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.