). As the pressure increases, viscosity also increases, protecting the surface in these lubricant films.

The very definition of viscosity alludes to pressure’s impact on Newtonian and non-Newtonian fluids. For example, with Newtonian fluids (regular lubricating oils), the shear rate is proportional to the applied shear stress (pressure) at any given temperature.

As seen above, the viscosity can be determined once the temperature remains the same. However, Non-Newtonian fluids, such as greases, only flow once a shear stress exceeding the yield point is applied (Pirro, Webster, & Daschner, 2016).

Hence, this is why the observed viscosity of grease is called its apparent viscosity and should always be reported at a specific temperature and flow rate.

Shear Rate

For Newtonian fluids, viscosity does not vary with shear rate (Pirro, Webster, & Daschner, 2016). In fact, per the definition of viscosity for Newtonian fluids (regular lubricating oils), viscosity is a constant proportionality factor between the shear force and shear rate. Thus, even when subjected to greater shear forces, the viscosity will not change for Newtonian fluids.

On the other hand, for non-Newtonian fluids, the viscosity is influenced by the shear rate. Some non-Newtonian fluids can include; pseudoplastic fluids, dilatant fluids, and a Bingham solid, the effects of shear rate on these fluids are shown in the figure below.

A Bingham solid is a plastic solid such as grease that only flows above a particular yield stress. It can be seen that pseudoplastic fluids decrease viscosity with an increasing shear rate, while dilatant fluids show an increase in viscosity with an increasing shear rate. (Hamrock, Schmid, & Jacobson, 2004)

Figure 2: Characteristics of different fluids as a function of shear rate vs. viscosity (a) and shear rate vs. shear stress (b). Source: Fundamentals of Fluid Film Lubrication by Hamrock, Schmid & Jacobson, page 102.
Figure 2: Characteristics of different fluids as a function of shear rate vs. viscosity (a) and shear rate vs. shear stress (b). Source: Fundamentals of Fluid Film Lubrication by Hamrock, Schmid & Jacobson, page 102.

The shear of a lubricant can influence its shear rate. Typically, longer-chain polymer viscosity index improvers can shear over time. When this happens, it can result in a decrease in oil viscosity. Similarly, non-Newtonian fluids, such as grease, experience a decrease in viscosity as a function of shear rate (Totten, 2006).

Another essential characteristic to note is whether a material is thixotropic or rheopectic. For a thixotropic material, if it is placed under a continuous mechanical load over a period of time, the viscosity will appear to decrease over this time.

However, the original viscosity is restored after a specific rest period, as shown in the figure below. On the other hand, for rheopectic materials, continuous shearing causes the viscosity to increase. (Mang & Dresel, 2007).

Figure 3: Flow characteristics of a thixotropic lubricant (Source: Lubricants and Lubrication edited by Theo Mang and Wilfried Dresel, page 30)

Oil Type, Composition, and Additives

Various oil types, compositions, and additives can influence a lubricant’s viscosity. For instance, the five groups of base oils all have varying characteristics, as shown in the figure below. One can note the differing viscosities for the various groups.

Figure 4: Base Stock property comparison (Source: Lubricants and Lubrication edited by Theo Mang and Wilfried Dresel, page 13)
Figure 4: Base Stock property comparison (Source: Lubricants and Lubrication edited by Theo Mang and Wilfried Dresel, page 13)

When a finished lubricant is made, it usually consists of a base oil and additives. Hence, the base oil will have a significant role in determining the final viscosity of the oil. However, with the advent of Viscosity Index Improvers, desired viscosities can be engineered regardless of the base oil type being used.

 

Want to read the entire article? Find it here in the Precision Lubrication Magazine!

What is Oil Viscosity?

Oil viscosity is the internal friction within an oil that resists its flow. It measures the oil’s resistance to flow and is one of the most important factors in lubricants. Viscosity is also defined as the ratio of shear stress (pressure) to shear rate (flow rate).

Understanding Oil Viscosity

Imagine walking through a swimming pool filled with water. While walking through the pool, your body experiences some resistance from the water. Now imagine walking through the same swimming pool, filled with molasses this time!

It takes someone much longer to wade through a molasses-filled pool than one filled with water. In this case, the molasses is more viscous than the water. Thus, it has a higher viscosity than water.

Viscosity_600x300_AMRRI

You can also apply this to using a straw for drinking water from a glass. Pulling the liquid from the cup will be easy using a big straw. However, getting the same liquid to the person using the straw would take longer if a thinner straw were used.

Engine Oil Analogy

We can draw this analogy to car engines over the last 30-40 years. These engines had larger clearances for the oil to flow throughout the engine. As such, most of these engines used a 50-weight (or straight 50) oil.

As the technology evolved, the size of the engines got smaller. The clearances also got smaller, and the engine oil was now required to flow faster, control the transfer of heat and contaminants and keep the engine lubricated.

A straight 50 oil could not pass through the smaller straw at the speed it should. This would be equivalent to the user using a smaller straw for drinking molasses. It could take a while!

However, if a lighter weight (or less viscous) engine oil was used (such as a 0w20 or 10w30), then this is like someone trying to drink water (0w20) with a smaller straw.

It will flow much faster than molasses (straight 50) with the same straw! The lighter-weight oil would also transfer heat and flow much faster than the heavier-weight (more viscous) oil.

 

Future Developments and Research in Oil Viscosity

As explained at the beginning of this article, the changes in technology (such as smaller engines) will demand more from lubricants, especially in viscosity. Thirty years ago, a 0w16 engine oil was unfathomable, but today, it is being integrated into our newer model vehicles.

Some of the concepts which will continue in the future can include:

  • Reducing viscosity – as seen in the examples above, with most pieces of equipment getting smaller, the need for lighter weight (lower viscosity) oils will continue as OEMs constantly evolve and push the boundaries of their equipment.
  • Measuring viscosity – traditionally, viscometers have always been used where the difference in the height of the liquid at particular temperatures (or under certain conditions) is measured. Given the advancements in technology, this may be subject to change very shortly into a more reliable and even more accurate method.
  • Viscosity-dependent parameters – temperature and pressure have the most significant impacts on the oil’s viscosity. However, some of these challenges can be overcome with the advent of viscosity index improvers. With enhancements in the formulation of viscosity index improvers, one can expect oils of varying viscosities to be used in parameters they could not have used in the past.
  • Alternative oils – more sustainable options are constantly being explored. Whether this lies in using plant-based oils or other alternative bio-based oils, these may introduce new ways or conditions under which different viscosities can exist.

Overall, viscosity is one of the most important characteristics of a lubricant. It can easily influence the impact of the oil on the internal surfaces of the equipment and its overall energy efficiency.

It is important to remember that oil viscosity should be determined by the application in which it is being used. Parameters such as temperature, pressure, and shear rate should all be considered when selecting the lubricant’s viscosity.

 

Want to read the entire article? Find it here in the Precision Lubrication Magazine!

Is Oil Analysis the Only Method of Varnish Detection?

Varnish will deposit in layers and adhere to the metal surfaces inside the equipment. As it continues to deposit, the layers will eventually accumulate until it reaches a point whereby it can cause significant changes to the clearances of the components.

There have been instances where shafts in rotating pieces of equipment have been moved due to the build-up varnish. This is where vibration analysis can be instrumental.

When the vibration analysis method is used, it can detect any small changes in the alignment of the shaft in rotating equipment. As varnish continues to build on the inside of the component, vibration analysts can detect if the shaft observes some misalignment over a period.

This may be easy to miss as sometimes the varnish which has built up can be wiped away, causing the shaft to resume its proper alignment. Thus, these technologies should be used in tandem before conclusions are made about the presence of varnish.

Another detection method that can be employed is the monitoring of temperature fluctuations. As stated earlier, varnish can form an insulating layer trapping heat. There have been case studies that demonstrate that bearings experiencing varnish tend to display temperature increases.

Typically, these temperature patterns assume a saw-tooth pattern where temperatures rise continuously as the varnish builds up. The varnish becomes wiped away, and the temperature is reduced drastically.

This saw tooth pattern of temperature variation is characteristic of varnish formation. In some cases, the formation of localized deposits on bearing surfaces may cause temperature escalations without a corresponding MPC increase. In this case, the bulk oil may not show any degradation, yet temperature excursions may be experienced at the bearing surface.

Want to read the entire article? Find it here in Precision Lubrication Magazine!

Varnish Badges of Honour

Varnish Badges_honour

Varnish is widely known as a primary culprit of equipment failure. This sticky enemy effectively finds its way into most of our equipment and causes operators, maintenance personnel and plant managers a series of nightmares. From unplanned shutdowns costing millions of dollars to sticking of servo valves on startup, or increases in bearing temperature, varnish usually announces its arrival. Once it has been found, there is typically a cause for panic but perhaps it just needs to be understood rather than feared?

 

The ICML VPR & VIM Badges

Recently (August, 2021), the International Council for Machinery Lubrication launched two new badges. These badges are, VIM (Varnish & Deposit Identification and Measurement) & VPR (Varnish & Deposit Prevention & Removal). These were created after the culmination of 3 years of work from the global varnish test development committee. It has been designed for those involved in all aspects of managing or advising lubricant programs especially those with the responsibility of recommending, selling or installing appropriate deposit control equipment or other mitigation strategies.

Most of the readers will already be familiar with my enthusiasm for understanding lubricant degradation. Thus, when these badges came out, I knew I had to secure them! While the requirements for taking the test suggest the possession of the MLT I or MLA I certification or 1 year of experience, I figured that my MLE certification would be an asset (as I haven’t gotten my MLT I certification yet, it’s on the list!). However, I wanted to make sure that I covered all of the elements in the BoK for both the VIM & VPR badges, so naturally I turned to the varnish guru himself, Greg Livingstone!

 

Fluid Learning – All the way!

Greg is the CIO at Fluitec but he’s also the facilitator for the ICML VPR & VIM badges. What a treat! If you’ve never heard the name Greg Livingstone then you’re obviously not in the lubrication field. Greg has penned hundreds of papers on varnish and can be thought of as the varnish guru since he has extensive experience in this area. It’s a no brainer that I chose Fluid Learning to get me up to speed on what I needed to know for these exams!

Greg was an amazing facilitator and not only covered information relevant to the BoK for the exams but gave students a full overview about everything you needed to know about varnish. These on demand sessions kept me scribbling notes and nodding to myself and saying, “Oh that’s what really happens!” He presents the information clearly and adds some much needed humour into the sessions. It was an absolute privilege having him as my tutor for these badges.

 

VPR & VIM- What you need to know!

Varnish Badges_need-to-know

VPR - Varnish & Deposit Prevention and Removal

The VPR badge ensures that candidates understand proactive methods and technologies which can be employed to reduce the degree of degradation. It is also designed to confirm that they can sufficiently evaluate combinations of technologies to prevent and remove varnish including the proper steps to set up and implement an effective varnish removal system.

The topics covered in the VPR include:

  • Problems associated with Varnish & Deposits (20%)
  • Factors affecting Breakdown (28%)
  • Proactive Methods that can be used to minimize oil breakdown (16%)
  • Methods / Technologies that can be used to remove oil breakdown products and/or prevent deposits (36%)

The complete BoK for the VPR badge can be found here.

 

VIM (Varnish & Deposit Identification & Measurement)

The VIM badge on the other hand is more ideally suited for personnel responsible for recommending suitable oil analysis tests and mitigation efforts related to the deposit tendencies of various in-service fluids (application dependent). They would also be responsible for monitoring and adjusting these strategies accordingly.

The topics covered in VIM include:

  • Problems associated with Varnish and Deposits (20%)
  • Varnish and Deposit Composition (24%)
  • How Breakdown Products / Contaminants become Deposits (24%)
  • Oil Analysis Techniques that can be used to gauge Breakdown and Propensity towards Deposit Formation (32%)

The complete BoK for the VIM badge can be found here.

 

Exam tips!

Varnish Badges_exam_tips

The actual exams for both the VPR & VIM are set at 45 minutes with 25 multiple choice questions. Candidates must achieve 70% grade to attain the badges. Currently, the fee for the exam is USD75. Since there were overlaps of the content and the exam durations weren’t that long, I decided to sit both exams in one day. I will only advise this for those who are comfortable with doing this as exam anxiety and all that comes along with it can be stressful!

Here are a couple tips for taking these exams:

  • Log into the system 30 minutes prior to your scheduled exam time. This allows you to clear your mind, settle yourself and gives you an extra 15 minutes to figure out where the email is with your credentials! If you can’t remember your password to login to the system, this also gives you enough time to get that reset and sorted before the actual exam time.
  • The session only opens 15 minutes before the appointed time. During this time, you will converse with the moderator as they do the checks of the room and your National Identification. The moderators will engage with you and ensure that you are sitting the correct exam.
  • Ensure you have your National Identification on hand (your passport can be used as well). As long as it has your picture and the expiration date on the same side, it will be acceptable. For the Trinidadians, do not use your National ID card as we have our pictures on the front with the information on the back (I used my Driver’s permit).
  • Candidates have the option of “Flagging” questions to come back to them later. This is a great tool to help you to mark those questions you want to return to or double check.
  • There is a timer in the screen layout which helps you to keep track of your time. 45 minutes passes very quickly when you’re running through the questions!
  • Exam results for these badges come back very quickly as much as within a few hours or one day depending on the time of your exam.

Why do you need these badges?

Varnish Badges_need-badges

As long as you work within the lubrication sector or interface with machines requiring lubrication, then you need to get these badges! Oil degradation occurs throughout the life of the lubricant whether it’s a small or large operation. By understanding how it degrades and ways to mitigate that degradation, you can save your equipment and avoid unwanted downtime. These badges were designed for the personnel in the field to allow them to make decisions regarding the lubricant and to empower them in taking steps to avoid degradation or mitigate it should the need arise. Consider it as getting your passport stamped by the ICML!

The courses offered by Fluid Learning are perfect for those seeking to understand lubrication deposits, what causes them and how they can be mitigated. While the content covered during these sessions align with the ICML VPR & VIM badges, they also add to a more holistic approach to varnish and deposits. Fluid Learning is an official ICML Training Partner and is currently the only one (of which I am aware) offering training prep for these badges. I highly recommend them for anyone seeking to learn more about or avoid sticky varnish situations. 

At the moment of writing this article, there are only 8 people globally who have acquired these badges from ICML. I am the first female in the world to attain these badges but I will not be the only female for very long. Varnish is an issue which affects us all and we need to understand it, so we can prevent it and keep our equipment safe. I hope to see many more candidates with these badges in the near future!