What Is Lubrication?

Wes Cash, Noria Corporation

Tags: industrial lubricants, synthetic lubricants, greasesLubrication is a word that’s often used in regards to machinery reliability and maintenance, but what is lubrication? The dictionary defines lubrication as the application of some oily or greasy substance in order to diminish friction. Although this is a valid definition, it fails to realize all that lubrication actually achieves.Many different substances can be used to lubricate a surface. Oil and grease are the most common. Grease is composed of oil and a thickening agent to obtain its consistency, while the oil is what actually lubricates. Oils can be synthetic, vegetable or mineral-based as well as a combination of these. The application determines which oil, commonly referred to as the base oil, should be used. In extreme conditions, synthetic oils can be beneficial. Where the environment is of concern, vegetable base oils may be utilized.Lubricants containing oil have additives that enhance, add or suppress properties within the base oil. The amount of additives depends on the type of oil and the application for which it will be used. For instance, engine oil might have a dispersant added. A dispersant keeps insoluble matter conglomerated together to be removed by the filter upon circulation. In environments that undergo extremes in temperature, from cold to hot, a viscosity index (VI) improver may be added. These additives are long organic molecules that stay bunched together in cold conditions and unravel in hotter environments. This process changes the oil’s viscosity and allows it to flow better in cold conditions while still maintaining its high-temperature properties. The only problem with additives is that they

can be depleted, and in order to restore them back to sufficient levels, generally the oil volume must be replaced.

Reducing friction is a key objective of lubrication, but there are many other benefits of this process. Lubricating films can help prevent corrosion by protecting the surface from water and other corrosive substances. In addition, they play an important role in controlling contamination within systems. The lubricant works as a conduit in which it transports contaminants to filters to be removed. These fluids also aid in temperature control by absorbing heat from surfaces and transferring it to a point of lower temperature where it can be dissipated.There are three different types of lubrication: boundary, mixed and full film. Each type is different, but they all rely on a lubricant and the additives within the oils to protect against wear.Full-film lubrication can be broken down into two forms: hydrodynamic and elastohydrodynamic. Hydrodynamic lubrication occurs when two surfaces in sliding motion (relative to each other) are fully separated by a film of fluid. Elastohydrodynamic lubrication is similar but occurs when the surfaces are in a rolling motion (relative to each other). The film layer in elastohydrodynamic conditions is much thinner than that of hydrodynamic lubrication, and the pressure on the film is greater. It is called elastohydrodynamic because the film elastically deforms the rolling surface to lubricate it.

Even on the most polished and smooth surfaces, irregularities are present. They stick out of the surface forming peaks and valleys at a microscopic level. These peaks are called asperities. In order for full-film conditions to be met, the lubricating film must be thicker than the length of the asperities. This type of lubrication protects surfaces the most effectively and is the most desired.Boundary lubrication is found where there are frequent starts and stops, and where shock-loading conditions are present. Some oils have extreme-pressure (EP) or anti-wear (AW) additives to help protect surfaces in the event that full films cannot be achieved due to speed, load or other factors. These additives cling to metal surfaces and form a sacrificial layer that protects the metal from wear. Boundary lubrication occurs when the two surfaces are contacting in such a way that only the EP or AW layer is all that is protecting them. This is not ideal, as it causes high friction, heat and other undesirable effects.Mixed lubrication is a cross between boundary and hydrodynamic lubrication. While the bulk of the surfaces are separated by a lubricating layer, the asperities still make contact with each other. This is where the additives again come into play.With a better understanding of this process, it should be easier to define what lubrication actually is. It is a process of either separating surfaces or protecting them in a manner to reduce friction, heat, wear and energy consumption. This can be accomplished by using oils, greases, gases or other fluids. So the next time you change the oil in your car or grease a bearing, realize there is more going on than meets the eye.

What Causes a Short Life for Gear Oil?

Noria Corporation Tags: gear lubrication, oil flushing, oil analysis, oil oxidation, contamination control

"About a year ago, we ran a lubricant too long in a high-duty gearbox, and it oxidized and threw sludge. Since then, we've been watching the oil more closely with oil analysis. My problem is that we are now seeing acid numbers increase and oil darken after only one month of service. The lubricant used to last a full year. We keep changing the oil, but the problem just repeats. Why does our gear oil have such a short life?"It sounds like the gearbox was not thoroughly flushed after the oil oxidized the first time. Sometimes a simple drain will leave more than 15 percent of the old oil behind, occluding to machine surfaces and becoming trapped within the casing. This also leaves behind a host of reactive chemicals (pro-oxidants) that rapidly deplete antioxidant additives, leaving the base oil unprotected.You refer to the gearbox as high-duty, which probably means high temperature and high wear metal production. The temperature and wear particles also accelerate the rate of oxidation, especially when sludge and other pro-oxidants are in the mix. Consider doing a thorough flushing of the gearbox.

How to Distinguish Between Mineral and Synthetic Oils

Noria Corporation

Tags: synthetic lubricants, gear lubrication “Relating to gearboxes on trucks, if the owner or driver doesn’t know if the gear lubes are synthetic, is there a fool-proof way to determine this without having to send a sample to the lab? Some oil manufacturers color their synthetic oils, while others don’t. What would happen if the oils were to be mixed or topped off with the wrong oil?”The color of the lube is simply a dye. There are no standards, and manufacturers can and do change colors whenever they please. Unfortunately, there is no reliable way of differentiating between mineral and synthetic in the field. However, because synthetic base oils are white (meaning transparent) as compared to mineral oils, which have a darker natural color (due to aromatics, sulfur and other impurities), this may be a distinguishing factor. Note, however, that despite the fact that the base oil of a synthetic is white, the additives can add considerable color (darkening) to the finished oil.In the laboratory, you could distinguish synthetics from mineral oil by looking at a combination of physical properties including VI, flash point, pour point and aniline point. There may also be different elemental additive chemistry.Generally, in the type of application you are talking about, the synthetic gear oil will likely be polyalphaolefin (PAO) based. PAOs are very similar chemically to mineral oils, so mixing the two should not cause a compatibility problem, especially if both oils are the same API classification.However, if a synthetic is required, such as for cold-temperature operation, using a mineral by mistake may cause other problems.Also, be aware that in industrial applications, some synthetic gear oils are polyglycol (PAG) base stocks, which are chemically incompatible with both PAO synthetics and mineral oils. In this case, mixing will result in serious incompatibility issues.

Should Synthetics be Mixed with Mineral Oils?

Noria Corporation

Tags: synthetic lubricants "What are the effects of mixing synthetic gear oil with mineral gear oil?"The effect depends on the types of synthetic bases that were mixed with mineral bases. Polyalphaolefin and diester synthetic bases can be mixed with mineral oil bases, which is done regularly to create “blend” products.Polyalkylene glycol (PAG) bases should not be mixed with any of the others unless specialized barrier fluids are used to minimize the incompatibility. When PAGs are mixed into other lubricants, you typically will get strong negative reactions (producing sludge and tacky residue) that require extra effort to flush, clean and correct.Even if the base oils are compatible, there is the prospect that the additives used to create necessary performance properties could conflict, producing lost lubricant effectiveness.It is advisable to perform filterability, oxidation stability, air release and demulsibility testing prior to mixing lubricant intentionally.Remember, modern lubricants are sophisticated products, formulated to meet the demanding lubrication requirements of modern equipment. The old saying, “oil is oil” no longer applies. Mixing lubricants is fraught with danger — to your equipment, to your business and to your wallet. When in doubt, don’t mix different lubricants. If it occurs accidentally, address the problem immediately.Don’t be afraid to bring in an expert, whether it is the lubricant manufacturer, the additive

supplier or an independent consultant to your site. Your response to a situation where different lubricants are mixed will depend on the products in the mixture, the end-use application, the relative concentrations of products and the total volume involved.In its mildest form, mixing different lubricants may lead to a degradation of lubricant performance. Mixing the same API grades of synthetic passenger car motor oil and mineral oil-based engine oil won’t damage the engine, but you will lose the performance features you expect from the synthetic. At the other end of the spectrum, adding typical turbine oil to an anti-wear hydraulic oil in a hydraulic pump could spell disaster. Deposits may form that could increase wear and plug filters.You can conduct some simple tests to confirm an oil mixing problem even without access to a formal lubricant laboratory. Heat an oil mixture or two oils you want to test for compatibility and examine for clarity. If the mixture is cloudy, the oils are not compatible. To check further, add a small amount of water, mix thoroughly and continue heating. Allow the mixture to sit at room temperature for several hours. If a solid forms in the oil, they are incompatible.

The Hidden Dangers of Lubricant Starvation

Jim Fitch, Noria Corporation Tags: industrial lubricants

For those who strive for lubrication-enabled reliability (LER), more than 95 percent of the opportunity comes from paying close attention to the “Big Four.” These are critical attributes to the optimum reference state (ORS) needed to achieve lubrication excellence. The “Big Four” individually and collectively influence the state of lubrication, and are largely controllable by machinery maintainers. They are well-known but frequently not well-achieved. The “Big Four” are:

1 Correct lubricant selection2 Stabilized lubricant health3 Contamination control4 Adequate and sustained lubricant level/supply

The first three of the “Big Four” have benefited from considerable industry attention, especially in recent years. Conversely, the last one has gone relatively unnoticed yet is no less important. Therefore, it will be the central focus of this article.Over the past few decades, researchers and tribologists have compiled countless listings that rank the chief causes of machine failure. We’ve published many of these in Machinery Lubrication magazine. The lists ascribe the causes of abnormal machine wear to the usual suspects: contamination, overheating, misalignment, installation error, etc. There’s typically a lubrication root-cause category that is a catch-all for one or more causes that can’t be easily specified or named. I’ve seen terms used like “inadequate lubrication” and “wrong lubrication.”Understandably, it is difficult for failure investigators and analysts to trace back the exact sequence of events beginning with one or more root causes. Evidence of these causes is

often destroyed in the course of failure or in a cover-up during the cleanup and repair. Having led several hundred such investigations over the years, I’ve learned that one root cause in particular is too often overlooked - lubricant starvation.

81%

of lubrication professionals have seen the effects of lubricant starvation in the machines at their plant, according to a recent survey at machinerylubrication.com

Although most everyone knows about this in principle and realizes the common sense of adequate lubricant supply, it is frequently ignored because many typical forms of lubricant starvation are largely hidden from view. For instance, who notices the quasi-dry friction that accelerates wear each time you start an automobile engine? This is a form of lubricant starvation. It’s not a sudden-death failure, but it is a precipitous wear event nonetheless. Each time controllable wear goes uncontrolled, an opportunity is lost to prolong service life and increase reliability.

The Nature of Lubricant StarvationMachines don’t just need some lubricant or any lubricant. Rather, they need a sustained and adequate supply of the right lubricant. Adequate doesn’t just mean dampness or the nearby presence of lubricant. What’s defined as adequate varies somewhat from machine to machine but is critical nonetheless. High-speed equipment running at full hydrodynamic film has the greatest lubricant appetite and is also the most punished when starved. Machines running at low speeds and loads are more forgiving when lube supply is restricted. Even these machines can fail suddenly when severe starvation occurs.The table below illustrates how lubricants reach frictional surfaces in numerous ways.

There are six primary functions of a lubricating oil. These are friction control, wear control, temperature control, corrosion control, contamination control and transmittance of force and motion (hydraulics). Each of these functions is adversely influenced by starvation conditions. The worst would be friction, wear and temperature control. Even partial starvation intensifies the formation of frictional heat. It also slows the transport of that heat out of the zone. This is a compounding, self-propagating condition that results in collapsed oil films, galling, adhesive wear and abrasion (Figure 1).

Figure 1. Starvation IllustratedIn the case of grease, starvation-induced heating (from friction) of the load zone accelerates grease dry-out, which escalates starvation further. Heat rapidly drains oil out of the grease thickener, causing volatilization and base oil oxidation, all of which contributes to hardening and greater starvation.Lubricating oil needs reinforcement, which is lost when flow becomes restricted or static.

Flow brings in bulk viscosity for hydrodynamic lift. In fact, lack of adequate lubricant supply is functionally equivalent to inadequate viscosity from the standpoint of film strength.

4 Keys to Solving Starvation Problems Using Proactive Maintenance

5 Identify the required lube supply or level to optimize reliability.6 Establish and deploy a means to sustain the optimized supply or level.7 Establish a monitoring program to verify the optimized supply or level is consistently achieved.8 Rapidly remedy non-compliant lube supply or level problems.

Oil flow also refreshes critical additives to the working surfaces. This reserve additive supply includes anti-wear additives, friction modifiers, corrosion inhibitors and others. Lubricant starvation produces elevated heat, which rapidly depletes additives.Next, we know that wear particles are also self-propagating. Particles make more wear particles by three-body abrasion, surface fatigue and so on. Impaired oil flow inhibits the purging of these particles from the frictional zones. The result is an accelerated wear condition.Finally, moving oil serves as a heat exchanger by displacing localized heat generated in load zones outward to the walls of the machine, oil reservoir or cooler. The amount of heat transfer is a function of the flow rate. Starvation impairs flow and heat transfer. This puts increasing thermal stress on the oil and the machine.

Common Signs of StarvationWhen you’re encountering chronic machine reliability problems, think through the “Big Four” and don’t forget about No. 4. It may not be the type of oil, the age of the oil or even the contamination in the oil, but rather the quantity of oil. How can you know? The chart on page 8 reveals some common signs of lubricant starvation.

Lubricant Starvation Examples by Machine TypeLubricant starvation can happen in a number of ways. Most are controllable, but a few are not. The following abbreviated list identifies how lubricant starvation occurs in common machines.

Starved Engines

Dry Starts - Oil drains out down to the oil pan when the engine is turned off. On restart, frictional zones (turbo bearings, shaft bearings, valve deck, etc.) are momentarily starved of lubrication (Figure 2).

Figure 2. Dry Engine Starts Cold Starts - Cold wintertime conditions slow the movement of oil in the engine during start-up. This can induce air in the flow line due to cold-temperature suction-line conditions. Low Oil Pressure - This can result from numerous causes, including worn bearings, pump wear, sludge and extreme cold. Oil pressure is the motive force that sends oil to the zones requiring lubrication. Dribbling Injectors - Fuel injector problems can wash oil off cylinder walls and impair lubrication between the piston/rings and the cylinder wall.

Common Signs of Lubricant Starvation Clogged Spray Nozzles and Orifices - Nozzles and orifices direct oil sprays to cylinder walls, valves and other moving components. Sludge and contaminants are able to restrict oil flow.

Starved Journal and Tilting-Pad Thrust Bearings

Oil Groove Problems - Grooves and ports channel oil to the bearing load zones. Grooves become clogged with debris or sludge, restricting oil flow. Restricted Oil Supply - Pumping and oil-lifting devices can become mechanically faulty. This also may be due to low oil levels, high viscosity, aeration/foam and cold temperatures. Sludge Dam on Bearing Leading Edge - Sludge can build up on the bearing’s leading edge and restrict the oil supply.

Wet-Sump Bearing and Gearbox Starvation

Oil Level - Many wet-sump applications require critical control of the oil level (Figure 3).

Figure 3. Common Splash Gear Drive High Viscosity - Many oil-feed mechanisms (oil rings, slingers, splash feeders, etc.) are hampered by viscosity that is too high (wrong oil, cold oil, etc.). Gears can channel through thick, cold oil, interfering with splash and other feed devices. Aeration and Foam - Air contamination dampens oil movement and impairs the performance of oil-feed devices (Figure 4).

Figure 4. How Aeration Retards Oil Supply Non-horizontal Shafts - This can cause drag on oil rings and may interfere with slinger/flinger feed mechanisms.

Bottom Sediment and Water (BS&W) - Sump BS&W displaces the oil level. On vertical shafts, the bottom bearing can become completely submerged in BS&W. Defective Constant-Level Oilers - This may be due to plugged connecting pipe nipples, mounting errors (tilted, cocked, mounted on wrong side, etc.), wrong level setting, empty reservoir, etc. (Figure 5).

Figure 5. Mounting Errors of Constant-Level Oilers Defective Level Gauge Markings - Level gauges should be accurately calibrated to the correct oil level. Level Gauge Mounting and Viewing Issues - These may be hard to see, goosenecks, fouled gauge glass, gauge vent problems, etc. (Figure 6).

Figure 6. What is wrong with this picture?

Starved Dry-Sump Circulating Systems

Restricted Oil Returns - Plugged or partially plugged oil returns will redirect oil flow away from the bearing or gearbox being lubricated. Sometimes called drip-and-

burn lubrication, the condition is usually caused by sludge buildup or air-lock conditions in the gravity drain lines returning to the tank. Worn Oil Pump - When oil pumps wear, they lose volumetric efficiency (flow decay results). Restricted Pump Suction Line - Strainers and pickup tubes can become plugged or restricted. This can aerate the fluid, cause cavitation and lead to loss of prime. Clogged/Restricted Oil Ways and Nozzles - Oil-feed restrictions due to sludge, varnish and jammed particles can starve bearings and gears (Figure 7).

Figure 7. Plugged Oil Flow Entrained Air and Foam - Oil pumps and flow meters perform poorly (or not at all) when sumps become contaminated with air (Figure 4). Lack of Flow Measurement - Components sensitive to oil supply require constant oil flow measurement. Defective or Miscalibrated Flow Meters - Flow meters, depending on the type and application, can present a range of problems regarding calibration. Low Oil Pressure - Oil follows the path of least resistance. Line breaks and open returns starve oil from higher resistance flow paths and the machine components they serve.

Starved Spray-Lubed Chains and Open Gears

Defective Auto-lube Settings - This relates to correctly setting the lube volume and frequency. Defective Spray Targets/Pattern - The oil spray needs to fully wet the target location. Spray nozzles can lose aim and become clogged (Figure 8).

Figure 8. Correct Lubricant Spray Patternson Open-Gear Tooth Flanks

Gummed Chain Joints - Many chains become heavily gummed, which prevents oil from penetrating the pin/bushing interface.

Starvation from Grease Single- and Multi-Point Auto Lubrication

Wrong Regrease Settings - Regreasing settings should enable adequate grease replenishment at each lube point. Cake-Lock - This occurs when grease is being pumped. Under certain conditions, the grease thickener movement is restricted. Oil flows, but the thickener is log-jammed in a line or component passage (Figure 9).

Figure 9. Cake-LockGrease Starvation

Defective Injector Flow - This is due to wrong injector settings or restricted injector displacement. Restricted Line Flow - Exceedingly long lines, narrow lines, numerous bends, ambient heat or cold, etc., can lead to partial or complete blockage of grease flow. Single-point Lubricator Issues - These include malfunctioning lubricators from various causes.

Starvation from Manual Lubrication Issues

Grease Gun Lubrication - This may include an inaccurate volume calibration, a faulty grease gun mechanism, the wrong relube frequency, an incorrect relube volume or an improper relube procedure. Manual Oil Lubrication - This would include the wrong relube frequency, volume or procedure. Lube Preventive Maintenance (PM) - Missed PMs may be due to scheduling, management or maintenance culture issues.

The Crux of the ProblemLubricant starvation is an almost silent destroyer. While there are telltale signs, they generally aren’t recognized or understood. Of course, there are varying degrees of starvation. Complete starvation is sudden and blatant. However, more moderate partial starvation is what tends to go unnoticed until failure. Then, other suspect causes (the bearing, lubricant, operator, etc.) may be falsely blamed.Precision lubrication supply is a fundamental attribute of the optimum reference state and is included in any engineering specification for lubrication excellence. It’s one of the “Big Four” and thus is overdue for significant attention..Machinery Lubrication (8/2012)

The Basics of Lubrication PM Procedures

Noria Corporation Tags: industrial lubricantsAccording to a recent poll, as much as 60 percent of all plant problems can be attributed directly to "human factors" (Figure 1), specifically a lack of proper procedure (23.78 percent), a lack of training (15.05 percent) or personnel/human error (22.54 percent), which, though not always, is typically due to either a lack of proper documentation (procedure) or a lack of adequate training. What's clear from this is that

machines are failing because we either don't know how to maintain them or haven't adequately trained our staff to do so.So, how does lubrication stack up? In this column, the first of a three-part series, I will look at the basics of lubrication preventive maintenance (PM) procedures. In Part 2, I'll talk about what I call "hybrid PMs", PMs that span multiple technologies. In Part 3, I'll discuss how you should use the information in the PM to maximum effect in the field.Knowledge Management Many companies are starting to wake up to the reality that the way in which their assets are being maintained is simply not getting the job done. They are looking at ways to address either the lack of procedure or lack of training, and lubrication is no exception.

Figure 1. How Reliable Plant readers attributed plant problems to various factors.While we're talking about lubrication PMs, electrical PMs or mechanical inspections, the key is to develop a standard approach to capturing, organizing and delivering information, a field often referred to as knowledge management. Knowledge management is simply information about any business process in a form that can be easily disseminated and used by those who need it. The key here is "easily disseminated and used". Take, for example, a library. Libraries contain tens of thousands of books. But unless each book is carefully catalogued in a system that is user friendly, and the book itself is carefully organized into relevant chapters and a subject index, the information is of little use. The same is true for lubrication knowledge.As an example, consider the following real-life extracts from lubrication PMs I've reviewed in the past year or so:Grease the motor bearing - Sure! How much? Which grease should I use? What should I watch for when applying grease?Check oil level and top off as necessary - But, how do I check the level? Should the machine be running or down when I do my check? What oil should I use?Sample gearbox - How? Should I crack the drain and insert a drop tube through the breather port, or is there a sample valve located somewhere?I could go on, but you get the point. When it comes to lubrication, the amount of explicit knowledge or information available to the technician at the point of use is often so limited that, by inference, the technician has no option but to make certain assumptions on the fly. But wait, you say, "Our lube technician has 30 years of experience; he knows what he's doing!"Let's examine this. So, Joe has been lubing for 30 years? Is it reasonable to expect that Joe has memorized every salient detail (how much, how often, which product or tool to

use) for every task? And even if Joe is a true professional with a penchant for memorizing data, what will happen when Joe moves on to that long overdue retirement? Knowledge needs to be captured in a way that leverages Joe's experience but insures that he or his successor is able to execute to a high level of precision and consistency each and every time.Tacit vs. Explicit Knowledge How do we capture knowledge? The first step is to recognize that knowledge comes in two distinct forms: tacit and explicit. Tacit knowledge is information that is stored in the minds of a few employees. My thoughts go back to a lubrication survey I did a few years ago where Joe (yes, that was really his name!) was unexpectedly sick on the day of the survey and nobody could tell me what lubricant was used in each machine because "Joe's our lube guy". I later learned that Joe had, in fact, suffered a mild heart attack, and while he fortunately recovered, things could have been much worse.Explicit knowledge, on the other hand, is knowledge that has been captured as a procedure, document, training video, etc. In this form, it can be used by others to determine how a specific task should be done.But wait, you say, "We have lubrication PMs. Our tasks are all documented in lube routes, so we've already captured our lubrication knowledge explicitly." Unless you've documented each pertinent detail (how much, how often, which tool or product), don't fool yourself - a PM cannot and should not be considered explicit unless all gray areas have been eliminated.Why have few companies taken the time and effort to capture explicit knowledge? Hopefully you all agree that the devil is in the details, not the simple task description. The answer, in my opinion, is that the time and effort to build truly specific lubrication PMs is so daunting, and there always seems to be a bigger fire that needs attention.The Difference is Accuracy This need not be the case. The incremental effort required to make a lube PM truly explicit is really not that much harder than writing a general guide, particularly if you take an asset class approach to design the optimum maintenance process. But the difference in the accuracy by which tasks are executed is profound, depending on how specific the task description is in the PM.Therefore, ask yourself if you have explicitly captured every detail necessary to lubricate your machines in your lube PMs, or if you are tacitly expecting that Joe will get it right every time.Read Part 2 of this series.Machinery Lubrication (7/2009)

Are Lubricants Hazardous to Your Health?

Noria Corporation

Tags: industrial lubricants “Are lubricants a health risk? I’ve heard reports that lubricants can cause skin cancer.”Material safety data sheets (MSDS) should be available in all work areas. Because they provide information relating to both health and environmental hazards, all personnel should have easy access to this important information. Use of appropriate safety protection is a must, including gloves and safety glasses when handling lubricants or greases. If lubricants accidentally contact the skin, wash immediately with an approved hand cleaner followed by normal soap. With respect to skin cancer, the International Agency for Research on Cancer (IARC) has classified mineral-based lubricants and rated them according to their risk. A summary of this system is given below. Note the groups do not relate to API base oil groups. Note also that additives and synthetic base oils are not included in this listing.Group 1: These are lubricants with sufficient evidence of carcinogenicity to humans. This group includes base oils that are acid-treated oils, mildly retreated solvent-refined oils, aromatic oils and mildly hydro-treated oils.Group 2: These are lubricants with no human data, but strong animal data exist that indicate possible or probable carcinogenicity. There are no base oils listed in this group.Group 3: These are lubricants not classifiable as to carcinogenic to humans. They include base oils that are severely hydro-treated oils.Group 4: These are lubricants that are probably not carcinogenic to humans. This group includes base oils that are white oils and petrolatums.Generally, the MSDS must state the cancer hazard of a lubricant and define its risk category. As with any risk, caution is advised when handling any lubricant.

How Temperature Affects Lubricants

Noria Corporation

Tags: industrial lubricants The primary physical characteristics of lubricants that are affected by temperature include viscosity, viscosity index, pour point and the base oil. Let's deal with these individually.

ViscosityThe viscosity of an oil has been said to be the most important consideration when selecting a lubricant. The viscosity of an oil is its ability to flow or its internal resistance to flow.For example, when an oil film forms between a bearing and a shaft, some of the oil's molecules are attracted to the surface of the shaft, while other oil molecules are attracted to the bearing surface. This is called the shear rate and is directly affected by the oil's viscosity and operating temperatures. A multi-grade oil with a lower (thinner) viscosity will generally have a higher potential shear rate, while a single viscosity oil will generally have a lower potential shear rate.Since oil with a lower viscosity and high potential shear rate must still maintain a sufficient oil film, it is quite apparent that as temperatures rise, the oil film may fail and metal-to-metal contact may occur. If the oil's viscosity is too high with a low potential shear rate, the internal resistance to flow will increase the temperature dramatically, causing an overheated condition, which can also cause a breakdown of the oil film and may cause oxidation of the oil. Therefore, it is critical that oils be selected by always taking the operating temperature of the equipment into account.The most common term describing viscosity is kinematic viscosity, which is measured in centistokes (cSt) at 40 degrees C and 100degrees C, respectively. These specifications are always listed on oil company data sheets.

Pour PointThe pour point of an oil is defined as the lowest temperature at which a lubricant will flow. It is frequently and erroneously used as the oil viscosity selection criteria.For example, let's say an oil has a pour point of minus 30 degrees C. Most people assume that this means that the oil will flow to the bearings of the equipment even when the ambient temperature is at minus 30 degrees C. This is a fallacy. At best, this oil with a pour point of minus 30 degrees C and operating in an ambient temperature of minus 30 degrees C will merely churn at the oil pump until the churning causes an increase in the

oil's temperature. This in turn allows the oil's viscosity to thin sufficiently so that it slowly begins to flow through the oil passages to the lubricated components.Frequently, this process takes 5 to 10 minutes or more, during which severe damage can occur at various components, because the oil is actually too thick to flow. Do not select lubricants based on pour point alone.

Viscosity IndexThe viscosity index (VI) of an oil is the term used to express an oil's "resistance to viscosity change as the temperature changes." For example, an oil that thins out (reduced viscosity) significantly as its temperature increases is said to have a low VI. An oil whose viscosity does not change significantly as it is heated up is said to have a high VI.This temperature/viscosity relationship is the most critical and important consideration when selecting oils that will be operated in temperatures that change dramatically. Viscosity index is of particular importance when selecting oils for northern U.S. and western Canadian winters or high arctic operations.Most industrial mineral lubricating oils that might be used in a manufacturing plant or production facility with controlled temperatures need only have VIs of 55B100. However, in an Alaskan mine facility or transportation operation, oils with VIs as high as 175 are available and may be necessary. Viscosity-index specifications are not always listed in oil company data sheets or specifications but should be.

Base OilThe base oil should also be considered when selecting lubricants. Mineral-based (non-synthetic) oils have various bases depending upon their molecular and chemical structure. Base oils can be paraffinic, naphthenic or aromatic, and the selection process should take into account the type of base oil.For example, naphthenic base oils have low natural VIs and may be selected for equipment where extreme temperatures do not affect operation. On the other hand, paraffinic base oils have natural VIs that are considerably higher than naphthenic types, making them desirable base stocks for lubricants used in outdoor applications. Fortunately, many of the natural mineral oils produced in North American oil fields are of the paraffinic type.

The Basics of Synthetic Oil Technology

Jeremy Wright, Noria Corporation Tags: synthetic lubricantsIn the 1930s, Dr. Hermann Zorn of Germany was searching for a lubricant with the properties of natural oils derived from crude oil but without the

undesirable properties (high pour points, tendency to gum or gel in combustion engines, low oxidation resistance at higher temperatures, etc.). Germany was also in need of a product that was not derived from crude oil, as the nation’s access to crude oil was becoming increasingly scarce. By the mid-1940s, the fruit of Dr. Zorn’s labor included more than 3,500 different blends of esters, including diesters and polyolesters.The first real-world trial for these lubricants came during World War II when both Germany and U.S. forces began using synthetic base oil in aircraft engines. They noticed the synthetics made engine starts much easier in colder climates (due to the high viscosity index) and significantly decreased soot deposits that would build up in oil radiators when using conventional (crude oil-derived) lubricants.

Types and TerminologyThere are two American Petroleum Institute (API) base oil categories that include synthetics. The first is API Group IV. The only synthetic base oil included in this group is polyalphaolefin or PAO. PAOs are made by polymerizing an alpha-olefin molecule like ethylene. In an alpha-olefin molecule, there is a carbon-carbon double bond with hydrogen branching off.

The second category is API Group V. These are non- PAO synthetic bases. Examples include diesters, polyolesters, alkylated benzenes, phosphate esters, etc. Basically, if it is a synthetic and it is not a PAO, it is a Group V.Some confusion has arisen recently regarding the use of the word “synthetic.” Several petrochemical companies have developed processes involving catalytic conversion of crude oil base stock under high pressures and temperatures in the presence of hydrogen to form very high-quality mineral lubricants. These oils, which are known as API Group III, are so highly refined that their properties almost match that of the Group IV synthetics. They are so close in fact that the U.S. court system sided with a manufacturer of these Group III “synthetics” when a lawsuit was brought up for false advertising. Even though these Group III base oils are derived from crude oil, they can now legally, from a marketing standpoint, call them synthetic.

Lubricating Gearboxes at High Temperatures

Noria Corporation

Tags: gear lubrication, synthetic lubricants “We have a cooling tower fan gearbox that runs very hot (more than 180 degrees F) due to the operating environment. We recently inspected the gearbox and found a lot of sludge and deposits and a strong sulfur smell. Someone suggested we use synthetic oil instead of the mineral oil currently used to prevent this from reoccurring. Would this help?”While it is true to say that synthetic oils can be used at higher temperatures, because they do not thin out as quickly as the corresponding grade of mineral oil and provide better oxidation resistance, this may not be the best solution in this instance. This is particularly true because the sulfur smell you refer to is likely the thermal breakdown of the EP additive in the oil. Switching to a synthetic oil will do nothing to prevent thermal additive decomposition, if this is the problem.A better solution may be to install an offline cooling system by piping out a line from the gearbox with a small gear pump to circulate the oil through an external cooling system, returning the cooled oil to the gearbox sump. Not only will this help to cool the oil and prevent thermal and oxidative breakdown, it will also have the effect of increasing the gearbox sump size, allowing the oil more opportunity to cool the gearbox.A nice side benefit of this arrangement is that the offline system can also be equipped with a filter to help keep the oil clean and an oil sampling valve to take oil samples on a component that is often difficult to sample on the run.

How to Protect and Preserve Spare Gearboxes

Noria Corporation Tags: contamination control, gear lubricationProper storage of spare gearboxes is critical for gearbox reliability. The following methods and illustrations are excerpts from Noria's Fundamentals of Machinery Lubrication training course.

Method 1 – Lip Seals

Spray shaft extensions with a suitable dry film or similar preservative. Some examples include Castrol Rustilo 181, ESSO Rust BAN 397 and Valvoline Tectyl 846.Pack grease around oil seals to prevent drying and crackingFill the gearbox casing completely with oil and seal tightly. Label the gearbox as "FULL – not ready for service"Allow some space for thermal expansionRemove the breather and replace with an airtight plug.Notes: While this method is simple and a relatively permanent solution it can be expensive for large gearboxes that require a lot of oil. It can also cause a hazard if the gearbox accidentally leaks.

Method 2 – Labyrinth Seals

Spray shaft extensions with a suitable dry film or similar preservative (examples given in method 1).For gearboxes with non-contact labyrinth seals, use internal vapor-phase rust protective coating instead of complete oil fill. Both oil wet and non-oil wet surfaces are protected by vapor-phase rust inhibitors.Consider using commercial vapor phase rust inhibitors such as Ashland Oil, Tectyl 859A or Cortec VP corrosion inhibitor. Typically, add 5 percent of the oil volume. Some inhibitors

require the oil/inhibitor mixture to be heated and agitated in order to perform effectively.Notes: This method may only be good for about six months and should be renewed if storage period is longer. Another disadvantage is that it may cause incompatibility and foaming problems when filled with the service oil. Flushing is recommended before putting the gearbox into service.

Method 3 – Oil Mist Method

As an alternative method for large gearboxes with lip or labyrinth seals, oil mist introduces a clean air/oil mixture (1 part oil to 200,000 parts air) into the headspace of the gearbox. Similar to fog, it keeps machine surfaces lightly lubricated to prevent corrosion. API-RP 686 3.2.1 recommends oil mist protection be used if equipment is stored for more than six months, especially if more than 10 pieces of equipment are stored at a time.Notes: Additives in the oil mist protect gear and bearing surfaces. The low pressure keeps environmental contaminants like dirt and moisture out. It is safe, non-hazardous and will not support combustion. One system can provide oil mist to multiple gearboxes. This method is more expensive and difficult to implement.

Maintenance Issues During Storage:

To distribute oil and prevent false brinelling and fretting corrosion, rotate the shafts at least once a month.Visual inspections – when rotating exposed machine surfaces, check to make sure applied protective coatings have not been removed.Do not store equipment on vibrating surfaces as this can also cause false brinelling and fretting corrosion.If possible, store gearboxes under constant temperature conditions.Get more reliability-improving ideas and techniques at Noria's Fundamentals of Machinery Lubrication training course.

How to Achieve Gear Coupling Reliability

Randy Riddell, International Paper Tags: gear lubrication, greases, maintenance and reliabilityGear couplings are among the most commonly used methods for connecting process equipment. When properly selected, installed and maintained, they can provide long life and good reliability. Gear couplings offer several advantages over other couplings, including moderate misalignment capacity, exceptional torsional stiffness and very high torque density.However, when it comes to gear coupling reliability, there are many areas where failures

may be initiated. Often these failures begin because of a lack of knowledge or a lack of execution of certain fundamentals, which are necessary for these couplings to run reliably.

Design, Selection and SizingSelecting the correct coupling for the application is critical for gear coupling reliability. Use the following steps to help make the selection process easier:

1 Choose the coupling style and design (Fast’s, Series H or Waldron; flex and rigid halves; close coupled or floating shaft; gear teeth specifications and misalignment requirements).2 Select the service factor (SF) from the original equipment manufacturer’s (OEM) gear coupling charts. Shock loads or variable loading can cause premature failure if adequate SF is not used. Typical service factors are in the 1.5 to 2.0 range. Some manufacturers may even specify a misalignment factor for gear coupling sizing when higher coupling misalignment is expected.3 Calculate application torque (T) requirements based on design brake horsepower (BHP), SF and speed.

4 Choose a coupling with a torque capacity greater than the torque requirements. Since the service factor is already factored in, there is no reason to add additional capacity.5 Confirm that the coupling selected has a bore capacity greater than the actual application bore (shaft size). Frequently the maximum bore size will drive the coupling sizing process and even increase the coupling torque capacity two to three times what was previously calculated.6 Verify the shaft depth available for the coupling hub and compare to the actual hub depth. If the hub is too long, it must be either overhung or machined off. Since the hub to shaft engagement is the same in either method, it is preferred to have the hub machined off due to torsional effects of the overhung hub. If the hub is overhung or cut off, further examination may be necessary to determine if there is enough torque transmission capacity available. The rule of thumb is a 1-to-1 ratio for the hub length to the bore.7 Check a dynamic balance chart to see if the coupling needs to be balanced. High-speed gear couplings may require balancing.8 Ensure the coupling will fit around the equipment and guarding. This is typically something that can become an issue when there is a design modification on existing equipment. Guards that allow maintainability will encourage proper maintenance in the long run.

InstallationSome couplings don’t get much of a chance at a decent life due to their installation. Just like other components that experience infant mortality, often times these parts don’t die but are murdered. Certain elements of gear coupling installation must be considered if optimum reliability is to be obtained, including:

Hub and Sleeve Fits - Determine the type of hub fit (clearance, locational or interference). Higher speed applications should have an adequate interference fit to offset centrifugal force effects on shaft/hub contact pressures. Excessive hub interference fits can lead to hub cracks and hub failure. Keys and Keyway Fits - Keyways should have a proper radius to reduce the risk for fatigue cracking. Key lengths should be measured to minimize the coupling imbalance. Hub Bore - Ensure the hub bore is concentric to minimize hub runout. Hub Installation - Choose proper heating methods so hub material properties are not compromised and select the proper heating magnitude for interference fit hubs so the hub slides easily on the shaft. Never use a hammer to install or remove hubs, as this can cause bearing damage. Correct Coupling Gaps - If floating shafts have a small coupling gap, the shafts may impact one another under misalignment as the shaft oscillates during operation. Proper Sealing - Always use proper gaskets and O-rings so the lubricant stays in the coupling. Alignment - Install the coupling so misalignment stays within manufacturer limits with respect to offset, angular and axial misalignment. Fastener Assembly - Choose the correct type of fasteners (fine or coarse, length, exposed, shrouded, etc.) and the proper arrangement. While standard bolts can work, they may put the threads in the shear plane. Coupling bolts need the correct preload, which is accomplished by proper bolt torque methods. Lubrication - Get the right product in the right amount at the right time for optimum gear coupling reliability.

Different coupling styles have different lube and bore capacities. (Ref. Kopflex)

LubricationPerhaps the most important operating factor for a gear coupling to be reliable is lubrication. Selection of the proper lubricant is the first step. Many coupling manufacturers supply their own lubricants for their couplings. Gear couplings may either be grease- or oil-lubricated depending on the design. Oil-lubricated couplings will not dry out like grease couplings, while Fast-style couplings have smaller bore capacities.It is fair to say that most gear couplings are grease-lubricated. Coupling greases have special properties, so general-purpose greases should never be used in gear coupling

applications. Gear couplings can be subjected to very high centrifugal forces, and oil separation is a critical element of coupling greases. Since greases are comprised of oil and mostly a thickener, special considerations must be made regarding the selection and application of coupling greases.Soap thickeners typically are heavier than the oils, so centrifugal forces tend to deposit the thickener at the gear teeth. Generally, a grease with a high oil content of high-viscosity oil and a grade 1 rating from the National Lubricating Grease Institute (NLGI) is preferred. A higher consistency grease may be considered for high-speed applications but should be avoided at low-speed applications.Grease specifications may include speed limits or certain tests such as the K36 separation factor. Any grease will have oil separation based on time, temperature and centrifugal force. The K36 factor determines the maximum oil separation of the grease while running at 36,000 Gs. A K36 factor of 8/24 means the oil separation was 8 percent in 24 hours. In comparison, a grease with a K36 factor of 3/24 would mean that it did not separate as much as the grease with a K36 factor of 8/24.Higher oil separation is desirable at lower speeds (lower G forces), while lower oil separation is preferred at higher speeds and higher temperatures. High-vibration equipment can also enhance oil separation and induce failures. Studies have even shown that gear coupling wear rates decrease as coupling speeds increase.The main function of a lubricant in a gear coupling is to reduce the friction between the gear teeth as they slide against each other. The relative motion between the mating gear teeth occurs in the axial direction due to slight shaft misalignment. This motion is oscillatory, low amplitude, relatively high frequency and a function of the magnitude of angular misalignment.This sliding axial motion between the gear teeth can generate lots of wear if lubrication is not sufficient. This is why the gear coupling lubricant plays such a critical role in the reliability and life of a gear coupling. Poor lubrication between the gear teeth generates higher friction between these teeth, resulting in gear coupling wear, heat generation and high axial loads to mating equipment bearings. The higher axial loads on the bearings will then decrease the life of the equipment.The pump shown on the left had a dry coupling that was operating in a torque-lock condition and creating high axial forces on the equipment. The coupling was replaced without making any adjustments to the pump or motor. The only change was a coupling with good lubrication, which reduced tooth friction and decreased the axial forces from the coupling to the pump and motor. The result was a noticeable decrease in the operating temperature of the pump bearing.

MaintenanceMaintenance is the final factor to ensure gear coupling reliability for long equipment life. While the first three factors have more to do with a lack of knowledge, maintenance often comes down to a lack of execution. Unfortunately, this requires discipline by operations and maintenance groups as well as managerial courage to dedicate the resources to ensure that it can happen.Typical recommendations from gear coupling manufacturers require regreasing at a minimum of 12 months. A regreasing procedure would include breaking, cleaning, inspecting and hand-packing the coupling with fresh grease. Using a grease gun typically is not recommended when the coupling has been broken and ready to receive new grease. When a gear coupling is greased through a fitting instead of hand-packing, it can result in overgreasing, and a hydraulic lock condition can occur, causing high axial forces on the equipment. A hydraulic lock condition can even make alignment difficult, as shafts may be hard to turn.

Some applications require regreasing at six months to ensure good reliability. These applications may include high speeds (high G forces), high temperatures, misalignment or vibration. Smaller lube sump capacity can also be a factor in regreasing intervals. However, deciding to go longer than 12 months without grease replenishment on a gear coupling is a high-risk move that is not recommended.Regular maintenance of gear couplings should involve special care with respect to many of the installation factors discussed previously. When inspecting gaskets and O-rings, ensure the lubricant stays in the coupling until the next maintenance task is scheduled.

Grease fittings should be removed before completing maintenance. These fittings have been known to leak lubricant and can hit guarding, causing loss of lubricant. Under high centrifugal forces, the grease must be completely sealed within the coupling. Guarding should also allow enough access so it does not have to be completely removed for normal coupling maintenance.Remember, reliability is not for the faint of heart. Most all of these factors must be executed correctly to achieve good gear coupling reliability. This is why the work of maintenance and reliability professionals is rarely ever finished.

About the Author

Randy Riddell is a senior mechanical reliability engineer for International Paper in Courtland, Ala. He is a certified lubrication specialist (CLS) by the Society of Tribologists and Lubrication Engineers and a certified level I machinery lubrication technician (MLT) by the International Council for Machinery Lubrication (ICML). He is also a certified maintenance and reliability professional (CMRP) by the Society for Maintenance and Reliability Professionals (SMRP).Machinery Lubrication (4/2012)

Identifying Service Classifications for Automotive Gear Oils

Noria Corporation

Tags: gear lubrication, automotive The American Petroleum Institute (API) service designations are based on the type of service in which components will be used. The designations are utilized by manufacturers to select lubricants for particular gear types and operating conditions. No attempt is made by the API classification system to classify gear oils by physical properties or test performance. It also recognizes that some lubricants are suitable for a wide range of operating conditions and may be recommended for more than one service designation.Although API designations may be very useful when making general recommendations, manufacturer recommendations should always be consulted to ensure that the lubricant being considered is not prohibited by that manufacturer.API-GL-1 designates the type of service characteristics of automobile spiral bevel and worm gear axles as well as some manually operated transmissions operating under such mild conditions of low unit pressures and sliding velocities in which straight mineral oil can be used satisfactorily. Oxidation and rust inhibitors, defoamers and pour-point depressants may be utilized to improve the characteristics of lubricants for this service. Frictional modifiers and extreme pressure (EP) agents are not used. This designation is recommended for use in some manual truck transmissions.API-GL-2 refers to the type of service characteristics of automotive type worm gear axles operating beyond GL-1. It may contain anti-wear and very mild EP agents, and usually includes fatty additives for worm gears. This service designation is obsolete.API-GL-3 describes the type of service characteristic of manual transmissions and spiral bevel axles operating under moderately severe conditions of speed and load beyond GL-2 but below GL-4. It may have mild EP agents but is not intended for hypoid gearing. This service designation is obsolete.API-GL-4 relates to the type of service characteristics of gears, particularly hypoid gears operated under non-critical, moderate speed, shock load; high speed, low torque; and low speed, high torque conditions.API-GL-5 designates the type of service characteristics of gears, particularly hypoid gears in passenger cars and other automotive equipment operated under high speed, shock load; high speed, low torque; and low speed, high torque conditions. This designation is still widely used for EP gear oils.API-GL-6 is associated with oils that reduce gear scuffing in older high-performance cars. This service designation is obsolete.API-MT-1 describes a high EP oil intended for some non-synchronized manual truck and bus transmissions.

Mack and Volvo trucks (as well as others) have their own specifications that address some conditions beyond GL-5. These are Mack GO-J+ and Volvo 97310, although these numbers change every few years.

Slight Changes Can Mean Big Problems

Tags: oil analysis, contamination control, gear lubrication, lubricant sampling, hydraulics

Copper readings can be particularly alarming when increases are in the hundreds of parts per million. However, huge increases are typically insignificant in terms of component wear. Ironically, small subtle increases in copper are of greater concern and should be examined closely. Copper alloy component wear is generally accompanied by lock-step increases in alloy metals such as lead, tin, aluminum and zinc. The amount of alloy metal present in brass/bronze components is only a small percentage of the total copper content. Changes in these alloys may be only a few parts per million but should be taken seriously when present with copper increases.

Controlling ContaminationPortable transfer/filter carts are versatile and can be used for more than just transferring fluids. Other possible uses include offline filtration, cleaning stored lubes, flushing after machine repair and rebuild, flushing during equipment commissioning and draining a reservoir or sump.

Greasing Gearbox Bearings

Does your gearbox have a sealed or open input shaft bearing? This bearing is often above the gearbox oil level and must be greased if it is an open bearing. Manufacturers may ship the gearbox with a plug where the grease fitting is needed to prevent damage during shipping.In addition, the manufacturer may change the input shaft bearing design from open to sealed and back to open without notification. Small changes such as no longer receiving an attached plastic bag with a grease fitting included with the replacement gearbox may be a clue to a change in design.Always check the manual included with the new gearbox to see if the lubrication needs have changed.

Advice for Coupling Grease ApplicationWhen changing the lubricating grease in a geared motor coupling, always apply a full coating of grease to the teeth of the coupling. Never fill the coupling housing completely with a grease gun due to expansion of the grease as the motor comes up to running temperature.This expansion of the grease will apply internal coupling pressure, pushing the motor shaft off magnetic center and onto the thrust surface of your bearing, causing bearings to overheat and leading to early bearing failure.Even after hand-packing the coupling, the motor should be run up to operating temperature, then shut down and the grease plug removed to allow excess grease and pressure to be released.

Inspect Your Level GaugesRoutinely inspect the vent hole in column-type vented level gauges. In dirty environments, the vent hole can become easily plugged, causing an air lock in the gauge headspace. This will result in a false oil level (higher than reality) in the gauge. Many prefer dual-port gauges instead (unvented).

‘Handy’ Sampling TipDuring regular weekly or monthly oil sampling, use a tube of “handy wipes” to keep your hands cleaner while handling sample equipment. This practice may not show directly in the cleanliness of the samples, but it feels cleaner, looks very professional and sends a

message about the importance of contamination control.

Keeping Hydraulics HealthyBaffles are an important component in a hydraulic reservoir. They allow the fluid time to cool, deaerate and to settle out water and dirt. A good rule of thumb for residence time in a reservoir is three to five times the pump output. If the system is highly contaminated, residence time may be 10 times the gallons per minute of the pump.

The “Lube Tips” section of Machinery Lubrication magazine features innovative ideas submitted by our readers. Additional tips can be found in our Lube-Tips e-mail newsletter. If you have a tip to share, e-mail it to us at editor@noria.com. To sign up for the Lube-Tips newsletter, visitwww.machinerylubrication.com and click on the “Newsletters” link at the top.Machinery Lubrication (2/2012)

Understanding Oil Analysis Results

Noria Corporation Tags: oil analysis, particle counting, contamination control, wear debris analysis

"Sometimes our oil analysis reports show high particle counts on a hydraulic system (as high as ISO 21/18). If wear metals and silicon are low (less than 4 parts per million), what are these particles?"To fully understand the composition of the particles, you should perform a spectrographic analysis and a metallurgy assessment of your system components, which will tell you what the particles are and where they are coming from. At 4 parts per million (ppm), the amount of wear metals is insignificant.Retest the system on a proper frequency and trend the rate of change. A significant change in the overall amount of wear metals is cause for concern. If the value of wear metals hovers around the same ppm over each test, then you are probably looking at a product of normal operation. Keep in mind that spectroanalysis can pick up particles only 7 microns and smaller at the absolute best. The accuracy can also be off by significant values on some metals.Approach your concern with ferrous density and a patch test after a particle count. Ferrous density should be considered a primary test for all machines where ferrous wear material is expected. Correlating ferrous density data along with other oil analysis test information can give you a wide picture and a solid understanding of the internal condition of your machine.Be sure to set your target cleanliness for a particle count. If the tested value is greater than the target value, proceed to a ferrous density test. Set a target for this value as well (maybe 15 percent ferrous). If the value of the ferrous density exceeds 15 percent, proceed to analytical ferrography.

Analytical ferrography allows wear particles to be observed by the analyst via microscopic analysis. In this evaluation, active machine wear as well as multiple different modes of wear can be determined. This method has an outstanding sensitivity for larger particles.If the value of the ferrous density is less than 15 percent, proceed to a patch test (filtergram). Keep an eye out for a high rate of change in any of the tested values and you will be able to catch problems before they occur.It is also a good idea to assess the condition and effectiveness of your breathers and filters to make sure you are keeping contamination out and removing it effectively when it gets in.

Using Oil Analysis and Daily Inspections to Improve Lubrication

Marc Vila Forteza, Petronor Tags: lubrication programs, oil analysisIn large industrial plants where a great number of machines are installed, it is necessary to implement an effective lubrication-management system. This type of system can help ensure that machines are well-lubricated and, if a fault or any abnormal situation is detected, further analysis or a corrective action can be carried out.To make the system work, a machine database with well-defined lubrication points and scheduled lube routes is required. It is also essential to make good use of the data collected daily by the lubrication crew. If this information is promptly introduced into the database and generates an alarm when the machine is in poor condition, the reliability engineer can fix many potential problems.

The information collected by thelubrication crew will help the reliability engineer focus hisanalysis only on the critical

machines and their specific problems.

Lubrication routes and preventive maintenance (PM) can be modified automatically by lubrication software based on simple oil analysis and field inspection information provided by the lubrication crew. These tailored routes can improve effectiveness by focusing on critical machines, which are checked more frequently depending on the condition of the lube oil and the lubrication system.

Lubrication Management and Scheduled Lube RoutesBefore providing details on tailoring lube routes, let’s define what an effective lubrication-management system is as well as its main objectives. Generally, the purpose of a lubrication-management system is to schedule and plan the lubricating tasks of the machinery in the plant and to properly manage the field information supplied by the lubrication crew. The correct grade of lubricant also should be delivered to the proper lubricating points in the right quantity and on schedule to optimize the human and material resources.When implementing such a system, several key factors must be taken into account to allow for the effective monitoring of the machines at a reasonable cost. The following tasks should be performed during the design of any lubrication-management system:

Develop a Machine Database

This first step involves recording all the machines to be lubricated in a database, along with their lubricating points and the appropriate lubricant. The database should be flexible enough to adapt to such changes as machine revamps or oil type upgrades. It should also allow for the historical recording of incidents that are documented on the lubrication routes.

A field inspection should provide information on the lube oil system conditions and the mechanical condition of the machine.

Audit Lubricant Types

Once a machine database has been developed, the location of the lubricant service stations and the machines that use those lubricants must be studied in order to optimize the distance travelled by the lubrication crew. At this point, it is also important to standardize the lubricant types to a minimum that meets the machine manufacturer’s requirements.

Create Lubrication Routes

The lubrication specialists or the reliability engineers must create the lube routes. These routes consist of a series of points to be lubricated (divided into geographical areas or into production units) with related tasks to be performed on a detailed schedule.

Design a Template

A template can be designed for use as a lubrication guide when performing field work. The template should include all the relevant information for the lubrication operators such as identification numbers of the machines to be inspected, lubricating points, the lubricant to be used at each point and tasks to be performed. There should also be open fields in the guide table in order to note any observation or anomaly detected.

Establish a Procedure for Work Orders

Lubrication work orders should be generated with a frequency that allows for proper

planning of the work and should be delivered with the specific work plan attached. Also, be sure to print and detail the work plan for the personnel who will actually carry out the job to avoid unscheduled work and downtime.

This template was designed for use as a lubrication route guideline.

Determine Who Performs the Lube Routes

It is important to decide which members of the staff will be in charge of lubricating the machinery to avoid delays in the task execution. Keep in mind that in this type of work, any problem will affect all subsequent lubrication routes, which can cause serious damage to machinery.If all of these steps are followed during the implementation of a lubrication-management system, it will be much easier to achieve the desired result in terms of machine reliability.

The Importance of Reliable Field DataOnce the lubrication plan has been created and the material and human resources required are clear, it is essential to utilize qualified personnel (or contact a qualified lubrication company) to carry out the lubrication tasks. Qualified personnel is needed not only to perform good quality work but also to provide reliable daily information regarding the lube and mechanical condition of the machines inspected during the route.

This is an example of a lube oil alarm panel.In addition to performing all the work and inspections detailed in the routes, any qualified member of the lubrication crew should be able to:

Carry out simple corrective maintenance jobs related to the lubricating systems. Perform quick visual inspections of the lube oil quality (moisture, particles, color, debris, etc.) and report its status in the lube route guideline table. Ask his or her manager or the reliability engineer about further analysis of critical machines that are considered to be in poor condition. Report any other observed anomaly that could affect the machine or personal safety.

The information collected about the machine’s condition must be reliable in order to allow for a complete subsequent analysis by the reliability engineer. This is of great importance because any information reported by the lubrication crew will help the engineer focus his analysis only on the critical machines and their specific problems. This will save time and labor, as the field information is first filtered by qualified personnel, which simplifies the job of the reliability engineer.If special care is taken during the filtering of the field information to register all of the data consistently and with a coherent structure, the task of the reliability staff will be simpler and the historic data will be easier to search.

Using Field Inspections from Lube RoutesDepending on the work experience of the lube staff and the available time intended for the lubricating tasks, the lubrication operator should provide the following information about the machine condition:

Visual analysis of the lube oil condition (water contamination, debris, oil

temperature, color, etc.) Lube oil system condition (oil leaks, tank cleanliness and superficial condition, oil filters, oil drains, etc.) Mechanical condition of the machine (vibration, noise, bearing temperature, etc.) Miscellaneous (information on new machinery installed at the plant, reports of other problems in the plant that affect the lubricated machines, etc.)

Qualified personnel is neededto provide reliable information

regarding the lube and mechanicalcondition of machines inspected during a route.

All of this information should be recorded by the lubrication crew in the report table of the route for the inspected machine. This data should be added to the system database as soon as possible in order to help the engineer promptly solve any problems detected within the machines. Remember, the reliability engineer takes care of the machines, and the faster the information is added to the system, the faster he or she can analyze the machine condition with the most advanced predictive technologies.By updating your lubrication-route software, you can automatically include in the next planned route every lube point that has been found to be in poor condition. With this automatic process, the lube points that are deficient are revised more frequently until the correcting actions have the desired effect. An alarm system for the machine’s lube condition can also be implemented based on the information collected from the lubrication routes.From this starting point, there are multiple strategies that can be implemented to optimize the lube-route schedule based on the machine condition and how often

anomalies are detected. If an integrated system is employed, other information about the machine status can be used to improve the schedule and inspect the machines that are in poor condition more frequently. The difficulty lies in how to combine all of this data and find useful rules to be incorporated in the software. Any strategy should be in accordance with the general lubrication schedule and should not change planned work orders.The lubrication frequency of points in poor condition that need to be inspected again will correspond to the maximum number of lube points included in the same processing unit of the plant. For example, let’s say the available lubrication frequencies in one unit will be a multiple of a fixed number of days (15, 30, 45, 60 days, etc.). This method allows the mechanical workshop to manage only the planned work orders. The difference is that the number of lube points will be slightly increased depending on the machine’s oil status.

A visual analysis of the lube oil condition in the inspected

machine should be reported bythe lubrication crew.

There are other improvements that can be implemented when tailoring lubrication routes and PMs based on the information collected from field personnel, including:

The status of the lube point inspected in the last route can be included in the guideline table for the next route. This allows personnel to pay more attention to the most critical points. Any valuable information or pending work orders on the machine can be included in the guideline table and taken into account by the lube operator. Any automatic alarm or advice intended for taking further action like oil analysis,

vibration measurements, etc., will improve the performance of the system. Other information based on the machine type and the organization of the reliability and maintenance departments can be utilized.

If an organization has obtained reliable information from the lubrication routes, it is critical to process all of this data in order to optimize the frequency of machine lube inspections. This is especially effective if you have lube points that are in poor condition and require more frequent inspections. Inspecting problematic points more often ensures better control of their status and helps the reliability engineer to take corrective action sooner.Also, if the industrial plant has a computerized reliability system with predictive, preventive and other related machinery condition information, the combination of this data (such as vibration and oil analysis) will allow for improved system performance, as more complex and effective strategies may be used.Machinery Lubrication (10/2012)

5 Common Lubrication Problems and How to Fix Them

Wes Cash, Noria Corporation

Tags: lubrication programs

One of the greatest opportunities I have as a technical consultant is the chance to walk through various plants around the world. I have visited power plants, food-processing plants, refineries, manufacturing facilities and a long list of others. During these trips and

audits, I have discovered several recurring lubrication issues that seem to be widespread throughout the industry. The following is a list of the most common problems and how they should be resolved.

1. Lack of ProceduresGreat lubrication programs are only as good as the people who do the work, just as a chain is only as strong as its weakest link. In many of my most recent projects, the retirement of technicians has been the problem of greatest concern. As Baby Boomers are reaching retirement age and subsequently retiring, they are taking with them a great deal of personal experience and knowledge of how they do their jobs. For some plants, the lube-tech position may have been held by a single person for decades. These professionals are the masters of their domains and know every sight, sound and smell of their machines. It is imperative to pass down this type of dedication and understanding to the next generation of professionals. Unfortunately, all of this knowledge usually is not passed down. This results in problems and a steep learning curve.

36%

of lubrication professionals say overgreasing is the most common problem at their plant, based on a recent survey at MachineryLubrication.com

Documented procedures can lessen the blow and help new personnel understand the proper way a task should be performed. While countless articles and books have been published on the best way to write procedures, once written, the procedures must be implemented for their full effect to be realized.

The Remedy

Thorough documentation of every task performed in the lubrication program offers the best method for creating procedures. You want to write a procedure not only for the application of lubricants (oil changes, regreasing, etc.) but also for how lubricants are handled in storage, decontaminated upon arrival and even disposed of after use.Procedures should be developed with best practices in mind and may not represent what is currently being done in your plant. For instance, if new oil is arriving and being put into service without any testing or decontamination, this is far from best practice. Instead, new oil should be sampled upon delivery to confirm its properties and tested for contaminants. If necessary, the new oil should be decontaminated before being released for service or put into bulk storage containers.The same holds true for inspections, top-ups and every small task in the lubrication program. It is not enough to simply document what is currently being done. You must design procedures in a manner that enables the program to reach a world-class level.

2. Improper Sampling Points and Hardware

If used correctly, oil analysis can be an extremely valuable tool. It allows you to monitor not only the health of the oil but also the health of the machine, as well as catch failures before they become catastrophic. In order to obtain all the benefits of oil analysis, you first must have the correct sample points and hardware.

Improper sampling points and hardware may result in samples that are full of historic data.Many plants regard oil sampling as a secondary function and simply take samples from a drain port or with the inconsistent drop-tube method. When sampling from drain ports, you may obtain a sample that is full of historic data (e.g., layers of sediment and sludge). Wear debris trends can also be hard to establish, as these samples often contain a high concentration of contaminants.In addition to being inconsistent, drop-tube sampling frequently requires the machine to be taken out of service. This can result in particles settling at the bottom of the sump, which may prevent a good, relative sample being taken from the system.Proper sampling ports can be achieved by modifying the machine. This will allow good samples to be taken consistently from “live” zones or areas inside the system where oil is experiencing turbulent flow.

The Remedy

All machines to be included in the oil analysis program should be evaluated for the proper sampling hardware. Splash-bathed components such as bearings and gearboxes can be equipped with minimess sampling valves with pilot tube extensions. These extenders can

be bent up into the “live” zone next to the bearing or gear teeth.Circulating systems should be examined for the best possible sampling points as well. These systems typically require several points.A primary point is where routine samples are drawn from to provide a snapshot of the entire system. The best place for a primary sample is on the main return-line manifold, before any return-line filters and in an area of turbulent flow (most often an elbow).Secondary points should be installed in the oil return line after each lubricated component. Secondary points allow you to pinpoint problems in the system after an alarm has been triggered by the primary point.In conjunction with sampling hardware installation, all technicians should be trained in the proper way to pull samples. All sample tubing should be flushed with five to 10 times the volume of dead space. Great care should also be taken to reduce the amount of contamination introduced into the sample during the entire process.

3. OvergreasingMost plants I visit do not recognize that grease guns are precision instruments. They also fail to see the problems that can be caused by the misuse of grease guns. Just like many other people, I was taught to grease a bearing by simply attaching the grease gun and working the lever until grease was seen purging from somewhere. While this may be effective for hinge pins and other applications where purging grease won’t cause damage, it shouldn’t be employed for all grease applications. Overgreasing is a very common problem and can result in higher operating temperatures, premature bearing failure and an increased risk of contaminant ingression.

Overgreasing can result in higher operating temperatures, premature bearing

failure and an increased risk of contaminant ingression.Bearings require a set volume of grease to be properly lubricated. A popular formula used to determine the volume of grease needed is the outside diameter (in inches) multiplied by the width (in inches) multiplied by 0.114. This will provide the volume of grease in ounces that the bearing requires.

Once you have calculated the volume of grease for the bearing, you need to know how much grease the grease gun is dispelling per stroke. To do this, simply pump 10 shots of grease onto a plate and weigh it on a digital scale. Next, divide the weight of the grease by 10. This will give you the amount per stroke of output. Remember, certain grease guns can produce pressures up to 15,000 psi and can cause numerous problems if not properly managed.

The Remedy

While calculating the regrease requirements for all bearings onsite and determining the output of grease guns are a great place to start, there are other concerns that must be addressed as well. For instance, the output of grease can vary between guns. The best way to counteract this problem is to standardize with a single type of grease gun so the output will be similar for each one. Grease guns should also be dedicated to a single type of grease and checked at least once a year.If possible, bearings should be outfitted with grease purge fittings that allow excess grease to be expelled without compromising the integrity of the seal. In addition, all professionals who operate a grease gun should be trained on their operation and the proper way to regrease a bearing.

4. Lack of a Labeling System

Labeling is a key part of any world-class lube program. Not only does it reduce the chance for cross-contamination by minimizing confusion as to which lubricants go where, it also allows individuals who may not be as familiar with the lube program to top-up with the correct oil or grease.

Anything that touches a lubricantshould be labeled and dedicated

to a single lubricant.Of course, labels can be used for more than just identifying lubricants. On a recent project, the lube labels were barcoded to allow all assets in the plant to be integrated into the computerized maintenance management system (CMMS) for automatic work-order generation. Although labeling assets is a great first step, a true world-class program would label everything from machines and top-up containers to bulk containers, grease guns and so on. Basically, anything that touches a lubricant should be labeled and dedicated to a single lubricant.

The Remedy

Developing a labeling scheme takes time, but when done properly, it can provide a variety of information not only about the lubricant but also about lubrication intervals as well. The best label design incorporates a color/shape scheme for each lubricant used. This offers a quick visual reference as to which lubricant is inside the machine. Noria has developed the Lubricant Identification System (LIS), which includes all basic information for a machine type such as base oil, application and viscosity. As mentioned previously, once a labeling system has been established, the labels should be applied to all lubricant storage containers and application devices.

5. Use of OEM Breathers and Dust CapsMost original equipment manufacturer (OEM) accessories like breathers do little to restrict the ingression of tiny particles into oil and critical spaces, which can damage machine surfaces. Some of these breathers are simply a cap filled with steel wool or a mesh screen that serves as a block for larger particles. Considering the lubricant film in a journal bearing is approximately 5 to 10 microns, any particles of this size contaminating the oil will greatly increase the likelihood of wear and subsequent machine failure. These tolerance-sized particles do the greatest damage and have the highest probability of

causing machine wear.

Most OEM breathers and dustcaps allow particles and moisture

to enter the oil.Not only do many OEM breathers allow particles into the oil, they also do nothing to restrict moisture from entering the oil. Oil is hygroscopic, which means it absorbs moisture from the ambient air. In areas with high humidity or steam, moisture will pass through these types of breathers and be absorbed into the oil, causing rust, increased oxidation and hydrolysis rates, and a higher corrosive potential of acids formed by oxidation and hydrolysis.

The Remedy

OEM breathers should be replaced with higher quality versions to restrict particulate and moisture ingression. With several breather manufacturers on the market, the key is to get the breather that is right for your particular environment and operating conditions. In very dry environments, a spin-on particulate filter may work fine provided that ambient humidity is low. In more moist environments, a hybrid-style breather may be the best choice. This type of breather employs a particulate filter to trap hard particles followed by a desiccating phase to strip moisture from the incoming air. All of these breathers can be threaded into the current breather port for quick and easy installation.

3 Other Lubrication Problems to AvoidBesides the top five problems, there are a few honorable mentions that should be included in any discussion of recurring lubrication issues affecting industry. These are problems that aren’t quite as common but still deserve to be mentioned.

Constant-level Oilers

Although constant-level oilers are great for providing small amounts of oil to a sump and replenishing lost oil, these devices require proper installation and maintenance. They should be installed on the appropriate side of the housing so the shaft rotation is toward the oiler. This is more critical on smaller sumps. Also, the oiler must be installed straight, i.e., level and perpendicular to the ground. Finally, the oil level inside these devices should be set so half of the bearing’s bottom element is submerged in oil.

When using constant-level oilers, it is best practice to install a bull’s-eye sight glass on the opposite side of the housing from the oiler to ensure the proper oil level is maintained. Sediment can block the piping and starve the bearing for oil. Air pressure can raise the oil level, causing increased drag and excess heat in the housing. With the sight glass in place, these issues can be recognized and corrected before any lasting damage is done.

High-speed Grease

Many facilities use a general-purpose grease for almost everything in the plant. However, a multi-purpose grease can cause problems in high-speed bearings. Fan bearings, motor bearings and other bearings that rotate at several thousand revolutions per minute may require a grease with a lower viscosity than what is used for slower, more highly loaded bearings.Most electric motors can be effectively lubricated by a grease with a base oil viscosity of 100 centistokes. If a higher viscosity grease is used, viscous drag can occur, which may result in higher operating temperatures and increased torque requirements to turn the bearings. As the temperature increases, grease can drain from the bearing quicker, which in turn can cause the bearing to fail due to high heat or lack of lubricant.To prevent this problem, assess all bearings and calculate the necessary operating viscosity. Next, select a grease that provides the required viscosity and the appropriate additive package for the application.

One-dimensional Filter Carts

Filter carts offer many benefits, including increased lubricant life and reduced equipment failures. They are great tools for any lubrication program and should be used extensively to decontaminate both new and in-service lubricants. They can be employed to drain oil quickly, top-up with clean oil, flush out lines and hoses, etc.Whenever I walk through a facility and see a filter cart not in use but sitting in the lube room, I think to myself, “what a waste.” These systems should never sit unused in a room somewhere. The term “one-dimensional” refers to how these machines are often utilized. Many plants only use these carts to transfer oil from a drum to a reservoir, thus limiting their purpose. So avoid type-casting filter carts into a single role and use them for everything you possibly can.While these are the most common lubrication problems across industry, there are many more. Some may be unique to certain processes or types of machines, but these five hold true for all facilities.It’s been said that, “The problems are all the same; the only thing that changes is the accent.” Throughout industry, many people are facing the same challenges in their plants. The successes and lessons learned from these problems should be shared and disseminated to everyone.As industry continues to change and evolve, it will become increasingly important to understand the problems being encountered and to look for new ways to solve them. By applying sound problem-solving techniques and searching for the low-hanging fruit, you can start to make lasting changes for the better.Machinery Lubrication (10/2013)

Oil Leakage: How Much of Your Profit is Going Down the Drain?

Jeremy Wright, Noria Corporation Tags: lubrication programsWhen it comes to oil leakage, at what point would you say enough is enough - 10 gallons, 100 gallons or 1,000 gallons? I recently started a lubrication process design where the client hadn’t reached the breaking point and was at 56,000 gallons of oil being lost per year due to leakage. When I explained it in terms of dollars lost (literally going down the drain), everyone’s ears perked up. It was a staggering sum. They had become complacent. It started as a small amount and grew week after week until they now have to bring in totes daily to set next to the trouble actors so they can feed them like an addict needing more and more.As with every article I write, I like to consult the massive amount of material that is kept on subjects in Noria’s library. Thumbing through the files designated “leakage” could have consumed days on end. I found folder after folder of material dating back well more than half a century. I decided to read one of the oldest I could find, and it read as if it were written yesterday. Why do these problems still persist today? There have been great advancements in fittings, hoses, seals, etc., yet just last week I found myself almost wading through the basement of a steel mill.While touring various plants, I am always amazed at how complacent they can become to leaks. I’m not sure they even realize the effects these leaks are having on their equipment, the environment and the morale and safety of the employees.

Possible Causes of a LeakThe following list does not include all of the possible root causes of a failure, but it does encompass the majority of the top contributors.Improper assembly

There are multiple fittings on the market today. Making sure the fittings match is critical to their function Over-tightening can lead to structural damage of the fittings. Under-tightening will result in improper sealing. Hoses that are too long or in a hazardous environment have a higher likelihood of being damaged.

Poor maintenance practices Improper or lack of cleanliness while reassembling components Becoming complacent with inspections or routine cleaning functions Not fixing the source of the leak because it is easier to just top-up the sump

Adverse operating conditions Large temperature swings can cause fittings to loosen over time.

Process waste and debris can eventually contribute to leakage. High levels of particulate ingression can promote leakage. Natural weather elements and sunlight can degrade seals.

Contamination Contamination causes premature degradation of surfaces and seals. An external leak not only will allow lubricant to exit the system but may also allow contaminants to enter.

Vibration Excessive vibration can cause fittings and hoses to become loose and experience premature wear. Hose abrasion is one of the most common causes of hose failure.

Loss of production, poor machine performance, environmental hazards, safety risks and high consumption costs all result from leakage and should be very important to the operation of any plant, yet I usually choose to investigate only one of these factors, as it is the one that seems to garner the most attention - cost. Keep in mind that the money saved from a fixed oil leak goes directly to the bottom line.Inevitably, when discussing cost, the client wants to do a simple calculation based on the number of drops per second or minute vs. the cost of the oil. I will let them run through the calculation and arrive at a value. After we ponder the loss for a second, I will then ask, “What about the labor?” Don’t forget the benefits, management, planning, paperwork, etc. That’s not all. Used oil disposal, new oil testing, safety costs, cleanup, purchasing ... I could go on and on.

So while the number calculated at the beginning was already a jaw-dropping number, it didn’t include any of these other forgotten associated costs. The next statement from their mouth is typically, “What do we do?”I prefer to take a preventive approach. First, develop a strategic plan that is both proactive and preventive. One of the easiest ways is to perform regular inspections with associated action items that are dependent upon the results of the inspections.The second step is to control the operational conditions as best as possible. This is fundamental to any reliability and lubrication program, but simply keeping the machines and fluid clean, cool and dry will help mitigate the leakage.Next, implement a detection and control program. Some popular leakage-detection

techniques include visual inspections, dye injections/black light, system pressure decay, pressure differential, ultrasonics and flow meters.

66%

of lubrication professionals use visual inspections to detect oil leakage at their plant, according to a recent survey at machinerylubrication.com

Finally, you must exercise proper contamination control. This not only will help with leaks but also will offer huge improvements in machine reliability.It is estimated that more than 100 million gallons of fluid leak from machines every year in North America. How much are you contributing to this number? At nearly every plant I’ve visited recently, I can calculate enough money lost to employ an entire team of technicians whose sole purpose is to identify and stop leaks. Down the drain are going hundreds of thousands of dollars that could have been added directly to the bottom line. So the next time you walk by that small puddle on the floor or that drip from a fitting, I want you to see dollar signs..Machinery Lubrication (4/2013)

How to Prevent Bearings from Overheating

Noria Corporation

Tags: bearing lubrication, greases, viscosity "Should all greased bearings be fitted with a vent (spring-loaded or other)? Most of the 3,500 rpm pillow blocks that I maintain have no vent, and the relubrication schedule was arrived at by ‘tribal council.’ The bearings heat up from about 104 degrees F to around 165 degrees F for about two days after relubrication and then return to normal (104 degrees F) conditions for the rest of the month. Will a vent help?"The issue of overheating is related to fluid friction, which is a result of fluid churning. This is a secondary effect of overfilling the cavity at the time of relubrication. Installing a relief vent port can help in this situation, but this would be only addressing the symptom rather than the cause.Two issues need to be addressed. First is the matter of relubrication practices based on tribal knowledge. While the old-school guidelines can sometimes be correct, the evidence here is that something is not quite right. You need to calculate the volume and the frequency based on the bearing type, size, speed and operating environmental factors. A correctly gauged interval and volume per relubrication event can help minimize overfilling the housing. There are a variety of texts available that can provide formulas for this effort.Second, you must consider the lubricant selection for the application. As bearing speeds increase, the oil viscosity requirement decreases. Obviously, the grease's oil viscosity decreases with temperature, but that notwithstanding, it is imperative to select a grease based on the bearing manufacturer's recommendations for an application, which is based on mean element speed. This is calculated with the following formula:NDm = Speed in rpm * ((bearing bore + bearing outside diameter) / 2)Bearing manufacturer relubrication guidelines are specific about minimum oil viscosities for mean element speeds. You should verify that the selected product meets the fundamental viscosity requirement and then factor in a slight cushion. If the viscosity of the oil at the bearing operating temperature is two times or more than the minimum operating viscosity (from the bearing manufacturer), then you should reconsider the lubricant selection, especially for bearings operating near 3,600 rpm.Churning and overheating both contribute to the loss of oil in the grease. This shortens

the grease’s life and the relubrication interval. Properly selected viscosity, volume and frequency each play a key role in sustaining bearing lifecycles.

Mapping Oil Pressure to Measure Bearing Wear

Gary Blevins, Wearcheck Africa Dan Burger, Wearcheck Africa Tags: bearing lubricationOne of the buzzwords used in regard to condition monitoring is oil pressure mapping. This article explains oil pressure mapping, why this diagnostic technique was developed and how it is used to measure engine bearing wear.Testing for Bearing Wear Traditionally, testing for abnormal wear or damage to the main or big end bearings was carried out by measuring engine oil pressure at idle and maximum engine speeds. The reasoning was that excessive bearing clearance would cause excessive oil leakage and a resulting drop in oil pressure.This test is no longer reliable as modern diesel engines are fitted with high-capacity oil pumps, which are needed to deliver oil to the spray jets used to cool the pistons. As a result, the pumps can cope with higher oil leakage rates, so there is little noticeable drop-off in oil pressure. This is why oil pressure mapping is used.

Before discussing oil mapping in more detail, it’s helpful to take an in-depth look at bearings, their importance in maintaining healthy equipment, and why oil pressure affects bearing wear.Bearings and Oil A bearing is often an inexpensive part in a machine, but the failure of a bearing results in a considerable amount of consequential damage to other components. It is for this reason that maintenance personnel are concerned about the health of bearings.Oil analysis is an important tool used to assess the soundness of a bearing. Once a problem is detected through oil analysis, it must be investigated to establish the cause and extent of the problem.The following are a few of the common causes of bearing faults:overloading or shock loadingcontamination of lubricating oiloverheating of lubricating oiloverheating of the bearing

misalignment or incorrect assembly of the bearinginsufficient pressure and/or volume of the lubricating oilThe secret to long bearing life, after installation and operational problems have been corrected, is to ensure that the bearing is supplied with the correct grade of oil in sufficient quantities, and that the oil is clean and runs at the correct temperature.Plain bearings, in particular, are sensitive to oil volume and pressure. Insufficient pressure will normally result in insufficient oil volume being delivered to the bearing. The decreased oil volume causes the bearing to wear out faster, due to increased operating temperatures and contact between the journal and bearing.Antifriction (roller or ball-type) bearings can normally run on relatively small volumes of oil. However, a drop-off in oil volume will cause wear on the cage due to the increased sliding contact in this area. The wear then allows the rollers or balls to move out of position and accelerate wear of the bearing races.Oil Mapping An oil pump, like most other pumps, produces a rapid increase in output as speed increases until a critical point is reached, after which the output drops off again.To prevent erosion damage to the bearing from the excessively high oil pressures possible with the high-capacity oil pumps fitted to modern diesel engines, a pressure-relief valve is fitted to the engine oil pump. This vents excess oil back to the sump when the maximum allowable pressure is reached.Oil pressure mapping is simply a method of verifying that the oil pump pressure follows this curve. When the shape of the curve changes, it indicates a fault with the oil pump or excessive oil leakage in the engine, possibly due to bearing wear.How to Map Oil Pressure To map the oil pressure, you need an accurate oil pressure gauge which can accommodate a range of pressures. Dashboard-mounted gauges are generally not accurate enough for mapping purposes. An accurate tachometer is needed to measure engine speed while performing the test. Graph paper to plot the resultant pressure curve is also useful.Step 1 Make sure the engine has reached full operating temperature. Water temperature is not a reliable indicator of oil temperature. The water temperature stabilizes quickly due to the action of the thermostat, but the oil temperature lags behind during warm-up. If possible, record the oil temperature when the pressure readings are taken.The oil temperature is important because the oil thins rapidly as the oil temperature increases, then thickens again when it cools down. The thickness of the oil (viscosity) affects the pressures obtained and may give inaccurately high readings if measured at too low of a temperature.Step 2Connect the oil pressure gauge to the main oil gallery before it enters the bearings; the oil pressure sender unit is generally a good point. Connect a tachometer if required.Oil pressure should then be measured at 10 or more speed intervals equally spaced between idle and maximum engine speed. It is helpful to draw a straight line from the first reading taken at idle to the last reading taken at maximum engine speed. All the intermediate points on the curve should lie above this line.

If the pressure falls below the line or follows the line closely, there is likely a problem with the oil pump or the pressure-relief valve, or excessive leakage is occurring within the engine itself. Even if the oil pressure is close to normal at full speed, it may be too low at peak torque where the bearings are subjected to maximum loading.There are many different designs of engines and pumps, so when a problem is suspected, it helps to have a reference graph against which to compare the results. It is, therefore, advisable to map an engine shortly after it has been run in, and then use this baseline for comparison with later graphs.Any change or drop-off in the graphs should be investigated. First, check the pump and pressure-relief valve. If no fault is found with the pump, the engine itself should be inspected for excessive leakage.Engines Fitted with Scavenge Pumps Engines on some earthmoving equipment are designed for operating on slopes and are fitted with scavenge pumps. It is generally not possible to check the function of the scavenge pump. It tends to wear out faster than the main pump due to oil aeration in the scavenge pump when the engine is running level. An undetected scavenge pump failure will soon result in bearing failure. Engines fitted with this type of pump must have the pump stripped and checked for damage at planned intervals of at least every 10,000 hours of operation.Practicing Oil Analysis (11/2008)

How Much Grease is Enough?

Noria Corporation

Tags: bearing lubrication, grease guns "All of the formal training I've had on the application of lubricants suggests that for greasable bearings, one should never pump in so much grease as to push out the external seals. However, the instruction manual that comes with Dodge Type-E bearings states:‘Operation in presence of dust, water or corrosive vapors - Under these conditions the bearing should contain as much grease as speed will permit, because a full bearing with

consequent slight leakage is the best protection against entrance of foreign material.’Won't this ruin the seal and allow for easier entrance of foreign material? I currently teach my technicians to add the amount of grease as determined by the SKF formula G = DB/10, where G is grease in ounces, D is bearing outer diameter, and B is bearing width; or as I've read in Lube-Tips, one shot per inch of shaft diameter. Is this not enough in dusty environments?"Several factors influence the quantity of grease that would go into a bearing at the selected interval. Critical factors include: 1. Design of the bearing (plain, roller, ball or spherical roller). 2. Type of shield used in the bearing. 3. Size and speed from which to calculate dN values. 4. Viscosity of the lubricant in the grease.The Dodge Type-E bearing has a shield and lip seal configuration, with an option for an additional two-stage lip seal. This type of seal, by design, will allow for discharge of grease without damage at the outer perimeter of the seal. You could consider this a type of shielded bearing configuration.A sealed bearing is not designed to be purged. If you apply too much grease too quickly, you can rupture the seal and compromise the life of the bearing.If you look closely at the manufacturer’s guidelines, you should see both general and specific directions for relubrication, including frequency and quantity for a given speed and load. The original equipment manufacturer (OEM) parameters are typically the best starting point for relubrication practices.The OEM will also suggest that if you have a highly aggressive environment, it may be necessary to adjust the interval or volume to increase the amount of grease to the bearing. The SKF formula also provides a good starting point. Again, the calculated value must be adjusted to accommodate the environment.The decision to flood or purge a bearing should be taken within the context of bearing construction, production environment and OEM guidelines. This is rarely a simple question.Related Articles

Why You Should Inspect Bearing Grease Discharge

Jim Fitch Tags: bearing lubricationThere are three opportunities to inspect the state of in-service grease. One is by disassembly (such as by removing the bearing cap), the second is by sampling the grease using a probe (ASTM D7718), and the third is by examining the purge discharge. The purge discharge is the grease that’s extruded from exhaust ports, seals and other openings during relubrication or machine operation.

Not all grease-lubricated machines have a purge stream, but many do. Machines (mostly bearings) that purge grease provide a valuable opportunity for inspection. The opportunity is significant because of the frequency and simplicity of the inspection. Machines that purge are generally “total loss” systems, meaning the grease is not recovered for reuse but instead is discharged to a catch-pan, trap, grease thief, exterior surface or straight to the floor (Figure 1).

Using a Grease Discharge TrapA grease discharge trap (GDT) is a perfect inspection device. One version of the GDT uses a simple barb fitting that is installed in the purge port (also known as a drain port, vent port or exhaust port). A 1½-inch zip-lock plastic bag (of various lengths) is positioned on the barb side of the fitting using an O-ring (see photos on the right). Grease that purges out of the fitting goes straight into the bag for easy inspection, disposal and sampling.

Reasons for Using the GDT Cleanliness - Purged grease is contained in the bag and not dispensed to the

ground, floor or side of the machine. Disposal - Once the bag is full, it can be removed, sealed (using the zip-lock) and discarded. It is replaced with a new bag. Contamination Control - The machine is protected from contamination ingestion through the purge port during normal thermal air exchange and wash-down sprays. Unobstructed Purge Path - During machine operation, grease can freely purge to the trap to avoid excessive grease volume buildup in the bearing (heat generation and premature bearing failure). Inspection of Grease Discharge Volume- The trap enables easy inspection of the amount of grease discharge (too much or too little) from auto-lubers and manual lubrication practices. Inspection of Grease Condition - Look at the color of the grease including mixed colors (cross-contamination). Touch the grease through the bag to inspect for solids, grit and grease consistency. Slide a strong magnet on the outside of the bag to attract large wear particles. Grease Sample - Remove the bag with the grease discharge sample. Zip it tight, place in a sample bottle and send to a lab for analysis.

Following are examples of machines that commonly have a purge stream: Electric motor bearings Pillow-block bearings (conveyors, etc.) Some blower/fan bearings Some grease-lubricated gearbox bearings Mechanical couplings Some process pump bearings Some compressor bearings Hinge pins and some journal bearings Agitator bearings Some extruder bearings Some calender roll bearings

In many cases, purging grease through a bearing is not recommended, although it is commonly practiced. The decision to purge or not to purge should not be trivialized. To understand this better, see the sidebar below about purge versus volume control methods for lubricating bearings.

Figure 1. In total loss systems, grease is discharged to a catch-pan (left), exterior surface (right) or straight to the floor. Source: OilDoc

Too often the opportunity to inspect grease discharge is dismissed largely due to ignorance. In fact, there is a story to tell from the condition and state of grease discharge. This relates both to the state of lubrication and the health of the machine. There is also information to be learned about the application of the grease, the relube frequency and the relube volume that can be assessed by inspecting grease discharge.

What can be Learned from Purge DischargeThe discharge from bearings and other machine components is basically a sample of the grease condition as it exits (its terminal state). It carries out a historical account of the bearings. This includes debris from the bearing, contaminants the bearing was exposed to and degradation byproducts from the grease. The state of the discharge correlates to the quality and state of lubrication and ultimately the reliability of the bearing.So what questions might the purge stream be able to answer? Take a look at the following list for examples:

Figure 2. This is an example of excessive lubrication.Wrong or Mixed Grease - A wrong or mixed grease color can be observed in the discharge. An incorrect grease consistency might also be detected.Degraded Grease - Evidence of oxidation (tar-like), thermal distress and/or dry, caky grease (oil loss) may be visible.Contaminated Grease - Signs of water, corrosion, dirt or other impurities can be seen.Inadequate Grease Volume or Frequency - This is shown from prematurely degraded and/or contaminated grease.Excessive Grease Volume or Frequency - Large piles of grease discharge reveal problems (Figure 2).

When to Stop Pumping Grease into a BearingBearings are often lubricated using a grease gun until a fresh grease purge is observed. While there are many cases when this is best practice, there are an equal number of cases when it is not.Anyone who lubricates bearings with a grease gun should understand the alternative methods and when each should be applied. Of course, the machine or component manufacturer should always be consulted.

Noria refers to the two options as the Fresh Grease Purge method and the Grease Purge and Volume method. These methods and target applications are described below:

Fresh Grease Purge (FGP) Method

The bearing is lubricated until fresh grease emerges from the purge port (vent) or shaft/seal interface, or back-pressure is encountered. When to use the FGP method:

Low speed-factor bearings (DNs less than 50,000) with a suitable purge path (purge port or shaft/seal interface) Bearings specifically designed for purge lubrication such as hinge pins, bushings, open bearings and some bearings with labyrinth seals Bearings exposed to high environmental contamination with a purge path (purge port or shaft/seal interface)

Grease Purge and Volume (GPV) Method

The bearing is lubricated until a pre-established maximum volume of grease has been introduced, fresh grease emerges from the purge port (vent) or shaft/seal interface, or back-pressure is encountered. When to use the GPV method:

Electric motor bearings (i.e., electric motors that are intended to be periodically relubricated) Bearings with speed factors greater than 50,000 (DN) Bearings with no purge path Bearings with a possibly restricted purge path Bearings with an alternate purge path that could send grease to an unwanted internal compartment such as a lube oil sump

Cake-lock Conditions - The telltale sign of this condition is when the catch-pan only has oil. This means the thickener is binding up in the bearing.Abnormal Wear Conditions - Visible evidence of wear debris is seen. Use a magnet to extract larger wear particles. Solvents can also be used to separate particles from the grease.

Figure 3. A grease thief (left) and a bellows-type grease discharge trap (right) can be connected

to a purge port.Obstructed or Diverted Purge Path - The normal amount of grease discharge is not observed, meaning that grease is being diverted to another purge path.

Auto-Lube Malfunction or Neglected Grease Gun Relubrication - The normal amount of grease discharge is not seen, resulting in a potential starvation condition.

How to Inspect the DischargeA quick, daily visual inspection is sometimes adequate. Look for abnormal grease discharge, color, consistency and location. Clean away the discharge so the amount of new discharge (since the last inspection) is easily recognized for inspection. Alternatively, use a simple grease discharge trap (see sidebar above). A discharge trap is a plastic bag, grease thief or bellows device connected to the purge port (Figure 3). Grease exhaust is held by the trap for later inspection, sampling and/or disposal.

Figure 4. A magnet placed under a gold pan or glass bowl can enable you to observe ferrous debris in a grease sample.

If the conditions of the discharge merit further inspection, consider the following: Lab Analysis - Many oil analysis labs can also analyze grease. Common tests include ferrous density, elemental spectroscopy, Fourier transform infrared (FTIR) spectroscopy, Karl Fischer, oil content, analytical ferrography and others. Artist Spatula/Light Table Inspection - Use a common artist’s spatula to spread grease across a smooth glass surface. Is the grease soft, buttery, gummy, tar-like, crusty, cake-like, stringy or inconsistent in color? Shining a strong light from below the glass can help you identify clumps, wear debris, contaminants, etc. Particle Inspection - This can be done using solvents (e.g., toluene, mineral spirits, petroleum ether, etc.) to break down the grease. Separate the particles for visual or microscopic inspection by employing a gold pan, patch test or ferrogram method. Ferrous Density - Put some of the grease in a sample bottle along with solvents. Tape a strong magnet to the outside of the bottle and then shake. Observe the ferrous debris collection against the magnet. You can also place a magnet underneath a gold pan or glass bowl (Figure 4) and swirl. Oil Content - Load some of the grease sample in a small bushing the size of a thick wedding ring. Place this on blotter paper and examine the amount of oil that wicks out into the paper over a couple of hours. The damp zone relates to oil content. Try this with new grease first.

3 of lubrication professionals never inspect the grease discharge from bearings and other machine components at their plant, based on

5%a recent survey at machinerylubrication.com

The routine inspection and analysis of grease discharge should be a part of the skill set of operators and technicians responsible for lubrication, maintenance and machine reliability. The discharge carries bits and pieces of potentially valuable information. This could range from a clean bill of health to the remnants of a building internal machine graveyard.Machinery Lubrication (10/2012)

When to Clean and Repack Bearings

Noria Corporation

Tags: bearing lubrication "Is there a standard method for determining if and when a bearing should be cleaned and repacked?"Given the practical challenges of hand-packing a bearing with any hope of maintaining grease and bearing cleanliness, it is often best to avoid opening a bearing to clean and repack.Simply stated, the benefit practically exceeds the costs and risks. However, if circumstances exist where this must be done, then some thoughtful planning is justified.We should look at the issue as a two-part problem. The first issue is if/when to repack a bearing. If a bearing is intended to be grease-lubricated, then it would be best to include a Zerk or similar fitting to enable replenishment without opening the bearing cavity.When the bearing is replenished according to sound engineering principles (right product

quality, right product selection, right amount, right frequency, no cross-contamination, etc.), the bearing does not require disassembly, cleaning and repacking to maintain lubricant and bearing health. If the bearing cannot be configured with a Zerk and a relief, and a “clean and repack” event is the only option, then scheduling the activity becomes a judgment call based on a multitude of factors as noted below.The second part of the question is about whether there is a standardized approach for making this decision. After reviewing a few well-respected lubrication texts and speaking with two well-known bearing manufacturers, we conclude that there is no recognized standard with which to make a decision to disassemble and repack a bearing.Several factors may influence the selected repack frequency decision, including the quality of the environment near the area where the work is to be done, the quality of the grease removed during previous repack events, the size of the housing, the extent to which spent grease has filled up available housing space, flexibility in configuring the housing for routine replenishment, flexibility in configuring the housing to “vent” spent grease during replenishment, evidence of bearing stress (rise in temperature, rise in high-frequency energy, etc.), ease of grease sampling and availability of grease analysis.The use of acoustics or other high-frequency metrics can be most helpful in supporting the scheduled frequency decision if a manual repack must occur.

5 Ways to Prevent Bearing Failures

Steven Katz, Emerson Bearing Tags: bearing lubrication, greases, contamination controlThe accurate diagnosis of a bearing failure is imperative to prevent repeat failures and additional expense. Rolling bearings are precision machine elements found in a wide variety of applications. They are typically very reliable even under the toughest conditions. Under normal operating conditions, bearings have a substantial service life, which is expressed as either a period of time or as the total number of rotations before the rolling elements or inner and outer rings fatigue or fail. According to research, less than 1 percent of rolling bearings do not reach their expected life.

You must be aware of the radial internalclearance (RIC) and maintain the properRIC that was established in theoriginal design.

Premature Bearing FailureWhen a bearing does fail prematurely, it usually is due to causes that could have been avoided. For this reason, the possibility of reaching conclusions about the cause of a defect by means of studying its appearance is very useful. It’s most important to correct the causes and prevent future failures and the costs that follow.Most bearing failures such as flaking, pitting, spalling, unusual wear patterns, rust, corrosion, creeping, skewing, etc., are usually attributed to a relatively small group of causes that are often interrelated and correctable. These causes include lubrication, mounting, operational stress, bearing selection and environmental influence.

Proper LubricationThe purpose of lubricating a bearing is to cover the rolling and sliding contact surfaces with a thin oil film to avoid direct metal-to-metal contact. When done effectively, this reduces friction and abrasion, transports heat generated by friction, prolongs service life, prevents rust and corrosion, and keeps foreign objects and contamination away from rolling elements.Grease typically is used for lubricating bearings because it is easy to handle and simplifies the sealing system, while oil lubrication is more suitable for high-speed or high-temperature operations.Generally, lubrication failures occur due to:

Using the wrong type of lubricant Too little grease/oil Too much grease/oil

Mixing of grease/oil Contamination of the grease/oil by objects or water

Grease Service LifeIn addition to the normal bearing service life, it is also important to take into consideration the normal grease service life. Grease service life is the time over which proper bearing function is sustained by a particular quantity and category of grease. This is especially crucial in pump, compressor, motor and super-precision applications.

Mounting and Installation of BearingsIn the mounting and installation process, it is critical to use proper tools and ovens/induction heaters. Employ a sleeve to impact the entire inner ring face being press fit. Also, verify the shaft and housing tolerances. If the fit is too tight, you will create too much preload. If the fit is too loose, you will generate too little preload, which may allow the shaft to rotate or creep in the bearing. Don’t forget to check for proper diameters, roundness and chamfer radius.Be sure to avoid misalignment or shaft deflection. This is particularly significant in mounting bearings that have separable components such as cylindrical roller bearings where successful load bearing and optimal life are established or diminished at installation.You must also be aware of the radial internal clearance (RIC) and maintain the proper RIC that was established in the original design. The standard scale in order of ascending clearance is C2, C0, C3, C4 and C5. The proper clearance for the application is important in that it allows for the challenges of lubrication, shaft fit and heat.Keep in mind that a proper film of lubricant must be established between the rolling elements. Reducing internal clearance and impeding lubricant flow can lead to premature failure. With regards to shaft fit, it is inevitable that there can be a reduction in the radial internal clearance when the bearing is press fit. Also, in the normal operation of bearings, heat is produced, which creates thermal expansion of the inner and outer rings. This can reduce the internal clearance, which will reduce the optimal bearing life.

Causes of failure in rolling bearings

Operational Stress and Bearing SelectionGenerally, it is the exception to find a bearing that has been improperly designed into an application. However, factors within the larger application may change. If loads become too high, overloading and early fatigue may follow. If they are too low, skidding and improper loading of the rolling elements occur. Early failure will follow in each situation. Similar issues arise with improper internal clearance.The first sign of these issues will be unusual noises and/or increased temperatures. Bearing temperatures typically rise with start-up and stabilize at a temperature slightly lower than at start-up (normally 10 to 40 degrees C higher than room temperature). A desirable bearing temperature is below 100 degrees C.There are typical abnormal bearing sounds that reveal certain issues in the bearing application. While this is a subjective test, it is helpful to know that a screech or howling sound usually indicates too large an internal clearance or poor lubrication on a cylindrical roller bearing, while a crunching felt when the shaft is rotated by hand normally suggests contamination of the raceways.Operational stresses in the application can impact bearing life as well. It is essential to isolate vibrations in associated equipment, as they can cause uneven running and unusual noises.

Environmental InfluenceEven with the best design, lubrication and installation, failures will occur if the operating

environment is not taken into consideration. While there are many potential issues, the primary ones include:

Dust and dirt, which can aggressively contaminate a bearing. Special care should be given to using proper sealing techniques. Aggressive media or water. Once again, sealing is key. The use of specialty-type seals that do not score the shaft is recommended. External heat. The ambient operating temperature mandates many choices in radial internal clearance, high-temperature lubricants, intermittent or continuous running and other factors that affect bearing life. Current passage or electrolytic corrosion. If current is allowed to flow through the rolling elements, sparks can create pitting or fluting on the bearing surfaces. This can be corrected by creating a bypass circuit for the current or by using insulation on or within the bearing. This should be an inherent design consideration in applications such as wind turbines and all power-generating equipment.

Remember, the first step in the overall prevention of bearing failure lies in the consideration of bearing technologies that are most suitable to the application with regard to specifications, recommendations, maintenance strategies, fatigue life and wear resistance of the bearing. Premature bearing failure within a proper application is typically attributed to one or more of the causes discussed (lubrication, mounting, operational stress, bearing selection or environmental influence), which can and should be corrected in order to avoid future bearing failures and additional cost.

About the Author

Steven Katz is the president of Emerson Bearing, a provider of bearings to OEMs (original equipment manufacturers) and MRO (maintenance, repair and operations) markets in the United States and internationally. For more information, contact 800-225-4587 or visitwww.emersonbearing.com.Machinery Lubrication (4/2012)

3 Suggestions for Removing Wear Debris

Noria Corporation

Tags: contamination control, bearing lubrication "We are experiencing sleeve bearing failures on a piece of equipment. The main cause of failure is bearing wear due to mechanical misapplication of the equipment. We are not in a position to change the bearing type yet because we have to meet current production demands. Would a simple magnetic plug help to remove 'free' particles of entrained bearing material and slow down the rate of wear until we can correct the root cause?”Unfortunately, magnetic plugs trap only large ferromagnetic wear debris (typically larger than 100 microns). Non-ferrous particles associated with babbitt used in sleeve bearings would not be removed, nor would ferrous particles (shaft metal, for instance) smaller than 100 microns.Therefore, wear metal is unlikely to be trapped by a magnetic plug. Instead, try the following: - Fitting a couple of quick connects to the bearing housing (top and bottom) would allow a small portable filtering unit to clean up the oil very rapidly. On the assumption that you would need to turn over the volume seven times, a 5-liter-per-minute pump would take less than 10 minutes to clean up the oil to a very clean level. In conjunction with the new breather unit, this would minimize the main cause of wear. - Upgrade the breather/vent units if these are fitted. Bear in mind that a 10-micron particle entering through a vent plug is like a snooker/pool ball rolling through a doorway — there is little chance of stopping it. A good breather will help ensure that no additional contamination is entering. - If the machine is being stressed, oil temperatures are probably higher. The OEM-specified oil may be too thin at the higher temperatures. Consider a change of lubricant viscosity specification, perhaps even to a multi-grade or synthetic.

Warning Signs of a Bearing Failure

Noria Corporation Tags: bearing lubrication "Are there any warning signs of when a bearing is about to fail?"

Think of a bearing failure as happening in four stages. During the first stage (or earliest

detectable point using vibration analysis), the signals will appear in frequency bands around 250 to 350 kilohertz (KHz). In the second stage, a signal around 500 to 2,000 hertz (its natural frequency) will begin to ring.At the onset of the third stage, the harmonics of the fundamental frequency will start to be very apparent. Defects in the races are now obvious and will be visible on vibration analysis of the noise signal. At this point, there will also be a significant temperature increase.During the fourth stage, there will be very high vibration. The fundamental frequency and harmonics begin to decrease as the random ultrasonic noise is boosted. Temperatures will start to skyrocket as the bearing self-destructs.So, the short answer is yes. There are definitely warning signs of a bearing about to fail. The real question is, "Do you know what to look for?" The most popular technologies today for bearing monitoring are vibration analysis, oil analysis, ultrasonics and thermography. We can use these tools to compare current states to historical data and accurately assess the remaining life of the bearing.Vibration analysis and oil analysis are considered the best at predicting a failure but are not always the most cost-effective. Bearing manufacturers have long known of the relationship between bearing life and temperature. They even have formulas that work very well at calculating safe operating temperatures. These formulas and calculators show that once a bearing starts operating outside its ideal temperature range, its life will begin to degrade at an accelerated rate. (Keep in mind that for every 15 degrees C above 70 degrees C that the base oil operates, its life is more than halved.)Knowing this, why is thermography not a more popular method for bearing life prediction? The monitoring of temperatures is not always considered reliable because of the sheer amount of variables that contribute to the heat generation. Ambient temperature, friction, speed variability, load and runtime all have an effect on the temperature that will be measured.Friction is the variable you should be the most concerned with if trying to predict a failure, but how do you separate it from all the others? If you could account for all the variables accurately, the increases you would get in operating temperature could be a great indicator of an impending failure.Perhaps the cheapest and easiest way to spot a bearing failure is to use a non-contact infrared thermometer. The caveat is that you must always account for the other variables as well.

What's Too Hot for Grease Lubrication?

Noria Corporation

Tags: bearing lubrication, greases "How hot is too hot for a grease-lubricated bearing?"In the final analysis, if the bearing is hot enough to evaporate the oil off the grease between relubrication cycles, then it is too hot for grease lubrication.The answer to this question, though, depends on several factors. Let's address a few of them.When dealing with elevated temperatures, we should first ask, "What is the source of the heat?" Is it ambient? Is it from the process (transmitted down the shaft)? Is it wear-related?Is it lubrication-related? These questions have a lot of impact on our selection of the grease type and in determining the appropriate answer to the question.If the temperature is from the process or atmosphere and we know that we have to deal with that condition perpetually, then we should adjust the grease composition to meet the requirements. Perhaps we should select a synthetic oil with a non-soap thickening system that gives us a low evaporation rate. If the temperature is not process or atmosphere-related, then we should make sure that we are not over-filling the bearing with grease.Too much grease in a cavity causes churning and excessive temperatures. Too little grease, or too infrequent relubrication, may cause friction-generated heat.If we are using precisely the right volume and we are sure that the heat is internally generated rather than atmospheric or process-related, then perhaps we should examine whether the grease has sufficient strength to support the dynamic load. In this case we might look at selecting a grease with a heavier viscosity base oil.

Time to Upgrade Your Grease?

Noria Corporation Tags: greases, bearing lubrication, contamination control

"Our supplier recently informed us about a new low-noise grease manufacturing process for motor greases. This appears to be an exercise in repackaging a product to sell it under a different name at a premium price. Does this new grease really offer extra value or should I continue with what I am currently using?"Low-noise level greases are those greases that have been purified sufficiently so that there are no, or at least very few, large particles in the grease that could enter into the load zone and cause rotating elements to bump and grind, generating noise in the bearing.These products were originally constructed for high-precision applications where the rise and fall of the bearing elements over contaminant particles entering the load zone through the grease could damage either the bearing or the driven component. Let's take a look at a few issues surrounding this type of product. First, there are plenty of everyday applications where low-noise grease is highly desirable. The motors that control your stereo electronics, computer drives and other micro-motor applications would clearly benefit from low-noise or high-purity greases.Second, bearing noise is eliminated by the removal of particles or contaminants that could cause the element to bump or impact the raceway. It makes sense that if there are contaminants that are large enough to interfere with the element's uniform movement through the load zone, that under the right loading conditions the contaminants could possibly have some effect on bearing longevity and motor reliability.This concept is consistent with the idea that particles in fluid systems can enter load zones and compromise load distributions, race and element surfaces, and eventually component and machine lifecycles.Also, there are several measures of grease quality. Grease cleanliness is characterized by the noise the grease produces in a bearing test cell. Standard off-the-shelf products are only visually checked for contaminants. The conscientious grease manufacturer would buy high-purity and high-quality materials from suppliers who demonstrate consistent quality. However, without testing the raw materials and the final product for contaminants, it is impossible to determine just how much solid contaminant is in the final product.There is a good argument that could be made for the use of low-noise grease in large grease-lubricated industrial motors from a reliability perspective. It is likely that the improvement in motor bearing life would cover the cost differential for the low-noise

grease product, assuming that the thickener, oil viscosity and other properties of the grease were acceptable.

Avoiding Grease Incompatibility Problems

Noria Corporation

Tags: greases, electric motor lubrication, bearing lubrication" We recently switched electric motor rebuild shops. Since switching, a number of bearings have failed, typically just a few months after putting the motor back into service. For the most part, these failures have been attributed to inadequate lubrication. On closer inspection, the grease appeared to have thinned out to almost a liquid consistency. We suspected that the rebuild shop was using a grease inferior to our electric motor grease, but they assure us that they are using a premium-quality synthetic grease. What is your opinion?"Without more details, it is difficult to attribute an exact root cause. However, with greases, one of the most commonly encountered problems is incompatibility between different types of grease made from different thickeners.For electric motors, the most commonly used greases are made either from a lithium-complex soap thickener or polyurea material. While both polyurea and lithium-complex based greases can be used in this application, the two are usually considered to be incompatible with each other and should not be mixed unless proper compatibility testing has been performed.To avoid these types of problems, it is advisable to request that the rebuild shop use the same grease that you plan to use to regrease the bearings, or at the very least, indicate the exact type and brand of grease being used so that you can determine if there are any serious compatibility issues between the two greases.

It is often advisable to provide a tube of grease to the rebuild shop whenever a motor is sent to rebuild to avoid these issues.Grease compatibility is often confusing to grease users, even though most grease manufacturers produce compatibility charts. This is because the charts from the various manufacturers often disagree with one another on certain thickener-type combinations.In bygone days, when simple soaps and clay were the primary thickener types, compatibility was relatively straightforward. Lithium and calcium soaps were compatible with one another, and neither was particularly good when mixed with a clay-based grease.Today, with not only the aforementioned thickeners but also complex soaps, polyurea, calcium sulfonate and even more exotic thickeners used in many greases, the issue of compatibility has become much more complicated.To add to the confusion, there are some grease specifications that are based solely on grease performance without regard to grease composition. If greases of different thickener types (both of which meet the performance requirements of the specification) get mixed in service, dire consequences can result.

Is Your Bearing Getting Fresh Grease?

Tags: bearing lubrication, greases, oil analysis, oil filters,lubricant samplingUse caution with grease lines that run out of the machine frame and are intended to offer easy lubrication access points. Since these line extensions often carry more than a few shots of grease, the grease entering the bearing will not be robust and fresh. Vibration, time and temperature changes can lead to leaching of critical oil components from the grease thickener, leaving a dry soap in the tube.

Also, without visual access to the bearing area, there can be numerous undetected problems. The best approach is to provide access to the lube point as close to the bearing as possible. This enables the bearing to be inspected and ensures that fresh grease enters the lube cavity.

Check Gear Reducers for CondensationIf you have a reducer that is water-cooled and the water temperature is too cold, it could condense and put water in the oil. If you notice the gear reducer sweating, water on the

floor or water on the cooling water lines going into the gear reducer, you probably have water in the gear reducer. When you find this problem, first increase the temperature until the water lines quit sweating. Second, perform oil analysis on the reducer and check for water. If this issue isn’t corrected, it could be catastrophic.

Infrared Scans Can Detect Reservoir ProblemsConsider performing infrared scans on your rotating equipment to monitor the operating temperature of your reservoirs. A routine scan of a large gearbox revealed that it was overheating (operating above 190 degrees F) due to failure of the oil cooler pump. The oil was foaming significantly out of the oil sight glass.

Sediment in Sight GaugesA fan pump recently lost an oil-filled bearing due to lack of oil in the sump. The oil level sight gauge used on this pump indicated that the pump was full, but actually it was not. The pipe coming out of the side of the pump to the level gauge was plugged with sediment and would not let oil out of the sight gauge to give a true oil level reading. To prevent this, lube technicians need to drain sight gauges periodically to confirm proper functioning.

How Long Should Oil Be Filtered?When filtering oil, it is a good rule of thumb to run your filtration unit until the total flow through the filters equals the volume of seven times the reservoir capacity. Because of differences in oil viscosities and the bypass valve used to keep the filter pressure in the acceptable range, you may not be able to use rated pump-flow rates to determine how long it will take to reach this goal. However, you can add flow meters on your filtration skid so you will know how much oil has actually gone through the filters. This way you can be sure that you are getting your minimum level of acceptable filtration.

Advice for Labeling Oil Sample BottlesWhen labeling oil sample bottles, consider labeling the bottle cap also. If you mistakenly place a cap from a bad sample onto a bottle containing a good sample, the sample is cross-contaminated. Testing of this cross-contaminated sample will yield false data. Labeling both the bottle and its cap will prevent this problem from occurring.The “Lube Tips” section of Machinery Lubrication magazine features innovative ideas

submitted by our readers. Additional tips can be found in our Lube-Tips e-mail newsletter. If you have a tip to share, e-mail it to us at editor@noria.com. To sign up for the Lube-Tips newsletter, visit www.machinerylubrication.com and click on the “Newsletters” link at the top.

How Contaminants Influence Bearing Life

Noria Corporation

Tags: contamination control, bearing lubrication How much of an effect do contaminants have on the life of a bearing?When bearings operate in a clean environment, the primary cause of damage is the eventual fatigue of the surfaces where rolling contact occurs. However, when particle contamination enters the bearing system, it is likely to cause damage such as bruising, which can shorten bearing life dramatically.Furthermore, when dirt from the environment or metallic wear debris from some component in the application is allowed to contaminate the lubricant, wear can become the predominant cause of bearing damage. If bearing wear becomes significant due to particle contamination of the lubricant, changes will occur to critical bearing dimensions that could adversely affect machine operation.In general, the important parameters influencing bearing wear are contaminant particle size, concentration, hardness and lubricant film thickness. Increases in all of these parameters except film thickness will increase bearing wear.Keep in mind that increasing the lubricant’s viscosity will reduce bearing wear for a given contamination level.Bearings operating in a contaminated lubricant exhibit a higher initial rate of wear than those not running in a contaminated lubricant. However, with no further contaminant ingress, this wear rate quickly diminishes as the contamination particles are reduced in

size as they pass through the bearing contact area during normal operation.Either dissolved or suspended water in lubricating oils can exert a detrimental influence on bearing fatigue life. Water can cause bearing etching, which can also reduce bearing fatigue life. The exact mechanism by which wear lowers fatigue life is not fully understood, but it has been suggested that water enters micro cracks in the bearing races which are caused by repeated elastic deformation stress cycles. This then leads to corrosion and hydrogen embrittlement in the micro cracks, which reduce the time required for these cracks to propagate to an unacceptable size spall.Water base fluids such as water glycol and invert emulsions have also shown a reduction in bearing fatigue life. Although water from these sources is not the same as contamination, the results support the previous discussion concerning water-contaminated lubricants.Another theory suggests that while mineral oils exhibit an exponential rise in viscosity with increasing pressure, water exhibits very little viscosity increase with a rise in pressure. Accordingly, water-based fluids will not generate an elastohydrodynamic film thickness equivalent to a petroleum oil of the same viscosity.

Common Causes of Machine Failures

Noria Corporation

Tags: contamination control "What is the most common probable cause for machine malfunction?"Machines fail for a variety of reasons. Likewise, not all failures are the same. The term "machinery failure" or "malfunction" usually implies that the machine has stopped functioning the way in which it was intended or designed. This is referred to as “loss of usefulness” of the machine or component. For instance, if a pump is installed to pump

100 gallons of oil per minute but over time can no longer keep up and now only pumps 75 gallons per minute, this is a loss of usefulness of the asset.This loss of usefulness is broken down into three main categories: obsolescence, surface degradation and accidents. Of these three, surface degradation of machine parts results in the machine’s loss of usefulness in the vast majority of cases. Surface degradation is comprised mainly of corrosion and mechanical wear.Corrosion of machine parts is quite common, especially for those with water-contamination issues. Water not only rusts iron surfaces, but it can also increase the oil’s oxidation rate, leading to an acidic environment within the component.Acids can also be formed as byproducts of reactions between certain additives in the oil and water. Product contamination through seals can create caustic environments and corrosive wear as well. Something as simple as having an aggressive extreme-pressure additive in contact with a yellow metal (copper, bronze, brass, etc.) can produce corrosive damage.

Mechanical wear occurs when machine surfaces mechanically wearing against each other. Abrasive wear is a method in which particle contamination causes the majority of the wear. Particles such as dirt or wear debris can lead to three-body abrasion or surface fatigue, which results in the surfaces becoming pitted and scored. Adhesive wear involves two surfaces coming in direct contact with each other, transferring material from one face to the other. This appears in areas where the lubricant can no longer support the load or in areas of lubricant starvation.Metal fatigue is similar to what happens when you try to cut wire without any tools. As you work the wire back and forth, the metal begins to work harder and fatigue. After enough cycles of this type of stress, the metal finally becomes brittle and snaps. The same process occurs in machines. For example, a particle can cause a stress riser on the

inner race of a rolling-element bearing. Over time and with constant flexing, the metal begins to fatigue. This propagates into a spall of the material.So as machines can lose their functionality in a variety of methods, it is the surface degradation of the machine parts that causes the majority of these problems. By keeping your machines properly sealed to restrict the ingress of particles and making sure the lubricants you use meet the operating demands of the components, you can extend

machine lBest Ways to Remove Water from Oil

Noria Corporation

Tags: water in oil, oil analysis, contamination control"What is the industry best practice for removing water from the oil reservoir of a piece of equipment? For example, routine oil analysis reveals 3,000 ppm of water in a gearbox oil reservoir of 15 gallons." Several technologies exist for removing water from oil, including vacuum dehydration, centrifugal separators, jet-dry devices, headspace dehumidification, aggregate adsorption media and hygroscopic polymer impregnated filter media.The oil type, volume of water, size of the reservoir and several other factors dictate what technology should be employed for a given situation.At approximately 0.3 percent water in a 15-gallon sump, you have nearly 5 to 6 ounces of

water either dissolved and/or emulsified in the oil. Given the application, I would either use a portable vacuum dehydrator or a hygroscopic polymer impregnated media filter.Filter the machine offline, preferably while it is operating. Be sure that the plumbing in your decontamination rig is full of new oil (the type used in the gearbox). Before filtering, open the drain valve to get rid of any free water (undissolved and unseparated water that can settle to the bottom of the sump).If you have some free water in the bottom of the sump, you will need to estimate the volume of free water and add it to the estimate of 5 to 6 ounces. You can do this by estimating the volume in the sump below the lowest point of the drain port (L x W x H). If the drain port is at the lowest point in the reservoir, the volume will be zero. However, most gearbox drain valves are set slightly above the bottom.If you employ hygroscopic polymer media elements, you need enough water-holding capacity to get rid of the dissolved and emulsified water, plus the free water that will become suspended during decontamination.You will probably be drawing from the drain port, so this will suspend the water. In addition, drying the oil will lead to free water being pulled into the dry oil via osmosis.Of course, in addition to removing the water, perform root-cause analysis to find its source. Breathers, seals and new oil are common culprits.The effects of water on the oil are often overlooked. Excessive water contamination can result in premature oil oxidation and promote the buildup of sludge and varnish. In some circumstances, water can also strip additives from the oil through water washing or hydrolysis resulting in premature oil degradation.ife and see fewer total failures.

How to Fix a Foaming Problem

Noria Corporation

Tags: contamination control, water in oil “We have recently

noticed a significant increase in foam in one of our lube systems. A supplier recommended adding an after-market anti-foam agent. Is this a good idea?”While in some circumstances adding an anti-foaming agent may resolve the issue, it generally is not a good idea to add any after-market additive to a lube system. If foam has traditionally never been a problem but has suddenly started, think about treating not the symptom (the foam), but the cause.If nothing has changed with the design of the lube system or reservoir, it is likely that this sudden increase in foaming tendency is caused by contamination. Because foam suppression in a lubricating oil is closely related to the air/oil surface tension, any contamination that can result in either an increase in air entrainment, such as solid particles, or a decrease in surface tension can cause this type of effect. Common contaminants that can decrease the surface tension include water, grease and surfactants, such as soaps and detergents used during machine wash-down.To diagnose the root cause of your problem, try looking for significant increases in water or particle contamination or the appearance of unexpected elements in your spectrometric analysis data, such as lithium, calcium, aluminum or barium that may signal some other ingested grease or chemical contaminant.

The Importance of Dirt-Holding Capacity in Oil Filters

Wes Cash, Noria Corporation Tags: oil filters, contamination controlThe enemy to any lubricated machine is particle contamination. In a perfect world, machines would be sealed up to block the ingression of particles before any problems occur, but unfortunately this isn’t the case. We live in a dirty environment. Particles exist everywhere, and lubricated components are constantly under attack from them. Whether the particles are ingested by poor-quality breathers or dirty oil from a recent top-up, the question remains what can be done to get rid of them. The obvious solution is filtration.Filters can extend the life of machines by removing harmful particles before they can cause surface degradation of the lubricated components. There are two common types of filters: surface or membrane filters and depth filters. Surface filters simply trap particles on the surface or face of the filter. Depth filters allow the oil to flow throughout the body or depth of the filter and trap particles throughout the media. Perhaps the most crucial attribute of any filter is the ability to trap and hold dirt.

6 of Lube-Tips subscribers use surface or membrane oil filters most frequently at their plant

0%Each filter has a specific pore size. This is the size of the openings within the media through which the oil and particles can pass. As the pore size gets smaller and smaller, the differential pressure across the media begins to increase as well. This differential pressure can lead to a condition in which the bypass or cracking pressure of the filter is reached, allowing oil to flow through virtually unfiltered. Also, if the pressure becomes too great, it can cause the actual filter media to burst.Once particles are captured, it becomes a measure of how well the filter can retain them. This is known as the dirt-holding capacity of the filter. Several factors contribute to how well filters hold the contaminants they catch. We’ve discussed the pore size of the filters, but pore density is equally important. Pore density can be described as the number of pores in a section of the filter. This is also known as the porosity of the filter. As pore size goes down, to maintain a low differential pressure across the media, the pore density must go up to account for the volume of oil in contact with the surface. Thus, filter depth and size also affect the dirt-holding capacity.

Cellulose (Wood Pulp) Filter MediaAnother thing to keep in mind when selecting filters is the material the media is composed of. This not only has an effect on the longevity of the filter and its adaptability to its environment but also its dirt-holding capacity. Two common types of filter media are cellulose and synthetics. Cellulose is comprised of wood pulp. These types of filter media have a large fiber size and a less consistent pore size throughout the entire filter. Cellulose has the advantage of being able to absorb some water from the oil it is filtering. Cellulose filters tend to fail quicker in acidic environments as well as in high-temperature applications.Synthetic filter media generally have a higher dirt-holding capacity than cellulose. This is due in part to their more consistent pore size throughout the media. Synthetic fibers are smaller than cellulose fibers, so they can be packed tighter together, creating more pores in which to trap and hold particles. Synthetic fibers also perform better in the harsh environments that tend to destroy cellulose filters.

Fiberglass Filter MediaIn examining the technical sheets of filters, you may have seen a filter’s beta rating. This describes how efficient the filter is at removing particles. There also may have been a value for the dirt-holding capacity. This value is obtained through a test known as ISO 16889 or the multi-pass test. In this standard test, a filter is put into a circuit that is filled with oil. The oil circulates through the filter. A set amount of sized particles is then released into the oil to test the filter’s ability to capture them. A particle counter before and after the filter measures the difference in particles. The results of this test will allow you to see how well or poorly a filter performs against different particle sizes.Keep these things in mind when selecting the next filter to clean your oil and protect your expensive machinery. Check the filter’s beta rating and pore size. Obviously, there is a big difference between a 40-micron filter and a 3-micron filter when you are talking about the size of particles allowed downstream. Also, whenever available, verify the results of the ISO 16889 multi-pass test. This not only will show you the efficiency of the filter, but also how well it is able to retain the particles it removes from the circulating oil.

Fiberglass vs. CelluloseSome filter manufacturers don’t show the results of this test as it pertains to the dirt-holding capacity of the filter, but by pressuring them and demanding to see the results, you can make the best decision for you and your machines. If they balk at the idea of providing the test results, there are labs across the country that can run the ISO 16889 test on the filter to give you the results. This is more expensive for the end user, but it offers the peace of mind that you have the right filters for your applications.

Prolonging Filter Service LifeSelecting the proper filter with a high dirt-holding capacity is only half the battle. You also must ensure these filters are put into use the right way. Filters can be expensive, so naturally you want to prolong the life of the filter to cut down on the costs associated with changing them.

Double the size of the filter and you can triple the service life (dirt-holding capacity). Reference Pall Corporation

One of the easiest ways to prolong the filter change-out interval is by simply oversizing the filter. As you can see in the chart above, by doubling the surface area of a filter, you can expect three times the life from it.There are different methods to oversizing filters. The most obvious is by increasing the physical size of the filters you are using. This is somewhat costly, as equipment modification is required to fit a larger filter in the lines. For some equipment where space is limited, this may not even be feasible. That is when you should start looking at putting filters in parallel.By placing multiple filters in parallel, you double the surface area in contact with the oil, thereby reducing the face velocity (the pressure of the oil on the surface of the filter media), and thus extend the life of the filter. This means less filter changes and the ability to capture more particles between change-outs.If the equipment won’t permit the extra piping to put in a parallel circuit, there are systems that stack filters one on top of another to increase the overall length of the media, again allowing for the decrease in pressure the media is experiencing.Machinery Lubrication (10/2012)

About the AuthorWes CashWes Cash is a technical consultant with Noria Corporation, focusing on machinery lubrication and maintenance in support of Noria’s Lubrication Program Development (LPD). He is a ... Read More

Anatomy of an Oil Filter

Bennett Fitch, Noria Corporation Tags: oil filtersThis is the second part of a series of “anatomy” lessons within Machinery Lubrication. In this issue, the oil filter will be examined to uncover its functional and performance characteristics. Several other related topics will also be discussed, including best practices for oil filter usage, possible filter failure modes, factors for proper filter selection and how to maintain an installed filter.By definition, an oil filter’s main role is to cleanse oil from destructive contaminants within a machine such as an engine, transmission, hydraulic system and other oil-dependent systems. In the case of automotive oil filters, canister-type filters are the most common. This filter configuration was most likely responsible for the advanced performance of oil filtration technology.In 1922, Ernest Sweetland invented the first oil filter device for automobiles. It was named the “Purolator,” which was short for “pure oil later.” The spin-on filters common in today’s automotive industry were introduced in the 1950s and were virtually a standard by the early 1970s.Aside from the automotive industry, oil filtration is an integral part of equipment within a wide variety of industries, including aerospace, power generation, oil refining, manufacturing, mining, etc. Although most current oil filter designs come in canister or cartridge types, several variations in size, filter media, dirt-holding capacities and flow arrangements are available. For this reason, it is important that filters and filtration systems are selected to meet the needs of the application and with cost, performance, ease of use and environmental conditions in mind.

Oil Filter TypesOil filters can be characterized by the method in which the contaminants are filtered or the method in which the oil flows through the housing. One technique used to control contamination in filters is through surface-type media. This is the type of filter used in automobiles. In depth-type filters, the filter media are designed to hold much higher levels of contamination and provide a more circuitous path for lubricant contaminants to become trapped.

Other possible contamination control methods include magnetic and centrifugal filtration. Magnetic filtration utilizes rare-earth magnets or electromagnets to attract and collect ferrous particles as the oil passes through a magnetic flux region. Centrifugal filtration works by integrating a rapidly rotating cylinder to produce a centrifugal force for contamination separation from the oil.Oil filters can also be categorized by the oil flow design. As its name implies, a full-flow filter will draw all of the oil through the filter media. On the other hand, a bypass filter only requires a fraction of the oil flow for sufficient flow rates within the system. The application’s oil flow and contamination control requirements will determine which design is the best option. Another alternative is the duplex filter system, which contains two side-by-side filters in parallel to allow one of the filters to be replaced during uninterrupted operation.With typical canister-type filters, it is standard for oil to flow from the outside in. This means that the oil travels through the cylindrical filter media from the outward-facing surface into the inner core. However, in some cases the flow direction is reversed, with the oil coming into the filter through the core and pushed outward through a unique pleat design. This is intended to improve flow handling and distribution as well as reduce filter element size.

Filtration Mechanisms and Filter MediaA filter’s primary function is to remove and retain contaminants as oil flows through the porous component called the media. The media operate under several types of filtration mechanisms, including:

Direct Interception and Depth Entrapment – Particle blockage on the media due to the particles being larger than the taken passages within the media. Adsorption – The electrostatic or molecular attraction of particles between the particles and the media. Inertial Impaction – Particles are impacted onto the filter media by inertia and held there by adsorption as the oil flows around. Brownian Movement – This causes particles smaller than 1 micron to move irrespectively of the fluid flow and results in the particles being adsorbed by media in close proximity. It is much less prevalent, especially in viscous fluids. Gravitation Effects – These allow much larger particles to settle away from fluid flow regions when there is low flow.

In addition, filter media can be designed to capture particles through two distinct methods:

Surface Retention – Contaminants are held at the surface of the media. This provides an opportunity for the contaminant to become trapped as it comes in contact with the media surface. Depth Retention – Contaminants are held either at the surface of the media or within the labyrinth of passages within the “depth” of the filter media. This creates several opportunities for contaminants to become trapped.

The graph below shows how depth-type filtration is more efficient in capturing smaller particles when compared to surface-type filters. This can be attributed to the deeper

media providing more chances for the particles to be trapped along with the adsorptive and Brownian movement effects being more predominant in depth-type filters. While these characteristics are beneficial, depth-type filters tend to have higher differential pressure across the media as a result of the increased flow restriction from the deeper filter media.

Particle size retention characteristics ofdepth-type and surface-type filter media.

Filter Media Types and Dirt-Holding CapacityIn the September-October 2012 issue of Machinery Lubrication, Wes Cash explained how the porosity of the filter media plays a role in how well the filter can retain captured particles. This is known as the dirt-holding capacity. As pore size goes down, to maintain a low differential pressure across the media, the pore density must go up to account for the oil volume in contact with the surface. The filter depth and size also influence the dirt-holding capacity. Another factor is the filter media material. There are three primary types of filter media:

1 Cellulose - Comprised of wood pulp with large fibers and an inconsistent pore size.2 Fiberglass (Synthetic) - Comprised of smaller, man-made glass fibers with a more consistent pore size.3 Composite - Comprised of a combination of cellulose and fiberglass material.

Cellulose media are advantageous because they can absorb some water contamination. However, these types of media tend to fail more rapidly than synthetic media in acidic and harsh oil conditions. Nevertheless, the primary reason synthetic filter media are preferred is their more consistent porosity and smaller fiber size, which contributes to higher dirt-holding capacity and longevity of the filter.

This example of a depth-type filter has an element that requiresoil to pass through 114 millimeters of filter mediafor maximum particle filtration. (Courtesy Triple R)

Understanding the Beta RatingOil filters are rated by a technique called the beta rating. In his Machinery Lubrication article “Understanding Filter Efficiency and Beta Ratios,” Jeremy Wright explained the methodology behind the beta rating in more detail. In short, the beta ratio is calculated by dividing the number of particles larger than a certain size upstream of the filter by the number of particles of the same size downstream of the filter. Every filter will have multiple beta ratios for different particle size limits such as 2, 5 or 10 microns.

Best Practices for Oil Filter UsageStorage - Filters can fail long before they are to be used for their intended purpose. Therefore, proper filter storage and handling are essential. Ensure filters are kept clean, cool and dry, and always follow the first-in/first-out rule.Installation - Even if a filter installation seems simple and routine, refer to the manufacturer’s recommendations for proper procedures. A classic mistake is over-tightening. Most recommendations suggest that a three-quarter turn after seal contact is optimal. Over- or under-tightening can inhibit the seal’s longevity and effectiveness. Confirm that connections, seals and ducts are fitted appropriately and are free of contaminants.Avoiding Pre-fill - In most cases, you do not want to pre-fill your oil filters before installation. In diesel engines, it is recommended that a pre-lube system be installed instead in order to counteract changes from dry-start conditions.Choosing Correctly - Many filters and filter housings are designed to be interchangeable, so just because a particular filter fits doesn’t mean it is the correct filter.

Make sure each filter is replaced with the right filter. This may not necessarily be the one found on the machine, as an incorrect filter might have been used during the last filter change.Training - Proper training must be conducted for all personnel involved with changing filters. Remember, a task that seems straightforward to most people may not be for a new employee.

Filter Failure ModesChanneling - During high differential pressures, filter media passages can enlarge to a point where unfiltered oil can pass through without an efficient contaminant capture. In addition, any particles that were previously contained within the filter in line with the enlarged passage may now be set free.Fatigue Cracks - In cyclic flow conditions, cracks can form within the filter media, allowing a breach of oil to pass through unfiltered.Media Migration - Media fibers can deteriorate and produce new contaminants made up of filter material. This may be caused by improper placement of the filter housing or an inadequate fitting of the filter, which can generate damaging vibrations. Embrittlement from incompatible oils or extremely high differential pressures can also result in media disintegration.Plugging - During operation, filter media can become fully plugged by exceeding the dirt-holding capacity. Plugging can occur prematurely if excessive moisture, coolant or oxidative products like sludge are present.

61%

of lubrication professionals say filter plugging is the failure mode seen most frequently in oil filters at their plant based on a recent survey at machinerylubrication.com

Factors for Proper Oil Filter SelectionStructural Integrity - Arguably the most critical factor, structural integrity relates to a filter’s ability to prevent the passage of oil through an unfiltered flow path. The International Organization for Standardization (ISO) has established procedures for testing fabrication integrity, material compatibility, end load and flow fatigue. These tests can reveal defects such as improper sealing of seams and end caps or breaks in the media from high-flow conditions, as well as the effects of high temperatures on the filter element.Contamination (Dirt-Holding) Capacity - This refers to the amount of contaminants that can be loaded onto the filter before the filter’s efficiency is limited.Pressure Loss - This involves the overall differential pressure lost from the filter’s placement on the system. The pressure loss will be influenced by the filter media’s porosity and surface area.Particle Capture Efficiency - This is the overall effectiveness of the filtration

mechanisms within the filter media to extract and retain contaminants from the oil.System/Environment - The characteristics of the system and environment in which the filter will be installed must be considered, including the contamination expectations, flow rates, location, vibration, etc.

Maintaining Installed FiltersThe best way to prevent filters from reaching their dirt-holding capacity is to avoid contaminants in the system from the beginning. The fewer external contaminants that ingress, the fewer contaminants that are generated internally (particles produce particles). Use the following guidelines to maintain installed filters:

Ensure proper breathers are installed to prevent contaminants and moisture from entering the system. Keep seals and cylinders clean and dry by using appropriate wipers and boots. Select the appropriate oil grade and additive package to counter contaminant ingression and internal friction.

Analyzing the FilterA filter not only is a trap for the machine’s undesirables but also a concentration of clues as to what’s occurring within the machine. Particles within the oil may be so highly diluted that practical analysis can become a daunting challenge. However, the particles trapped in the filter may be so plentiful that they can be easily visible to the naked eye.Metal contaminants are a primary indication of an issue within the machine. Although some amount of metal contaminants can be expected, an unusual amount should be recognized by trending the filter’s visual appearance after each oil change. Cutting open the filter and suspending a strong magnet over it can aid in pulling out the metal contaminants to more easily distinguish them.If the machine is suspected to have an issue, the filter should not be discarded, as this would be similar to throwing away key pieces of evidence. Maintain the filter in the same condition as when it was removed and have it analyzed by the manufacturer or a laboratory.

Filter DisposalOil filters are not designed to be dumped into any wastebasket. Increasing regulations by the Environmental Protection Agency dictate proper filter disposal. While each type of oil filter may have its own requirements, common practices include oil draining, crushing or incinerating the filter. Many disposal services or filter distribution centers will accept used oil filters at little or no cost.

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The Advantages and Disadvantages of Biodegradable Lubricants

Josh Pickle, Noria Corporation

Tags: bio-based lubricants, viscosity, oil oxidation,synthetic lubricants

Vegetable oils can be used as lubricants in their natural forms. They have several advantages and disadvantages when considered for industrial and machinery lubrication. On the positive side, vegetable oils can have excellent lubricity, far superior to that of mineral oil. In fact, their lubricity is so potent that in some applications, such as tractor transmissions, friction materials must be added to reduce clutch slippage.Vegetable oils also have a very high viscosity index (VI). For example, a VI of 223 is common for vegetable oil, compared to 90 to 100 for most mineral oils, about 126 for polyalphaolefin (PAO) and 150 for polyglycol. Viscosity index can be defined as a frequently used measure of a fluid’s change of viscosity with temperature. The higher the viscosity index, the smaller the relative change in viscosity with temperature. In other words, oil with a high VI changes less with temperature than oil with a low VI.Another important property of vegetable oils is their high flash points. Typically, this might be 326 degrees C (610 degrees F) for a vegetable oil, compared to a flash point of 200

degrees C (392 degrees F) for most mineral oils, 221 degrees C for polyalphaolefin (PAO) and 177 degrees C for polyglycol. Flash point can be defined as the temperature to which a combustible liquid must be heated to give off sufficient vapor to momentarily form a flammable mixture with air when a small flame is applied under specified conditions, according to ASTM D92.More importantly, vegetable oils are biodegradable, generally less toxic, renewable and reduce dependency on imported petroleum oils.On the negative side, vegetable oils in their natural form lack sufficient oxidative stability for lubricant use. Low oxidative stability means the oil will oxidize rather quickly during use if untreated, becoming thick and polymerizing to a plastic-like consistency. Chemical modification of vegetable oils and/or the use of antioxidants can address this problem, but it will increase the cost. Chemical modification may involve partial hydrogenation of the vegetable oil and a shifting of its fatty acids.

The challenge with hydrogenation is determining at what point the process should cease. Depending on the required liquidity and pour point of the oil, optimum hydrogenation is established. Recent advances in biotechnology have led to the development of genetically enhanced oil seeds that are naturally stable and do not require chemical modification and/or use of antioxidants.Employing tests developed by the American Society for Testing and Materials (ASTM) and the Organization for Economic Cooperation and Development (OECD), oil is inoculated with bacteria and kept under controlled conditions for 28 days. The percentage of oxygen consumption or carbon-dioxide evolution is monitored to determine the degree of biodegradability. Most vegetable oils have shown to biodegrade more than 70 percent within that period, as compared to petroleum oils biodegrading at nearly 15 to 35 percent. For a test to be considered readily biodegradable, there must be more than 60-percent degradation in 28 days.Similarly, by using a variety of tests involving fish, daphnia and other organisms, the toxicity of vegetable oils can be measured. In this case, both mineral oil and vegetable oil in their pure forms show little toxicity, but when additives are included, the toxicity increases.

6 of lubrication professionals do not use any biodegradable lubricants at their plant, according to a recent survey at

2%machinerylubrication.com

Another disadvantage of using vegetable oils is their high pour point. Pour point is defined as the lowest temperature at which an oil or distillate fuel is observed to flow when cooled under conditions prescribed by test method ASTM D97. The pour point is 3 degrees C (5 degrees F) above the temperature at which the oil in a test vessel shows no movement when the container is held horizontally for 5 seconds. This problem also can be addressed by winterization, the addition of chemical additives (pour point suppressants) and/or blending with other fluids possessing lower pour points. Various synthetic oils can be used for this purpose.If a high degree of biodegradability is required, then biodegradable synthetic esters are added to improve cold-temperature properties. On the other hand, if the goal is to maintain the so-called biobased property, where at least 51 percent of the lubricant is made of natural biomaterials, then a portion of the blend could be light mineral oil with low pour points. The latter will show a higher degree of toxicity and a lower degree of biodegradability.

Why Use Biodegradable Lubricants?Approximately 2.5 billion gallons of lubricants are sold annually in North America. Studies show that much of this fluid (60 percent) is not accounted for and ends up in ground water, rivers, lakes and on the ground itself, causing untold harm to the environment, fish and wildlife. Marine, forestry and agriculture industries in particular, along with citizen groups and governments, are becoming more and more concerned about our responsibility to the protection of the environment. The use of biodegradable fluids can help to maintain the environment and relieve some of the demand on mineral oils in the future.Machinery Lubrication (2/2012)

What You Should Know About Environmentally Friendly Lubricants

Dr. Anoop Kumar, Royal Manufacturing Tags: bio-based lubricantsBuzzwords like biodegradable, bio-based, eco-friendly, renewable, non-toxic, green, etc., are often heard echoing throughout industry. Over time, these words have become powerful tools and selling points for lubricant manufacturers and marketers. However, they can also be misleading.Along with legislative compliance, one of the reasons for this recent green initiative is the

growing awareness and demand to use more environmentally safe products. The fact that petroleum-derived mineral stocks have finite resources has also created a pressing need to find alternative/renewable sources.While there is no universally accepted definition for environmental safety, factors like biodegradability, eco-toxicity, bio-accumulations and renewability must be taken into consideration when accounting for the safety of the environment. Lubricants, by virtue of being petroleum based, have been classified as being of environmental concern. In the past, large quantities of industrial lubricants have been irresponsibly disposed of into the environment as used oils and spills or accidentally, which is a matter of grave environmental concern requiring immediate attention.There are two basic approaches for dealing with environmental safety with regards to lubricants. The first is to find ways to eliminate the disposal of lubricants into the environment. The second is to use environmentally safe products in environment-sensitive applications such as agriculture, forestry, municipalities, mining, marine, etc.In addition, the different terms floating across industry to measure/evaluate environmentally safe products are not well-defined and need better understanding.

BiodegradableIn simple terms, biodegradable refers to the chemical degradation of a substance (lubricant) in the presence of micro-organisms/bacteria. Although there are different definitions of biodegradability across industry, perhaps one of the most reasonable is found in ASTM D6064, which describes biodegradability as “a function of degree of degradation, time and test methodology.”

There are two generally used measurements for biodegradability. The first is primary degradation, which is measured as the reduction of the carbon-hydrogen bond. This is determined with infrared spectroscopy (IR), which corresponds to the direct measure of the percentage of lubricant breakdown. The most widely used way to measure this degradation is by the Coordinating European Council (CEC) L-33-93 test method run for 21 days.The other type of biodegradability measurement is secondary degradation, which is better known as ultimate biodegradability. This measures the evolution of carbon dioxide through the degradation process over a period of 28 days. The most common method used to determine ultimate biodegradability is by the Organization for Economic Cooperation and Development (OECD) 301B/ASTM D5864.The benchmark for qualifying a lubricant as biodegradable is if its biodegradability is more than 80 percent by the CEC L-33-93 method or more than 60 percent by the OECD 301B

method.

Bio-BasedBio-based is a term that was mainly coined in the United States and based on the necessity to derive renewable products from vegetable/plant/animal-based materials. The industry or regulatory authority (USDA) did not intend for bio-based to imply a 100-percent vegetable oil-based formula, as other non-bio-based ingredients might be necessary to meet industry performance standards. The USDA and other regulatory/industry organizations have established that the use of 50 percent or more bio-based material in a formulation could allow a product to be considered bio-based. Thus, the more accepted definition of bio-based lubricants would be those products formulated with a majority of renewable and biodegradable base stocks.For example, fatty acids used in making grease thickener components qualify as bio-based even though they are not biodegradable. Therefore, bio-based products may not necessarily be 100-percent biodegradable, but they must be agro-based and renewable.

GreenA synonym for being environmentally friendly, green is probably one of the most attractive terms in industry, yet it often can be misleading. Some products that are not even based on vegetable oil may still be marketed as environmentally friendly lubricants. While these types of lubricants may be free of heavy metals and other potential toxic ingredients, they are not biodegradable. Consequently, it’s important to be careful when selecting such products and to be aware that green does not necessarily mean biodegradable. Just being a green color or free from heavy metals does not make a product environmentally friendly in the real sense. This requires being biodegradable or derived from renewable sources.

Theoretically, environmentally safe products are those that degrade quickly and naturally with non-toxic decomposed fractions and that are based on renewable sources. These lubricants must be formulated with renewable/vegetable oils in majority, readily biodegradable and free from heavy metals and other toxic ingredients/byproducts.

Performance ComparisonEnvironmentally safe products offer certain performance advantages. When formulated with vegetable oils, these lubricants exhibit better lubricity, which means reduced friction

and wear, a high viscosity index and high flash points for improved safety.The inherent drawbacks associated with these types of products include their limited high-temperature capabilities as a result of inferior oxidation and thermal stability, restricted low-temperature applicability due to higher pour points, and poor pumpability at sub-zero temperatures. As these lubricants are expected to degrade over the course of time in the presence of oxygen, their shelf life also is limited and does not compare with that of mineral/synthetic oils.Another aspect that should be considered when switching to vegetable oil-based greases is their compatibility with mineral oil or synthetic oil-based greases. Recent studies indicate that some vegetable oil-based greases have been found to be incompatible with mineral oil-based greases due to the chemistry differences between vegetable and petroleum oils.While our knowledge of environmental safety is still in its early stages, more concerted efforts are needed to clearly define the related terms. If choosing vegetable oil-based environmentally friendly lubricants, keep in mind that there are dual objectives to fulfill, with one being environmental safety and the other the quest for alternatives to petroleum base stocks. The future of these classes of lubricants will greatly depend on how these disadvantages are overcome while still being competitive in price..Machinery Lubrication (12/2012)

When to Choose a SyntheticWhen designing a lubrication program, I use a very simple set of rules to know when to choose a synthetic for an application. They are as follows:

when equipment-performance demands exceed the capabilities of mineral-based fluid, when synthetic properties can become problem-solvers, when life-cycle cost savings can be realized, or when safety and environmental issues can be enhanced.

Machinery Lubrication (11/2011)

Are Synthetic Lubricants Really That Good?

Noria Corporation Tags: synthetic lubricantsOne of the most common questions I'm asked when teaching lubrication courses is "are synthetics any good?" Oftentimes, the basis for this is question is a specific machine or group of machines, where a conversion from mineral to synthetic has either recently occurred, or is being planned. In doing so, the questioner is looking for validation of a decision that he or she has made, or advice on whether such a change is warranted for machines currently using a conventional mineral-based lubricant.No Magical Solution First, let's set the record straight. No lubrication problem due to poor system design, poor PM practices or lack of fundamental contamination can be solved by the use of synthetics. The notion that selecting a different lubricant can some how magically make up for under- or overgreasing, inattention to lubricant condition or an inadequate breather or filter is fundamentally flawed. But for those machines where these issues have largely been resolved, are synthetics truly better? The answer to the question is - "it depends".For those dissatisfied with this apparent cop-out, let's look at the facts. For machines to run at optimum performance, they require the lubricant to provide certain fundamental performance properties. In addition to separating moving surfaces to prevent wear, these include minimizing internal friction, preventing corrosion, resisting breakdown due to high

localized or bulk operating temperatures, removing or suspending contaminant such as soot or water, and in a hydraulic system, providing the force necessary for motive power.

Are Synthetics Always a Wise Choice?Choosing Between Synthetic Lubricants and Conventional OilsSynthetic Lubricants for Automotive ComponentsSelecting Synthetics for Off-Highway Crankcase ApplicationsSynthetic Gear Oil SelectionChanging Oil Preference - Synthetic vs. Mineral Oils

Ultimately, these fundamental performance properties can be related back to the chemical and physical properties of the oil: properties such as viscosity and viscosity index, wear prevention (for example, four-ball wear testing), oxidation resistance, foaming tendency and demulsibility. In selecting a lubricant properly, the diligent lubrication engineer carefully examines the design and operation of the machine (bearing type, speed, load, operating temperature, etc.) and decides the minimum performance requirements for a given machine under these "normal" machine operating conditions.So the question becomes not whether a synthetic is any better than the equivalent mineral oil, but rather, which lubricant provides the best overall combination of performance properties, based on the assessment criteria?There are numerous applications where synthetic lubricants can and should be used. But in each instance, it is because the available mineral oil-based lubricants from which the plant has to choose are not able to meet the prescribed physical, chemical or tribological requirements for the machine in question.Pros Needless to say, synthetic lubricants provide an array of improved performance in certain key areas. These include generally better oxidation resistance, which can translate into longer life; higher flash or fire points, important in high-temperature and fire-resistant applications; better cold-temperature fluidity, important where low-temperature start-ups are required; and in some cases, lower internal friction, which can result in lower energy consumption and better natural solvency, helping to prevent the formation of deposits.Cons But synthetics also have some drawbacks, the most obvious of these being costs. Depending on the type of base stock, the cost for a synthetic lubricant may be anywhere from three to several hundred times the cost for the equivalent grade and class of mineral oil. Because many synthetics are made from raw materials extracted from crude oil, their cost is no more or less immune from increases due to increasing crude oil prices.But cost isn't the only downside. Some synthetic lubricants such as certain types of phosphate esters are hazardous, requiring special care and attention when handling and disposing. Yet others have a limited ability to dissolve additives, making formulation and

additive suspension under less-than-ideal conditions difficult, while yet others are incompatible with petroleum-based products, requiring care and attention when storing, handling and dispensing. And increased solvency is not always a good thing - particularly when a mineral oil has been in use for some time and the removal of deposits can result in seal leaks.

Figure 1. Advantages and Disadvantages of Synthetic LubricantsSo you see, it really does depend. If you require one or more of the enhanced performance properties listed in Figure 1, and that property cannot be met by a conventional mineral oil - even a premium product - then you really have no choice but to use a synthetic. But if you can achieve the level of performance required with a mineral oil, chances are, cost or one of the other downsides with synthetic lubricants listed above makes a mineral oil a much wiser choice.As always, this is my opinion. I'm interested in hearing yours.Machinery Lubrication (5/2007)

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