Archive | Lubrication


3:23 pm
January 4, 2017
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Understand Motor and Gearbox Lubrication


Over-lubricated bearings will produce excess heat through internal fluid friction that can easily be detected with an infrared camera. Photo: Fluke Corp.

Among other factors, motor and gearbox lubrication programs require understanding and a controlled lubrication approach.

By Ken Bannister, MEch Eng (UK)CMRP, MLE, Contributing Editor

When a driven component is required to operate at a speed different than that of the attached motor (driver), a designer can choose from two basic power-takeoff speed-reduction/increaser methods. The first uses pulleys or sprockets of different diameters mounted to the motor and driven shaft, with power transmitted by a connective belt or chain. The second design connects the motor to the driven component through a gearbox, with the motor connected to the gearbox input shaft and the driven device connected to its output shaft.

When viewed in a maintenance-management-system database for lubrication purposes, belt/chain-drive motors and motor/gearbox units are rarely handled with separate PM work orders. Rather, the lubrication requirements are integrated as line items on a much broader machine PM work order. This is fine for sub-fractional and smaller horsepower motors. Larger, more expensive (and re-buildable), motors—usually 20 hp and more (there is no set rule to this)—require treatment as a separate entity from the parent machine, with their own asset numbers and PM/lubrication regimes, so as to compile work-history files. Furthermore, in the case of  motor/gearbox combinations there are two specific entities, one electro-mechanical (motor), the other purely mechanical (gearbox), that are best treated individually when assessing and managing lubrication needs.

Assuring motor and gearbox reliability is the result of good alignment practices and, more importantly, effective lubrication practices.

Bannister on Lubrication

Accompanying this article is the first of a new series of monthly lubrication podcasts with Ken Bannister. This month, he provides additional information about factors involved in lubricating motors and gearboxes.

Motor lubrication

Motors are electro-mechanical devices that turn electrical energy into mechanical energy. Motor magnets and windings are wound on and around a central shaft. This shaft is simply supported by two or more rolling-element bearings at each end of the motor frame and housing. These bearings are the only lubrication points on a motor, and are virtually always grease lubricated. With rare exception, fractional- and small-horsepower motors use sealed bearings and make no provision for external bearing lubrication. If the motor is balanced, aligned, and not overloaded, it should deliver a long life with no additional lubrication. This is not usually the case with larger motors, which are often subjected to heavier and often more variable loads, requiring larger bearings.

Depending on the motor design and manufacturer, external grease fittings usually are installed on motors rated at 5 hp and become much more prevalent on 20-hp units. When motors become more powerful and heavier, they place more load on the bearing points, therefore requiring grease replenishment on a more-frequent basis.

If a motor is to operate at peak efficiency, its bearing cavities (the available space between the balls, raceways, cage, and seals) need only be filled to 30% to 50% capacity, at any time. Because the bearings are hidden behind end plates, they are lubricated “blind” and are often subject to overfilling—especially with manual greasing. When this happens, the grease has nowhere to go except through the bearing cavity into the winding! Grease-filled windings lead to premature failure and a rapid decrease in motor energy efficiency, evident by the rise in motor’s amperage draw.

To alleviate this condition, larger motors are designed with a drain-plug or screw in the end cases that, once opened, will allow excess grease to flow through the bearing and out of the motor end case. If this is kept closed during the greasing process, excess grease will channel directly into the motor windings. If your motor has a grease fitting but no drain plug, use extreme caution not to over-lubricate, as the excess will make its way into the winding.

Over-lubricated bearings will produce excess heat through internal fluid friction that can easily be detected with an infrared camera. This can also be achieved by adding contaminated grease with a dirty grease nozzle or through cross contamination with a non-compatible grease.

Grease-gun inconsistency can be ironed out through use of a single-point auto lube (SPL) setup to deliver a small amount of lube on a continuous basis for as long as a year, depending on the size of bearing and lube reservoir.

SPL manufacturers have setup guidelines based on bearing size and altitude (atmospheric pressure is relational to constant-pressure grease flow) for initial setup, which can then be fine-tuned by monitoring amperage draw and/or bearing temperature. These signatures will be unique to each motor and will differ based on size and load.

Gearbox lubrication

Gearboxes are self-contained mechanical devices that allow power to be transmitted from an input shaft to an output shaft at different speeds through the meshing of different-sized gear sets held on each shaft. The gears and shafts are supported on bearings contained within a sealed “box” that also serves as a reservoir for the lubricating oil. Gearbox dimensions can range from palm-sized to room-sized. With few exceptions, all are oil lubricated.

Depending on the style and size, gearboxes employ a number of methods to move the lubricant over the gears and bearings, the most popular being:

• Splash lubrication. This is a common gearbox-lubrication method in which the reservoir is filled part way with lubricating oil to ensure partial coverage of all the lower mating gears. At speed, these gears use surface tension on their teeth to “pick up” lubricant and transfer to other gears and bearings through meshing and by “flinging and splashing” the lubricant in all directions within the sealed reservoir.

• Pressure lubrication. This method is frequently found on mid- to large-sized gearbox assemblies that use a gear-driven pump, typically located inside the gearbox, to work in conjunction with the “splash” method. Pressure-lubrication systems draw lubricant from the reservoir through a pickup-filter screen and pump oil at pressure through an internal piping system to bearings and gears that would be difficult to service with splash lubrication.

• Mist, or atomized, lubrication. This approach, reserved for the largest of gearboxes, uses a vane-style pump that picks up lubricant from the reservoir and “slings” it at a plate, causing it to atomize into a micro-drop mist. The mist saturates all of the mechanical components within the sealed gearbox.

In all three lubrication methods, choosing the correct oil viscosity and additive package is most important. Typical to all gearboxes is the need to ensure:

No cross-contamination of lubricants occurs during oil top-ups or change-outs. Label your gearbox with the correct oil specification.

No dirt or water contamination is allowed into the gearbox.

The drain, fill, and breather caps are always tightly in place.

The gearbox is regularly wiped clean of dirt and debris that will act as a thermal blanket and unnecessarily heat up the oil.

The gearbox is not over-filled creating churning (foaming) of the oil that can rapidly deplete the anti-foam additive, causing the oil to oxidize. This requires attaching low- and high-level markers to the gearbox sight gage.

If you have all of the above practices in check, make enquiries regarding the use of synthetic gear oils. These not only last longer but can cut your energy consumption as much as 4%. MT

Ken Bannister is co-author, with Heinz Bloch, of the recently released book Practical Lubrication for Industrial Facilities, 3rd Edition (The Fairmont Press, Lilburn, GA). As managing partner and principal consultant for EngTech Industries Inc. (Innerkip, Ontario), he specializes in the implementation of lubrication-effectiveness reviews to ISO 55001 standards, asset-management systems, and training. Contact him directly at, or telephone 519-469-9173.

learnmore2“A Real-World Approach to Electric Motor Lubrication”

“The Inner Life of Bearings, Parts 1 and 2”


3:30 pm
November 15, 2016
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Control and Avoid Lubricant Contamination

Conveyor belt detail on mining site

Clean lubricants increase the life and performance of bearings and ensure the success of your operations.

By Ken Bannister, MEch Eng (UK), CMRP, MLE, Contributing Editor

I am astounded by the number of companies that continue to believe bearing failure and its associated replacement and downtime costs are an acceptable part of doing business. In my experience, this point of view is most apparent at sites with severe and semi-severe operating conditions, wherein water, heat, and fine particulate matter (dust, dirt, and manufacturing debris) are present.

If a machine has any form of replaceable/washable filter, screen, or breather as part of its fluid-management systems—lubrication, hydraulic, and pneumatic-air systems—we can assume the OEM (original-equipment manufacturer) machine designer/engineer expected the equipment and its operators/maintainers to contend with and manage fluid- and air-borne contaminants. These built-in sacrificial filtration elements are specifically designed to provide an inexpensive method of managing and controlling potential contamination issues—externally and internally—to protect delicate, close-tolerance, machine-bearing surfaces at work under a range of operating conditions.

In the majority of operating conditions, effective levels of contamination control and avoidance are achievable with minimum effort when the requirements and basic relationships of and between a machine, its operator(s), and maintainer(s) are understood.

The fact that a piece of equipment begins to run a process or make a product indicates the OEM has done its part: supplied a machine that’s adaptable enough to work in an array of different operating environments or, if the end user is fortunate, one designed and built specifically for a unique operating environment. This means the machinery is fitted with a number of built-in contamination-control/filtration devices that are ultimately designed to fail in their own right. (They also require monitoring for condition and cleaning and/or replacement when their filter media is close to being exhausted.) These devices offer secondary protection through their ability to trap and control the ingress of contaminants into lubricating oil(s), grease(s), and air-flow systems.

Contamination control

When two precision-bearing surfaces interact, they rely implicitly on a lubrication film devoid of particle or water presence to separate—and protect—themselves from each other. The filter is designed to trap and extract any particles or moisture before these contaminants can enter the lubricated zone(s) and cause surface damage.

Almost exclusively in contamination control, filters incorporate a passive surface-attractant medium, designed to work in the direct-flow path of the lubricant and capture any dirt particles (contaminants) held in colloidal suspension as the lubricant, or lubricated air, flows through or across it. Depending on the working conditions, particle size, and fluid-flow rate, the porous filter media can be constructed of a variety of materials, including simple wire-mesh gauze, wire wool, pleated paper, cellulose, porous metal, fiberglass, diatomaceous earth, or felt. Due to higher fluid viscosity and line-delivery pressures, grease systems use heavy-gauge coiled wedge-wire or wire-mesh filters to attract large solid contaminants that may be introduced from a dirty grease-gun nozzle.

Enclosed, sealed gearboxes and reservoirs require breather devices to equalize pressure and control solid and moisture contamination. Old-style breathers constructed of wire wool can only prevent large solid contamination (40+ microns in size), and are now regularly replaced with newer-style breathers that employ desiccant-like silica gel hydrophilic media.

This media type allows the reservoir to breathe and prevent airborne particulates (3+ microns) from entering the reservoir. It also wicks and captures moisture from inside the reservoir, while preventing outside moisture from entering the reservoir or gearbox chamber.

Heavy water contamination usually enters a system as a result of maintenance or production personnel using oil that has been incorrectly stored in the outside elements, or through production-process-water spillage or high-pressure machine-cleaning (prevalent in food-manufacturing machinery).

Contamination avoidance

Ironically, while contamination avoidance is the primary strategy for reducing and eliminating premature bearing failure, it is absent/avoided in many lubrication programs. A good contamination-avoidance program requires little-to-no capital outlay, fits perfectly into any preventive-/predictive-maintenance (PM/PdM) program, involves cooperation of operators and maintenance personnel, and will drastically reduce the reliance and maintenance requirement of what essentially become secondary contamination-control systems.

In simple terms, contamination-avoidance means taking actions to ensure that contaminants don’t come into contact with a machine and its bearing-protection systems. Success relies, largely, on a good relationship between operations and maintenance personnel and a healthy respect for the machine and components in question. The following points outline the foundational requirements of any contamination-avoidance program:

Good housekeeping. Ensuring that dirt does not accumulate on equipment surfaces is preventive maintenance 101 and the responsibility of operator and maintainer. Implementing a simple 5S program will facilitate this element. This applies to the machinery and the lubricant-storage area and transfer equipment.

Lubrication training. Understanding the effect and consequence of failing to arrest contamination is mandatory. Use processes and procedures that ensure consistent effort.

Lubricant storage and transfer engineering. Using dedicated, color-coded, and closeable storage and transfer equipment protects lubricants from the elements and cross-contamination exposure. Make sure all grease guns and nipples are cleaned with lint-free rags before and after use.

Condition-based oil changes. Performing oil/filter changes too frequently risks exposure to contaminants. Performing them too infrequently risks exhausting filtration media and, in turn, lubricating-fluids degradation. Condition-checking allows operators and maintainers to become more familiar (or in tune) with a machine.

Lubricant cleanliness. Testing new lubricants and bulk fluids to verify their cleanliness and additive-package formulations before they’re put into use is a must. This is the only way to ensure that they’ve been delivered in a clean state and meet referenced specifications. In addition to the above behavioral changes, the following equipment and workspace changes can be put in place if the production process and workplace environment warrants:

Room-ventilation system. Positive or negative room pressurization or exhaust-air ventilation can be used to reduce or eliminate airborne contaminants.

Machine design. If the production process involves water or sand, mechanical deflector shields can be used to protect, divert, and channel contaminants away from bearing and lubricant-reservoir areas. Fill-cap and drain-port plugs can be replaced with positive-lock fill/drain connections that hook to closed-system transfer carts. Conventional breathers can be replaced with a closed-loop expansion tank on larger reservoir systems.

Taking small contamination-avoidance steps will significantly reduce your site’s lubricant-contamination-control requirements. The savings from these efforts can then help fund your world-class lubrication-management program. MT

Ken Bannister is co-author, with Heinz Bloch, of the soon-to-be-released Practical Lubrication for Industrial Facilities, 3rd Edition (The Fairmont Press, Lilburn, GA). As managing partner and principal consultant for EngTech Industries (Innerkip, Ontario), he specializes in the implementation of lubrication-effectiveness reviews to ISO 55001 standards, asset-management systems, and training. Contact him directly at, or telephone 519-469-9173.

learnmore2“Store and Handle Lubricants Properly”

“How Clean is the New Oil in Your Equipment?,”

“The Inner Life of Bearings, Part I: How Lubrication Really Works”


2:56 pm
September 13, 2016
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Win the War with ‘Lubrication by Design’

Use aviation-style checklists to eliminate ambiguity and errors in your lubrication-maintenance procedures.

By Ken Bannister, MEch Eng (UK) CMRP, MLE, Contributing Editor

The Sample Gearbox-Lubrication Checklist in the table below points to Hi-Lo fill indicators that help personnel make simple, yet correct, Go/No-Go decisions when checking lubricant reservoirs. Image courtesy of EngTech Industries.

The Sample Gearbox-Lubrication Checklist in the table below points to Hi-Lo fill indicators that help personnel make simple, yet correct, Go/No-Go decisions when checking lubricant reservoirs. Image courtesy of EngTech Industries.

Arguably, the most used and abused instruction in the field of practical lubrication is “lubricate as necessary.” The origin of that advice is often attributed to the OEM’s (original equipment manufacturer’s) machine operation and maintenance manual.

OEMs typically prefer to use subjective language when outlining a maintenance approach in their manuals. As a consequence, they rarely provide accurate lubrication instructions based on the ambient condition factors found in the end-user’s working environment. This is especially true when the OEM sells its equipment globally through third-party agencies and retains little control—or understanding—of how and where that equipment is used. The level of subjectivity is further amplified when an unsuspecting and/or unenlightened maintenance-department person follows, without question, the unaltered written instructions.

A key component in reliability and performance improvement—with regard to maintenance personnel and machines—is consistency of effort. This type of consistency is afforded through an understanding in two major areas:

  • the impact that a current operating environment has on machinery requirements
  • who, exactly, performs lubrication tasks.

The highest level of reliability possible with any machine is primarily achieved as a result of the simplest of maintenance observations and tasks, based on the equipment’s weakest links. A machine’s weak links typically present themselves in two formats: consumables and adjustables. Often thought of as “nuisance” or “pain” points, weak links are instantly identifiable systems or components of an equipment system that require regular or constant replacement or modification. Lubrication falls into both of these categories.

Recognizing your work environment

The checklist below points to number- and color-identification of grease nipples and grease guns as a way to quickly and accurately determine the correct lubricant amount and type for each bearing in the referenced gearbox. The solution shown here is from OilSafe (, Rockwall, TX.

The checklist below points to number- and color-identification of grease nipples and grease guns as a way to quickly and accurately determine the correct lubricant amount and type for each bearing in the referenced gearbox. The solution shown here is from OilSafe, Rockwall, TX.

Lubricants are considered consumables because of their propensity to leak out of a closed environment or deteriorate in service, thus requiring replenishment or full replacement. A machine’s working environment can dictate how quickly the lubricant will deteriorate. For example, a bearing operating in an extreme wet, damp, hot, or dirty environment, similar to that in a foundry, mining operation, or steelmaking operation, will call for a more intensified approach to lubrication management than bearings that are operating in “white-room” HEPA-filtered environments such as those found in pharmaceutical-manufacturing operations.

Lubrication-delivery systems also require monitoring to determine application requirements and schedule adjustments based on changing needs. For example, using a manual greasing approach in bearing lubrication will require a change in PM (preventive maintenance) frequency when moving from a single-shift to double-shift operation. Similarly, in changing to an automated lubricant-delivery system, note that the lubricant reservoir will likely require replenishment at twice the previous (manual) rate and necessitate an adjustment of the lubricant-fill cycle.

Recognition of your working environment, and tailoring your lubrication approach accordingly, is the first step to implementing a “lubrication by design” method and, ultimately, achieving true lubrication effectiveness.   

Objective instruction and interaction

Instructing an operator to “lubricate as necessary” will only guarantee a subjective decision about which lubricant is to be used, as well as how much and how often. Subjectivity, in turn, invokes inconsistent behavior leading to lubricant cross contamination, over or under filling reservoirs, bearing-seal breaching, or starving bearings. These situations all reflect high-risk behavior that can easily result in premature, yet preventable, machine failure and downtime. They don’t have to be a problem in your plant.

In Dr. Atul Gawande’s 2009 best-selling book, The Checklist Manifesto: How to Get Things Right (Metropolitan Books, New York), he described the first military test flight, more than 75 years earlier, of the Boeing B17 bomber that had been introduced in the late 1930s. Ending in a crash due to a simple oversight by the most experienced pilot in the U.S. Army at the time, this flight led to the aviation industry pioneering operational and maintenance checklists.

Designed to overcome human ineptitude, attitude, and ignorance, the aviation checklist, written in simple and exact language familiar to the profession, was instituted to ensure that each and every pilot, from that point on, followed a consistent, set procedure prior to takeoff and landing. As head of the World Health Organization’s “Safe Surgery Saves Lives” program, Dr. Gawande successfully adapted that checklist into a simple, innovative tool for the medical field—and subsequently credited its use for a dramatic reduction in hospital and surgical deaths, regardless of hospital conditions. There’s a significant takeaway from this story for those of us who have an interest in the health and well being of industrial equipment and processes.

Lubrication checklists that don’t challenge or insult maintainers or operators (but are designed correctly and written in a concise manner similar to those used in the aviation and medical fields) can overcome ignorance and ineptitude and promote low risk through a high degree of consistency.


Take, for example, the sample checklist in the table above. Written in objective language, it points to minor, required steps for making modifications to the lubrication-system components of a gearbox. It specifically references Hi-Lo-fill indicators on the lubricant-reservoir sight gauge that help personnel make simple, yet accurate, Go/No-Go decisions when checking the reservoir, and a number and color identification of the grease nipple and grease gun that’s used to visually identify the correct lubricant amount and type for each bearing.

Color, though, is just one aspect of identification called out on the checklist. It also references the exact grease point and reservoir number, the specific grease that is to be used, and the amount of the grease to be deployed in displacement and grease-gun shot action. To correctly perform the procedures in this sample checklist, a grease-gun consolidation program—wherein all current grease guns are surrendered and replaced with one grease-gun style—must be implemented. This allows the maintenance group to determine the exact displacement by volume and gun “shot” action for all grease deployed in the plant. Different greases are assigned specific grease-gun and grease-point colors.

Bottom line

This “lubrication by design” approach requires almost no capital outlay. With some minor organizational effort up front, it can be rolled out systematically, machine by machine. In these times of diminishing technical skills and experience across industry, the alternative really isn’t much of an option. MT

Ken Bannister is managing partner and principal consultant for EngTech Industries Inc., (Innerkip, Ontario), an asset management-consulting firm specializing in the implementation of certifiable ISO 55001 lubrication-management programs and asset management systems. For further details, phone 519-469-9173, or email

Quick Tips for Successful Checklists

As I wrote in a March 2013 “Don’t Procrastinate, Innovate” column for Maintenance Technology, Dr. Atul Gawande’s 2009 book The Checklist Manifesto–How to Get Things Right, was, and still is, an intriguing read. It offers some invaluable insight for those in the reliability and maintenance field.

In his book, Gawande details how he pioneered the “Safe Surgical Checklist,” based on a model that the aviation industry adopted following the infamous World War II Boeing 299 crash. That checklist has certainly stood the test of time.

According to Daniel Boorman of Boeing (Seattle)—the person charged with developing aviation checklist manuals for all of the company’s planes for 20+ years—the secret of a good one is how it’s written, starting with using simple and precise language familiar to users in the profession. Among Boorman’s other tips:

— A checklist doesn’t have to be too comprehensive to be effective (usually between five and nine items).

— Well-designed checklists fit the flow of the specific work, encourage users to read each point out loud, and help them detect potential failures before they occur.

— A successful checklist ideally fits on one page, is free of unnecessary color and clutter, and uses upper and lower case in a sans-serif font such as Helvetica.

learnmore2“Power from Making Lists and Checking Them Twice”

“Safe Surgical Checklist” on the World Health Organization website


8:17 pm
August 9, 2016
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Practical Oil Analysis: Why and What For?

Simply hoping your lubricants are operating  within their protective-specification limits doesn’t make it so.

By Ken Bannister, MEch Eng (UK) CMRP, MLE, Contributing Editor

Lubricants are designed and chosen to perform as finite and perishable, integral components of host machines. Rarely, if ever, will a lubricant be employed in identical application and environmental conditions. Enter oil-analysis testing.

Why we test

The uniqueness of lubricants reflects how and when they must be tested, maintained (filtered and temperature controlled), and changed out. Stresses and influences such as load-induced shear stress, thermal degradation, various types of contamination, and wear-metal-catalyzing alter and prematurely degrade lubricant properties.

Oil is made up of a base oil and an additive package that’s designed to combat ambient and working environmental stresses/influences and deliver reasonable lubricant life. Outside stresses produce an array of detrimental effects, including oxidation, polymerization, cracking hydrolysis, and evaporation that manifest as thickening or dilution of viscosity, acid buildup, and sludge. Additionally, when oil loses some of its protective ability, its host bearings can come into contact with one another and release metal-wear particles into the lubricant, which then act as a bearing-attacking abrasive material (three-body abrasion).

These effects and conditions are why we analyze oil. This testing is how we ensure lubricants are serviceable and bearing surfaces are protected.

Screen Shot 2016-08-09 at 3.15.01 PMWhat we test for

Oil analysis is analogous to a blood test wherein a single, properly extracted fluid sample is used for a variety of diagnostics that indicate machine and lubricant conditions. To ensure an accurate interpretation of results every time—reliable ones suitable for trending and historical analysis—samples must be collected in a consistent manner and sent to the same laboratory for testing on the same equipment.

The lab will also require a virgin sample of any lubricant to be tested. This sample is used to document baseline measurements of base-oil type, additive-package levels (metals and chemicals), cleanliness level (dirt-contamination level), and viscosity and acidity. A set of initial samples detailing how and where each was taken will also be required for each machine.

Good laboratories also document an operational profile for each machine tested. Based on it, they can recommend additional beneficial testing, e.g., a Karl Fischer water-contamination test for a food plant with daily machine wash downs; tests for soot and glycol in mobile equipment and generator engines; or ferrographic analysis of metal particulates to determine specifically how a bearing is failing.

Basic oil analysis concentrates primarily on fluid property and fluid contamination.

Fluid-property testing

In analyzing fluid properties, laboratories typically look at viscosity, acidity, and additive elements—the “big three” characteristics that make oils unique—and which, through their changes in service, can tell us how to better maintain our lubricants.

Viscosity. The viscosity rating of new oil is typically measured in centistokes (cSt), i.e., oil’s kinematic viscosity depicting measured resistance to flow and shear by the force of gravity. As oil thickens or dilutes over time, however, its specific gravity changes, leading to errors in gravity-based tests. A more consistent measurement is achieved by checking for the absolute viscosity rating depicting oil’s resistance to flow and shear through measurement of its internal friction. Because absolute viscosity is measured by multiplying kinematic viscosity by the actual specific gravity, it’s an accurate, error-free trending method of choice for most laboratories. To understand which tests your lab used, note the measurement scales: kinematic viscosity (good test) is measured in centistokes (cSt), absolute viscosity (best test) in centipoise (cPs).

Given oil’s many variables, it’s best to work with a laboratory that’s experienced in setting up caution and critical limits for your industry type. Most labs typically start with a clearly defined set of viscosity limits of –10% CL (critical lower), –5% CaL (caution lower), +5% CaU (caution upper), and +10% CU (critical upper) for industrial oils. In more severe environments, the CaU and CU limits can be reduced to +4% and +8%, respectively. For oils with viscosity improvers, the lower limits are usually doubled.

Thickened, more viscous oil points to oxidation (depleted additives), air entrainment, and/or contamination. Thinner, less viscous oil points to a wrong substitution or fuel dilution. 

Acidity. The acid number, or AN, is a measurement of the acid concentration in the oil, not the acid strength, and is greatly affected by the presence of water within the oil. Most oils start with an AN of less than 2.

Setting limits for acidity isn’t as easy as setting those for viscosity. The caution and critical limits are dependent on the type of additive package used in the oil. Most standard mineral oils are considered corrosive over AN 4, whereas AW (anti-wear) or R&O (rust-and-oxidation-inhibited) oils are considered critical well below AN 3. Working with your oil supplier’s engineering department and/or a reputable oil lab with experience in your industry is the best way to set up meaningful acceptable limits for your environment.

A change in oil’s acidity (TAN) points to base oil deterioration, oxidization, and contamination.

Additive Elements. The table on p. 38 lists the typical standard elements for which oil analysis tests. Since some perform in multiple functions, they must be checked against a virgin sample and operational profile to determine if they are beneficial or detrimental when their values are compared with known values.

Fluid-contamination testing

Dirt, water, and chemical contaminants are highly destructive to lubricants. For the most part, however, they’re easily avoidable.

Solids contamination. Testing for solid contaminants involves particle counting based on ISO Cleanliness Code ISO 4406:1999. One method requires a technician to use a light microscope and manually count the number of particulates in a 100-ml oil sample that are >4 microns, >6 microns, and >14 microns in size. The total is then compared with the ISO 4406 cleanliness chart to derive a three-number ISO cleanliness rating. An alternative, automated approach leverages sensors and light-absorption principles to detect and count particles. With this method, ISO 4406 calls for three sample size counts at >4 microns, >6 microns, and >14 microns.

Water contamination. Water in oil promotes rust and corrosion—and, in a dissolved state, will accelerate oxidation. Water can be introduced as contamination through wash downs of equipment or leakage. Prevention measures include coalescing filters/breathers and physical waterproof protection around areas susceptible to moisture ingression.

Testing for water contamination typically involves the Karl Fischer moisture titration method: A vaporized oil sample is carried by oxygen-free nitrogen into a reaction-vessel containing methanol. Trapped moisture is titrated to an end point with a reagent to establish the presence of water in parts per million.

Beyond why and what

The procedures discussed here represent the major components in standard, inexpensive oil-analysis testing. In most cases, they’ll indicate when to change oil, based on condition. Unusual or inconclusive findings should generate more-specific testing that can lead to positive outcomes for both lubricant and machine. MT

Ken Bannister is managing partner and principal consultant for EngTech Industries Inc., Innerkip, Ontario, an asset management-consulting firm now specializing in the implementation of certifiable ISO 55001 lubrication-management programs and asset-management systems. For further details, telephone 519-469-9173, or email