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.
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).
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 firstname.lastname@example.org, or telephone 519-469-9173.
With a 20-yr. history in the industrial sector, and $2.2 billion in capital raised since inception, IGP has extensive experience building global manufacturing businesses. According to the company, it concentrates on leading niche manufacturers of engineered products used in critical applications, and partners with their management teams to pursue strategic initiatives focused on achieving long-term shareholder value.
Founded in 1983 when it brought the first desiccant breather to market, Des-Case now provides an array of fluid-cleanliness products, services, and training that improve equipment reliability and extend lubricant life in industrial plants around the globe. It, in fact, has enjoyed the growth-opportunity benefits of private-equity investments since 2013, when it was acquired by Pfingsten Partners L.L.C.
In 2014, Des-Case announced its own acquisition of the visual-oil-analysis line of ESCO Products Inc., the well-known, family-owned, Houston-based manufacturer of various fluid-monitoring technologies and distributor of Copaltite and Dow Corning products. The acquired portfolio included ESCO’s 3-D BullsEye Viewport, oil sight glasses, indicators and level monitors.
“I am honored and excited to be a part of writing the next chapter in the Des-Case growth story alongside our valued customers, partners and investors,” noted company president and CEO Brian Gleason. “IGP has over two decades of experience investing in the industrial sector with a proven track record of building world-class global businesses. We are looking forward to the partnership.”
Other than the report that Des-Case’s management team has retained a substantial ownership stake in the company, terms of the July 6, 2016 transaction haven’t been disclosed.
For more information on Des-Case, CLICK HERE.
To learn more about Industrial Growth Partners, CLICK HERE.
Despite years of concerted efforts by industry experts and suppliers, some dangerous lubrication myths continue to swirl around many maintenance operations. Motion Industries lubrication specialist Chris Kniestedt takes a down-and-dirty approach to debunk six of them.
Myth 1: All lubricating oils are the same.
From hydraulic fluids to gear lubricants to motor oils, each lubricant, be it synthetic or mineral-based, is uniquely formulated for its application with a specific viscosity; additive package; physical, chemical, and performance properties; and regulatory requirements. Various products may or may not be compatible with each other (see Myth 6).
Myth 2: If a little is good, more is better.
Take grease, for example. Over-greased bearings are a major cause of equipment failure. Blown seals and overheating are just two negative results of using too much grease. A general rule of thumb for normal- or high-speed machinery is that it’s better to err on the side of caution and to always check the OEM’s recommendations.
Overfilling gearboxes will also lead to problems, including failed shaft seals or increased operating temperatures. A gearbox that has too much oil will have to work harder to move through the lubricant, subsequently generating more heat or churning the oil into foam.
Myth 3: Blue, red, or black grease is better than white or clear grease.
Color is not a key factor in selecting grease for an application. There’s no standard for doing so. Instead, pay attention to base-oil viscosity (based on speed, load, and expected operating temperature), thickener type to mitigate incompatibility issues and consistency, and/or how well a product will pump at operating temperatures.
Myth 4: Tacky and stringy greases and oils offer better protection than non-tacky products.
It’s important to understand that lubricants are only 10- to 20-microns thick at the point of contact. Moreover, film thickness is a function of base-oil viscosity at operating temperature and speed (to a lesser degree, load). Thus, always use caution when applying tacky lubricants or greases with higher percentages of thickener at high operating speeds.
Myth 5: Food Grade (NSF H-1) products are never as good as Non-Food Grade (NSF H-2) products.
Advances in base-oil technology and additive chemistry have made Food Grade H1 products stronger than ever, particularly with synthetics. There are many applications where a correct, strong Food Grade H1 product will work as well as a non-Food Grade H2 mineral-oil-based equivalent.
Myth 6: All products are compatible.
Consider greases. In addition to their base oils and additive packages, greases are formulated with various thickeners (lithium, lithium complex, aluminum complex, calcium, polyurea, bentone, and silica gel), which aren’t necessarily compatible with each other. Always exercise caution when changing greases. Laboratory compatibility testing will clear up any doubts. If incompatibility exists between old and new products, purge bearings before changing to the new one. Oils aren’t always compatible either, especially with the new generation of synthetics. Finally, mixing Food Grade H1 lubricants with Non-Food Grade H2 will create contamination issues, which will cause you to lose H1 designation. MT
Chris Kniestedt is lubrication specialist for the San Francisco Division of Birmingham, AL-based Motion Industries. For more information visit www.motionindustries.com.
Add visual management to your lube-program toolbox through an array of color-coded solutions.
By Ken Bannister, MEch Eng (UK), CMRP, MLE, Contributing Editor
When you hear the word lubrication, what color comes to mind? If you answer brown, or allude to some shade of it, you’re in good company. More than 80% of maintainers to whom I’ve posed this question over the past 30 years have responded the same way.
The reality is that oil and grease products come in a rainbow of colors and shades, including white, gray, black, silver, blue, green, red, purple, and every variation of brown, from golden honey to dark, earth tones. Manufacturers typically color these products for their own purposes. Unfortunately, there’s no formal industry standard or convention regarding their choices, with the exception that most food-grade greases tend to be white.
Most lubricant colors are naturally influenced by the color of the crude base-oil stock and its additive package. For example, when molybdenum disulphide (MoS2) is added in any quantity, it can significantly darken the lubricant to near black in color. Manufacturers, though, add colorants to their respective lubricants to help identify different brands and/or make products more appealing and marketable to the end user.
Despite incongruent colorization, maintenance departments can take advantage of differences in lubricant colors in their plants. For example, if two or more grease brands or different colors are employed in a facility, personnel can be made aware of which color belongs to what bearing by a photo of that grease color posted on the machine or close to the grease nipple. If a trace amount of the previously used grease is evident at the bearing or grease nipple, maintainers would (should be made to) understand that they are not to pump a grease of a different color or shade on top of the original grease.
Oil colors are a different matter. Oil ages in service and its additive package will deplete through contamination, heat, and oxidation. This causes a natural darkening in color. That visual cue has been used for many years in industry and the automotive world to manage oil changes. Sadly, this somewhat risky strategy can fall flat when an oil is changed out with one of a different color and additive composition—especially in the case of darker oils.
Introducing color coding
In 1950, the prestigious UK Scientific Lubrication Journal published an article by M.J. Harrison titled “Color Codes.” In it, Harrison, who at the time was an engineer in the technical department of the UK’s C.C. Wakefield & Co. (now known as Castrol), detailed a symbol/color-control system methodology for identifying the lubricants used in an industrial plant. As he pointed out, employing symbols to denote frequency of application and colors to signify lubricant type would ensure that unskilled workers were able to perform “factory lubrication” in a consistent manner, with scientific precision.
Harrison went on to recommend the use of different 1-in.-high geometric symbols painted on lubricant reservoirs or at lube points to represent lubrication-interval schedules. He proposed a circle to represent the need for daily lubrication, a triangle for weekly lubrication, and a square to represent monthly intervals between lubrication activities. For activities conducted on a quarterly basis (or over longer periods), the square was to again be used, but this time with a number painted inside the square to highlight the number of interval months.
To determine the correct lubricant to apply, each symbol was to be painted one of three primary colors: yellow, red, or blue to correspond with an already-determined lubricant legend. If more than three lubricants were to be used, the same colors were used again, but with the addition of a bold black diagonal stripe across the symbol.
But Harrison didn’t stop with the design and color of symbols and shapes to help identify different lubricant and application intervals in a facility. He also advocated color-coding reservoirs and dedicated transfer equipment to eliminate cross-contamination problems.
Which colors to use
Color identification is an ideal means of ensuring that the right lubricant ends up in the right place, at the right time. The actual colors themselves are not as important as their consistent use, i.e., assigning a specific color to a single lubricant and all dedicated equipment employed in its use, storage, and transfer within the plant environment, as depicted in Fig. 1.
Harrison initially promoted the three primary colors of red, blue, and yellow for his system. In modern plant environments, however, we’re comfortable using primary and secondary color palettes, including green, orange, and purple. This is clearly evidenced by the breadth of today’s commercially available, color-coded lubrication-handling systems, including the example transfer products shown in Figs. 2 and 3.
Lubricant storage and transfer systems, though, reflect just one area where colorization pays off for a site. Another important use of color identification involves a condition-based approach to filling oil reservoirs.
Figure 4 is a good example of this Hi-Lo technique. It involves using red, amber (yellow), and green lines taped on the side of an automated-lubrication-system reservoir. This arrangement is known as a RAG (red/amber/green), or the traffic-light indicator system:
- The green line indicates the upper fill level.
- The amber (yellow) line indicates a level at which the operator is to contact the maintenance department with a first request to fill the reservoir.
- The red line alerts the operator to call in a priority request to fill the reservoir.
Coloring your efforts
Today, you’ll find an array of color-coded tags and transfer equipment in the marketplace. These types of innovative solutions are relatively inexpensive to purchase and implement—and highly effective when used consistently. The question is, “Just how colorful are your lubrication efforts?” MT
Ken Bannister is managing partner and principal consultant for EngTech Industries Inc., (Innerkip, Ontario, Canada), 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 email@example.com.
The actions of personnel can either lead to great success in lubrication programs or, as this case study shows, to costly calamity.
By Ken Bannister, MEch Eng (UK), CMRP, MLE, Contributing Editor
Winston Churchill wrote, “Responsibility is the price of greatness.” These words have special meaning for those of us in the lubrication field.
In organizations that seek to become great, all personnel must understand the negative upstream and/or downstream impact that their individual actions could have should they neglect to effectively and efficiently fulfill their roles. This is especially true of lubrication team members, who, through daily interaction with machinery and moving parts, are directly responsible for the successful lubrication of equipment in their charge—as well as for any consequences resulting from their activities. Their failures will manifest directly in the loss of equipment availability, reliability, and life-cycle longevity, and indirectly through production yield and quality losses.
A case in point
My look into the oil and grease purchasing patterns of a major North American automotive-assembly manufacturer during a lubrication-operations effectiveness review (LOER) was a real eye opener. I was astounded by the many tens of thousands of dollars per month the corporation was spending on just one type of chain-lubricant oil.
This automatic-chain-lubricator oil was a name brand, premium-quality, molybdenum disulphide, high-temperature formulation. Designed specifically to lubricate power- and free-conveyor chain pins and bearings passing through the types of high-temperature paint-bake ovens found in automobile assembly lines, it was an ideal match for the application. So, given those facts, why was the facility using so much of the product for just four conveyor-lubricator systems? Moreover, why had the lubrication staff or the lubricant supplier neither noticed nor brought to management’s attention the systems’ dramatic (more than 10-fold) increase in lubricant consumption over the past two years?
Further investigation revealed that the chain-oil consumption increase had coincided with the hiring of a new lubrication technician. The PM (preventive maintenance) job plan and frequency for checking and filling the automated lubricator reservoirs, though, had remained unchanged—from the time the devices were installed and commissioned more than three years prior. This discovery prompted a physical investigation of the four lubricators themselves. The findings were more than surprising!
The four lubricators were a popular, highly reliable brand. Low-tech in design, they used a pneumatic pump-to-point-style pump connected to dynamic injectors that would “volley” or “shoot” a small fixed amount of oil into either the unshielded trolley rolling-element bearings or the chain-link pins that connected the trolleys.
All of the devices were in excellent condition—and still located where they had been originally installed—complete with reservoirs full of oil. Curiously, though, all had been shut off electrically at the breaker and their pneumatic air supplies had been shut off at the feed-line valves. As a result, all of these units were totally useless.
Investigators subsequently learned that the four original lubricators had been “replaced” further down the conveyor line by a makeshift gravity-lubrication system that featured 1-gal. paint cans clamped to the conveyor I-beam as oil reservoirs. Installed in the bottom of each can were two small cock valves fitted with copper lines dropping down to two commercial, adjustable oil-drip brushes that were very wet with lubricant—just like the over-lubricated conveyor chain and roller bearings they served.
Questioned about this state of affairs, the plant’s production and quality supervisors told a story of numerous paint-quality problems that, they believed, had been caused by lubricant over-spray. After complaining about the matter to the new lubricant technician, they said, the situation eventually seemed to improve, i.e., fewer quality incidents occurred.
When interviewed, the lubrication technician reported that upon assuming his new role he had received no formal training or direction other than to follow the instructions on the work orders and use common sense. Shortly after starting the job, because of the workload, he decided to ignore the automated lubricator PM work order and, instead, rely on the lubricator-reservoirs’ low-level lights as condition indicators for adding oil. After the first three months, all low-level indicators had activated, at which time the technician had correctly filled the reservoirs with the correct oil (or so he thought).
During later lubricant checks, however, the reservoirs appeared full, and didn’t seem to be dispensing oil at all. Consequently, after multiple unsuccessful attempts to alert his supervisor to the situation, the technician took it upon himself to exercise his personal version of common sense and engineer a new system. Thus was born the gravity system of paint cans and brushes—for which, incidentally, almost a year had been spent working out the settings so that oil wouldn’t drip off the conveyor on to the painted vehicles. (To his credit, the technician did show the new system to the lubricant supplier’s representative. Accordingly, after approving the design, the rep also began enjoying increased orders and commissions for his product.)
In the end, simple diagnostics performed on the automated chain-oil lubricators found the units to be in perfect working order. The reason they had failed to dispense lubricant? At some point, their oil levels had been allowed to drop so low that the injectors and pumps lost their prime. The devices simply needed to be re-primed.
As this case study shows, a few simple lapses in responsible behavior resulted in serious quality issues requiring many hundreds of thousands of dollars in vehicle repaint costs, many tens of thousands of dollars in excess lubricant costs, and overall reduced conveyor life due to ineffective lubrication practices.
Many readers might vote to place blame wholly on the lubricant technician for this calamity. In this story, though, he should only take partial blame: A millwright by trade, with no formal lubrication training, he had been placed in his position based solely on seniority. To exacerbate the situation, there were no specific priming instructions regarding the automated lubricators, either in the work-order job plan or on or near the units themselves.
Still, while the technician tried unsuccessfully, on several occasions, to notify his supervisor of the lubricator problem, he also chose to ignore the initial PM in favor of a different lubrication approach without performing a risk analysis. His McGyver-style paint-can fix could definitely be construed as irresponsible for a tradesperson. He should, at the very least, have tried to find an operations manual or learn more about the specific lubricators he was dealing with before condemning them so quickly and creating a bigger downstream problem.
Much of the blame, however, really belongs to the site’s supervisory personnel:
- the maintenance supervisor who irresponsibly did not adequately support his technician or notice the makeshift lubricators and/or the massive increases in his monthly lubricant spend
- the production supervisor who irresponsibly bypassed the maintenance supervisor in favor of speaking directly to the lubrication technician.
Final blame goes to the irresponsible actions of the lubricant supplier. From an ethical standpoint, its representative certainly should have discussed the massive increase in chain-oil consumption with the plant’s maintenance supervisor and/or the purchasing department.
Responsibility is born out of knowing what to do and when to do it. In the case of the four referenced automated chain lubricators, problems could have been prevented with:
- lubrication certification training
- clear workflow processes
- improved PM work-order job plans
- standardized operating procedures
- failure risk analysis on critical equipment
- improved inter- and intra-departmental communications.
To be sure, the lubrication technician in this story was out of his depth. With a little effort, however, the costly scenario that he created could have been avoided. MT
Lubrication expert Ken Bannister is principal consultant with EngTech Industries, Innerkip, Ontario. He is the author of Lubrication for Industry and the Lubrication Section of the 28th Edition of Machinery’s Handbook (both Industrial Press, South Norwalk, CT), contact him at firstname.lastname@example.org.
Hydraulic systems rely on vital fluids to transfer and amplify power and lubricate critical components. Protecting those fluids from contamination should be a top priority.
By Ken Bannister, CMRP, MLE, Contributing Editor
Despite their complexity, hydraulic systems are very forgiving beasts—almost too forgiving for their own good. They’ll tend to perform inefficiently for a long time before catastrophic failure occurs. Unfortunately, this forgiving nature can foster a widespread, apathetic approach toward failure prevention, efficiency optimization, and service life-cycle management. Fluid is the most important part of any hydraulic system and when systems fail, the cause is most often related to fluid/fluid contamination. Those failures usually take other critical equipment and processes with them.
Exorcise the “big three”
Hydraulic-fluid contamination comes in three major forms: solid particulate, water, and air. All of these can seriously affect the fluid and the equipment components it serves. Maintaining hydraulic fluids in optimum condition requires measuring, controlling, and preventing the introduction of these contaminants. Since contamination in any form can be inherent and induced, understanding how the three types enter a system is important in developing effective preventive-maintenance (PM) strategies.
Solid-particulate contamination. Hydraulic system components are designed to operate with tolerances that can be as close as 1.5 microns. Solid particulate most often manifests itself as grit or dirt that, if allowed into a system, can be extremely damaging to bearing surfaces and hydraulic seals. The solid particles, which can be more than 100 microns in size, will set up in a three-body abrasion state and easily score the mated machined surfaces, creating rapid bearing and component-surface wear, leading to unwanted fluid bypass that reduces operating efficiency. Solids contamination will also cause valve stiction, increased fluid viscosity, and unwanted fluid leakage through nicked and scored cylinder seals.
If your equipment is new or rebuilt, solids contamination in the form of leftover dirt or swarf from the manufacturing/rebuild process could be present in the hydraulic lines. Prior to initial startup, lines should be wad cleaned, existing oil flushed from the system, and new, correct-viscosity fluid added.
Many end-users are unaware that solids-contamination levels can be excessive in new oil supplied from the manufacturer or introduced by the supplier if bulk-transferred through dirty transfer hoses and equipment. When receiving new—especially bulk—oil, always perform an oil analysis to detect solids and water contamination.
While new oil can often be found at a 19/17/14 cleanliness level on the ISO solid-contamination code, that’s not clean enough for high-pressure hydraulic systems. These systems require fluids with a minimum 16/14/11 cleanliness level. To protect your site’s hydraulic systems, establish a cleanliness contract with your oil supplier who will then be bound to provide proof of cleanliness upon delivery.
Other sources of solids contamination, all of which are preventable, include:
- improperly stored oil
- dirty equipment used to transfer the oil into the equipment reservoir
- reuse of dirty “leaked” oil
- “open to air” reservoirs due to missing fill ports or reservoir breathers
- lack of filter maintenance, causing dirty oil to bypass into the system
- poor housekeeping practices.
Water contamination. Water, a universal contaminant, will saturate hydraulic fluid at a mere 300 ppm or 0.04% concentration level. It can be present in:
- a free state, separated from the fluid in an unstable form
- an emulsified state, in a stable form that appears cloudy
- a saturated, dissolved form that appears invisible.
Water depletes vital oil additives or, even worse, reacts with additives to create corrosive acids that attack system components. It can also reduce a lubricant’s film strength and its ability to release air, which can increase wear, corrosion, and cavitation.
Some hydraulic fluids—such as brake fluids—are designed to be hygroscopic and entrain moisture in the fluid until its saturation point is reached. In high-heat applications, water can boil off and create great inefficiency in the hydraulic power-transfer motion.
Typical water-contamination sources include:
- incorrect outdoor lubricant storage practices that cause hot-cold cycle condensation
- “open to air” reservoirs into which washdown and/or process water can splash/spill.
- In most instances, water can be detected visually in its free and emulsified state. To remove water contaminants use:
- polymeric-style filtration media designed to absorb the water as it passes through a filter
- vacuum distillation to boil off the oil
- dehumidification in the reservoir headspace.
Air contamination. This type of contamination presents in a number of forms, of which entrained air can be the most problematic. In this form, air bubbles (<1 mm dia.), dispersed throughout the fluid, reduce viscosity and, thus, film strength. This situation, in turn, can cause premature component wear; a reduction in the oil’s bulk modulus, causing a lack of efficiency and control due to the sponginess of the oil condition; an increased heat load, leading to fluid deterioration; and system erosion, due to cavitation.
Air bubbles greater than 1-mm dia. create foam, which can quickly deplete any antifoam additive and cause fluid oxidization.
Typical causes of air contamination include:
- over-/under-filled lubricant reservoirs
- clogged inlet/suction filters
- clogged reservoir breathers
- restricted inlet lines
- loosely clamped inlet lines
- pump-shaft seal failures.
Fortunately, the contamination problems discussed here are easily preventable—in most cases at minimal cost. While the following advice is not all-inclusive, this list provides an excellent starting point for a successful hydraulic-fluid PM strategy:
- Implement a fluid cleanliness standard.
- Store all lubricants in a cool, dry place and practice FIFO (first in-first out) stock rotation.
- Practice good housekeeping, ensuring that reservoirs are clean of dirt and debris.
- Cap all system hoses and manifolds during fluid-handling and system maintenance.
- Wad-clean all lines prior to initial system startup.
- Flush all lube systems and change oil, prior to startup.
- Use a dedicated filter cart for each hydraulic-fluid type, with quick-connect fittings to transfer/clean hydraulic fluid before it enters a reservoir.
- Install external sight gauges marked with high- and low-level marks in reservoirs to check for fluid levels and the presence of water.
- Use polymeric oil filters and desiccant reservoir air breathers.
- Specify rod wipers and replace all worn actuator seals.
With a little care and common sense, your plant’s hydraulic systems—and the vital fluids that keep them up and running—will be efficient, reliable, and long-lived. MT
Contributing editor Ken Bannister is a Certified Maintenance and Reliability Professional and certified Machinery Lubrication Engineer (Canada). The author of Lubrication for Industry (Industrial Press, South Norwalk, CT) and the Lubrication Section of the 28th Edition of Machinery’s Handbook.(Industrial Press), he can be reached at email@example.com.
When two incompatible greases are mixed, either deliberately or accidentally, the results can be disappointing, if not devastating.
By Jane Alexander, Managing Editor
The problems associated with grease incompatibility manifest themselves in various ways. According to bearing manufacturer NSK Americas, Ann Arbor, MI, scenarios include:
- A lab technician tests grease from a problem bearing and finds that, while it meets all specifications, it doesn’t perform as it should.
- A mill switches grease based on glowing reports from other facilities, then finds the new product doesn’t deliver the promised results.
- A critical plant motor fails during rush production, despite having been lubricated as specified in the maintenance manual.
In each case, NSK representatives said, these sites had changed from one type of grease that met specifications to another type, which also met specs. They all fell victim to grease incompatibility.
Although maintenance organizations should be well aware of this information, not everyone remembers that some greases can’t be mixed with other greases—even when both types meet specifications. Unless incompatibility is understood and accounted for, switching grease can be catastrophic.
Incompatibility occurs when a mixture of two greases shows properties or performance significantly inferior to those of either grease before mixing. Some grease bases are intrinsically incompatible. Different fatty acids and/or additive packages also affect compatibility. To make things even more confusing, sometimes two types of greases that are manufactured as a mixed-base product are incompatible when mixed in operation.
Unfortunately, issues associated with grease incompatibility usually aren’t apparent until the bearing is in use. At that point, major problems can develop. Thus, it’s best to know in advance which types of greases can be used together and which can’t (see table).
Make grease changes safely
What if switching grease is necessary? Several steps ensure safe changeovers. The good news is that incompatible greases don’t have to be eliminated completely. Preparing carefully and paying close attention to details can prevent problems:
- Ask your lubricant supplier(s) about product compatibility.
- Use up as much of the old grease as possible before introducing the new grease into the system. The ideal course of action is to completely drain and clean the system before changing over.
- Once the new product is added, grease flow should be increased temporarily. This will move the interface (the area of grease mixing) through and out of the system as quickly as possible. The increased flow also assures good lubrication and proper sealing while overly soft grease may be in the bearings.
- When in doubt, expect incompatibility and watch for problems. MT