Common belief is that to follow the lubricant recommendation of the Original Equipment Manufacturer (OEM) when servicing machinery in an industrial plant is the safest and most effective route. This opinion originates from trust in the OEM’s knowledge of their machine. In this three-part series of our newsletter we debate whether it is universally applicable – especially in large industrial plants. To answer this question, we will delve into two critical areas. In this issue of OilChat we will examine the underlying objectives and considerations behind the OEM’s recommendations.

OEM lubricant recommendations are based on several considerations, including the following key areas:

Machine Design and Operating Requirements: OEMs select a lubricant to match the machine design needs and test the lubricant under specific conditions with focus on reliability and durability. Operating conditions will include factors like temperature, load conditions, speed and environmental factors such as dust and moisture.

Industry Standards and Certifications: Lubricants must often meet certain industry standards or certifications and may require extensive lab testing and validations for performance in specific equipment categories.

Warranty Liability Concerns and Other Commercial Factors: Recommended lubricants are often a stipulation for maintaining a warranty. This requirement stems from the OEM’s confidence in specific lubricants. OEMs frequently sell these lubricants directly, sometimes under their own brand.

Overall Ease of Maintenance and Cost-Efficiency: OEMs consider the balance between the cost of the lubricant and the overall cost of operation and maintenance. The goal is to recommend a lubricant that provides cost-effective operation over the lifespan of the equipment.

Selecting one lubricant for a specific machine is easy. For smaller plants, the lubricant is a minor cost. The answer is therefore normally to simply use the OEM-recommended lubricant. For larger plants, lubricants are a much more substantial expenditure and one bad choice could cost the organization significantly in repair and downtime. It is, therefore, often the same answer – the OEM recommendation.

This approach may be adequate at first. However, several shortcomings require a more strategic approach, particularly when considering the specific environment and operating conditions of the plant, as well as the typical challenges of managing maintenance across dozens of machines. In this case the “safe choice” may have far-reaching implications that influence lubricant selections.

In the next issue of OilChat we will  focus on the lubrication requirements of the environmental and operating conditions of the plant. If you have any questions concerning lubricant consolidation in the interim, simply mail us at info@bcl.co.za. Our experts are at your disposal and ready to provide you with advice and guidance.

Reference
Bennet Fitch: Warning! The OEM-Recommended Lubricants Might Not the Best Choice, Machinery Lubrication Magazine: November 2023.

Tribology (from the Greek word ‘tribos’ meaning rubbing) can be described as the science of friction, wear and lubrication of interacting surfaces in relative motion to one another. Peter Jost, a British mechanical engineer, can be considered the founder of the discipline of tribology. In 1966 he published a report which highlighted the cost of friction, wear and corrosion to the British economy. It was in this report that the term tribology was originally used. The earliest systematic studies of tribology were, however, performed by Leonardo da Vinci, the first tribologist of the world, more than 500 years ago. He did not publish any of his findings but some of his notebook pages discovered more recently, contain amazing illustrations and observations related to friction.

FRICTION: Our ancestors first became familiar with friction in the Stone Age, when they discovered that they could create fire by rubbing pieces of wood against each other. We do not know for sure exactly when they mastered the art of making fire, but indications are that it was approximately 400,000 years ago. Leonardo da Vinci (1452 -1519) studied friction for more than 20 years of his life and understood very well that friction was a limiting factor in the design of his ‘revolutionary’ machines. He distinguished between various types of friction (the force that opposes the motion of a solid object over another) and noted that surface roughness has an impact on how easy it is to move different materials in contact with one another.

There are primarily four types of friction:

Static Friction is the frictional force between contacting surfaces when they are at rest with respect to each other. The magnitude of the static force is equal to and in the opposite direction of a force applied to move one surface. The maximum static friction is reached just before the surface starts to move.

Sliding Friction occurs when the surface of one object moves relative to the surface of another object. It is also called Kinetic Friction and it is the force required to keep a surface sliding over another surface.

Rolling Friction is defined as the force which resists the rolling motion of a round object (ball or wheel) over a surface. Rolling Friction is lower than Static and Sliding Friction.

Fluid Friction occurs between the layers of a fluid that are moving relative to each other. This internal resistance to flow is termed viscosity.

WEAR: Humankind has been faced with the problem of wear since the invention of the wheel more than 5000 years ago. Wear can be described as the removal of material from surfaces in sliding or rolling contact with each other. Wear is a universal phenomenon and rarely do two solid bodies slide over each other without a measurable material transfer or material loss, e.g. coins become worn as a result of continued contact with fabrics and human fingers. There are essentially three types of mechanical wear:

Adhesive Wear occurs during sliding when fragments of material are pulled off one surface and adhere to the other.  This is the most common and least preventable type of wear.

Abrasive Wear is caused by a hard surface (or hard particles) rubbing against a soft surface.  The hard material cuts and ploughs the opposing softer surface.

 Surface Fatigue Wear.  Repeated sliding or rolling over a surface causes subsurface cracks to initiate and grow and eventually lead to material breakup.  This generally occurs if all the other wear mechanisms are very low, such as in rolling element bearings.

 LUBRICATION: In a world that depends a great deal on machines, lubrication is absolutely essential. The science of tribology has advanced significantly in recent times, but the roots of lubrication extend back further than one might imagine. Lubrication in simple form has been in existence at least since the beginning of documented times.

A lubricant is a substance introduced between two surfaces, which are in relative motion to each other, to reduce friction and wear between them. Most fluids, including water, can be used as a fluid lubricant in appropriate applications. In fluid lubrication, the lubrication regime is determined  by the type of lubricating film that is created and the degree of contact between two surfaces. The three distinct lubrication regimes between two sliding surfaces are Boundary Lubrication, Mixed Lubrication and Hydrodynamic Lubrication. In addition to these we also have Elastohydrodynamic Lubrication. It is the condition that occurs when a lubricant is introduced between surfaces that are in rolling contact, such as roller bearings. These lubrication regimes were discussed in detail in OilChat 22.

The early focus of tribology was to improve the efficiency and durability of machinery. Today tribology research extends to a much wider range of macro and nano disciplines in areas as diverse as  the movement of continental plates, biomedical materials, computers and robotics, alternative energies, and many more.

Q8Oils offers a comprehensive range of high-quality lubricants to reduce friction and wear in a wide variety of automotive, construction, industrial, mining and agricultural applications. For more information about the complete range of Q8 lubricants, phone 011 462 1829, email us at info@bcl.co.za  or visit www.bcl.q8oils.co.za.

The U.S. Department of Transportation (DOT) classifies brake fluid into four main categories i.e. DOT 3, DOT 4, DOT 5 and DOT 5.1. The primary differences are their composition and boiling points. (We have discussed brake fluid in detail in OilChat 27 and suggest you revisit it to refresh your memory). Discussions in this newsletter will be restricted to DOT 3 and DOT 4 brake fluids.

Since 2006 DOT 4 is the most common brake fluid used in cars and light commercial vehicles. This is due to higher brake system temperatures, as well as widespread use of anti-lock braking systems (ABS), Electronic Stability Programmes (ESP) and traction control systems (TCS). Nonetheless some (mainly older) vehicles still require DOT 3, but since it is no longer readily available the question is often asked whether one can use DOT 4 instead of DOT 3 brake fluid. Unfortunately there is no straightforward answer to the question.

Both DOT 3 and DOT 4 brake fluids are glycol-ether based and therefore these fluids can be mixed without compatibility issues. Brake fluids are exposed to very high temperatures during braking and and the U.S. Department of Transportation have therefore included minimum boiling points in their Federal Motor Vehicle Safety Standards (FMVSS) 116 brake fluid specifications:

There are no standard formulations for brake fluids, but DOT 3 generally includes about 80% glycol-ether while DOT 4 typically has 50 to 65% glycol-ether with 20-30% borate-ester to improve the high temperature characteristics of the fluid. And this is the reason for the confusion.

Older vehicles that are still on the road today may have had their brake systems designed before DOT 4 brake fluid was introduced. Some brake hoses used in these vehicles, particularly those with inner tubes made of SBR rubber, were found to be incompatible with certain DOT 4 formulations in laboratory testing. The suspect brake fluids appear to be ones with high borate-ester content. It is believed that these formulations permeate the inner tube and then react with the PVA reinforcement braiding to produce a viscous liquid which could build up between the layers of rubber and make the hose considerably weaker. Attempts to reproduce this problem in real life conditions have proven to be difficult though. Most vehicle manufacturers today, however, use a different rubber (EPDM) in their brake hoses which is much more resistant to permeation.

There are several 2006 and older vehicles on the road today that still operate perfectly with their original brake hoses, but when considering what can happen when brakes fail, it is better to be safe rather than sorry. Standard rubber brake hoses do not cost a fortune and are considered consumables, i.e. they need to be replaced. Most vehicle manufacturers recommend you do so at least every six years. This implies that the original brake hoses still fitted to 2006 and earlier vehicles are long overdue.

IMPORTANT: Glycol-ether based brake fluids are hygroscopic which means they absorb moisture from the atmosphere and need to be replaced at least every two years – see your vehicle owner’s manual. It is also important to remember that brake fluid is toxic and combustible and can damage the paintwork of your vehicle.

Blue Chip DOT 4 Brake Fluid is compatible with all materials used in the brake and clutch systems of late model vehicles and exceeds the boiling point requirements of FMVSS 116 as shown below:

If you have any questions about brake fluid, you are welcome to email us at info@bcl.co.za and one of our technical experts will respond to your query.

Informally viscosity is known as the ‘thickness’ of a fluid. If you pour water into a container with a hole at the bottom, it drains in no time. However, if you fill the same container with honey, it drains much slower. Reason is that the viscosity of honey is high compared to that of water. You can therefore say the viscosity of a liquid is its resistance to flow.

Informally viscosity is known as the ‘thickness’ of a fluid. If you pour water into a container with a hole at the bottom, it drains in no time. However, if you fill the same container with honey, it drains much slower. Reason is that the viscosity of honey is high compared to that of water. You can therefore say the viscosity of a liquid is its resistance to flow.

More formally, viscosity is a measure of the internal friction of a fluid. Most liquids are cohesive. Cohesiveness is the intermolecular attraction by which the molecules of the fluid are held together and result in the internal friction of the fluid. This internal friction must be overcome by some force for the fluid to flow. A fluid with low viscosity flows easily because its chemical structure results in little friction when the molecules are in motion. There are various methods to measure the internal friction or resistance to flow, with the following two being the most frequently used for oil:

Kinematic Viscosity:

In kinematic viscometers the fluid flow is driven by gravity. This means the weight or density of the fluid helps it to flow. These viscometers measure the time that the fluid takes to flow through a capillary section in a viscometer tube. Each viscometer tube has a capillary constant. To obtain the kinematic viscosity, you multiply the measured flow time by the capillary constant. The unit for kinematic viscosity is centistoke (cSt). 1cSt equals 1 millimeter squared per second (mm²/s). The standard reference temperatures for kinematic viscosity measurements of lubricating oil are 40⁰C and 100⁰C

Dynamic Viscosity:

Fluid flow is induced by an external force in dynamic viscometers. Rotary viscometers are frequently used to measure the  dynamic viscosity of oil. The test oil, kept at a stipulated temperature, is poured into the viscometer sample container and a spindle is inserted in the oil. The spindle is rotated at a specified RPM and the torque required to maintain the RPM is measured. The results are reported in centipoise (cP). 1cP is equal to 1 millipascal-second (mPa-s). Pascal is a unit of torque similar to kW and HP. Dynamic Viscosity is also known as Absolute  Viscosity.

 

In summary of the above we can say that:

• Kinematic viscosity is the internal resistance of the oil to flow and shear under gravity.
• Dynamic viscosity refers to the resistance of the oil to flow when an external force is applied.

Simply put, kinematic viscosity indicates how fast the fluid flows under gravity, while dynamic viscosity denotes what force is required to make the fluid flow at a certain rate. 

Kinematic viscosity incorporates fluid density as part of the measurement and therefore density provides a means to convert between kinematic and dynamic viscosity. The conversion formula is:

Kinematic Viscosity (cSt) x Density = Dynamic Viscosity (cP)

Kinematic or capillary viscometers are normally used to measure the viscosity of lubricating oils, typically at 40⁰C and 100⁰C. Rotational or absolute viscometers, however, are often employed for certain specific measurements. Multigrade motor oil is a typical example.

The viscosity grade of motor oil is specified by the Society of Automotive Engineers (SAE). Multigrade oils must conform to several viscosity requirements and their viscosity grade consists of two numbers, e.g. SAE 10W-40. The 10W represents the low temperature (Winter) specifications and the 40 specifies the high temperature requirements. The SAE Engine Oil Viscosity Standard J300 defines the limits for multigrade engine oils, using the following viscosity categories:

Kinematic Viscosity in cSt

• Low-Shear Viscosity at 100⁰C

Absolute Viscosity in cP

• Low-Temp Cranking Viscosity*
• Low-Temp Pumping Viscosity*
• High-Shear Viscosity at 150⁰C

*Temperature depending on viscosity grade.

In conclusion we emphasize that viscosity units of measure and viscometers are not restricted to what we have discussed above but we trust that this newsletter will clear some of the confusion around kinematic and dynamic viscosity.

If you have any questions about viscosity, you are welcome to email us at info@bcl.co.za

Over the centuries all sorts of materials have been employed as grease. In the very early days of the wheel animal fats were used as grease. It is believed that compounded grease was first used by the Romans and Egyptians on their horse-drawn chariots more than 3000 years ago. Grease from that era is thought to have been prepared from olive oil or animal fat mixed with lime.

It was not until the middle of the 1800’s that real progress was made with grease technology. During the First Industrial Revolution (1760 to 1840) the development of larger machines with tighter specifications running at greater speeds for mass production, triggered the search for more sophisticated and specialised greases. In response sodium based grease was formally invented in 1845. Lithium grease, discovered in the first half of the 20th century, was an even more advanced development. It was patented in the United States in 1950 and rapidly came into wide use as a multi-purpose grease.

In terms of use, lithium based grease is by far still the most popular type of grease today. Although it is suitable for a wide variety of automotive, industrial and other applications, lithium based greases should, however, not be considered as an all-purpose grease because their:

• Dropping point of less than 200°C is lower than various high-temperature applications
• Water resistance is not as good as some other grease types
• Adhesion properties are not all that suitable for sliding and reciprocating applications

In fact, there is not one grease type that is suitable as an all-purpose grease for every single grease application and hence the term all-purpose grease is misleading.

Moreover, the concept of “standardisation” is very attractive when it comes to reducing the number of lubricants in large operations. It is believed one can decrease the risk of accidentally using the wrong product by reducing the total number of lubricants in storage. Even more appealing is to reduce the inventory levels of lubricants that may only be used in a very specific application. While consolidation efforts are necessary to save money and reduce accidents, grease is often the focus of overenthusiastic consolidation.

While there are options available to reduce the number of greases in use, careful thought and consideration should be exercised to avoid over-consolidation and subsequent substandard lubrication for grease-lubricated components. After all, not all greases are the same, regardless of what the description may lead you to believe.

Q8Oils offers a comprehensive range of high-quality lubricants for a wide variety of automotive, construction, industrial, mining,  agricultural and other applications. For more information about the complete range of Q8 greases, phone 011 462 1829, email us at info@bcl.co.za  or visit www.bcl.q8oils.co.za.

Oxidation is a phenomenon that occurs in various formats around us every day of our lives. In simple terms oxidation can be described as a process in which oxygen combines with an element or substance – either slowly, as in the rusting of iron, or rapidly, like burning wood. Either way, oxidation has a variety of consequences. Some of its manifestations, like the combustion of fuels and the digestion of food in our bodies, are beneficial. Inversely many of its side effects are harmful, such as air pollution from burning fuels and food rancidification.

Likewise, oxygen has benefits and disadvantages for the human body. Every cell in our body needs oxygen to survive. Simultaneously some forms of oxygen are toxic to human cells and may produce a significant amount of the cellular injury that is associate with ageing and death, such as heart diseases and certain cancers. Little wonder humankind is consuming large quantities of antioxidants every day.

Lubricating base oils are also prone to oxidation but in this instance it only has undesirable effects.  The complex chemical reaction that occurs when oil combines with oxygen leads to increased viscosity, organic acids, the formation of sludge, varnish and deposits, additive depletion and the loss of other vital base oil performance properties. The ultimately result is reduced service life of the lubricant. The rate of oxidation is accelerated by the presence of water, acids, catalysts such as copper and, last but not least, high temperatures. In fact, the rate of oil oxidation doubles with every 10⁰C increase in temperature.

Antioxidant additives (also known as oxidation inhibiters) are incorporated into lubricant formulations to increase the oxidative resistance of the base oil and to maximize the service life of the lubricant. Antioxidants also allow lubricants to operate at higher temperatures than would be possible without them. Antioxidants retard the oxidation process but unfortunately nature is relentless and all lubricants will eventually oxidize to some degree. While antioxidants can significantly slow down the degradation of the lubricant in a machine, they do not last forever. Antioxidants are sacrificial additives that are consumed while performing their duty to control oxidation. Eventually all the antioxidant additives will be consumed, leaving the lubricant exposed to uncontrolled attack by the oxygen in the air.

The changes that are the most obvious in oxidised oil are a rancid smell and darkening of the oil. Other indicators can be visible in the viscosity and density of the oil. If you are still not sure you can do the following simple tests:

Blotter Spot:

A distinct brownish coloured outer ring around the deposit zone indicates the oil is badly oxidised – see OilChat 72 for details.

Interfacial Tension:

Place a drop of oil on the surface of water. If the oil drop spreads out over the surface of the water (instead of clustering up like new oil), it is a sign that the oil is oxidised.

All Q8 lubricants are formulated with high quality, oxidation stable base oils and proven antioxidant additives to maximise oxidative resistance and prolong service intervals. For more information about the complete range of Q8 high performance lubricants phone 011 462 1829, email us at info@bcl.co.za  or visit www.bcl.q8oils.co.za

A question often asked is can one use grease containing solid lubricants in wheel bearings?

Heavy duty greases fortified with solid lubricants are commonly used in arduous applications where  sliding or reciprocating motion is present. Typical examples are journal bearings, pins and bushes, guides, slides, sleeves and pivots. Solid lubricants prevent wear, scuffing/scoring, binding/sticking, and seizure very effectively in these applications. It is, however, debatable whether grease with solid lubricants is suitable for use in rolling bearings.

Molybdenum disulfide (moly) and graphite are the solid lubricants most commonly utilised in grease formulations. When a grease containing these ‘solids’ is used in high-speed rolling bearings, problems can be experienced with roller “skidding” when the rollers fail to rotate. The sliding of the rolling elements on raceways could lead to the following problems:

Overheating

As the rollers skid along on the raceways, they force the grease out of the way, resulting in metal-to-metal contact between the rollers and the raceways. This in turn generates heat and may well cause overheating of the bearing. Higher temperatures also reduce the hardness of the metal and can cause premature failure.

Flat Spots

When a roller skids, the wear on the roller is concentrated on the area where the roller is in contact with the raceway. As a result, the roller develops flat spots, and its service life is reduced. The raceway also wears, but the wear is spread out over a larger area and is therefore less severe.

Smearing

The removal and transfer of metal from one component of a rolling bearing to another is generally known as smearing. In severe cases of skidding the rise in temperature can be so drastic that it causes a collection of small seizures between bearing components.  Surface roughening occurs along with melting and the damage can quickly extend to the whole contact area. Various degrees of smearing can be described as scuffing, scoring or galling.

Greases containing moly are nonetheless recommended for some roller bearings that are subjected to very heavy loads and shock loading, especially bearings in slow or oscillating motion.  Typical examples are universal- and CV-joints. If in doubt, consult the equipment/vehicle/bearing manufacturer or your lubricant supplier.

Now back to the opening question Can one use grease containing solid lubricants in wheel bearings? Normally vehicle wheel bearings are adequately lubricated with a lithium based, NLGI 2, multipurpose or EP grease with oil viscosity 200 centistokes +/- 10%. For heavy duty applications a lithium complex grease will provide additional protection. Manufacturers generally do not recommend greases with solid lubricants for wheel bearings in highway applications.

But be warned, even if you are using the correct grease, skidding may occur. Over-greasing can also cause the rollers to skid on the raceways. As they slide forward, they push the grease out of the way, resulting in metal-to-metal contact, temperature increase and accelerated rate of oil bleed. This in turn will cause the grease to harden and hinder lubrication even more – leading to oxidation and bearing failure. 

Q8Oils offer you an all-embracing range of greases for an extensive range of application. For more information about our grease portfolio phone 011 462 1829 or email us at info@bcl.co.za. Our lubricant experts are at your disposal and ready to provide you with advice and answer any questions you may have. Alternatively you can visit www.bcl.q8oils.co.za.