Increasingly sophisticated machines and operations require more than legacy PM approaches.
By Ken Bannister, MEch Eng (UK), CMRP, MLE, Contributing Editor
The term “time-based maintenance” is well understood in industrial operations. The premise is simple. A regular maintenance/lubrication event is scheduled on the basis of a calendar anniversary, i.e., weekly, monthly, quarterly, yearly, or other interval, or on a machine’s run-time clock, i.e., 100, 250, 1,000 hr., or some other specified number of hours. Foundational to legacy preventive-maintenance (PM) programs, this type of event scheduling has served industry well for decades.
Plant equipment systems and processes, however, are becoming more complex and demanding by the day. In turn, they are requiring increasingly sophisticated maintenance approaches. Going forward, if they haven’t already done so, sites will need to adapt to an integrated, proactive-maintenance approach that maximizes machine availability and reliability. The economic justification is simple.
In a legacy time-based event, a forced machine downtime is usually scheduled to perform maintenance or lubrication, e.g., oil change. Older equipment designs usually dictate that a machine must be shut down and locked out to determine its status and conduct scheduled activities in a safe manner. This method obviously has an impact on an operation’s throughput capability.
Given today’s fast-paced operating environments, a forced two-hour downtime to change oil on a calendar schedule—whether it needs to be changed or not—is no longer acceptable. We still need to change oil, but we need to treat that oil as we would any asset and maintain it over an extended lifecycle. That means changing it only when conditions warrant change. This type of monitoring strategy reduces machine intervention and increases production throughput, as well as reduces costs related to the purchasing, handling, and disposal of lubricants at a site. It also fits perfectly in any corporate asset lifecycle or sustainability initiative.
Moving from a time-based to a condition-based lubrication program is an ideal change-management vehicle for transforming and improving an operation’s state of lubrication. Successful design and implementation of a condition-based lubrication program can manifest itself in different forms, depending on a plant’s industry sector and current state of lubrication. Several “conditional” strategies can help your site gear up for this move with little effort and expense.
Implementing conditional strategies
Two basic elements underpin a condition-based lubrication program. The first speaks to the integrated, proactive-maintenance approach through involvement of operators as the primary “eyes and ears” in performing daily machine condition checks. The second element assures consistency and accuracy in the execution of value-based condition checks and lubrication actions.
Some maintenance personnel might argue that the old PM job tasks stating “Fill reservoir as necessary” or “Lubricate as necessary” are perfect condition-based instructions. Not so fast: Those instructions, unfortunately, rely solely on maintainer experience. They will not deliver consistency and accuracy without controls that dictate how we assess a machine’s condition and take appropriate actions built into the “necessary” part of the work-task equation. That’s where implementation of the following conditional strategies pays off.
Strategy 1: Reservoir-fill condition
If a lubrication system is to deliver peak performance, it will require an engineered amount of lubricant. In re-circulating and total-loss systems alike, designated minimum and maximum fill amounts aren’t always clearly indicated on the reservoirs. In such cases, the first step is to ensure that a viewable sight gauge is in use, complete with hi-lo markers for manual checks.
For critical equipment, an advanced approach can utilize a programmable level control to electronically indicate the fill state to operators and maintenance personnel. Some equipment, of course, is designed with reservoirs inside the operating envelope that require machine shutdown to perform checks or fill up. These systems can be inexpensively redesigned with remote “quick-connect” fill-lines piped to the machine perimeter that will allow the reservoirs to be filled to correct levels while the machine runs. (For additional tips, see this article’s “Learn More” box at the bottom of this article.)
Strategy 2: Oil condition
When the term “condition-based” is used, oil analysis often comes to mind. The first stage in controlling the oil’s condition is to ensure the product is put in the reservoir at the correct service-level of cleanliness and that a contamination-control program is in place. This will require a number of things: an effective oil-receiving and -distribution strategy, operators and maintainers working together to keep the lubrication system clean, use of desiccant-style breathers, and remote, “quick connect” fill ports that can be hooked up to filter carts outside of a machine’s operating envelope. (For additional tips, see the “Learn More” box at the bottom of this article.)
The second stage is to monitor the oil’s condition for contamination, oxidation, and additive depletion through the use of oil analysis. Extracting oil samples for testing purposes is predominantly a manual process that can be conducted outside of a machine’s operating envelope through a remote-piped “live” re-circulating line or by using a remote-piped sight-level gauge with a built-in extraction port.
Based on a condition report, the machine’s oil can be cleaned by using a filter cart, with no downtime, or replaced at a conveniently scheduled time. An advanced alternative is to use an inline sensor to monitor and electronically indicate pre-set oil cleanliness and water-presence alarm levels. (For additional tips, see the “Learn More” box at the bottom of this article.)
Oil-temperature condition is important wherever ambient temperatures fluctuate and an oil might become too viscous to be pumped through a system. This situation can create a bearing-starvation effect. In environments where this could happen, a thermostat-controlled automotive block heater or battery blanket heater can be incorporated in the system to ensure lubricant usability and machine uptime.
Strategy 3: Machine condition
The ultimate lubrication-control is based on equipment running condition. Effectively lubricated machinery will require less power to operate and bearing life will be extended by as much as three times that of ineffectively lubricated machines. Correctly engineered and set up, automated, centralized lubrication-delivery systems ensure the right amount of lubricant is applied in the right place, at the right time. If your plant’s equipment is predominantly manually lubricated, investigate converting to automated systems that require less maintenance and return their investment in weeks or months. (For additional tips, see the “Learn More” box at the bottom of this article.)
Automated systems are highly adaptable to new IIoT (Industrial Internet of Things) protocols. The capability now exists to install bearing-heat sensors (that set temperature ranges of different bearings) for monitoring, amperage metering (needed because friction demands an increase in motive power that translates through amperage draw), and sensing of oil levels and cleanliness.
Condition signals can be sent to an automated system’s lubricator to turn on and off for a timed or actuation cycle, or to indicate an alarm state. These conditions can be monitored with software tools and used for computer-based automated decision making to reset a lubricator program based solely (and precisely) on condition needs of a machine within its ambient operating environment.
Condition-based lubrication respects and treats the oils that a site relies on as integrated assets in equipment and process uptime. The condition-based approach is an excellent first step for a site that wants to shift its focus from legacy PM approaches to integrated, proactive-maintenance strategies. Regardless of industry sector, this type of maintenance is what plants of today and tomorrow require to be competitive. MT
Condition-based lubrication and system design are among the topics covered in contributing editor Ken Bannister’s 2016 book, Practical Lubrication for Industrial Facilities–3rd edition (Fairmont Press, Lilburn, GA), co-written with Heinz Bloch. Contact Bannister at email@example.com, or 519-469-9173.
Heed these tips to simultaneously befriend your budget and the environment.
By Ken Bannister, MEch Eng (UK), CMRP, MLE, Contributing Editor
There was a time when the terms “used oil“ and “waste oil” meant the same thing and could be used interchangeably. Not anymore. Federal, state, and local environmental regulations have effectively redefined both terms as distinct oil states that must be dealt with in very different ways. Because legislation differs among authorities and jurisdictions, it’s the responsibility of plant owners/operators to contact appropriate authorities for clarification on regulations under local law regarding the definition, management, and disposal of the used and waste oils at their sites.
Identifying ‘used’ oil
Used oil is generally defined as a product refined from crude oil or any synthetic oil that has been used and, as a result of such use, is contaminated and unsuitable for its original purpose due to the presence of impurities (water or dirt) or the loss of original properties (through loss of additives).
Like virgin stock oils, used oil should be thought of as a resource that can be reprocessed in situ with an industrial filter cart to clean and polish the oil while it’s in the machine reservoir. Or, it can be shipped to an oil recycler where it will be treated using settling, dehydration, filtration, coagulation, and centrifugation to remove contaminants and, if needed, refortified with its required additive package and placed back into service—all at a fraction of the cost of new oil, with no disposal management and associated fees.
Alternatively, used oil can be re-refined into lubricant or fuel oil products that can legally be sold as new oil. Re-refined products must be processed to meet the same stringent requirements and standards set for their virgin-oil counterparts. Once the re-refining is completed, the products are considered brand new oils.
Less expensive to manufacture and purchase, re-refined products conserve virgin-oil stocks—10 barrels of crude are conserved for every barrel of re-refined new oil made from used oil—and minimize the negative environmental impact of oil disposal.
Typical used-oil candidates for re-refining include:
• compressor oil
• electrical insulating oil (except that likely to contain PCBs)
• crankcase (engine) oil
• gear oil
• hydraulic oil (non-synthetic)
• industrial process oil
• neat (undiluted) metalworking fluids and oils
• refrigeration oil
• transfer oil
• transformer oil
• transmission oil
• turbine oil.
In some jurisdictions, used oil is allowed as a fuel oil and can be burned for heat.
Although used oil is generally considered a commodity, in a handful of states it is viewed as a hazardous material and, as such, must be treated as hazardous waste when stored for disposal. Plants must check with their local authorities in this regard.
Identifying ‘waste oil’
Waste oil differs from used oil in that it reflects new oil that has become contaminated and, consequently, is deemed no longer useful for service. In the view of many jurisdictions, such oil is a hazardous waste. Used oil, cross-contaminated with chlorinated products or other chemical products, must be treated as a hazardous liquid and disposed of accordingly. Once again, it’s imperative for facility personnel to check with their local authorities to understand the legislative definitions and requirements.
Collecting used and waste oil on site is a natural occurrence in any industrial plant and allowable in all jurisdictions. There are, however, regulations regarding its labelling, storage, spillage, and disposal.
The photo above reflects a typical outdoor storage area for the collection of used and waste oils in a plant. Although it shows a designated area, it exposes a very poor—and expensive—oil-management approach that contravenes most of today’s regulations in the following ways:
Used- or waste-oil tanks must be clearly labelled and accessible.
The tanks in the photo are grated pits that would be classified as confined spaces and not allowed in many jurisdictions. Only one of these two restricted-access pit tanks is labelled as “Waste Oil,” a fact that’s partially obscured by the barrels.
Given the proximity of the two pits to each other, poor access to the rear one, and their uncontrolled exposure to outside elements, most regulatory agencies would probably classify oil pumped from both of those tanks as hazardous waste, requiring costly disposal procedures.
• Decommission the pits.
• Install two above-ground steel tanks in accordance with regulations, designating each separately for used oil and waste oil. For correct tank sizing, work with your oil-disposal company to ascertain its minimum and maximum haulage capability.
• Clearly label each tank in accordance with local regulations.
• Move tanks into a controlled indoor space or cover the area to protect from outside elements.
• All tanks are to be bunded (placing the tank inside a leak proof bermed concrete, asphalt, or steel/plastic catch-basin control area. The bund must equal or exceed the volume of the largest tank in that bunded area.
• Padlock tanks shut when not in use.
Dedicated oil-transfer containers must be used to control cross-contamination.
In the photo example the company has a variety of different-sized open pails containing non-descript oils and what appears to be a white chemical product. Once again, all of those fluids are exposed to the elements and to each another. That automatically makes all of them hazardous waste. The only way to be sure used oil does not become contaminated with hazardous waste is to never mix it with anything else and store used oil separately from all solvents, chemicals, and other incompatible products.
• List all oil and non-oil products used in the plant and work with your oil-disposal partner to decide which products are to be treated as recyclable used oil, waste oil, and hazardous materials (chemicals and non-oils).
• Use closed, dedicated containers for used oil, waste oils, and other products stored in the same area.
• Log any bulk transfer of oils into the tanks.
• Record all products being held in the area on a manifest and log their release to the disposal company.
• Retain all records in a accordance with the company’s record-retention schedule.
Spill controls are mandatory.
Although the photo above also shows evidence of a contained spill around the oil pallet, the contaminated spill material hasn’t been removed and is itself an uncontained, contaminated oil product.
In accordance with most safety legislation, every oil-storage facility will generally be required to have and keep the following information and equipment up to date:
• spill contingency plan and procedures
• spill-control equipment
• fire plan
• emergency-evacuation plan.
If a site’s oil-storage building is indoors or in a closed area, it will require ventilation as regulated by local building codes.
The cost of doing business
Disposing of hazardous waste can be time-consuming and costly. Research local oil recyclers and hazardous-waste haulage companies to determine what they charge for their services. Some will handle both oil reclamation and disposal of hazardous waste. Such organization should be able to work with your site to set up a value-based program that adheres to all local regulations. MT
Editor’s Note: Recycling and disposing of old oil is closely associated with lubrication-consolidation efforts in a plant. This feature addresses that topic with insight from Des-Case.
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), Bannister specializes in the implementation of lubrication-effectiveness reviews to ISO 55001 standards, asset-management systems, and development of training programs. Contact him at firstname.lastname@example.org or telephone 519-469-9173.
Don’t set up a lube program without one or more of these multi-taskers.
By Ken Bannister, MEch Eng (UK)CMRP, MLE, Contributing Editor
The ability to control contamination is an important aspect of any lubrication-management program, especially where lubricant cleanliness is concerned. A constant supply of clean oil is essential to lubricant life and, more important, bearing life.
One of the most efficient and practical tools available to ensure lubricant cleanliness is the portable filter cart. In a typical industrial environment, portable filter carts are used to transfer and clean all types of lube, gear, and hydraulic oils. The carts’ three principal applications in a lubrication-management program are:
• transferring oil from its original container into a machine reservoir
• pre-filtering and cleanup of virgin stock (new) oil in preparation for machine use
• reconditioning and cleanup of oil currently in service.
In addition, use of specialized filters on the outlet side can extract any free and emulsified water present in the oil.
The primary function of any filter cart is to filter fluids. A typical cart design will employ a two-stage filtration approach in which a gear pump is connected to both filters. The inlet, or suction, side is the first-stage, low-pressure side (approximately 5 psid) designed to capture larger contaminant particles exceeding 150 microns in size.
Oil is pumped through the inlet filter to the second-stage, high-pressure (approximately 25 psid) outlet (or delivery side) filter designed to capture much smaller particulate matter that can be filtered to less than 5 microns in size, depending on the filter rating used.
Listen to the latest in a series of monthly lubrication-related podcasts with Ken Bannister. The May podcast focuses on the selection of and best practices regarding portable filter carts.
How clean should your oil be?
Oil cleanliness is universally measured using the ISO 4406 cleanliness code rating system. This is a standard that quantifies the number of contaminant particles, 4, 6, and 14 micron in size, that are present in a 1-ml lubricant sample and compares them with a particle concentration range, resulting in an ISO-range number value.
For example, a 19/17/14 lubricant sample value (typical of new oil) translates to the presence of 2,500 to 5,000 particles >4 microns in size, 640 to 1,300 particles >6 microns in size, and 80 to 160 particles >14 microns in size present in the oil sample.
When new or virgin stock oil is received from the supplier, many sites believe they are receiving a “ready-to-use” product. This is not always the case, as depicted in the table. New oil is typically received around a 19/17/14 ISO cleanliness level that may only be suitable for non-critical gear systems. All other applications will require the oil to be cleaned and polished by passing it through a filtration system prior to use in service.
The table also notes that “In service” oil dirtier than 19/17/14 is unsuitable for any lubrication or hydraulic system. Such oil will require replacement or cleanup using a kidney loop set-up with a portable filter cart.
The number of passes through the filter cart to achieve the appropriate cleanliness level will depend on the “start” and “finish” cleanliness level and the filter types and rating in use. Oil analysis will be required to establish cleanliness levels. Choosing a suitable combination of pump and filter size/type will require consultation with the filter-cart manufacturer who will need to understand your working environment and type/viscosity of oil(s) you use.
The rate of cleanup (speed) will depend on the reservoir size, pump flow rate, and the cleanliness-rating delta. What can be measured immediately is the time to perform one complete filter pass through the cart, as calculated using the following formula:
(Reservoir size x 7)/filter-cart flow rate = time for a single-pass filtration
Example: 60 gal. x 7/10 gpm = 42 min. for a single-pass filtration (1 x filtration of reservoir capacity)
If the plant’s lubricants are consolidated and cleanliness levels are known, a matrix can be developed to determine how many passes are required to filter to an acceptable cleanliness level.
As in all other facets of maintenance, there are a number of best practices associated with the use of portable filter carts:
• Work with the filter cart supplier to determine the right pump and filter choice for your plant requirements.
• To eliminate cross contamination of lubricants, each filter cart must be dedicated to a single lubricant use for transfer and cleaning of lubricants. Pilot the filter cart program with the most-critical and/or most-utilized plant-lubricant type.
• Always clean the unit after each successful transfer operation, paying particular attention to the wand ends and open drip tray under the filters and pump area. Open oil is a dirt attractant and can be transferred unwittingly if the cart and its components are not kept scrupulously clean.
• Unless specified, most filter carts are sold with open-end transfer wands fitted to the delivery and suction hose ends designed to slide easily into the reservoir openings of the donor and recipient reservoirs. In a program designed to filter contaminants from the oil, this type of delivery fitting can allow moisture and dirt contamination into the respective reservoirs during the transfer process. To combat this, and ensure a contamination-free transfer process, fit the filter cart delivery/return hose ends and reservoir fill/drain ports with quick-lock-style couplings. As the reservoir is now airtight, it will also require a quality desiccant-style breather to be fitted and, in the case of larger capacity reservoir, a closed-loop expansion tank.
• Specify kink-resistant flexible suction and delivery hose to prevent pump cavitation. Clear hoses allow a visual reference of the oil flowing through the lines.
• The cart’s electric motor will require access to electricity. Ensure that an electrical outlet is within easy reach of the unit’s electrical cord. If the cord is short in length, consider mounting a retractable electrical cord caddy on the unit with enough cord length to reach the nearest electrical outlet.
• Paint a lined box similar to a lay-down area as close as possible to the oil reservoir that’s to be serviced. This allows a cart to be positioned and used quickly without obstruction, and within reach of its hose and wand assemblies.
• Place the cart on a preventive-maintenance (PM) check program prior to every use to ensure the unit’s filters don’t go into bypass mode from being too dirty. 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 55001standards, asset-management systems, and training. Contact him at email@example.com, or telephone 519-469-9173.
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:
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.
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.
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 firstname.lastname@example.org, or telephone 519-469-9173.
Your gauge of choice can have a significant impact on your PM efforts.
Use performance measurements to focus and improve your lubrication program and overall uptime.
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.
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.
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 email@example.com, or telephone 519-469-9173.