COMMON GREASE PROBLEMS #Oil Chat 105

In this three-part series of articles, we will focus on some of the most common problems you may experience with grease lubrication and endeavour to give you easy ways to prevent or fix them.

Identifying lubrication problems can be problematic when dealing with oils – and it gets even more difficult with greases. While oil analysis is fairly standard in most applications, in-service grease analysis is not done all that often and is harder to interpret. Grease specifications normally report the same basic properties, such as NLGI grade and dropping point, but critical details like base oil type, thickener chemistry and additive content may not even show up on technical data sheets. Physical characteristics like tackiness, water washout resistance and rheological behaviour are equally important, but are often undocumented.

Grease analysis is even harder once the grease is in service. Analysis options do exist – like ASTM D7918 (Standard Test Method for Measurement of Flow Properties and Evaluation of Wear, Contaminants and Oxidative Properties of Lubricating Grease by Die Extrusion Method and Preparation) or specialized wear debris testing. They are, however, not commonly used. Since grease operates mostly out of sight (inside bearings and housings, etc.) it is easy for problems to develop unnoticed until there is a major failure. Proactive grease sampling and monitoring should be part of a good preventive maintenance program, but it is still the exception rather than the rule.

Changing from one grease to another should be considered with due diligence. Before you switch products, it is critical to understand what is happening in the system. A few examples where trouble may arise include:

  • Mixing greases unintentionally because someone used the wrong grease gun.
  • Equipment speed increasing due to operational changes without evaluating if the grease can keep up.
  • Rising operating temperatures stressing the grease beyond its rated limits.
  • Storage conditions changing — hotter warehousing or outdoor locations causing grease degradation.

Another widespread “glitch” with grease is oil separation. When you open a container, chances are you may see a thin layer of oil at the top of the grease. The first thought that usually jumps to mind is whether the grease is suitable for use. Fortunately the answer in most instances is yes. A little oil pooling in a grease drum or pail is normal — especially after transportation or heat cycling.

If oil separation is minimal (up to about 6 mm), simply stir the oil back in. Excessive oil separation, however, can signal trouble. If the grease looks heavily separated or runny, contact your supplier.

Most grease performance problems do not boil down to grease chemistry alone — handling, application methods and operating conditions may play a huge role too. In the next issue of OilChat we will address more common grease problems and how you can fix, or even better, prevent them.

If you have any questions concerning grease in the interim, you are welcome to phone 011 462 1829, email us at info@bcl.co.za or visit www.bcl.q8oils.co.za.

CRUDE OIL EXTRACTION #Oil Chat 103

A question often asked is what happens to all the empty spaces when billions of litres of crude oil is pumped out of the earth? To answer the question we need to understand how crude oil was formed.

Crude oil is also known as petroleum. The word petroleum literally means “rock oil” and is derived from the Latin words Petra (rock) and Oleum (oil). Wherever crude oil is found today the earth was covered with water millions of years ago. Crude oil and petroleum are called fossil fuels because they are mixtures of hydrocarbons that formed from the remains of animals and plants that lived millions of years ago in oceans, lakes, and swamps.

It all started 300 to 400 million years ago. Aquatic plants and animals (organic matter) died and  dropped to the bottom and were covered by sand and sediment – Fig 1. With time more and more layers of sediment deposited on top of the plant and animal remains and formed porous rock – Fig 2. Over millions of years heat from inside the earth and pressure from the layers of sedimentary rock above turned the organic matter into crude oil and natural gas – Fig 3.

Today we drill down through the layers of sand and sedimentary rock to reach the porous rock formations that contain the oil and gas deposits. Contrary to what you may have believed up to now, extracting the crude oil is more like sucking liquid from a sponge with a straw than from a puddle of liquid.

Now back to the initial question. You may assume that gravel or tumbling rocks fill the void, but the truth is much simpler. The pressure underground is extremely high and as the oil and gas are removed, other matter will be forced in to replace it. Consequently underground water from the adjacent area moves in to take up the space that has been vacated.

If you have any questions about petroleum topics or the complete range of Q8 lubricants, simply phone 011 462 1829, email us at info@bcl.co.za or visit www.bcl.q8oils.co.za.

WIRE ROPE LUBRICATION #Oil Chat 102

The terms wire rope and steel cable are often used interchangeably, but there is a difference between the two. Wire ropes generally have diameters larger than 3/8 inch (10 mm). Sizes smaller than this are designated as cables. The major difference between the two, however, is in their construction.

Wire ropes are made up of multiple strands of wires twisted together. Each strand consists of several wires, and the strands are then twisted around a core (which can also be made of wires or other materials) as shown on the right. The construction allows for flexibility and strength, making wire ropes suitable for heavy lifting and rigging applications such as cranes, elevators, mine hoists and marine applications.

Cables are much simpler in design and normally consist of a single strand of wire or a few wires twisted together. They do not have the same multi-strand construction as wire ropes. A typical example is the brake cable on a bicycle.

Wire ropes wear from the outside, as well as from the inside. The outside wears as the wire rope moves over sheaves and pulleys and around winches or retaining drums. Along with dirt contamination, the rope is subjected to abrasive wear. The inside wears due to the inner strands rubbing and scuffing against each other as the rope is flexed and bent.

The extent to which wires move in a rope when it bends, is illustrated by the example of what actually happens when you wrap a 1 inch (25 mm) rope over a 30 inch (760 mm) sheave. The circumference of a 32 inch circle is slightly more than 6 1/4 inch longer than that of a 30 inch circle. Since the rope only touches half of the sheave at any time, the length differential which the rope must accommodate is 3 1/8 inch – almost 80 mm. This change of dimension is achieved by the sliding and adjusting of the strands in relation to one another, and a similar sliding and adjusting of the individual wires within each strand.

In addition to external and internal mechanical wear the rope also wears due to rust and corrosion.

Traditionally bitumen-based lubricants were used to protect wire ropes. These products must be heated before they can be applied since they are hard and thick at ambient temperatures. Some formulations contain a diluent or solvent to allow easier application. In low temperature conditions bitumen-based lubricants become very hard and brittle and fling off the rope. Environmental impact is another critical aspect of rope lubrication. Bitumen-based lubricants, when exposed to fire, release toxic fumes which pose significant health risks.

Nowadays more and more grease type wire rope lubricants are being used. Greases used for this application generally have a soft to semifluid consistency within NLGI grades 00 to 1. Wire rope greases typically offer the following benefits:

  • Good covering properties
  • They are water-repellent, water-resistant, and not emulsifiable
  • Are not subjected to significant embrittlement
  • Do not contain grit, abrasives, water, chlorine and impurities
  • They are free from additives or compounds which can form corrosive products caused by water contamination or additive degradation.

Last, but not least, grease-based wire rope lubricants penetrate readily into the core of the wire rope when applied with a high-pressure lubricator.

If you require more information about wire rope lubrication, simply phone 011 462 1829 or email us at info@bcl.co.za. Our lubrication experts are at your disposal and ready to provide you with advice and answer any questions you may have.

STOP/START SYSTEMS AND ENGINE OIL #Oil Chat 101

The Stop/Start system is a technology found in many modern vehicles. Car manufacturers are being pushed to meet ever increasing emission standards and Stop/Start technology helps them to achieve the targets. A large number of vehicle owners, however, are concerned that this feature may be harmful to their engine and they simply switch the system off. The frequent stopping and starting of the engine is the reason for this concern.

Most of us are aware that the Stop/Start system automatically turns the engine off when the car is idling (at traffic lights, in traffic jams, etc.) to reduce fuel consumption and emissions. The engine restarts almost instantly when you lift your foot off the brake or press the accelerator.  Unfortunately the technology has downsides too. For some of these the motor oil has to compensate. The drawbacks include increased wear, high static friction and elevated engine temperatures.

The automatic Stop/Start systems in vehicles place much greater demands on the engine oil. The constantly interrupted lubrication and cooling of engine components during shutdown requires superior quality oils that meet certain high performance standards. We will delve into the specific requirements, why they arise and whether special lubricants are indeed required.

Increased Wear

A thin hydrodynamic lubricating film (see OilChat 22) separates moving surfaces during normal engine operation. Each time the engine is stopped, this oil film breaks down and the surfaces come into contact with each other. When the engine is restarted, the components operate in the boundary lubrication regime with increased friction and wear, especially when a substandard oil is used.

Furthermore, high static frictional forces are present in the stationary engine.  To overcome the static friction between mating surfaces, high forces are required to get the engine going again. This has a negative influence on the service life of timing chains, starter motors and batteries.

To compensate for these technical hitches motor oil for Stop/Start vehicle operation must provide maximum wear protection and should maintain an extremely tough and durable lubricating film. In addition, the oil needs to contain active chemicals that offer effective wear protection in boundary lubrication conditions.

Increased Temper­ature

When the Start/Stop electronics cut the engine out, flow of oil also stops. This can have fatal consequences on components subject to high thermal loads, such as the turbocharger. Since it is no longer cooled by circulating oil, the temperature inside the turbocharger increases dramatically. Heat from the extremely hot turbine wheel flows to the shaft and bearings and these components can heat up to temperatures exceeding 300°C. This can lead to oxidation and carbonisation of the oil and increased deposits.

So, do Start/Stop systems require special oils due to the increased engine loads? The answer is a surprising NO.

There is no need for such oils because there are no specific Stop/Start engine oil specifications that determine the suitability of a lubricant. Instead the overall performance credentials of the oil determine relevancy. For example an engine oil that conforms to the industry specifications ACEA A3/B4 and API SN/CF will perform satisfactorily in vehicles with Stop/Start technology. In addition, individual vehicle manufacturers may have their own engine oil specifications (e.g. Mercedes-Benz 229.3, Volkswagen 505.01, etc.) that take into account the requirements of their Stop/Start engines.

Q8 oil formulations meet and exceed the requirements of modern engine oil specifications. Our oils offer the highest possible lubricating film stability and their special wear protection chemistry ensures reduced wear and increased engine life, even under the most adverse conditions. Simply put, Q8 engine oils are so advanced that you do not need any special lubricants for engines with automatic Stop/Star systems. In fact, the high performance lubricants in the Q8 Formula engine oil range have been suitable for the severe requirements of vehicles with Start/Stop systems even before the technology existed.

For more information about the range of Q8 engine oils suitable for Stop/Start operation, phone 011 462 1829, email us at info@bcl.co.za or visit www.bcl.q8oils.co.za.

VOLATILITY OF LUBRICATING OIL #Oil Chat 100

In this centenary issue of our newsletter the discussion topic is volatility – an important characteristic of lubricating oil that is often overlooked. Volatility is the tendency of a substance to evaporate since volatile matter has the capability to go into the vapor phase. In the case of oil this usually happens at elevated temperatures. Volatility has a critical impact on the performance of lubricating oils – low viscosity engine oils in particular – that are operating at high temperatures.

The base oil used to manufacture lubricating oil is a complex mixture of lighter (low viscosity) molecules and heavier (high viscosity) molecules. Low viscosity multigrade engine oil contains a larger percentage of lighter fractions. These lighter molecules are more volatile and vaporise (evaporate) first when the oil is heated, leaving the heavier molecules behind and the viscosity of the remaining oil is increased.

Many motorists do not realise that when they notice that their vehicle is “using” oil, they are often witnessing the effects of volatilisation. Motorists usually just buy extra oil to replace what they assume the engine has “used”, but is adding more oil necessarily the best solution to the problem? What they are doing by adding more oil, is burning up their money. Extra oil is not the only expense motorists face when dealing with volatilisation. As motor oil goes through the process of volatising, the chemically lighter (or more volatile) portions are always the first to “boil off”. This leaves the heavier, less pumpable portions behind. This heavier oil cannot be relied upon to flow easily and quickly to all engine components. The result is decreased fuel efficiency, premature component wear and deposit formation within the engine. The expense to the motorist can be quite substantial. It is therefore no surprise that concern about engine oil volatility has increased over the last number of years.

The following factors have a major influence on the performance of engine oil:

LOWER VISCOSITY ENGINE OILS
Vehicle manufacturers are very concerned about fuel economy. Thinner, low viscosity oils are being recommended to reduce fuel consumption. Traditionally SAE 20W-50 and SAE 15W-40 multigrade engine oils were used, but today many manufacturers recommend oils as thin as SAE 5W-30 and even SAE 0W-20 to improve fuel efficiency.

HIGHER ENGINE TEMPERATURES
Many modern internal combustion engines are turbocharged and have higher compression ratios. Oil sump capacities are reduced to minimise engine size and weight. To aggravate matters airflow around the engine is reduced due to better aerodynamics. All these lead to increased engine oil operating temperatures.

EXTENDED DRAIN INTERVALS
Engine oil volatility strongly effects drain intervals. Many manufacturers have introduced oil service intervals of 30,000 km or two years (whichever comes first) for petrol engines and 50,000 km for light duty diesel engines. Drain intervals for heavy duty diesel are typically between 80,000 and 120,000 km. These extended drain intervals lead to increased stresses on the oil.

ADDITIVE VOLATILISATION
The most widely used and effective anti-wear and anti-oxidation additives in engine oil contain phosphorus that can partially volatilize during high temperature engine operation. Volatile phosphorus in the exhaust stream degrades the function of the exhaust catalyst in reducing air pollution. Early studies have indicated that phosphorus volatility is not related to base oil volatility or to phosphorus content in the unused engine oil. More recent research has shown that phosphorus additive chemistry is the main contributor to catalyst poisoning and major additive suppliers have since come up with improved phosphorus technology to minimise additive volatilisation.

Based on the above it is evident that the volatility characteristics of the base oils used to manufacture low viscosity engine oils are key to the performance and longevity of the final product. The Noack Volatility Test is a critical measure of lubricating oil quality. There are several variants of the test, but in principle they all determine the evaporation loss of oil at high temperatures.

In the most commonly used Noack Volatility Test (CEC L-40-A-93, ASTM D5800 and DIN 51581) a 65 gram sample of oil is heated for one hour at 250°C while a controlled stream of air carries the volatile components away. Results are reported as a percentage of the mass an oil has lost during the test – the lower the percentage, the better, as this demonstrates resistance to oil volatility and breakdown. There are no formal Noack Volatility limits or specifications for lubricant base oils, but experience has confirmed that a maximum limit of 15% allow engine oils to perform satisfactorily for long periods at elevated temperatures.

Q8Oils offer a comprehensive range of multigrade engine oils blended with high quality base oils and the latest additive technology to minimise volatilisation. 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.

RHEOLOGY OF LUBRICANTS PT3 #Oil Chat 99

In this final part of our Rheology series we conclude with a discussion of the rheological properties of lubricating grease. Two key characteristics of grease are consistency and viscosity. It is therefore not surprising that these rheological properties appear in all grease specifications and product literature. Another key rheological characteristic of grease that is often overlooked, is deformation (visco-elasticity). The deformation behaviour of lubricating grease under shear or stress is critical in the satisfactory performance of the grease.

The smooth and reliable operation of oil lubricated machinery depends on consistent lubrication between moving surfaces. To achieve this the lubricating oil must be of Newtonian nature to uphold a robust film to separate the moving surfaces. The viscosity of Newtonian oils does not change with shear, stress or rate of flow.

For most machines in intermittent service it is desirable to have a non-Newtonian lubricant with a thicker consistency to remain in place during shutdown, but it must, however, have the fluidity of an oil when the equipment is in operation.

The American Society for Testing and Materials (ASTM) defines lubricating grease as “A solid to semifluid product of dispersion of a thickening agent in liquid lubricant. Other ingredients imparting special properties may be included” The thickener holds the oil in place but releases it under shear or stress to give the effect of oil lubrication with similar viscosity as the base oil used in the grease. When the shear/stress is removed, the thickener ‘absorbs’ the oil again and the grease thickens to its original consistency. In this instance the rheological behaviour of the non-Newtonian grease is thixotropic. In fact, most greases available today are of thixotropic nature.

In some instances a non-Newtonian grease that hardens when subjected to stress is preferred. Typical examples are large opencast mining machines where the grease must be pumped long distances from a central grease reservoir to the actual lubrication points. The grease needs to be soft enough to be pumped and then thickens under mechanical pressure to adhere to heavily loaded components and provide superior lubrication, especially under shockload conditions. The rheological behaviour of such non-Newtonian greases is rheopectic. These greases require a gentle touch when being pumped. It is crucial to employ a special pumping system with low shear for rheopectic greases. High shear forces can accelerate the thickening process and may cause grease feed lines to get clogged. Tailor-made pumps are therefore required that deliver a smooth, controlled flow to preserve the rheopectic nature of the grease.

Q8Oils offer a comprehensive range of high-quality greases for a wide variety of automotive, commercial, construction, mining, agricultural and other 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.

RHEOLOGY OF LUBRICANTS PT2 #Oil Chat 98

In OilChat 97 we discussed rheology in general. In this issue we will address the rheological behaviour of lubricating oil.

The most important rheological parameter of liquid lubricants is viscosity, hence viscosity is reported on all oil specifications and product data sheets. It also affects the tribological properties like friction and wear between moving surfaces in contact with each other.

The smooth and reliable operation of machinery and mechanical components depends on consistent lubrication at the contact area between moving surfaces. To achieve this, the lubricating oil must be of Newtonian nature to maintain a robust film to separate the moving surfaces. The viscosity of Newtonian oils does not change with shear/stress or rate of flow. Most monograde lubricating oils (mineral and synthetic) can be classified as Newtonian.

Having said that, monograde oils may become non-Newtonian in service. A typical example is diesel engine oil that is loaded with soot (partially burned fuel). When the soot concentration in engine oil reaches a level that can no longer be dissolved by the dispersant additive, the soot particles clump together to increase the viscosity of the oil. High viscosity may result in cold-start problems and risk of oil starvation. Once the oil is circulated by the oil pump the soot particles are dispersed in the oil and the viscosity will decrease, but when the engine is shut down the oil will thicken up again. In this instance the rheological behaviour of the oil is thixotropic.

Multigrade oils may also exhibit non-Newtonian behaviour when subjected to stress. Multigrade oils are formulated with Viscosity Index Improvers, also referred to as Viscosity Modifiers. These are normally long chain polymers that expand with increase in temperature to improve the “thickening characteristics” of the oil at elevated temperatures. The rheological behaviour of these polymers is described below:

 

 

 

 

Fig 1: When the oil temperature is low, the polymers curl up into tight balls that flow readily with the oil molecules and with no effect on the oil viscosity.

Fig 2: As the temperature increases, the polymers expand into large stringy coils that restrict the normal oil flow, which has a thickening effect on the oil. When the oil cools down, the polymers return to their original shape. The result is that when these polymer based additives are blended in the correct proportion with for example SAE 15W base oil, the oil flows like a SAE 15W at low temperatures and similar to a SAE 40 oil at high temperatures. The outcome is a SAE 15W40 multigrade oil that will provide adequate protection over a wide temperature range. It should be noted that there is actually no SAE 40 base oil in a SAE 15W40 formulation.

Fig 3: The viscosity of most multigrade engine oils decreases with increase in the rate of oil flow or shear. This is because the ‘viscous grip’ of the oil on the expanded polymers is reduced with increased stress which causes distortion and rotation of the polymers. The decrease in viscosity of these non-Newtonian multigrade oils is recovered when the shear rate is reduced and the phenomenon is called Temporary Viscosity Loss or TVL.

Fig 4: When the oil is violently sheared, the polymers may be stretched beyond their ability to accommodate the motion of the oil and one or more of the polymers may be broken. Consequently, the viscosity of the oil-polymer solution decreases permanently because the viscous contributions of the broken, shortened polymers are less than that of the original long chain polymers before degradation. In contrast to TVL, this polymer degradation phenomenon is called Permanent Viscosity Loss or PVL since, in this case, the viscosity lost is not recovered and the rheological behaviour of the oil is non-thixotropic. In the early days of multigrade oils, PVL was a factual problem but with modern, shear-stable polymer technology it is unlikely to occur if the oil is used for the intended application. If, however, a modern multigrade oil is used incorrectly, PVL may still occur. A typical example is when a multigrade engine oil is used in a heavily loaded gear system.

Q8Oils offer a comprehensive range of shear stable multigrade oils for a wide variety of automotive, commercial, construction, mining, agricultural and other 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.

RHEOLOGY OF LUBRICANTS PT1 #Oil Chat 97

Rheology is the science of flow and deformation of matter and describes the interrelation between force, deformation and time. Rheology is applicable to all materials, from gases to solids. Fluid rheology is used to describe the consistency of liquid matter by referring to viscosity and elasticity. Viscosity is the resistance to flow or thickness and elasticity relates to stickiness or structure.

Newtonian behaviour is a phenomenon that is firmly embedded in the science of Rheology and is also a key property that affects the performance of lubricants.

NEWTONIAN substances are matter of which the viscosity does not change with shear/stress or rate of flow. Typical examples of Newtonian fluids are water, alcohol and oil.

NON-NEWTONIAN materials are liquids or gels of which the viscosity does change when subjected to stress. Non-Newtonian fluids may thin down or thicken up when sheared or stressed as discussed below:

Thixotropy is the property of certain fluids and gels to become thinner when a constant force is applied, and after removal of the force the viscosity recovers fully to the initial state in a finite period of time. The higher the force that is applied, the lower the viscosity becomes. Thixotropy is a time-dependent phenomenon, as the viscosity of the substance must recover within a certain timeframe when the applied force is removed. Tomato sauce is a typical example. It is usually quite thick, leaving you frustrated waiting for it to run out of the bottle. In response you shake it, giving you that red shower that drowns the fries on your plate. Reason is that tomato sauce is thixotropic. Its thickness and viscosity decrease depending on for how long and how fast you shake it. When you allow the tomato sauce to settle for some time it “gels” again.

In some materials the structural strength/viscosity decreases while shearing but the viscosity does not fully recover after an appropriate rest period. It remains thinner than the initial state which indicates that the structure does not recover completely. A typical example of this behaviour is yogurt. After stirring, the viscosity of yogurt remains thinner than it was initially. Such substances may be classified as non-thixotropic.

Rheopexy is the rare property of some Non-Newtonian fluids to show a time-dependent increase in viscosity; the longer the fluid undergoes shearing forces, the higher its viscosity becomes. Rheopectic fluids, such as cream, thicken or solidify when stressed. Fresh cream usually flows readily, but when you shake or whip it long enough, its consistency changes, it stops to flow and eventually becomes solid. In summary, Rheopectic fluids thicken when subjected to shear forces.

In the next issue of OilChat we will discuss the significance of rheology in lubrication. If you have any questions about rheology (or any other lubricant related issues) in the interim, you are welcome to email us at info@bcl.co.za.

DEMULSIBILITY OF LUBE OIL #OilChat 96

demulsibility of lubricating oil

Demulsibility is a term commonly used in the language of lubrication. Demulsibility is the ability of oil to release or separate from water. In other words, it is a measure of how well the lubricant can resist emulsification. A high demulsibility rating means that the lubricant will resist forming an emulsion with water, while a low number indicates that it will not.

Oil and water separate readily because similar molecules attract each other, i.e. oil sticks with oil, water sticks with water. However, when a mixture of oil and water is agitated, an emulsion is formed. Three oils with various degrees of demulsification and emulsification are shown on the right:

In the sample on the left all the oil and water are demulsified.
There is an interface (emulsion) of oil and water in the middle sample,In the sample on the right all the oil and water are emulsified.

In most instances the oil and water will separate completely when left to settle for an adequate period of time. The water drops to the bottom since water is denser than oil.

In lubrication the demulsification property of oil is a benefit since water shedding is important for systems that have the potential to become contaminated with water. Water that enters a circulating system and emulsify can increase wear and corrosion, reduce load-carrying capacity, promote oil oxidation, deplete additives and plug filters. In hydraulic systems it can also adversely affect the operation of valves, servos and pumps. Although highly refined oils permit water to separate readily, demulsibility can be affected negatively by the presence of impurities and contaminants in the oil. Some oil additives such as rust inhibiters and dispersants can actually promote emulsion formation.

The impact of demulsibility depends on the level of contamination and the residence time (the time the oil spends ‘resting’ in the reservoir) of the system. When the resident time is sufficient the demulsified water can be removed by engineering solutions such as drain valves, suction, etc.

Demulsibility testing can show failure in the lab, but with sufficient residence time, the oil may shed water at an acceptable rate that does not impact oil performance. Small oil reservoirs with lower residence times require better demulsibility performance than larger sumps. It is recommended that testing for demulsibility should be conducted on a regular basis if the oil system is exposed to water or if demulsibility performance is suspicious.

The ASTM D1401 demulsibility test method is commonly used to determine the ability of oil to separate from water. A 40 ml sample of the test specimen and 40 ml of distilled water are stirred for 5 minutes in a graduated cylinder at a specified temperature. The time required for the separation of the emulsion is recorded after every 5 minutes. If complete separation or emulsion reduction to 3 ml or less does not occur after standing for 30 minutes, the volumes of oil, water, and emulsion remaining are reported.

Regardless of what is said above, a few equipment manufacturers do not recommend hydraulic oils that shed water. Caterpillar hydraulic oil is for instance formulated to hold water in dispersion.

The oil contains emulsifiers specifically designed to disperse water. Caterpillar does not recommend oils that “separate,” “shed,” or “release” water. They claim that separated water drawn through the hydraulic system can damage pumps and other components. If the water freezes, it can also cause serious damage to hydraulic systems. Notwithstanding this many Caterpillar machines in mixed fleet operations are operating satisfactorily with lubricants that do demulsify or shed water.

Q8Oils offer a comprehensive range of demulsifiable lubricants for a wide variety of automotive, construction, industrial, mining, agricultural and other applications. For more information phone 011 462 1829, email us at info@bcl.co.za or visit www.bcl.q8oils.co.za.

Finally we would like to wish all our loyal followers a prosperous and rewarding 2025.

FZG GEAR TEST #OilChat 95

The FZG gear test evaluates anti-wear characteristics and load carrying capacities of lubricants. The test rig was developed by the Technical Institute for the Study of Gears and Drive Mechanisms (Forschungsstelle für Zahnräder und Getriebebau) at the Technical University of Munich.

The test rig simulates a misaligned gear set operating in the test lubricant. The gears are loaded in 12 increasing “stages”. Tooth-wear is examined after each stage. The performance of the fluids is determined by the load stage at which excessive wear occurs. A high pass load stage indicates better resistance to wear. If failure does not occur at load stage 12, it is reported as >12.

 

 

There are a number of different FZG load tests with different speeds, oil sump temperatures, gear types and direction of rotation. Following are the most commonly used test procedures:

FZG Gear Wear (ASTM D5182) evaluates gear scuffing resistance of fluids using A profile gears. The rig is operated at 1450 rpm up to 12 progressive load stages at 15-minute intervals. Standard tests are run at a fluid temperature of 90oC. Gear teeth are inspected for scuffing after each load stage. In addition to a visual evaluation of the gear teeth condition, gear weight loss is also measured.

FZG Gear Wear (ASTM D4998) assesses gear wear resistance of fluids using A profile gears. The rig is operated at 100 rpm under constant load for 20 hours. A visual tooth surface rating and gear weight loss are measured.

FZG Pitting Type C Gears evaluates gear pitting resistance of fluids using C profile gears. Tests are run up to 300 hours under constant load, temperature, and speed. Inspections are conducted at predetermined intervals for pitting damage on the gear tooth faces.

FZG A10/16.6R/120 is a more severe version of the ASTM D5182 Load Stage Wear test. This test requires A10 gears (half the tooth width of the A gears) and is run at 2880 rpm in reverse mode.

These tests are also defined by the German Institute for Standardization (DIN), the International Organization for Standardization (ISO) and others. In addition to the standard FZG gear tests, some test facilities may offer customised FZG tests. The gear type, oil temperature, load, test duration, direction of rotation and speed can all be altered to meet specific customer requirements.

The FZG gear test is primarily used to assess the resistance to scuffing of mild additive treated oils, such as industrial gear oils, transmission fluids, and hydraulic oils. High EP type oils, for example, oils meeting the requirements of API GL-4 and GL-5, exceed the capacity of the test rig and therefore cannot be evaluated with FZG gear tests.

Q8Oils offer a comprehensive range of wear inhibiting lubricants for a wide variety of automotive, construction, industrial, mining, agricultural and other 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.