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An Engineer, Entrepreneur, Author and Activist: – Expertise in reliability and lubrication engineering and advocacy for women in STEM

sanya in front of factory copy

A Chat with Engineer Sanya Mathura, one of the New Faces of Engineering in Trinidad and Tobago with the Board of Engineering Trinidad & Tobago

 

Engineer Sanya Mathura, BSc. MSc. MLE, FLCAT I, MAPETT, R.Eng.

 

For more info on the BOETT check out their website: www.boett.org

Sanya is a young Engineer, entrepreneur and author with a distinguished record of achievement and with many first associated with her accomplishments. She is the first engineer to be registered with the Board of Engineering of Trinidad and Tobago in the specialist category of Machinery Lubrication Engineer and before that, the first female in the Caribbean to become an ICML certified Machinery Lubrication Engineer (MLE) and sits on the board for this exam. Sanya was also the first female in the world to achieve the ICML Varnish badges (VIM & VPR), and again, she was the first female in the world to achieve the Mobius Institute FL CAT I (Field Lubrication Analyst) certification. Sanya is the Managing Director of Strategic Reliability Solutions Ltd, a consulting firm which she founded and which specializes in helping clients improve their asset reliability and maintenance practices across a wide range of industries, including oil and gas, manufacturing and transportation, locally and across the globe.

 

Sanya holds a Bachelor's degree in Electrical & Computer Engineering as well as a Masters in Engineering Asset Management and has over 15 years’ experience in industry. She has been recognized for her exceptional work in the field of reliability and lubrication engineering and her expertise in developing and implementing asset management strategies, risk assessments, and root cause analysis has earned her a reputation as a subject matter expert. Apart from being the author and co-author of six technical books in her area of specialty, when not writing or managing her business, she is an activist supporting projects for women in STEM and has been assigned the Series Editor of the book series by CRC Press, Taylor & Francis, “Empowering women in STEM”.

 

Sanya is an active member of several professional organizations, including the International Council for Machinery Lubrication and writes technical papers for several organizations. She is also a sought-after speaker and has presented at various conferences and seminars on the topics of reliability engineering and lubrication. She is part of the editorial board for Precision Lubrication Magazine and writes a lot of technical articles on various platforms. She is also part of the Advisory board for the Lubricant Expo North America & The Bearing Show North America. Sanya is also a digital editor for the STLE (Society of Tribologists and Lubrication Engineers) TLT magazine and writes a column for the Equipment Today magazine.

 

Sanya's passion for excellence, coupled with her expertise in the field of engineering and reliability, has made her a respected and highly sought-after professional in the industry. Her dedication to providing exceptional service to clients and her commitment to staying up-to-date with the latest industry trends has earned her the respect of her peers and the admiration of her clients.

Q1. Can you provide an overview of your academic and professional background, including relevant training related to machinery lubrication engineering?

I am a proud graduate of the University of the West Indies, St Augustine campus where I completed my BSc in Electrical & Computer Engineering and afterwards, my MSc in Engineering Asset Management. After getting my Bachelors, I worked in the industry for 2 years before joining Shell Lubricants as their Technical Advisor for Trinidad & Tobago. This is when I fell in love with reliability as I realized that lubrication is the lifeblood of machines and essentially affects every part of the operation.

It was during my time with Shell that I decided to pursue my MSc and wrote my thesis on lubricant degradation. While writing my thesis, I realized that I wasn’t producing the quality of work that I should be and decided to quit my job (with no back up plan!).

During that time, I reached out to several global experts to assist with some research that I was doing for my thesis, and they all knew someone who knew something. Then I thought, wouldn’t it be great, if there was a hub in Trinidad & Tobago where people could go to for Reliability Solutions from trusted experts…but it had to be Strategic. That’s how Strategic Reliability Solutions was formed, and the vision has never strayed.

We continue to provide quality information, consulting, and training services globally with trusted affiliates in the USA, Canada, Australia and the UK to our clients within the Caribbean and across the globe.

Q2. As a newly Registered Engineer in the specialist category of Machinery Lubrication Engineering, what motivated you to pursue a career in this field, and what specific skills or experiences do you bring to this role?

While I’m newly registered with the BOETT, I’ve been in machinery lubrication for the past decade. I’ve received training in Houston, the Caribbean and got to work with globally recognized product application specialists in this field for several years. After writing my first book, “Lubrication Degradation Mechanisms – A Complete Guide” published by CRC Press, Taylor and Francis, I decided to earn my MLE (Machinery Lubrication Engineer) certification from ICML (International Council for Machinery Lubrication).

This is one of the highest levels of certifications that they offer and while it is advised to build your way up to this badge by earning the other badges (MLT, MLA, LLA) because of my extensive work with supporting customers in lubrication related issues globally, I was sufficiently prepared to pursue this certification and got it.

Afterwards, I wrote a couple more internationally published technical books such as:

With my background in engineering and extensive knowledge of machinery lubrication, I am equipped to help customers with their challenges in this arena.

Q3. Could you discuss a challenging lubrication problem you encountered in your work experience? How did you approach and solve it?

We had a client in Qatar who began experiencing some issues with their hydraulic lifters for a particular machine. These lifters got jammed at an ad-hoc rate and caused a lot of unplanned downtime for them. They had to keep stopping the equipment, cleaning the system, and then restarting the equipment which caused some losses in production. They were not performing oil analysis as they did not recognize this component as being critical to their operation hence they did not monitor it.

We worked with them to re-evaluate all their components throughout the plant (determining which ones were critical, semi-critical and non-critical). Then, evaluated the lubricants being used, ensured that they were all meeting the required standards and specifications. Next, with the information gathered, we curated an oil analysis program which aligned with their plant and all its equipment.

From the data collected through oil analysis, we were able to spot when the issue with the hydraulic system began to appear again. The condition of the oil drastically changed after their technician performed a top up. The results also revealed that there were some additives specific to gear oil which were appearing in the hydraulic oil samples.

Apparently, the technician kept topping up the hydraulic systems with gear oil (used in another area of the plant). They thought that any oil should work and used the closest oil to their location (which in this case was the gear oil). We did some training and reorganization of their storage and handling practices, so now, their system is working without any more delays due to the incorrect oil being used.

Q4. In your opinion, what are the most important properties or characteristics to consider when formulating a lubricant for a specific application? How do you prioritize these factors?

There are a lot of things to consider when formulating a lubricant. The most important characteristic is viscosity. One of the main purposes of a lubricant is to reduce friction between two surfaces. It can only do so if it provides an adequate reduction in the coefficient of friction. When formulating lubricants, it’s all about balance.

There should be enough additives to enhance, suppress or add new properties to the base oil. Various types of oils have different ratios of additives to base oil, for example turbine oils usually have only 1% additives while motor oils have 30% additives. That means 1% of additives in turbine oils need to be formulated to have the right amount of oxidation resistance, wear protection, viscosity index improvers and many more which do not counteract each other.

When formulating oils, we must look at the application, the load, the speed, and the environment before even thinking about the formulation. There are complex calculations to determine the correct viscosity (largely based on the load, speed and in some cases temperature).

Understanding the metallurgy of the components is also helpful in the formulation of the lubricant as this can dictate which additives can and cannot be used.

Lubricant formulators also work alongside OEMs to ensure that the lubricant is meeting their specifications as it relates to the efficiency of the machine as well as any regulatory standards.

Q5. How do you stay updated on advancements in lubricant technology and industry best practices? Can you provide examples of any recent developments or trends that have caught your attention?

I read a lot, especially content from OEMs, Global lubricant suppliers and attend a lot of webinars where experts are sharing their knowledge. Being a part of the Precision Lubrication Magazine Board, STLE (Society of Tribologists and Lubrication Engineers) Digital TLT magazine and a columnist for Equipment Today magazine also mean that I have access to this type of content.

I am also the co-chairperson for the Lubrication & Reliability Virtual Summit which features speakers from across the globe within this area. I help to organize and facilitate and participate in some of the discussions for the various regions, AMER (Americas), APAC (Asia-Pacific) and EMEA (Europe- Middle East & Africa).

I was also on the advisory board for the Lubricant Expo North America and facilitate workshops across the globe especially in the Kingdom of Saudi Arabia, UK, USA and other regions.

Additionally, I work with a global group of consultants specific to the lubrication industry with its headquarters in Australia. We all work together on challenges from our customers and have knowledge sharing sessions which helps to keep each other informed about the latest trends.

Q6. Describe your experience with conducting tribological testing and analysis. What methods or techniques have you used to evaluate the performance of lubricants under different operating conditions?

I am not a lab personnel nor do I have access to a lab. My expertise lies in interpreting the reports and relaying this information to the customer along with recommendations on how to solve some of the challenges they may be experiencing. I work with global labs to help my customers to understand what is happening inside their equipment and develop a solution for these challenges.

Q7. Lubricant selection is critical for maximizing equipment performance and lifespan. How do you approach the process of selecting the most suitable lubricant for a given application?

This varies for every piece of equipment. The first part is to understand what the OEM requires of the lubricant, what the lubricant should be able to tolerate before pushing it outside of its operating envelope.

Most OEMs have tolerance limits based on environmental and/or operating conditions as well as industry standards. For instance, if we’re looking at turbine oils, many people make a comparison of their spec sheets (TDS – Technical Data Sheet) with the values given.

Often, they look at the RPVOT value (Rotating Pressure Vessel Oxidation Test) which gives a value in minutes (estimating the lifespan of the turbine oil). This should not be done, especially since the RPVOT is not a repeatable test in that, if it is performed 10 times, it will yield 10 different results.

Additionally, the result is given in minutes (the length of time for the oil to attain a particular characteristic in the test) which is not easily related to the field. Instead, for a better comparison of oils (in particular turbine oils), it may be a wise decision to perform the TOPP (Turbine Oil Performance Prediction) test where the oil is stressed for 4-6 weeks (with catalysts for oxidation such as heat, temperature, oxygen) and then their characteristics are compared. This is one of the best ways to compare oils before determining which of them to purchase in the turbine oil realm.

When evaluating oils for maximizing your equipment performance, most OEMs suggest a range of oils both mineral and synthetic and provide the operating characteristics in which these perform best. Depending on your environment, the oil can be selected accordingly.

For instance, there may be no critical applications which require the components to keep moving with minimal stressors or extra loads. In those cases, mineral oils would be the most effective and possibly last longer just because of the application.

In other instances, such as a harsh environment or high temperatures, synthetics may perform better but may still not have a longer lifespan because they can degrade quickly because of the environment. Essentially, it all depends on the application being evaluated.

Q8. Can you discuss a situation where you had to troubleshoot lubrication-related issues in machinery and the steps you took to resolve them?

We had a customer in Italy who was having some issues with the cranes on their ship. The oil was degrading quickly and continuously causing them lots of downtime. We ran the oil analysis for the oil and discovered that the viscosity was breaking down too quickly and there were lots of deposits being produced.

The crew were able to remove one of the filters and we sent it for testing but upon removal, they noticed that there were areas of the filter membrane which were burnt. This is one of the effects of ESD (Electrostatic Spark Discharge).

We were able to immediately identify this and worked with them on finding a solution to this issue. They could not make any adjustments to their current operations, so we decided to change their filters to antistatic filters. This dramatically helped to reduce the buildup of static in the oil and they do not have deposits in their oils anymore.

Q9. Effective communication and collaboration are essential in lubrication engineering, especially when working with cross-functional teams or external stakeholders. Can you provide any example of how you've successfully communicated technical concepts or recommendations to non-technical stakeholders?

Typically, when I get called into an organization it’s because something went wrong. This means that I need to be able to communicate with all the stakeholders from the CEO to the people working at the plant. I remember one high-level meeting where both the technical and C-suite members were present.

The trick to being able to deliver technical information to a mixed audience is to find common ground, for everyone. For this meeting, I started off with using an analogy of the human body to the manufacturing plant and then proceeded to explain the importance of the oil, its functions as likened to the blood in our bodies.

Then, for explaining the oil analysis results (which the technical team needed to see but the non-technical team did not fully understand), this was likened to performing blood tests and the results that we got were likened to tests for diabetes, either you are pre-, post or need to monitor.

This was a great way to get everyone in the room to understand what went wrong, and how we intended to fix it. Although, some have now referred to the plant as having type II diabetes after the meeting, they still got the message.

Q10. Finally, where do you see opportunities for innovation and improvement in the field of lubrication engineering in Trinidad and Tobago? How do you envision contributing to advancements in this area in T&T?

Trinidad & Tobago has a rich history of Oil & Gas and manufacturing. Nothing moves in these industries (or any other industry) without proper lubrication. I think it’s a concept that not many are familiar with as they are in other parts of the world. But this is where we can grow and evolve.

It’s been my mission to bring Trinidad & Tobago to the forefront in this industry. Through my internationally published technical books, presence on technical boards, articles and certifications, we are showing other Caribbean islands that we are not “too small” to partake in the conversations happening in this industry. Just recently I attained my FL CAT I (Field Lubrication – Category I) from the Mobius Institute becoming the only female in the world to attain this (as per their published records).

This is not a new accolade as I was also the first person in the Caribbean to attain the ICML MLE certification and the first female in the world to attain the ICML VIM & VPR badges.

I’m bringing the T&T name to the forefront and letting others know that we have talented people here who are willing to do the work and advance the industry through their insights.

I may write a couple more technical books in the future (having already published 4 technical books and 2 non-technical), I can safely say that it is a strong possibility. I will continue my work in advocating for more women in STEM (especially in this industry) and though my series of books, “Empowering Women in STEM” published by CRC Press, Taylor and Francis.

The first two books are already out and feature women from various parts of the globe in different industries in STEM. The third book will be out before the end of the year and the fourth is already in progress.

I firmly believe that if we all work together that we can create more opportunities for others to also shine brightly in this space and inspire the future generations.

Oil Properties

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.

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December 23, 2023
Oil Properties

Types Of Antiwear Additives and How They Work

There are many types of antiwear additives, but they typically all fall under the category of polar materials such as fatty oils, acids, and esters, according to Pirro, Webster & Daschner, 2016. According to Mortier, Fox, & Orszulik, 2010, several compounds can form surface films to help protect against friction and wear.

These include:

  • Oxygen-containing organic compounds (with a polar head that can adsorb to surfaces). These can include alcohols, esters, and carboxylic acids.
  • Organic compounds containing nitrogen groups
  • Organic sulphur compounds which can form reacted films at surfaces
  • Organic phosphorus compounds which can form reacted films at surfaces
  • Organic boron compounds which may form reacted films at surfaces
  • Organic molybdenum compounds which can form MoS2 film on surfaces
  • ZDDPs, which can form polymeric films on surfaces

While this is an exhaustive list, the more popular ones are listed below. In this next part of the article, we will also dive into how they function.

Organic Oxygen Compounds

According to Mortier, Fox, & Orszulik, 2010, these compounds usually include esters, alcohols and acids. These are generally responsible for improving the “oiliness” or reducing the friction for most lubricants. However, how does this work?

Carboxylic acids form metallic soaps with the contacting surfaces. According to Mortier, Fox, & Orszulik, 2010, some evidence suggests that the upper limit of friction coincides with the melting point of the metal soap. As such, when the upper limit of friction is reached, the metallic soap melts, protecting the surface and performing its antiwear function.

Interestingly, there has been a debate concerning whether these long-chain surfactant friction modifiers reduce friction by forming adsorbed films of monolayer thickness or if they form thick films equivalent to several or many multilayers.

Again, as per Mortier, Fox, & Orszulik, 2010, after experimenting, it was concluded that some of these types of additives form thick boundary films while others do not.

The thick boundary films result from the formation of insoluble iron (II) oleate on the rubbing surfaces. For metal oleates, this will only occur for metals lower than iron in the electrochemical series.

Thus, when speaking about organic oxygen compounds, they help to reduce the friction in lubricants by forming layers on the contacting surfaces.

Organophosphorus Esters

These types of esters have long been used as antiwear additives, according to Mortier, Fox, & Orszulik, 2010. There are two different types of reaction films which are typically formed:

  • Films derived from tricresyl phosphate which form thin films (0.1-2nm) consisting of low shear strength FePO4 and FePo4.2H2O
  • Films consisting of iron (III) monoalkyl/aryl phosphate oligomers are thicker (approximately 100-300nm) and polymeric.

It is important to note that for the tricresyl phosphate (TCP) to be effective, the presence of oxygen, water, and other polar impurities is necessary to form the reaction film. Typically, the hydrolysis of the ester occurs initially, which releases phosphoric acid. This is then critical in the formation of the surface oxide film.

Another noteworthy function of the ester of phosphoric acid is that it helps ensure the solubility of the product in the oil. It can also aid in rust protection by hydrolysis to the phosphoric acid.

During the formation of the film, there is a loss of an alkyl group by hydrolysis, which generates two P-O ligands for coordination. This phosphate anion, which was formed, has reduced oil solubility, which allows for the boundary layer of oil covering the metal surface.

Eventually, as the polymer continues growing, the film moves from a soft, viscous liquid to that of a glass-like solid. This glass-like solid allows the surfaces to stay separated, thus reducing wear.

Essentially, organophosphorus esters form films that can either be very thin or thicker and glass-like, depending on their nature. While they act as antiwear additives, they can also perform the function of rust inhibition in the appropriate environments.

Molybdenum Sulfur

Coyle et al., Patent No. 4,995,996, 1991 recognize Molybdenum disulphide as a lubricant additive and discuss its origins. They mention that molybdic xanthine typically decomposes under particular conditions to form the molybdenum sulfide on protected materials. The use of thiosulfenyl xanthates has also been formulated for particular ashless lubricants.

As per Mortier, Fox, & Orszulik, 2010, compounds such as MoDTC (molybdenum dithiocarbamate) or MoDDP (molybdenum dithiophosphate) typically react with the surfaces to produce the famous molybdenum disulphide. In this compound, there is an ease of shearing, which leads to unusually low coefficients of friction.

A synergistic relationship exists between MoDTC and ZDDP. While MoDTC does not form low friction layers independently, these layers are only formed when ZDDP is present. The layer of MoS2 is only formed on top of the glass of ZDDP reaction products. The ZDDP layer acts as a source of sulphur, reduces the oxidation of MoS2 and limits the diffusion of sulphur from MoS2 into the ferrous substrate.

Interestingly, Molybdenum disulphide (also commonly known as “Moly”) is extremely popular in grease applications especially in the mining industry. “Moly” is known for being a solid additive to grease thickeners for specific applications.

As seen above, it may not exactly be “Moly” added to the lubricant, but rather, it is only created when its parent compound decomposes and is formed.

Zinc Dialkyldithiophosphates (ZDDP)

These are the most commonly used antiwear additives on the market and are known by their chemical abbreviation ZDDP. Originally, ZDDP was developed as an antioxidant additive. However, it has been used in many applications, such as engine, hydraulic, and even circulating oils, as both an antiwear and antioxidant additive.

According to Bruce, 2012, The Ecole Centrale de Lyon / Shell Corporation collaboration made significant conclusions on ZDDP performance. This study shows that ZDDP produces a thin film of iron sulfide and zinc sulfide nearest to the metal surface. Next, there is a zinc polyphosphate layer, made up of long-chain zinc polyphosphates and then soluble alkylphosphates, closest to the oil layer.

According to Zhang & Spikes, 2016, at very high temperatures (above 150°C), ZDDP reacts slowly to form films on solid surfaces. This occurs despite the absence of rubbing and is called “thermal films .” However, at lower temperatures (below 25°C) in the presence of rubbing films in a ZDDP lubricant, these ZDDP films are generated more rapidly. These are called “tribofilms”. Based on analysis, it is suggested that both films have similar structures.

It has also been shown (through inelastic electron tunneling spectroscopy, IETS with Yamaguchi and Ryason) that secondary ZDDP is adsorbed much more readily than primary ZDDP. On the other hand, alkaryl ZDDP is hydrolyzed on adsorption onto aluminum oxide surfaces.

According to Mortier, Fox, & Orszulik, 2010, ZDDP reduces wear by forming relatively thick boundary lubrication films. These are usually 50-150nm thick and are based on a complex glass-like structure (as mentioned earlier). The figure below, taken from Mortier, Fox, & Orszulik, 2010, shows the structure of this ZDDP glass film.

Structure and composition of a ZDDP glass film (taken from Mortier, Fox, & Orszulik, 2010)

The strength of the ZDDP’s antiwear function lies in the structure of the alkyl groups. Chain branching and chain length have critical roles in this determination. Short-chain primary alkyl groups are more reactive than long primary alkyl groups.

As Mortier, Fox, & Orszulik, 2010, explain, the ZDDPs most efficient at antiwear film formation typically suffer depletion due to thermal effects. Under very high temperatures and/or long drain service, the most active ZDDP may not provide the best wear protection.

 

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

by
December 23, 2023
Oil Properties

What Are Antiwear Additives?

As the name suggests, antiwear additives help to prevent wear in one way or another. However, what makes them unique compared to other additives in lubricants? Why are they used more predominantly in specific applications than other applications? This article explores antiwear additives, why they are needed, and how they work.

What Are Antiwear Additives?

According to (Bloch, 2009), antiwear agents can also be called mild EP (Extreme Pressure) additives. In some cases, they may also act as antioxidant additives (depending on their chemical structure). In essence, antiwear additives protect against friction and wear when the surfaces experience moderate boundary conditions.

During moderate boundary conditions, the full film of the lubricant has not yet formed, and asperities on both surfaces can come into contact with each other. As such, antiwear additives can also be called boundary lubrication additives.

antiwear-addtives-work-2

Usually, these antiwear additives react chemically with the metal to form a protective layer. This layer or coating will allow the two surfaces to slide over each other with low friction and minimal metal loss. As such, antiwear additives have also adopted the nickname “anti-scuff” additives.

According to Pirro, Webster, & Daschner, 2016, the adsorbed film on metal surfaces is formed from long-chain materials. In these cases, the polar ends of the molecules attach to the metal while the projecting ends of the molecules remain between the surfaces.

Under mild sliding conditions, wear is reduced; however, under severe conditions, molecules can be rubbed off such that the wear-reducing effect is lost. When this happens, it is evident in the oil analysis data with the presence of wear metals in large quantities.

In essence, antiwear additives help protect the oil while reducing friction, protecting the surfaces, and, in some cases, enhancing the oil to be more resistant to oxidation. While they can perform these functions, it must be noted that there are many different types of antiwear additives.

 

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

by
December 23, 2023
Oil Properties

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.

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December 23, 2023
Oil Properties

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.

 

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December 23, 2023
Oil Properties

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.

 

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December 23, 2023
Lubricant Degradation

Can Lube Oil Varnish be Eliminated? 

Varnish can be likened to cholesterol in the human body. It can build up in our arteries and eventually clog those, causing restrictions in blood flow to our heart which may lead to a heart attack.

Humans cannot simply change their blood to remove the cholesterol build-up. However, cholesterol is controlled through proper diet, exercise, and with some condition monitoring in the form of blood tests to help gauge the presence of it in the bloodstream. Similarly, a couple of approaches can be used to reduce the varnish build-up or eliminate it.

As per Livingstone et al. (2011), the lifecycle of varnish is critical. Particular attention should be paid to the double arrows between the stages of Solubility to Varnish formation in the figure below.

This means that even after varnish has been deposited, it can be solubilized back into the oil. This can only occur if conditions are met per Hansen’s Solubility principles where the solvent and degradation products meet using the three parameters of Polarity, Hydrogen Bonding, and Dispersive Forces as discussed in “The Hansen Solubility Principles and Its Relation to Varnish” (2022).

mechanisms-oil-varnish-formation

The Varnish Lifecycle as per Livingstone et al. (2011)

Varnish exists in various forms and can consist of differing compositions. Hence, it is essential to understand the characteristics of the varnish being formed in a system before attempting to eliminate it.

There are certain technologies, such as solubility enhancers or specifically engineered filtration media, which can be effective at removing lube oil varnish. However, this technology is heavily reliant on the type of varnish being formed and can be customized as per the system accordingly.

Solubility enhancers can solubilize the varnish back into the oil solution. When these deposits are reintroduced into the oil, they can be removed using resin-based filtration. In this method, the media is specifically designed to allow for the adsorption and removal of the varnish which presently exists in the oil.

When these methods are used together, they can prove quite effective and prevent manufacturing plants from experiencing unwanted downtime.

To summarize, it is of utmost importance to first understand the characteristics of the varnish being produced in your equipment before attempting to remove it from your system.

There is no cookie-cutter method to eliminate varnish from a system as it is a complex deposit. Similar to practices we observe with our bodies in the instances of cholesterol build-up, we can employ methods of dissolving the varnish and removing it while monitoring for possible recurrences in the future.

 

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References:

Livingstone, Ameye, & Wooton. (2015.). Antioxidant Monitoring as Part of Lubricant Diagnostics – A Luxury or a Necessity? OilDoc, Rosenheim, Germany.

Livingstone, Overgaag, & Ameye. (2011). Advanced removal Techniques for Turbine oil Degradation Products. Powergen Milan.

Mathura, S. (2020). Lubrication Degradation Mechanisms (CRC Press Focus Shortform Book Program) (1st ed.). CRC Press.

The Hansen Solubility Principles and its Relation to Varnish. (2022, July 31). Fluitec International. https://www.fluitec.com/the-hansen-solubility-principles-and-its-relation-to-varnish/

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December 23, 2023
Lubricant Degradation

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.

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December 23, 2023
Lubricant Degradation

Can Lube Oil Varnish be Detected? 

Detecting something is the first step towards formulating a solution to minimize its effects or eliminate it from a system. In the case of varnish for lubricated assets, a few technologies are currently being used to detect its presence.

As seen at the beginning of this article, varnish can exist with various characteristics depending on the degradation mechanism which aided in its formation. For this article, the degradation mechanism of oxidation will form the main focus as it is the most prevalent pathway to lube oil varnish formation.

During oxidation, the first chemical change which can be observed in the lubricant is the depletion of the antioxidant additives. This is where the knowledge of phenols and amines is critical.

As per Livingstone et al. (2015), these antioxidants can form synergistic mixtures in mixed antioxidant systems. When the free radicals react with the phenols, they become depleted but can regenerate amines. Thereby, the phenols are sacrificial.

Thus, when performing the RULER analysis, one can find that the concentration of the phenols will typically deplete quicker than the amines. This provides the analyst with a good overview of the amount of oxidation that has taken place in the lubricant.

The RULER analysis is one of the oil analysis methods which can provide early detection of the occurrence of oxidation.

It has been shown that the physical changes, such as polymerization, will only begin after this chemical change of the depletion of antioxidants. It is at this point that the actual deposits will begin formation.

Unfortunately, oil analysis tests such as viscosity and acid number only show significant changes after the deposits have been formed. At this time, it may be too late to implement technologies to mitigate varnish formation.

The Membrane Patch Calorimetry (MPC) oil analysis test (ASTM D7843) can offer analysts insight into the estimated amount of insoluble varnish currently within the system. These results have three main ranges which identify the severity of the varnish, namely, 0-20 (Normal), 20-30 (Abnormal), and >30 (Critical). Oil analysis tests can effectively provide the operators with some awareness of the current condition of the lubricant and its tendency to form varnish.

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December 23, 2023