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Lubrication FAQs & Myths

Lubrication FAQs and Myths

MYTHS DIE HARD. Myths about industrial lubricants and lubrication are no exception. Most plant engineers know the ins and outs of machine lubrication, but, with industrial technology taking giant strides forward and lubrication technology keeping pace, it is not surprising that some engineers still retain a misconception or two. A group of field lubrication engineers, asked to share some of the more common engineers’ tales they heard, listed 31 recurrent myths, and then gave the real story behind each point. Click on any item to discover the true facts.

Myth #1: Oil is oil.
Some characteristics differ obviously between oils -- for example, viscosity. But other differences are not so obvious. There are hundreds of industrial lubricants, each formulated for specific applications, and each contains additives specially blended for those applications. Using the wrong lubricant is a major cause of lubricantrelated machine breakdowns. Using the right lubricant can help improve machine efficiency and extend component life.
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Myth #2: Pennsylvania crude oil makes the best lubricants.
When Pennsylvania crude oil is refined, it readily yields a lubricant base stock that has relatively high resistance to oxidation and a high viscosity index (that is, its viscosity changes little over a wide temperature range). This feature was important when separating lubricant stocks from other crude oils was difficult, but for several decades oil companies have known how to get equally good lube base stocks from many different crude oils. And additives are much more important in today’s lubricants, and lube makers have learned how to adjust for variations in base stocks by modifying the additive package.
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Myth #3: Oil never wears out.
Oil does wear out. The primary enemy of oil life is heat. At operating temperatures of 150º F and higher, oil begins to oxidize and thicken. Sooner or later, depending on oil quality and operating temperature, the oil will leave a trail of sludge and varnish throughout the machine. To prevent sludge and varnish, change the oil every 6 months in machines that operate at high temperatures, and every year in others. Some oil suppliers will take regular oil samples from critical industrial machines, run them through a battery of tests, and provide a report on oil condition. Such reports can pinpoint the right change intervals.
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Myth #4: Old oil is the primary cause of lubricant-related equipment breakdowns.
The two most prevalent causes of lubricant-related breakdowns are: (1) use of the wrong lubricant, and (2) high concentrations of contaminants, especially dirt and metalwear particles that bombard machine components and cause premature wear and breakdowns. Again, monitor the condition of the oil. Testing can identify metalwear particles and warn of impending breakdowns.
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Myth #5: To be able to select the right oil, you need to know only the physical specifications.
Physical specifications such as color, flash point, and gravity allow oil companies to manufacture lubricants to exacting standards. These characteristics tell very little about the lubricant’s intended applications, how it will perform, or the benefits provided by its additives.
The additives, primarily, improve performance and longevity. They reduce the pour point, and broaden the temperature range over which satisfactory viscosity is maintained. They inhibit foam formation, control oxidation and its harmful effects, prevent formation of varnish and sludge deposits, and reduce friction wear. But additives distort the results of conventional tests so that they have no meaning.
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Myth #6: Viscosity determines the lubricity, or "oiliness," of an oil.
Heavier oils do form thicker lubricating films, but in today’s oils, additives also provide lubricity. Addition of fatty materials increases lubricity without necessarily increasing viscosity. Sulfate and metallic lubricity additives have no significant effect on viscosity.
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Myth #7: Oils of the same SAE or ISO numbers are interchangeable.
SAE and ISO numbers are intended only as guidelines in selecting the proper viscosity. They tell nothing about other characteristics. A hydraulic oil and a motor oil with the same SAE number, for example, may have the same viscosity, but they cannot be used interchangeably.
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Myth #8: An increase in viscosity always indicates an increase in harmful insolubles.
Detergent/dispersant additives can keep a substantial volume of insolubles in fine, uniform particles distributed throughout the body of oil so they will not form sludge or harmful deposits; viscosity increases but no harm is done. Eventually, however, the oil can carry no more of the potentially harmful insolubles. Viscosity tests indicate when that point (the "condemning limit") has been reached.
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Myth #9: Neutralization number measures inherent acidity of an oil.
This number is rarely indicative of inherent acidity. Metallic additives increase the neutralization number in most oils. An increased neutralization number of an oil in service may mean that the oil is becoming increasingly corrosive, though contaminants and non-corrosive products of deterioration can also be the cause.
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Myth #10: Ash content measures abrasive constituents In an oil.
Metallic additives may form ash that is not abrasive. Ash content does not reveal much about an oil. Abrasive constituents may be detected by forcing the oil through a fine (5 micron) filter disc and viewing the residue with a magnifying glass. The quantity of such constituents can be measured in the lab by spectrophotometry.
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Myth #11: The oil’s Conradson carbon residue (CCR) rating should be known.
This test was developed to measure carbon residue in steam-cylinder lubricants. The procedure measures the residue after readily consumed components have been cooked off. In modern lubrication applications, oil is not cooked off. Carbonaceous deposits result, instead, from oil deterioration or contamination, and the CCR rating has little meaning.
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Myth #12: High specific gravity in an oil indicates poor oxidation resistance.
Some high-specific-gravity (low API gravity) petroleum base stocks are less stable than lighter base stocks. Consequently, a high specific gravity has sometimes been interpreted as an indication that an oil is more subject to oxidation and other chemical deterioration. Improved refinery practices and additives can enhance oil stability. Specific gravity no longer tells anything about an oil’s performance or longevity.
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Myth #13: Pour point is the lowest temperature at which a pump will pick up an oil and move it through the system.
Pour point tells only at what temperature the lubricant will be most viscous just short of solidification. It is determined by a carefully controlled laboratory test. In the test the head making the oil flow is about ¼ in. Under operating conditions, however, the head can be much higher or lower.
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Myth #14: The performance of a hydraulic oil can best be determined by its Turbine Oxidation Stability Test (TOST) value.
The Turbine Oxidation Stability Test was devised when oil-additive technology was in its infancy, to measure the effectiveness of oxidation inhibitors in turbine oils. More meaningful tests have since come into prominence.
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Myth #15: An oil’s only job is to lubricate.
In many applications, oil must also flush away dirt and wear particles and carry them to the machine’s filters. Oil also dissipates heat. Both oil and grease may help seal bearings to prevent the entry of contaminants.
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Myth #16: If a little oil or grease is good, a lot is better.
Applying too much grease can rupture seals and thus allow contaminants to enter the machine. In an electric motor bearing, the grease can also penetrate the motor windings and cause the motor to burn out. Excessive grease in a bearing can also generate heat because fluid resistance is greater, contributing to a costly bearing failure.
Excessive oil can also generate heat because of increased fluid resistance; this heat shortens oil life. Overflowing reservoirs -- sometimes noticeable only after the machine stops and all oil has returned to the reservoir -- can contaminate the process and create unsafe work conditions. Overfilling splash systems can rupture seals.
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Myth #17: The cleaner the oil is, the better the oil is.
In some cases, a dirty oil is satisfactory. Internal combustion engines, for example, create large amounts of unburned carbon and other materials that are carried in suspension in the oil until they can be deposited in the filter or the oil can be changed. Here, a dirty oil is probably doing its job. But in hydraulic systems in numerical control machines, even minute amounts of contaminants are intolerable because they quickly clog the servovalves. In short, for some applications the oil should look dirty, and for others, it must be clean. Monitoring oil condition is always advisable.
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Myth #18: Hydraulic oil isn’t a good lubricant.
Although many people believe that hydraulic oil is in a class of its own, it is still an oil. In addition to providing a means of transmitting energy, it lubricates hydraulic pumps, bearings, cylinders, and other system components. It must be of high quality because hydraulic systems demand a lot from an oil -- long oil life, pump protection, oxidation resistance, anti-wear properties, and more.
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Myth #19: Fire-resistant hydraulic oils don’t burn.
Fire-resistant hydraulic oils will burn as long as a flame is present. When the flame is removed, however, the oil will stop burning. A regular mineral oil, once ignited, continues to burn until smothered or drastically cooled. And a fire-resistant hydraulic oil will usually be more difficult to ignite than a petroleum oil is.
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Myth #20: Quality of a grease can be evaluated by smelling, feeling, or tasting it.
A generation ago, many specialized greases were manufactured for particular applications. One may have been tacky, and another smooth and soft; some tasted good, and some didn’t. People who worked with many different greases were soon able to distinguish among them simply by feeling or smelling them or even tasting them.
Today’s greases are able to handle a variety of applications. By and large, they are soft, buttery, and short-fibered, and they are very hard to tell apart. They all taste equally bad, and some contain constituents that, if ingested, could be hazardous to health.
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Myth #21: Molybdenum disulfide (moly) is an extreme pressure (EP) agent in grease.
Many people believe that only a grease containing moly should be used for EP applications. But moly is a solid lubricant, not an EP agent. An EP agent reacts with the lubricated surface to form a film, and moly acts as the lubricant.
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Myth #22: Grease color has a lot to do with grease quality.
The color of a grease has nothing to do with quality. A dull, brownish-gray grease can be just as effective as a sparking red grease. Color is used only as a control in lubricant manufacturing or when a plant desires a specific color.
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Myth #23: A water-resistant grease completely repels water.
Water almost always gets into greases during use. Water (usually from 20 to 100 percent of the grease’s volume, depending on the type of soap thickeners) combines with the grease without diluting it. Only after water has been absorbed does the grease repel water. A good, water-resistant grease will absorb water without losing its consistency.
Certain greases, such as sodium greases, absorb water and have no water resistance. The more water a grease absorbs, the softer it becomes. It eventually becomes fluid and washes away.
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Myth #24: Dropping point determines the usable temperature range of a grease.
Dropping point is the temperature at which a grease will release a drop of oil. The usable temperature range is usually 100 to 150º F below the dropping point. (Lubrication frequency must be increased drastically as the operating temperature approaches the dropping point.)
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Myth #25: The higher the dropping point is, the better the grease is.
Dropping point has nothing to do with the quality of a grease. Greases with higher dropping points are made for higher temperature applications.
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Myth #26: Machine manufacturer’s warranties usually require the use of particular lubricants.
Most warranties cover only defects in materials and workmanship. Only a few specify that certain lubricants must be used. It is wise to check with the manufacturer before making a substitution, especially during the warranty period.
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Myth #27: Anyone can do the job of lubrication.
In addition to being careful and thorough in following a machine’s lubrication chart, a good oiler knows the machines he works with and will look and listen for problems. He has been trained to check for excessive heat, unusual machine noise, and any abrupt changes in color or odor.
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Myth #28: Lubrication is a costly headache.
Lubrication, when compared to the cost of downtime, is not costly. In plant after plant, machine breakdowns can be traced to half-hearted or unsystematic lubrication practices. When these same plants have tightened their lubrication practices, they have seen downtime rates plummet, production increase, and overall operations run more smoothly.
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Myth #29: The cost of lubricants is the highest of all lubrication costs.
The ratio between the cost of the lubricants and the cost of applying the lubricants is usually about 1:5. That is, it costs five times as much to apply the lubricants (lubricator, supervisor, storage, handling, and dispensing manhours, and equipment) as it does to purchase the lubricants. In some plants, this ratio is much higher.
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Myth #30: A lot of money can be saved by conserving fuel, but conserving lubricants isn’t worth the effort.
By using lubricants best suited to the machines and operating conditions, practicing efficient machine maintenance, filtering or reclaiming lubricants, and, when appropriate, lengthening drain intervals, a plant can reduce lubricant consumption dramatically. Often, thousands of dollars can be saved. Consider these two examples:

Myth #31: When it comes to lubrication, nothing is new.
Industrial machines have been getting more powerful and more complicated, and industrial lubrication has had to keep in step with technology. For example, synthetic oils have been developed to meet the simultaneous demands of high-power machines and energy conservation. Today’s lubricants offer superior performance and, because they last longer, lower application costs.

Forgetting all these myths, and selecting lubricants on the basis of performance and using them as long as they are doing their job safely, will help hold down the rising cost of maintenance.
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