Archive | Lubricants

108

4:47 pm
May 15, 2017
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Beware Self-Inflicted Reliability Problems

modern manufacturing industry and mechanization concept, abstrac

Think of this expert advice as a reality check for your operations and take action accordingly.

By Jane Alexander, Managing Editor

The root cause of poor reliability can come from many sources, including aging plant assets, poor design decisions, even disregard for reliability by those who built and/or installed the equipment. Then, there are the many other reasons outside of your control that could be contributing to the reliability problems your site is experiencing today. While any reliability-improvement initiative will require that all of those issues be addressed, according to Jason Tranter of Mobius Institute (mobiusinstitute.com, Bainbridge Island, WA), operations must first deal with those of the “self-inflicted” variety.

Don’t think you have self-inflicted reliability problems? Tranter begs to differ. It’s a bitter pill to swallow, but yes, you do,” he said. “That’s good news, though, since it is much easier to deal with the self-inflicted root causes than the inherent reliability problems you adopted.”

What does Tranter mean by self-inflicted? To determine why equipment fails prematurely and/or why you experience slowdowns, safety incidences, or quality problems, he explained that personnel could go through a detailed reliability-centered maintenance (RCM) analysis process, or perform root-cause failure analysis (RCFA) after each failure occurs. “Better yet”, he said, “they can learn from the experience gained at thousands of plants around the world and consider some of the most common root causes of equipment failure.”

Focusing on rotating equipment, Tranter outlined those types of problems as follows, starting with the most obvious and working backward to their root causes.

#3. Cause of Reliability Problems: Imperfect operating and maintenance practices

Most of the equipment in a plant or facility, i.e. motors, pumps, fans, compressors, and turbines, is designed to run for many, many years without unplanned downtime. While those types of assets may incorporate some components that wear out, many items, such as bearings and gears, are designed to provide years of trouble-free operation. This, however, assumes that all of the parts were installed correctly, the components are precision aligned, the bearings and gears are correctly lubricated, all fasteners are tightened to the correct torque, there is no resonance, belts are tightened to the correct tension, and the rotors are precision balanced.

It also assumes that the equipment is operated as designed. Pumps, for example, should be operated at their best efficiency points (BEPs). “If you are unsure these types of situations are occurring,” Tranter cautioned, “then they almost certainly are.” He pointed to several areas where seemingly minor issues could be causing serious problems:

1705fvibration2

Just 5/60th of a degree of angular misalignment can cut bearing life in half. (Reference: Harris, Tedric A., A Rolling Bearing Analysis, John Wiley & Sons, New York, 1984.)

Shaft alignment. When two shafts are “collinear” (no angle or offset between their centerlines) it reduces stress on the bearings, couplings, shafts, and the rest of the machine components. Research has revealed that just 5/60th of a degree of angular misalignment can cut bearing life in half (see Fig. 1).

If you use laser alignment with appropriate tolerances, and you remove soft foot, then this will not be a source of poor reliability. By the way, just because your vibration analyst does not detect misalignment does not mean that your machines are precision aligned.

The life of a bearing is inversely proportional to the cube of the load.

The life of a bearing is inversely proportional to the cube of the load.

Balancing. When you balance to ISO 1940 grade G 1.0, the cyclical forces on the bearings, shaft, and structure are minimized and you gain reliability. If you do not have a balancing standard, then unbalance will be a root cause of failure. If you wait until the unbalance generates “high” vibration, then you will have reduced the life of the equipment and supporting structure. That’s because the life of a bearing is inversely proportional to the cube of the load (see Fig. 2). Tranter noted that, while this calculation sounds very complicated, it basically means that if you double the load, a bearing’s life will be reduced to an eighth (23).

Tiny 3-µm particles cause more damage than 40-µm and 10-µm particles (Reference: A Study by Dr. P. B. McPherson)

Tiny 3-µm particles cause more damage than 40-µm and 10-µm particles (Reference: A Study by Dr. P. B. McPherson)

Lubrication. When you correctly lubricate bearings and gears, whether with grease or oil, and that lubricant is free of contaminants, you will achieve maximum life. But if bearings are not adequately greased, their life will be reduced. If the oil is contaminated, the viscosity is incorrect, or additives are depleted, then the life of gears and bearings will be greatly reduced.

Research was performed to determine which particles caused the greatest damage. It wasn’t the 40-µm particles or the 10-µm particles, it was the tiny 3-µm particles (see Fig. 3).

By the time you can see water in oil, the life of the bearing has been halved.

By the time you can see water in oil, the life of the bearing has been halved.

According to Tranter, personnel may think that if they can’t see water in oil then the oil must be fine. Sadly, that is not correct (see Fig. 4). By the time water can be seen in the oil, the life of the bearing has been halved. “We could continue the discussion,” he said, “but suffice it to say that there is a great deal we can do to avoid problems that arise due to imperfect maintenance and operating practices.”

#2. Cause of Reliability Problems: Desire and organizational culture

It’s one thing to understand all of the above root causes. “It’s another,” Tranter observed, “to obtain approval to establish standards and purchase all of the tools, such as laser-alignment systems, that enable technicians and operators to do their jobs correctly. But owning the tools and having standard operating procedures won’t solve the problem.” As he put it, the problem will only be solved when technicians and operators want to use those tools properly and are given the time and encouragement to do so.

Thus, the issue of “desire” and its link to organizational culture must be considered as a root cause of self-inflicted reliability problems and addressed accordingly.

#1. Cause of Reliability Problems: Inadequate management support

Tranter believes a strong case could be made that the root cause of all failures derives from lack of senior-management support for a culture of reliability. Without their support it will be impossible to change the culture and thus change behavior.

“Think about initiatives to improve safety at your plant,” he said. “If senior management didn’t support them, would those initiatives have been successful? Senior-management support leads to people being employed in safety roles, investment in training and tools, and posting of signage that provides warning and feedback on progress, among other things. It also keeps sites from cutting corners that would risk safety, and it makes it clear how important safety is to the future of the organization.”

According to Tranter, the type of management support that drives safety at a site needs to be leveraged to drive reliability improvement. “Everyone within the organization,” he said, “needs to understand that reliability is critically important to the organization and that senior management will stand strong when shortcuts that compromise reliability are available.” Without adequate senior management support, he concluded, meaningful culture change won’t occur, and reliability-improvement initiatives won’t be able to eliminate self-inflicted root causes of problems. MT

Jason Tranter, BE (Hons), CMRP, VA-IV is CEO and founder of Mobius Institute (Balnarring, Victoria, Australia, and Bainbridge Island, WA). For more information on this topic and other reliability issues, including vibration monitoring and training and certification of vibration analysts, contact him at jason@mobiusinstitute.com, or visit mobiusinstitute.com.

Where Does Condition Monitoring Fit?

By Jason Tranter, Mobius Institute

Condition monitoring plays several crucial roles in the battle against self-inflicted reliability problems. For example, providing an early warning of impending problems minimizes the impact of premature failure, and detecting and eliminating the root causes ensures that we achieve the greatest life and value from our precious assets.

Many plant personnel, however, believe that if they have a condition-monitoring program in place, equipment reliability will be optimized. That, unfortunately, is not true.

Most detected faults are avoidable. While it is important to get an early warning, it is much more important to avoid the problem in the first place. Condition monitoring can help by detecting the root causes of failure, including misalignment, unbalance, lubrication issues, and looseness, among others. If those problems are cost-effectively nipped in the bud, then we avoid future failures.

Another way condition monitoring plays a role in plants is in acceptance testing. As part of the purchase agreement, condition-monitoring specialists can perform tests to ensure the new or overhauled equipment is “fit for purpose.”

You may be surprised at how many problems you actually bring into your plant.

184

8:01 pm
April 13, 2017
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Listen Up: Stop Lube-Related Bearing Failures

Ultrasound technology can help reduce bearing and equipment failures associated with improper lubrication procedures.

Ultrasound technology can help reduce bearing and equipment failures associated with improper lubrication procedures.

Regardless of industry sector, lubrication methods are crucial to plant reliability and maintenance efforts. Consider the fact that lube-related failures account for 60% to 80% of premature bearing failures. While lack of lubrication and use of the wrong lubricant for an application have been cited as major causes of such failures, over- and under-lubrication are also harmful. Preventing those last two scenarios is one area where ultrasound technology can play an important role.

— Jane Alexander, Managing Editor

According to UE Systems (Elmsford, NY), by using an ultrasound instrument to listen to a bearing while applying lubricant and then monitor, i.e., watch, the decibel level, a technician can determine when adequate grease has been applied and, just as important, the threshold at which over-lubrication begins.

In short, when bearings aren’t lubricated properly, friction can cause damage and threaten processes. Ultrasound equipment can read the decibel levels of over- and under-lubricated bearings and indicate to maintenance personnel if adjustments are in order. Consistent dB levels let a technician know that the level of lubrication is where it should be.

Experts at UE Systems describe three tiers of acceptable lubrication practices and where ultrasound technology fits into them.

randmGood practice

The baseline lubrication practice is to follow the bearing manufacturer’s recommendations to determine the exact amount of lubrication necessary based on bearing size, speed, and type, and rely on runtime and operating conditions to develop a lubrication schedule. While “good” is a starting place, there is room to improve.

Better practice

The next level uses ultrasound equipment for more exact lubrication procedures. These tools tell maintenance technicians when to stop lubricating a bearing, rather than hoping the schedule is accurate and guessing at bearing condition. Ultrasound can also inform technicians if there are other problems with the bearing, unrelated to lubrication.

Best practice

A best lubrication practice is to combine a frequency schedule and ultrasound tools with data collection and trend analysis. By examining the history of lubrication with dB levels and other sound files, maintenance technicians can begin to predict when bearings may be approaching failure and take preemptive action. Alarm levels can be set to alert technicians when lubrication is approaching dangerously low levels.

The best ultrasound programs allow easy integration of data analysis with probes, listening devices, and lubrication tools. MT

How Ultrasound Technology Works

Air- and structure-borne ultrasound is high-frequency sound that human ears can’t hear. These high-frequency sounds travel through the air or by way of a solid. The ultrasound instrument senses and listens for the high-frequency sound, and then translates it into an audible sound that is heard through the inspector’s headset. The unit of measurement for sound is a decibel (dB) level, which is indicated on the display of the ultrasonic instrument.

Ultrasound can be used in conjunction with (and is supportive of) vibration analysis and other predictive-maintenance approaches. In addition to mechanical inspections of rotating equipment and associated condition-based lubrication programs, applications for ultrasound include detection of compressed air and gas leaks; inspection of energized electrical equipment to detect corona, tracking, and arcing; and inspection of steam traps.

For more ultrasound information and to download a printable infographic on “3 Ways to Incorporate Ultrasound in Lubrication Testing,” visit uesystems.com.

150

6:03 pm
April 13, 2017
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A Hoarder of Information

When it comes to lubrication, Scott Arrington relies on 34 years of information gathering to ensure he always has the correct answer for his customers.

High-tech equipment helps Arrington and his team provide accurate analysis and improve the reliability of all equipment.

High-tech equipment helps Arrington and his team provide accurate analysis and improve the reliability of all equipment.

By Michelle Segrest, Contributing Editor

Screen Shot 2017-04-13 at 12.24.37 PMScott Arrington is a hoarder—a self-described hoarder of information, that is. The World Wide Web is not big enough to hold all the information upon which he relies. In fact, he has so many manuals, binders, and oil samples, he needs two offices—one to work in, and another to contain all the valuable records, documentation, and research he will never throw away.

Arrington is the Lubricants Technical Manager at G&G Oil Company, Muncie, IN. When a customer calls with a question, he wants to be sure he has the correct answer. “I have abundant resources to make sure we make the correct recommendation the first time and can quickly answer questions from customers. I keep all records of opportunities we have already experienced.” 

As a college student, Arrington worked part-time for the company painting convenience stores, bumper poles, and canopies, and performing maintenance.

“It was a great summer job, and it helped me to get familiar with the business,” Arrington said. “When I graduated from Depauw University (Greencastle, IN) in 1986, I was still looking for a full-time job and the owners of G&G Oil (Bill Gruppe, deceased; Hoyt Neal, retired; and Dale Flannery, retired) were gracious enough to allow me to come work for them in a sales position. They helped me get interviews with a couple major oil companies. I received some nice offers, but when I measured what I really wanted to do and where I really wanted to be, staying here was the best option for myself and my family.”

When making that crucial decision, the opportunity to work with people and with a smaller company were key factors.

“When I graduated from college with my science and physics background, I knew I didn’t want to spend my life in a lab,” he explained. “I was looking around at different options and the owners of G&G Oil offered me a position where I could use my science background to help sell lubricating products while not being tied down to a desk. I was able to get out in the field and see many different and interesting mechanical operations. It was something new every day.”   

Thirty-four years later, Arrington remains loyal to G&G Oil, and now makes significant contributions—in particular with his deep technical knowledge and impact on the lubrication and oil-analysis programs. 

1704fvoice04pMajor responsibilities

It is Arrington’s passion to help customers and prospects solve lubricant-related issues. “From my numerous years of experience and attendance at many major oil companies’ learning seminars, I have been able to absorb quite a bit of knowledge to assist companies and individuals with their lubricating problems,” he said. “I can also assist them with ideas and programs to decrease their total lubrication expenses.”

It is Arrington’s responsibility to answer technical questions from customers and prospects, working directly with key accounts, assisting salespeople with technical sales calls, maintaining current formulas and developing new products, maintaining and updating technical data sheets, approving all raw materials used in formulations, and approving new finished products that G&G distributes for other companies. 

Arrington’s team includes a customer-service manager, a logistics manager, a production manager, and a sales manager. He also works closely with the sales representatives to make sure they are supported with sales opportunities and assistance with current customer questions.

Many of the customer’s questions include inquiries about machine recommendations. “Customers will call in with questions about a certain brand of product for a certain machine,” Arrington explained. “I will delve into the exact specifications of the product they are telling me about and come up with a recommendation of a product we represent—whether it is a G&G Oil-branded product, a Shell Oil-branded product, or from many of the other brands of products we distribute. I try to take away the aura of the name of the specific brand, and assure them that if you don’t have that exact brand, the machine will not keel over and die. I educate the customer about my recommended product and that their warranty won’t be voided if they use another product brand. The warranty will still be in good standing by using the specification of the product, and not necessarily the brand of that product, in their machinery.”

Screen Shot 2017-04-13 at 12.24.49 PMThe importance of lubrication

Arrington said he lives and breathes with a simple philosophy—“Learn all you can, and don’t be afraid to ask questions.” For him, the importance of good lubrication is simple.

“If you don’t have proper lubrication in your equipment, it won’t run the way it’s designed, which will lead to unscheduled maintenance opportunities,” he explained. “If your machinery doesn’t run, you can’t make products to sell. If you can’t make products to sell, your business will suffer and you possibly won’t be around very long! If you are using improper lubrication practices, your machinery will not run at the optimum level. Your maintenance costs will go up because you will have to replace components more often and you will have more unscheduled downtime. Your total maintenance spend will increase if you are not using the correct lubrication product and applying it at the right time, or monitoring it at the right times to make sure your machinery is running at its optimum level.”

Arrington recommends the following lubrication best practices:

• Follow OEM instructions.

• Develop an oil-analysis program that emphasizes:

• condition of the machinery
• trending how the machinery is functioning
• tracking excessive wear of components
• information about the oil (oxidation, contaminants, additives).

If you don’t have your own in-house oil-analysis laboratory, partner with a reputable and certified independent oil-analysis provider. Even if you have your own lab you should use an independent lab to occasionally check your results.

• Use different testing procedures to ensure customers can fully see the condition of their machinery.

• Use proper sampling equipment and procedures.

“A good oil-analysis program is like having a blood test for a human. It can tell you if you have problems with a vital organ or some other part of your body that you may need to look into to take medicine for or have surgery,” Arrington said. “It’s the same with oil analysis—it tells you if the ‘organ’ in the machine is running properly or if it needs to be examined or replaced because it may have excessive wear or other problems, causing it not to work to its optimum level. A good oil-analysis program allows you to be proactive to schedule maintenance instead of being reactive to a break down.”

scottgraphic

Challenges

One of Arrington’s biggest challenges, he said, is developing and producing formulas for new products that G&G Oil can offer to its customers. 

“It’s challenging because of the many different obstacles you’re trying to overcome, especially in the metal-working and metal-removal fluids field. You’re trying to formulate a product for the customer that will have a long life span for the fluid, a good clean finish for the part, and will provide long tool life,” Arrington explained.

There are several different types of additives that can be used, depending on what kind of metal is being manipulated or type of operation being performed. “You have to use the correct balance of those additives to give you an optimum performing product,” he said. “I rely heavily on my additive manufacturers to give me guidance. When I have special projects, I consult with them. I design a product in the lab and then collaborate with my suppliers to get their opinion on whether they think it will work or not.  Fortunately they agree with me most of the time! The formulating depends a lot on what the application is. You have a pool of additives and base oils that you know about. It’s just trying to blend them together correctly to give you the best-performing product for the customer.”

Finding inspiration

Learning and then hoarding information provides constant inspiration for Arrington. As an example, he points to the adage, “Give a man a fish and feed him for a day. Teach a man to fish, and feed him for life.” It is advice he implements in his own work, every day.

Arrington has been married to Stephanie for 20 years and has two teen-aged daughters, MiMi and Ellie. He gives similar advice to his children.

“I’m sure they get tired of it,” he said. “I try to give them advice of the failures I have had in the past—no matter how big or how small—and remind them how important it is to learn from them. I also try to get them to look at the big picture. I want them to see the repercussions of their actions. It may seem like a small thing, but it could be a big thing down the road. I try to be a great representative of myself and my family and my company. My children are growing up in a different time with different challenges and problems, but we all need to learn from history and our mistakes.” MT

Michelle Segrest is a professional journalist and specializes in the industrial processing industries. If you know of a maintenance and/or reliability expert who is making a difference at their facility, send her an email at michelle@navigatecontent.com.

306

8:39 pm
April 12, 2017
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Specify the Right Lube-Delivery Line

Fig. 1. Cost should not be a factor in your lubrication-delivery-line choices. While the steel-tubing in this progressive-divider-lubrication system block took more time to install than plastic lines, the additional, but small, up-front cost will pay long-term dividends, especially if leaks or blockages occur.

Fig. 1. Cost should not be a factor in your lubrication-delivery-line choices. While the steel-tubing in this progressive-divider-lubrication system block took more time to install than plastic lines, the additional, but small, up-front cost will pay long-term dividends, especially if leaks or blockages occur.

The wrong lubrication-delivery line can compromise the reliability of your production equipment.

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

During lubrication-training workshops, I ask participants to name the components that make up a centralized lubrication system. Most will answer in the context of an automated-delivery system by citing the pump, reservoir, metering devices, and pump controller. Rarely do they actually include the lube-delivery lines in their answers.

Lubrication-delivery lines are important and integral components within centralized lubrication systems—be they state-of-the-art automated designs or simple, manual arrangements. Specifying the wrong type can put machinery reliability at risk.

The function of a lubrication-delivery line is straightforward: It must connect a bearing point to a lubricant source (indirectly from a meter or gang block, or directly from the pump) and allow the lubricant to be contained within the line to flow without constriction. As lube-delivery systems are hydraulic in nature, the line must also be capable of withstanding pressures ranging from hundreds to, in some cases, many thousand of pounds-per-square-inch (psi) of pressure.

Listen to the latest in a series of monthly lubrication-related podcasts with Ken Bannister. This edition of the podcast focuses on lubrication-delivery line matters.

Line size and material

Correct choice of size and material is essential if a lubricant-delivery line is to provide reliable service. For the most part, the line plays a passive role within a centralized system and is typically fixed to the side of a machine (the exception being where a lubricated part moves independently of a piece of fixed machinery, in which case, the line is used to provide the flexible connection.) Before a delivery line can be specified, however, a number of basic questions regarding the overall lube-system design must be answered, including:

Fig. 2. The bundled plastic tubing in this progressive-divider system are difficult to individually trace from pump to the lube block. These types of lubrication-delivery lines are also difficult to physically attach to a machine’s frame and, consequently, more vulnerable to damage.

Fig. 2.
The bundled plastic tubing in this progressive-divider system are difficult to individually trace from pump to the lube block. These types of lubrication-delivery lines are also difficult to physically attach to a machine’s frame and, consequently, more vulnerable to damage.

Is this system automated or manual? The answer is crucial in assessing line material, diameter, and wall thickness, which relate specifically to the line’s material-burst pressure rating.

• Manual systems designed to “gang” grease nipples in a central block can be lubricated by grease guns capable of developing as much as 15,000 psi.

• Manual hand pumps and automated systems operate at much lower pressures (between 100 and 2,000 psi).

What type of automated/engineered delivery system is specified? Some system designs require a single line size throughout, whereas others require a main and secondary line of different diameters and flow rates. For example:

• Single-line-resistance and pump-to-point systems are low-pressure systems designed to deliver the total amount of lubricant in one pump cycle. In such systems, i.e., total-loss, single-size-diameter delivery lines are sufficient.

• Single-line positive-displacement-injector, dual-line-injector, and progressive-divider systems require multiple cycles of the pump connected to a larger diameter main line used to rapidly fill the injectors/main distribution blocks, and smaller-diameter secondary lines that connect the metering outlets to the lubrication points,

• Re-circulating-oil systems usually require single-size-diameter delivery lines and a larger-diameter, return-line system.   

How many lubrication points are included in the system and where are they located on the machine? This question is required to map out a central pump location and injector or delivery block locations so the line distances can be measured for material take-off amounts, and in the case of long line lengths, to calculate pressure drop so the correct line diameter(s) can be calculated.

What lubricant type and grade/viscosity are you planning to use? The fact that grease requires higher pressure than oil to move through blocks and lines will affect the choice of line material type and diameter.

Fig. 3. If single-chamfered compression fittings designed for nylon lines are mistakenly used on steel lubrication-delivery lines that require double-chamfered fittings, seals can be compromised, causing leaks at the fittings. (Courtesy Bijur Delimon International, Morrisville, NC, bijurdelimon.com.)

Fig. 3. If single-chamfered compression fittings designed for nylon lines are mistakenly used on steel lubrication-delivery lines that require double-chamfered fittings, seals can be compromised, causing leaks at the fittings. (Courtesy Bijur Delimon International, Morrisville, NC, bijurdelimon.com.)

In what type of working environment will the system be used? Ambient and working temperatures can affect line integrity. Furthermore, if unprotected, copper, brass, and plastic lines can be easily damaged in high traffic areas—especially where lift trucks are used regularly.

What is your budget? Cost should not be a factor in line choice. Figures 1 and 2 show progressive-divider blocks, one piped in correctly rated plastic tubing and the other in steel. While steel tubing (Fig. 1) takes considerably longer to install, the additional, but small, up-front cost can pay long-term dividends, especially when a problem, such as a leak or a blocked line, occurs. The plastic tubing (Fig. 2) is bundled together. making it difficult to individually trace a line from the pump to the lube block. In addition, these lines are difficult to physically attach to the machine frame and, consequently, more vulnerable to damage.

Although the steel lines used in Fig. 1 are dirty, they all have line-ID (identification) tags that make them easy to trace and troubleshoot. The steel-line system also looks more engineered and permanent in comparison with the bundled-plastic-line example.

Once you’ve gone through these six questions, present the answers to your lube-system designer or manufacturer/supplier. These resources can help you determine the best line material for a specific application.

Main problem causes

Problems in lubrication-delivery lines manifest as leaks or blockages. A leaking line will starve lubricant from one or many bearing points and seriously affect the associated production equipment’s reliability. Leaks are invariably found at connection points and line-bend areas. Keep the following in mind:

• Copper lines are very soft and can easily work-harden at bend points if significant machine vibration occurs.

• Nylon lines can be easily over-tightened or not cut square at the connection points. This can cause a leak at the compression fitting.

• If a single-chamfered compression fitting designed for nylon lines is mistakenly used on a steel line, which require a double-chamfered compression fittings (see Fig. 3), they can be compromised, causing a leak at the fitting.

• To reduce cost, nylon lines can be used as a substitute for flexible-hose lines in moving-bearing-point applications found on, among other things, machine slides and rams. Plastic lines, in most cases, are not rated for cyclic repetitive-movement duty.

Blockages in lubrication lines usually occur when they’re pinch-damaged from being hit by a foreign object that crimps or flattens the line shut. This situation causes a line backpressure that can blow the fitting or eventually stall an entire progressive-divider system, starving many bearings in the process. Steel lines offer the best defense against pinched lines.

Best practices

To ensure no bearing is starved after a lubrication-system implementation or line replacement, always pre-fill the lubricant line with the correct grease lubricant before final fastening to the bearing. Or, in the case of oil, operate the lube system and open all bearing points to ensure oil is flowing at each point before final tightening.

Finally, never forget that lubrication-delivery lines are a matter of choice. Reliable lube systems, in turn, depend on making the correct choice. MT

Contributing editor Ken Bannister is co-author, with Heinz Bloch, of the 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 at kbannister@engtechindustries.com, or telephone 519-469-9173.

1082

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

1701flube01opto

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 kbannister@engtechindustries.com, or telephone 519-469-9173.


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

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

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