SKF packaged solutions “pump up” uptime Hydrocarbon processing pumps battle hot, corrosive conditions that eventually defeat bearings and cause premature failure. The resulting downtime costs the industry hundreds of millions of euros a year in maintenance and lost productivity. While you can’t change the harsh operating environments in your facility, you can change the way you defend your pumps – and your operating budget. The SKF pump solution SKF ® offers a “systems approach” of products and services to overcome the heat, contaminants, inadequate lubrication, and shaft misalignment that contribute to bearing failure and pump downtime. Drop-in replacement with SKF Explorer bearings – which can outlast conventional bearings by as much as 300% – is a simple, cost-effective way to extend pump life. Advanced SKF alignment and mounting services help achieve longer bearing life and quieter, smoother pump operation. And SKF automatic lubrication systems and condition monitoring services add another line of defense against pump downtime. Combined with the expertise of the SKF reliability specialists who will help you implement it, this “systems approach” of products and services offers an optimum means of extending Mean Time Between Failure (MTBF) and cutting maintenance costs for your facility’s pumps. SKF pump solution components include: SKF Explorer bearings Laser shaft alignment tools SKF induction heaters SKF seals Condition monitoring tools and services • • • • • Cut maintenance costs and extend MTBF on pumps HYDROCARBON PROCESSING Benefits Extends Mean Time Between Failures (MTBF) Reduces maintenance costs Reduces vibration and noise Easier, safer, and more accurate mounting of bearings Single-source responsibility Typical applications Crude charge Reflux and tops Intermediate reflux Gas oil Tops crude Naptha, paraffin and diesel Flasher bottom Slurry • • • • • • • • • • • • • For more information on SKF products and solutions for the hydrocarbon processing industry, contact your SKF Authorized Distributor.
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Transcript
SKF packaged solutions “pump up” uptime
Hydrocarbon processing pumps battle hot, corrosive conditions that eventually defeat bearings and cause premature failure. The resulting downtime costs the industry hundreds of millions
of euros a year in maintenance and lost productivity. While you can’t change the harsh operating environments in your facility, you can change the way you defend your pumps – and your operating budget.
The SKF pump solution
SKF® offers a “systems approach” of products and services to overcome the heat, contaminants, inadequate lubrication, and shaft misalignment that contribute to bearing failure and pump downtime.
Drop-in replacement with SKF Explorer bearings – which
can outlast conventional bearings by as much as 300% – is a simple, cost-effective way to extend pump life.
Advanced SKF alignment and mounting services help achieve longer bearing life and quieter, smoother pump operation. And SKF automatic lubrication systems and condition monitoring services
add another line of defense against pump downtime.
Combined with the expertise of the SKF reliability specialists who will help you implement it, this “systems approach” of products and services offers an optimum means of extending Mean Time Between Failure (MTBF) and cutting maintenance costs for your facility’s pumps.
SKF pump solution components include:
SKF Explorer bearings
Laser shaft alignment tools
SKF induction heaters
SKF seals
Condition monitoring tools and services
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Cut maintenance costs and extend MTBF on pumps
HYDROCARBON PROCESSING
Benefits
Extends Mean Time Between Failures (MTBF)
Reduces maintenance costs
Reduces vibration and noise
Easier, safer, and more accurate mounting of bearings
Single-source responsibility
Typical applications
Crude charge
Reflux and tops
Intermediate reflux
Gas oil
Tops crude
Naptha, paraffin and diesel
Flasher bottom
Slurry
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For more information on SKF products and solutions for the hydrocarbon processing industry, contact your SKF Authorized Distributor.
Increase the return on your plant machinery investment with SKF.The SKF 360˚ Solution programme embodies our goal to help you get more out of your plant machinery and equipment investment. This means lowering your maintenance costs, or raising your productivity, or both! Here’s an example of the SKF 360˚ Solution programme at work in the petrochemical industry.
Refinery realises significant maintenance cost savings with SKF pump solutionsUsing a combination of SKF Explorer bearings, laser shaft alignment, and improved mounting and lubrication methods, a major refinery was able to increase the Mean Time Between Failure (MTBF) among a large percentage of their pumps from 18 months to 54 months, over a period of 10 years. The posi-tive financial impact of this for the refinery is shown below.
Publication 6385 EN • October 2006
SKF 360° Solution ROI calculations are from the SKF Documented Solutions Programme. Ask your SKF Authorized Distributor for more details.
Net benefit ....................................................................8 559 657 €
SKF solution ROI over 54 months .............................. 497%
Achieve optimum centrifugal pump performance
By David R. Mikalonis, SKF USA Inc.
ChemicalProcessing.com
Proper bearings, lubrication and seals as well as proactive maintenance are crucial.
Centrifugal process pumps often must perform in hostile and stressful operating conditions. As a result, the likelihood of their premature failure increases over time — raising risks of incurring considerable costs and lost productivity from downtime. With pressures mounting to achieve better pump reliability, reduced maintenance and lower energy consumption, the quest to identify and implement viable solutions for relief ranks as a top priority.
Evaluating pump maintenance and repair practices — paying particular attention to bearings, lubrication and seals — can serve as a crucial tool for attaining higher levels of pump reliability and longer service life. The proper bearings, lubricants and sealing systems can boost economies and efficiencies and, when supported by proactive condition-monitoring approaches, can help extend the service life of pumps and minimize the need for untimely pump replacement or rebuilds. Selecting the bearings Bearings in centrifugal pumps support hydraulic loads imposed on the impeller, the mass of the impeller and shaft, as well as loads due to couplings and drive systems.
They also keep the shaft axial and radial deflections within acceptable limits for the impeller and shaft seal.
A variety of conditions tend to continually put bearings in many centrifugal pumps to the test. The bearings often will face high axial loads, marginal lubrication, and high operating temperatures and vibration, all while the bearings attempt to minimize friction — which, if uncontrolled, can result in power loss, excessive heat generation, increased noise or wear, and early bearing failure.
All these influences can dramatically impact the service life and reliability of bearings and, in turn, pumps. So, first and foremost, evaluate bearings (types, designs and arrangements) in the context of their anticipated operating environment.
Suitable bearings are available to satisfy even the most difficult conditions faced by centrifugal pumps. As an example, thrust-type bearings (to support axial loads created by hydraulic forces in the pump) include various versions of angular contact ball bearings that suit many applications:
Single-row 40° angular contact ball bearings. These are the most popular API pump thrust bearings in service today and generally are used in moderate-speed centrifugal pumps where high thrust loads can be expected.
Variations designed with robust machined brass cages suit applications where thrust loads vary greatly during operation and periods of ball skidding are likely. These bearings also will resist destructive vibration forces should cavitation occur. They normally are mounted in back-to-back paired arrangements to accommodate reversing thrust loads and to provide
adequate shaft support to promote long mechanical-seal life.
Pay particular attention to internal clearance. When mounted and at operating temperature, the bearings should have enough residual internal clearance to operate cool but not so much as to promote skidding of the inactive bearing.
Double-row angular contact ball bearings. These (Figure 1) are used extensively as the primary thrust bearing in ANSI standard centrifugal pumps and some older API-style pumps. The most effective types feature a Conrad-design, ABEC-3 precision tolerances, a 30° contact angle per row, one-piece heat-treated pressed steel cages, and multiple sealing options. Because their contact angles diverge outwardly, the bearings exhibit greater rigidity and increased resistance to misalignment. As with paired single-row
angular contact ball bearings, operating conditions dictate the need for normal or greater-than-normal (C3) internal radial clearance.
Design variations are becoming more popular. Examples include steeper (40°) contact angles to deliver increased thrust capacity, machined brass cages to offer robust performance under heavy-duty and poor-lubrication conditions, reduced axial internal clearances to promote load sharing between the two rows of balls and a reduced possibility of skidding in the inactive ball set, and ABEC-3 (P6) tolerances to contribute better control of the bearing’s mounted condition and smoother bearing operation.
Specialized angular contact ball bearing sets. For pumps with minimal thrust, paired 15° angular contact bearings generally suffice. However, for high-thrust-load conditions, use high-performance matched sets of 40° and 15° angular contact ball bearings to provide improved robustness by reducing the susceptibility of ball skidding in the inactive bearing. These designs are intended for centrifugal pumps that don’t reverse or only periodically reverse.
The primary benefit of these sets is that the 15° bearing is designed with considerably less internal clearance than the 40° bearing, making it less susceptible to centrifugal and gyroscopic forces producing ball sliding and shuttling, while providing additional radial stiffness to maintain integrity of the shaft and seals.
Split-inner-ring angular contact ball bearing sets. These, by matching a single-row 40° angular contact ball bearing with a split-inner-ring ball bearing or four-point contact ball bearing, are designed to accommodate thrust loads in either direction. This arrangement commonly is used in vertical pumps to handle the primary thrust load but also can be utilized in horizontal arrangements, provided the loading is such that the split-inner-ring bearing doesn’t support radial load on its own.
Because two bearings acting in tandem share the thrust load, this arrangement offers an extremely high thrust-carrying capacity. Reversing thrust load can be accommodated on the backside of the split-inner-ring bearing. These two-bearing sets behave like “triplex” sets with the added advantage of saving space and costs.
Supplying the lubrication Proper lubrication for pump bearings is essential for reliable service — improper lubrication accounts for more than 30% of bearing failures, according to some studies. Good lubricants primarily provide a separating film between a bearing’s rolling elements, raceways and cages to prevent metal-to-metal contact and undesired friction that otherwise would generate excessive heat that could cause wear, metal fatigue and potential fusing of the bearing contact surfaces. Adequate lubrication for bearings also acts to inhibit wear and corrosion and help guard against contamination damage.
The common methods for the effective lubrication of pump bearings include:
Grease. Easy to apply, grease can be retained within a bearing’s housing and provides extra sealing protection. Depending on the rotational speeds and operating temperatures, relubrication may be required to combat short grease life. When the operating conditions allow, “greased-for-life” bearings, which eliminate requirements for relubrication and related maintenance tasks, can offer an attractive alternative.
Oil bath. This option establishes an oil level at the center of the bearing’s bottom rolling element and represents the comparative baseline of bearing friction among the lubrication methods. Best results over time can be achieved using a constant-level oiler.
Oil ring. In this method, an oil ring is suspended from the horizontal shaft into an oil bath positioned below the bearings. The rotation of the shaft and ring flings oil from the bath onto the bearings. The lower oil volume in the bearing reduces the viscous friction in the bearing system to allow higher shaft speeds and better cooling.
Oil mist and air-oil. Here, oil is atomized and carried by an air stream to the bearing. Among all pump bearing lubrication approaches, this one generates the least amount of friction (allowing rotational speed to be based on the bearing design instead of lubrication limitations) and creates a positive pressure within the bearing housing (fending off invasive contaminants).
Regardless of lubrication method, always specify lubricant according to the demands on vertical shafts and resistance to solids, pressure, temperatures, loads and chemical attack. Where pump locations may be difficult to access, fully automatic systems can be integrated to enable timely, proper and effective delivery.
Sealing the system Bearing seals in centrifugal pumps handle four crucial tasks. They retain lubricants or liquids, exclude contaminants, separate fluids and confine pressure. So, the seals have their work cut out for them. Solid contaminants, depending on particle size, hardness and brittleness, will produce either indentations or wear on the bearing surfaces; water will affect the efficiency of the lubricant; and contamination in the lubricant can dramatically reduce bearing life.
When a seal fails, contamination can infiltrate the bearing area, entering the lubricant and then the bearing. In addition, loss of lubricant from the bearing can lead to dry-running operation, which ultimately can cause bearing failure.
The choice of seal for centrifugal pump bearings depends on the unique demands and operating conditions of the application. Keep in mind, though, that the bearing and sealing arrangement represent an integrated system.
Dynamic radial seals generally are the best choice for centrifugal pumps. These seals create the barrier between surfaces in relative motion (one usually stationary while the other rotates).
Typically, radial shaft seals incorporate:
Steel or elastomer shell. This is bonded to the sealing material and enables the requisite interference fit of the seal in the housing bore to be maintained (as well as facilitates proper installation); and
Elastomer sealing lip. Usually installed against the shaft, this provides dynamic and static sealing against the shaft and features a sealing edge formed by pressing, cutting or grinding. Most sealing lips are made from a formulation of nitrile rubber.
However, materials specifically for use with fuels, industrial fluids and highly compounded lubricants are available.
Seal selection ultimately must be based on a thorough review of application parameters and environmental factors. Particularly in pump applications, for example, seals will be exposed to relatively constant pressure differentials — making pressure seals (in which the seal cavity is pressurized) the preferred choice.
Due to the nature of their design and the harsh operating environment, seals usually provide a much shorter life than the components they protect. So, don’t fall into the common but unfortunate habit of scheduling seal replacement only at intervals dictated by requirements of other components such as bearings. Many bearing failures can be prevented if seals are replaced when the first signs of wear or leakage have been detected.
To get an inkling of how long seals should last, consider the amount of contamination a seal will encounter, cycle times, speed and heat. Of course, contamination isn’t the only reason for premature seal failures. Others culprits can include:
• poor selection;
• improper installation, resulting in leakage; and
• change of lubricant, causing adverse reactions in common sealing materials.
To head off problems, institute a rigorous seal inspection and replacement program.
Don’t automatically replace a failing seal with another of the same design. For example, if an oil analysis shows higher-than-anticipated ingress of contaminants, it may be time to upgrade the entire sealing arrangement (perhaps using a more chemically resistant material or adding elements to bolster the sealing system). Or, in cases of excessive wear, it may make sense to switch to a non-contact labyrinth seal design.
Monitoring pump health Taking a more proactive approach to pump maintenance can play an important role in boosting uptime. So, it’s not surprising there’s increasing interest in condition monitoring. This involves regular measurement and analysis of key physical parameters such as vibration and temperature, and enables detection of pump system problems before they can result in unscheduled downtime, high repair or replacement costs, and lost productivity.
Basic instruments can assess and report on vibration, temperature and other parameters. More advanced tools include online surveillance systems and software that can deliver real-time data for review and foster more timely remedial action should this become necessary.
Many problems will manifest as vibration, which is widely considered the best operating parameter to judge pump-train condition. Vibration can detect problems such as imbalance, misalignment, bearing oil-film instabilities, rolling bearing degradation, mechanical looseness, structural resonance and a soft foundation.
Vibration measurements are quick and fairly non-intrusive because pump equipment remain undisturbed. In addition, established industry standards identify vibration levels for specific types of equipment.
A significant increase in “overall vibration” (the sum of all vibration within the frequency range of the instrument) compared to a baseline value will signal an impending problem, allowing it to be addressed before equipment failure occurs.
A wide range of technologies from hand-held vibration monitoring tools such as low-cost vibration pens and overall vibration meters to more sophisticated portable data collectors and related instruments combining compact size with data storage capabilities (Figure 2) can handle data collection.
Figure 2. This instrument provides a range of testing and analysis techniques as well as data recording.
Regular monitoring of temperature also can shed light on system conditions. It’s a useful indicator of mechanical condition or the load applied to a specific component such as a thrust bearing. For example, as a thrust bearing fails, friction causes its temperature to rise. Thermocouple sensors installed in the housing of a bearing and measuring temperature changes within the bearing or lubricant can send a signal about problems beginning to develop, enabling appropriate maintenance actions to be scheduled.
The technology toolbox for condition monitoring also includes online surveillance systems. These perform round-the-clock monitoring of pumps regardless of their location. Such technology can collect data continuously or at a predetermined frequency from permanently installed sensors and then send its findings to a host computer for subsequent analysis.
Involving the operator Operators can play a pivotal part in proactive maintenance strategies and boosting pump uptime — by serving as the “eyes and ears” in a plant to detect equipment faults before problems can escalate.
Under Operator Driven Reliability (ODR), the operators perform basic maintenance activities above and beyond their classic duties (Figure 3). ODR enlists operators to observe and record the overall health of pumps by checking for leaks, listening for noises, monitoring temperature, lubrication and vibration, and taking responsibility to identify any abnormal equipment conditions — and, in some cases, to respond with the appropriate corrective actions. Hand-held technology allows operators to translate early detection of developing problems into prompt corrective action.
Figure 3. Operators can serve as a plant’s eyes and ears to detect developing problems.
Operators can monitor:
Bearings. Detecting faults in a bearing’s outer ring, inner ring, rolling elements and cages also can suggest potential problems elsewhere in a pump system.
Lubrication. Spotting under- or over-lubrication within pump bearings can lead to a more-effective lubrication program.
Shaft. Checking pump shafts can uncover imbalance, misalignment, bending, rub, excessive thrust and looseness.
Seal integrity. Watching for leaks and inspecting lubricant cleanliness can provide an indication of the condition of pump seals.
Foundation. Inspecting pump foundations and bases can warn of looseness caused by loose or corroded hardware, deteriorated grouting, base-plate straightness, and pump housing soft- and sprung-foot conditions.
Vane blade pass. It’s important to look for conditions such as wear, blade/vane failure and looseness of shaft fit, as well as contamination and obstructions due to foreign debris within the process.
Impeller clearance. Proper settings are key for optimum performance and represent a good indicator of pump impeller and wear ring conditions.
Cavitation and flow turbulence. Such problems can impact performance and overall pump health over time.
Temperatures. This should involve monitoring several aspects, including bearings, lubrication, sump and the pump housing.
Process parameters. Shaft speed, head pressure, discharge pressure, differential pressure, vacuum, suction, flow, reservoir levels, valve positions and product consistency all deserve attention.
Coupling operator oversight and effective proactive maintenance with proper pump bearings, lubrication and seals can contribute to smoother flowing operations, better performance and service life and, ultimately, optimum uptime.
David R. Mikalonis is sales manager, pump industry, for SKF Industrial Division, SKF USA Inc., Kulpsville, Pa. E-mail him at [email protected].
A bearing must always be subjected to a given minimum load in order to prevent skidding of the balls along the raceway•Adhesive wear, increased friction, increased heat, lower bearing
service life
Bearings running under high speeds, high accelerations or rapid changes in the direction of loading are particularly susceptible• Inertia forces on the balls and cage and the friction in the lubricant have a
Extra internal clearance and centrifugal forces cause the ball to contact at different angles between the inner and outer ring. This causes skidding as the local rotational speeds vary and the axis of rotation varies.
Best practices for lubing API centrifugal pump bearing housings Rojean Thomas Tags: bearings, maintenance and reliability
More and more plants have goals focused toward extending the mean time between repairs (MTBR) for their rotating equipment, which includes centrifugal pumps for use in petroleum, petrochemical and natural gas industries. Maximizing the lubrication effectiveness in API process pumps will be a big contributor toward meeting this goal. In this article, you will learn about optimal ways of lubricating the bearings in API process pumps, including data on discs vs. oil ring lubrication, maintaining the proper level and contamination control. Bearings that are properly lubricated with minimal contamination will operate at lower temperatures and for longer periods of time.
Introduction
This article is focused on horizontal centrifugal API (American Petroleum Industry) process pumps but many of the topics/concepts can also apply to ANSI pumps. There have been various studies done on why rolling element bearings fail prematurely, and consistently, the No. 1 cause can be attributed to poor lubrication. One particular study stated that 50 percent of damage is caused by defective lubrication. Poor or defective lubrication can be classified as:
The API Standard 610 requires a minimum bearing life (L10) of 25,000 hours with continuous operation and rated conditions and at least 16,000 hours at maximum loads and speed. The L10 life is the number of revolutions that 90 percent of a group of identical bearings under identical conditions will endure before the first sign of fatigue failure occurs. If we assume 80 percent run time per year (292 days per year), the minimum expected bearing L10 life would be 3.5 and 2.2 years, respectively.
As cited above, poor lubrication will cause 50 percent of these bearings to fail before any signs of fatigue occur. These failures can occur within a few hours after installation, after one year, or just before fatigue. At what point prior to fatigue do these bearings fail can be extended by following the 5 R’s of Lubrication: Right lubricant, Right quantity, Right location, Right time and Right quality.
Many companies are requesting L10 life ratings of 40,000 hours (5.7 years) when purchasing new pumps, but it is still important to address poor lubrication practices.
Incorrect Lubricant
Anti-friction bearings in process pumps can either be grease, mineral oil or synthetic oil lubricated. The primary purpose of oil, or the oil constituent of grease, is to separate the roller elements and raceway contact surfaces, lubricate the sliding surfaces within the bearings, and provide corrosion protection and cooling.
Viscosity is the single most important property of a lubricant. Use of the correct viscosity lubricant for the speed, operating temperature and load ensures the development of a full oil film between rotating parts. When the incorrect viscosity is used, the load-carrying ability of the lubricant is negatively affected. The oil degrades to a point where it is too thick to penetrate between the surfaces and the oil supply may not be adequate to prevent sacrificial contact. Viscosity is influenced by load, temperature, water, contaminants and chemical change. The OEM operation manual should be consulted for recommendations on viscosity, but it is also important to measure the oil sump operating temperature since viscosity decreases as temperature increases.
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Table 1: SKF Recommendation for Ball Bearings in Pumps
Oil in process pumps is typically an ISO grade 46, 68 or 100. These numbers relate to the Kinematic viscosity in centistokes. The oil is usually hydrocarbon oil, although synthetic oils are sometimes used for specific lubrication applications. The viscosity of synthetic oil is less sensitive to temperature changes and more widely used when temperature fluctuations exist. If temperature also exceeds 100 degrees Celsius (212 Fahrenheit), a synthetic is recommended as the oxidation rate of mineral oil accelerates faster at higher temperatures.
Incorrect Quantity of Lubricant
Selecting the right lubricant for the application was the first step, and the next is to determine the correct quantity is initially applied and maintained. It is important to understand the design of the bearing housing assembly and, more specifically, the designed oil level.
Oil Level – Design
The most common types of methods for lubricating rolling element bearings in horizontal process pumps are:
• Grease
• Oil splash (direct contact, rings or flingers)
• Pure oil mist
• Purge oil mist
The use of grease is primarily limited to lower horsepower pumps where the parameters are in the size and speed range of rolling element bearings. Oil splash lubrication is the most common method utilized. Oil splash designs include direct contact, oil rings, flinger discs or combinations of each.
In direct contact, as the shaft rotates, the rolling elements in the bearing make contact with a level of oil. The bearings should not be submerged in the oil more than one-half the diameter of the lowest rolling element or ball (Figure 2). Oil rings are utilized where speed or loads are factors and the oil is not in direct contact with the bearing. Oil rings make contact with the oil and provide splash type lubrication without direct bearing contact. Flinger discs are similar to oil rings in that the oil is not in direct contact with the bearing. The discs make contact with the oil and provide splash type of lubrication. Oil rings are more dependent on the shaft speed relative to the depth of submersion, but a good rule of thumb to use is to use three-eighths of an inch
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at the deepest point. Flinger disks are less susceptible to problems of over-lubrication since they are attached directly to the rotating shaft and they should also submerge about 3/8 inch into the oil. A combination design would incorporate a metallic disc and direct contact. The bearings directly contact the oil and the disc provides additional splash lubrication for cooling.
The basic concept of the oil mist lubrication system is dispersion of an oil aerosol into the bearing housing. Air atomizes the oil into particle sizes of one to three microns. Airflow transports these small oil particles through a piping system into the pump housing which flows through bearings. It is a centralized type of low-pressure lubrication system. In pure mist lubrication, the oil/air mist is fed under pressure to the housing. There is no reservoir of oil in the housing and oil rings are not used. Purge mist lubrication utilizes the same principles of pure mist, but a reservoir of oil in the housing exists. A slinger/flinger disc or oil rings can also be used to provide splash lubrication.
Low Level
In a low-level operating condition, the bearing will not receive enough lubricant necessary for proper film strength – a precursor to surface contact, skidding and possible catastrophic failure. Without enough oil to prevent friction, thermal runaway can happen quickly to a steel bearing. As the temperature of the bearing increases, the ball and race both expand, which creates an even tighter fit. This increases the temperature even more, and the cycle continues to a rapid, catastrophic failure.
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A low level of oil will affect all types of oil splash lubrication. In direct contact, there will be insufficient film strength and rings or discs may not be able to pick up enough oil to satisfactorily lubricate the bearings.
High Level
In a high-level operating condition, churning of the lubricant will occur, accelerating the oxidation rate due to excessive air and elevated temperatures. It is a common mistake to believe that more is better – especially when it comes to oil sump lubrication. Too much oil can affect the operation of oil rings, flingers and direct bearing contact. Another result of high lubricant levels is leaking seals. If the oil level is too high, the ring will become submerged and no longer sling the oil. Flinger discs are less susceptible to this as they are directly attached to the shaft.
Maintaining Proper Level
Oil sump lubrication does not require that a specific level be maintained for proper bearing load – only that oil levels do not reach critically low or high points (Figure 3).
Figure 3.Typical Oil Level Conditions
Maintaining the proper quantity of lubricant is perhaps the easiest means of increasing lubrication life and effectiveness. Consult with your equipment manufacturer or the operation manual for recommended oil levels, optimum lubricating equipment and preferred practices. The majority of equipment will have an external marking on proper oil level that is either cast into the housing or a tag is applied.
One of the most widely used methods of maintaining the proper level lubricant in a bearing housing is the constant level oiler (Figure 2). The constant level oiler replenishes oil lost by leakage through seals, vents and various connections, and plugs in the bearing housing. Once
Page 5 of 10Best practices for lubing API centrifugal pump bearing housings
the proper level has been set, replacing the oil in the reservoir is the only required maintenance. View ports (bullseyes) can also be used to verify proper oil level.
Constant level oilers have a “control point” that must align with the proper oil level of the equipment. The oiler is installed on the equipment and oil is filled to the proper level. All constant level oilers require air to function properly. If the oil level within the sump lowers, the seal at the control point is broken, allowing air to enter the reservoir, displacing the oil until the seal is re-established. If the constant level oiler is set correctly and there is oil in the reservoir, the equipment will always have the optimum oil level within the sump.
Contaminated Lubricant
The quality of lubrication is affected by contamination, which is a large contributor to premature bearing failures. The major types of contaminants are particulate, moisture, incompatible fluids and air entrainment. Particles impede lubricant performance and further localize pressure on components causing denting, fatigue, spalling and abrasion to the surface of mating surfaces. Water will affect the lubricant’s ability to provide a proper fluid film, causing premature failure and excessive wear. Corrosion, cavitation, and premature oxidation and filter plugging of the oil are other symptoms of water contamination. Air contamination affects oil compressibility, causes poor heat transfer, film strength loss, oxidation and cavitations.
The sources of these contaminants are:
• Generated contamination
• External ingression of contaminants
• Maintenance induced
Generated Contamination
Particle contamination can be generated during the break-in or during operation of the pump. Oil rings are typically made of bronze and are sensitive to horizontality of the shaft, speed and oil levels. They can tend to skip or hang up due to these sensitivities and make contact with other components. The rings will wear, being a softer material, and particle debris is generated. These small particles can penetrate the critical area between the rolling elements and the raceway resulting in abrasive wear.
External Ingression of Contaminants
Pressure differentials between the equipment housing and surrounding atmosphere are a leading cause of contamination ingression. Pump operation where housing temperature fluctuations occur during frequent on/off running conditions, process fluid temperature changes, outdoor use and air flow over the pump create this atmospheric exchange as pressure is equalized. During this air exchange, contamination (dirt, water, etc.) from surrounding environment is “breathed” into the oil sump through vents, seals and oilers.
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Housing components – including oilers, seals and vents – when specified properly can be very effective in preventing contamination. For many years, constant level oilers were used to maintain oil levels. Most of these were vented to the surrounding atmosphere, which can lead to contamination ingression to the housing sump. By switching to a non-vented oiler and removing vent plugs, ingression can be significantly reduced. Bearing isolators are used to prevent lubricant leakage and contaminant ingress. Labyrinth-type bearing isolators are most widely used on horizontal pumps. Bearing isolators allow increased pressure created by normal pump operation to vent through the seal and have proved to be very effective at reducing contamination ingression. The rotor and stator are not in contact, which allows for the venting to occur while preventing wear – prolonging the life of the seal. Magnetic or face seals are used to prevent damage to bearings due to contamination and lubricant leakage. Face seals are characterized by optically flat stationary and rotating faces loaded together by magnetic force or springs.
Maintenance Induced
Contamination can exist in the oil prior to being put into the equipment. It cannot be assumed that new oil is clean. Proper storage of oil and proper dispensing containers will also decrease the possibility of water or other contaminants from entering into the bearing housing. Proper care should be taken during the pump rebuild process to ensure any contamination is properly removed.
Lubricant Degradation
All lubricants will degrade over time, requiring the oil to be changed. The frequency of these changes can be extended by maintaining the quality of the lubricant.
Elevated operating temperatures are a major contributor of oil oxidation. Combined with air, particulate and water contamination, the chain reaction of oil oxidation begins. Additives are affected first, followed by the basestock, which leads to machine and component surface wear and fatigue. For every 8 degrees C (18 F) increase in oil operating temperature, the oxidation rate doubles. This can be significant when considering pump operating temperatures are frequently near, or above, 60 C (140 F). By simply lowering the operating temperature of the oil to 50 C (122 F), a 50 percent reduction in the rate of oxidation would be realized – doubling the effective life of the oil.
The most basic methods to reduce (or maintain) lower oil operating temperatures are:
• Use the correct viscosity oil.
• Use quality oil.
• Use the right amount of oil.
• Keep the oil clean.
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Air entrainment is a primary source of oxygen in the oxidation failure of oil. New oil can contain as much as 10 percent air at atmospheric pressure. Splash-type bearing housings utilizing flinger rings or slingers are all aeration-prone applications. Excessive aeration has a negative effect on acid number (AN), oil color, film strength and viscosity. In addition, air entrainment can lead to accelerated surface corrosion, higher operating temperatures and oil varnishing.
Operating temperatures can vary with each type of lubrication method. The graph below was based on laboratory testing measuring operating temperature of the oil sump from startup until the temperature leveled off. Two tests were run using ISO 68 weight oil and operating speed of 3,600 rpm. One test had the oil level at mid-ball of the lowest rolling element and the other had the oil level dropped below and a flexible flinger disc was installed to provide splash lubrication. The flexible flinger disc operating temperature was 9 F lower than the direct contact operating temperature. As stated above, this reduction in temperature results in a 25 percent decrease in rate of oxidation.
Graph 1. Temperature vs. Run Time
Summary
The importance of proper lubrication in process pumps is well known, but achieving it is not always easy. It is important to start with the basics:
Use the correct lubricant for the application Viscosity Mineral or synthetic Understand how the pump is designed to properly lubricate the bearings Oil splash, oil mist Maintain the lubricant at the proper level Constant level oilers Visual verification of level via bull’s-eyes or sight gauges Keep the lubricant free of contaminants Close up housing – reliable seals, breathers, non-vented oilers, expansion chambers Proper storage and handling of lubricant
Page 8 of 10Best practices for lubing API centrifugal pump bearing housings
Oil analysis for verification of type of contaminant Maintain the operating temperature within the pumps’ design parameters Follow above guidelines
Understanding the pumps’ components as well as the surrounding environment is critical for applying the correct and most economical lubrication management system. Obtaining the designed L10 rating of the bearing can be obtainable by eliminating poor lubrication.
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Page 9 of 10Best practices for lubing API centrifugal pump bearing housings
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Demands:• Reliable operations• Available when needed• Safe design
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Bearing cages:• High temperature resistance• Chemical resistance• Fatigue resistance
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The most common cause of pump bearing failure is not fatigueThrust bearings for centrifugal pumps seldomachieve the theoretical life specified by API andANSI standards. This is because pump bearingsusually fail from causes other than fatigue.
Users tend to ignore the fact that bearings aredesigned for specific operating conditions anduse the same bearing for most pump applica-tions. Consequently, the 40O single-row angularcontact ball bearing is applied in applicationswhere it may not be the best choice.
High contact angle vs. low contact angleBearings with low contact angles are designedprimarily for radial loads. Bearings with highcontact angles are most suitable for thrust (axial)loads. Neither bearing does both well andcompromises are often required to achieveacceptable bearing performance. Pump applica-tions are not consistent and loads may vary fromhigh thrust, to near zero thrust, to thrust in theopposite direction. High contact angle bearingsrequire substantial thrust load in order to over-come the centrifugal and gyroscopic forcesacting on the balls and prevent ball skidding. (The higher the contact angle, the more thrustload required.) Low contact angle bearingsrequire little or no thrust load to prevent ballskidding. In addition, remember that only onebearing in a pair, mounted back-to-back or face-to-face, is thrust loaded. However, the unloadedbearing has the same minimum thrust loadrequirement as the loaded bearing. Therefore, anaxial preload must be applied to the pair to besure that both bearings have adequate thrustload to overcome the centrifugal and gyroscopicforces.
Assuring minimum required thrust loadOperating preload plus the external thrust on theprimary bearing is additive and the load may be
high enough to cause unacceptably highoperating temperatures. In this publication, theminimum required thrust load for all bearings islisted. To select the proper bearing, the externalloads, temperatures, shaft fits and speed mustbe considered. Only with this information can anoptimum bearing solution be found. If the aboveconditions cannot be determined, reasonableassumptions must be made in order to make theinitial bearing selection.
Reasonable assumptions are:• Open impellers develop relatively
high thrust load, usually toward theintake (suction)
• Double suction impeller pumps(always closed) usually have little orno thrust load
• Thrust load in a direction opposite theintake (suction) is usually low
These assumptions should be used only as aguide for tentative bearing selection. Once thebearings have operated, the loads can be moreaccurately determined by observing the locationand width of the ball path on the raceways.
MRC offers the widest selection of ballbearings for pumps in the bearing industry A solution exists for nearly every combination ofloads and speeds. Start the selection processby referring to pages 2 and 3. The informationon these pages will guide you to the properbearings. Please contact MRC Bearing Servicesat 1-800-MRC-7000 for additional informationregarding bearing selection.
Bearings for Centrifugal Pumps:Selection of the Proper Bearing Solution
For moderate speed centrifugal pumps. Used as thrust bearing where high thrustloads are expected. A retrofit-free bearing upgrade for API 610 Standard (5th Edition)and ANSI pumps in order to meet ANSI+ standards.
SeePages
20 – 23
ApplicationsFor
Details
Most often used in ANSI pumps with moderate thrust loads. 5200C and 5300C seriesball bearings can also be used in the radial position when the radial load is excessivefor 200S and 300S series single-row deep groove ball bearings.
For moderate speed centrifugal pumps. Used as thrust bearings where highthrust loads are expected. Temperatures, loads, and shaft fits should beknown in order to establish proper preload or axial clearance.
For vertical or other types of pumps where endplay is not a major concern. Thisbearing type will be specified for speeds higher than those accommodated by the97000UP2 series. This product is often used in ethylene stirrer motor applications.
For vertical or other types of pumps, as well as electric motor applications, where anextremely high thrust load is possible. Often used in ethylene reactors and deep waterpumps.
For centrifugal pumps with heavy thrust loads that are not reversing or reverse onlymomentarily. Very effective as a thrust bearing in high speed pumps when directionof thrust is known. Forgiving in an application when thrust loads and temperatureshave not been determined.
Balanced pumps, operating with light or no thrust loads at high speeds. (Forexample, double suction impeller pumps; including the popular axially split case or“between bearings” design.) Similarly, pumps with closed impellers, balance holes,and pump-out vanes that result in light thrust loads.
Steady rest positions to accommodate radial load in centrifugal pumps.Most electric motors use this bearing to accommodate radial loads. Seldom used as a primary thrust bearing in centrifugal pumps.
For high speed centrifugal pumps. This bearing can run at higher speeds than the7200PDU and 7300PDU series and requires less thrust load to maintain propertraction forces between the ball and raceway surfaces.
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14 – 19
SeePages
24 – 29
SeePages
30 – 45
SeePages
58 – 61
SeePages
58 – 61
SeePages
46 – 49
SeePages
54 – 57
SeePages8 – 13
For pumps involving very heavy primary thrust loads. A PumPac “triplex” setcontains two 40° bearings in tandem matched back-to-back with one 15° bearing.
SeePages
50 – 53
3
Bore Preload (unmounted)diameter Class
d GA GB GCover incl. N lbf N lbf N lbfmm min max min max min max min max min max min max
Angular contact bearings require a minimumthrust load to keep the balls tracking at thedesigned contact angle. With less than theminimum required thrust load, centrifugal forcewill cause the balls to track at different contactangles on the outer ring and inner ring raceways.This condition will eventually result in prematurebearing failure.
The thrust load is assured by providing anadequate operating preload. Operating preload is dependent upon:
• Manufactured preload/clearance• Shaft and housing fits• Temperature differential between the
inner and outer rings
Angular contact bearings with a high contactangle require a heavier minimum thrust load than a bearing with a low contact angle.
Due to this fact, bearings with a low contactangle like the MRC PumPac® Diamond 8000BBseries often work best in pumps where little orno thrust load is present and the loads areprimarily radial in nature.
MRC offers a wide range of angular contactbearings for various application conditions,including 15°, 29° and 40° contact anglebearings.
Call MRC Bearing Services at 1-800-MRC-7000 for assistance with selecting the proper bearing.
Why a Preload or Clearance?
MRC 7000PJDU bearings are stocked with the GA execution.
MRC 7000PJDE bearings are stocked with the CB execution.
These charts show the manufactured axial clearanceand preload standards for angular contact sets.
Back-to-back
Face-to-face
Back-to-back
Face-to-face
5
ContaminationA high percentage of ball and roller bearingproblems can be attributed to foreign matterentering the system. Because bearings arehighly sensitive to dirt and moisture, care mustbe taken to keep the bearings and pump cavityclean. Testing has shown that particles passingthrough a filter as fine as 5 microns may causesevere damage. Experience has shown thatlubricating systems that pressurize the bearingcavity, such as air-oil-mist, greatly reducecontamination and increase bearing life.
LubricationGenerally, for ball bearings, it is a good rule toselect an oil that will have a viscosity of at least 70 SUS (13 cSt) at the bearing operating temper-ature. From the chart on page 6, the operatingviscosity of an ISO grade oil can be determined atthe bearing operating temperature. The frequencyof oil change depends upon the operatingconditions and the quality of the lubricant. Mineraloils oxidize and should be replaced at three monthintervals if operated continuously at 212° F (100° C).Longer intervals are possible at lower operatingtemperatures. Synthetic oils are more resistant todeterioration from exposure to high temperaturesand may allow for less frequent replacement. Earlyblackening of the oil strongly indicates a poorlubrication condition and can result from manysources. Multi-grade oils, and lubricants withdetergents and viscosity improvers, are notrecommended.
Shaft and Housing FitsThe standard recommended shaft and housingfits are included in the technical data section foreach individual bearing. The tolerances arethose recommended for bearings mounted onsolid steel shafts. The interference fit betweenthe bearing bore and the shaft journal causes areduction of clearance in the bearings and anincrease in operating preload. Excessive preloadmay result in a hot running condition. Bearingssuch as the 7000PDU that have a GA preload inthe unmounted condition usually employ a lightinterference fit such as an ISO h5 shaft fit. Withbearings that have internal axial clearance CB,heavier interference fits are usually acceptable.Each time a pump or motor is rebuilt, both theshaft diameter and bearing bore should bemeasured to be absolutely sure that both meetspecification and to eliminate the chance ofcreating excessive operating preload.
Stainless steel shafts have a higher coefficient of thermal expansion than carbon steel shafts.When bearings are installed on stainless steelshafts, it may be necessary to reduce theinterference fit and/or select a bearing havinggreater clearance.
Handling and Maintenance
6
MRC Bearing Services 1-800-MRC-7000
Operating Viscosity Chart
7
Recommended for• Service, maintenance, machine repair, and
plant/facility engineering staff of an industrialplant, OEM facility, institution, public utility, or commercial building who use rollingbearings and related equipment.
• Managers and technicians at industrial plantsand OEM facilities responsible for rollingbearing performance and reliability.
All individuals should have direct involvement or responsibility for pump maintenance andinstallation.
Course ObjectiveTo provide attendees with a thorough knowledgeof the design, function, and maintenancerequirements of rolling bearings in a centrifugalpump. Additionally, the course describes thepreferred methods for installation, start up, andrun-in of rolling bearings in pumps. Lastly,troubleshooting and solutions for common pumpbearing problems are covered. Knowledge ofthese areas allows the attendee to be betterprepared to maximize the service life andreliability of pumps in their facility.
Course Schedule/LengthThe course is offered twice during the calendaryear. The first offering is during the spring of the year (April/May) and is held in Hanover, PA;while the second offering is during the autumn of the year (September/October) and is held inSan Diego, CA. The course is two days in length.Successful completion of the course will earnthe attendee 1.6 CEU’s.
Course DescriptionThe topics listed below are addressed in a seriesof lectures, discussions, and hands-onworkshops.
Pump classification and function• Different styles of pumps• General concepts of pump function• Theory and design of centrifugal pumps
(overhung impeller vs. split case)• Basic information on pump curves, head,
pressure/velocity relationships, specificspeed, best efficiency point (BEP), NPSHR vs. NPSHA, and cavitation
• Impeller and volute designs• Origins of radial and axial (thrust) loads
Bearing selection and internal dynamics• Bearing basics• Bearing selections for the radial and thrust
positions of a centrifugal pump; including API and ANSI specifications
• Axial clearance vs. preload• Appropriate contact angle and cage style• Fundamentals of lubrication; including
grease vs. oil, relubrication intervals,lubrication systems, vertical shafts, and compatibility issues
• Behavior of angular contact ball bearingsunder application conditions
Installation, maintenance, and troubleshooting• Shaft and housing fits• Hands-on workshop: Preferred methods of
mounting and dismounting ball bearings• Hands-on workshop: Bearing failure analysis;
including load zone interpretation, staticvibration (e.g. false brinelling), impact (e.g. brinelling), electrical arcing (e.g. fluting),misalignment, overloading, insufficientloading, parasitic loads, contamination,fretting corrosion, and inadequate/ineffectivelubrication
“Bearing Reliability in Centrifugal Pumps” – The MRC Pump School
Please contact our Reliability Maintenance Institute Toll Free: 1-866-753-7378 or visit us on the web at www.skfusa.com/rmi
for official schedule dates, tuition fees, and cancellation policy.
9
200S and 300S series single-row deep groove ball bearings (non-filling slot)
S-type bearings are used in the radial position innearly every centrifugal pump and are commonlyused in electric motors and magnetic drivepumps.
• 30% full of polyurea grease in a bearing with double closures
The API 610 Standard recommends thatbearings, other than angular contact bearings,have greater than Normal internal radialclearance. All MRC single-row deep groove ballbearings, without filling slots, have greater thanNormal internal radial clearance (e.g. C3clearance) as standard.
MRC single-row deep groove ball bearings areassembled with a two-piece, riveted steel cage.API 610 strongly recommends against the use of filling slot bearings. MRC product is API 610compliant.
S-type bearings are available with a wideassortment of seals, shields and snap rings.
Sealed and shielded bearings are prepackedwith a premium quality polyurea grease suitablefor non-continuous operating temperatures ashigh as 300° F (150° C).
Hybrid BearingsMRC 200S and 300S series single-row deepgroove ball bearings are also manufactured ashybrid bearings. These bearings combine SAE52100 steel rings with silicon nitride (ceramic)rolling elements. They are typically utilized inapplications where there is ineffective lubrication,excessive contamination, or stray electricalcurrents. Even under poor lubrication conditions,metal-to-metal contact between the raceways andballs is eliminated due to the use of the ceramicmaterial. Hybrid bearings can achieve a servicelife which is three to thirty times longer than thestandard all-steel bearing under these adverseconditions. Most of the sizes found on thefollowing pages are available as hybrid bearings.For more information, please contact MRCBearing Services at 1-800-MRC-7000 and requestMRC Hybrid Ceramic Ball Bearings publicationM880-600.
A typical application of a single-rowdeep groove ball bearing in the radial
1) Fillet radius indicates maximum fillet radius on shaft or in housing which bearing corner will clear2) Values have been determined through historical application and practice3) Rating for one million revolutions or 500 hours at 331⁄3 RPM
200S series single-row deep groove ball bearings (non-filling slot)
1) Fillet radius indicates maximum fillet radius on shaft or in housing which bearing corner will clear2) Values have been determined through historical application and practice3) Rating for one million revolutions or 500 hours at 331⁄3 RPM
300S series single-row deep groove ball bearings (non-filling slot)
Double-row angular contact ball bearings areused extensively in ANSI standard centrifugalpumps and some older API style pumps. Theyare typically used as the primary thrust bearing;however, in some rare cases, they have beenused as the radial bearing of some pumps andmotors. MRC 5000C bearings are compliant withANSI requirements. Double-row bearings withball loading grooves (filling slots) are notrecommended for pump applications.
Proven Track RecordLong service life and reliable performance haveearned MRC angular contact ball bearings anexcellent reputation in the pump industry. Thestandard product features which have contributedto this exceptional performance include: ABEC-1precision tolerances, a 30° contact angle per row,ABMA C3 internal radial clearance, one-piece heattreated pressed steel cages, as well as multiplesealing options. In addition, the contact anglesdiverge inwardly, which provides greater rigidityand increased resistance to misalignment. Thesefeatures have allowed MRC double-row bearingsto accommodate combined axial and radial loads,high speeds, poor lubrication conditions, andcontaminated environments.
Technical Improvements*Improved materialsMRC double-row angular contact ball bearingsare manufactured from an extremely high qualitybearing steel with a very low oxygen content anda minimum number of impurities. The rings aremanufactured from cold rolled blanks, and bothrings are heat treated to provide dimensionalstability up to 300° F (150° C). These advantagesallow the bearings to maintain built-in clearancesover their entire service life.
Improved internal geometryTwenty-first century computer-aided design andmanufacturing programs have permitted subtle
improvements in the bearings. These small, buteffective, modifications to the bearing’s internalgeometry lead to measurable improvements inboth performance and service life. One benefit ofthis fine tuning is that MRC double-row ballbearings are less sensitive to axial overloading.
Improved precision tolerancesMRC double-row angular contact ball bearingsare manufactured to ABEC-3 (P6) dimensionaland running accuracies. This feature providessmoother and truer operation with less heatgeneration, lower vibration, and more preciseshaft guidance.
Improved ball qualityThe balls used in MRC double-row angularcontact ball bearings are one ISO grade betterthan the balls previously utilized. The moreprecise ball diameter improves running accuracyeven at high speeds, while reducing noise andbearing operating temperature.
New crown cageMRC double-row angular contact ball bearingshave a newly developed one-piece crown cageof heat-treated pressed steel. The new cagedesign will allow for improved ball guidance andbetter lubricant film formation.
*While a significant number of the bearings incorporate thetechnical improvements described above, the implementationof the improvements across the entire product range is anongoing process. Please contact MRC before ordering todetermine which sizes have been converted.
15
5200C and 5300C series 30º double-row angular contact ball bearings
Typical application of double rowbearing in an ANSI process pump.
16
MRC Bearing Services 1-800-MRC-7000
1) Fillet radius indicates maximum fillet radius on shaft or in housing which bearing corner will clear2) For thrust rating, multiply C by 0.81 and Co by 1.523) Values have been determined through historical application and practice4) Rating for one million revolutions or 500 hours at 331⁄3 RPM5) Based on 1800 RPM for 5218C through 5222C6) Based on an oil viscosity of 16 centistokes (mm2/s) at bearing operating temperature
5200C series 30º double-row angular contact ball bearings
mm AT 3600 RPM L10 AT 3600 RPM GREASE OIL MAXIMUM MINIMUM MAXIMUM MINIMUMin N N mm mm mm mm
lbf 6) lbf RPM RPM in in in in
18
MRC Bearing Services 1-800-MRC-7000
1) Fillet radius indicates maximum fillet radius on shaft or in housing which bearing corner will clear2) For thrust rating, multiply C by 0.81 and Co by 1.523) Values have been determined through historical application and practice4) Rating for one million revolutions or 500 hours at 331⁄3 RPM5) Based on 1800 RPM for 5316C through 5322C6) Based on an oil viscosity of 16 centistokes (mm2/s) at bearing operating temperature
5300C series 30º double-row angular contact ball bearings
Upgrading the double-row angular contact ball bearings in API 610 Standard, 5th Editionand ANSI-style pumps to duplexed single-rowangular contact ball bearings to meet ANSI +standards typically meant expensive and time-consuming modifications.
MRC has taken the features of the industry leading 7000PJDE single-row angular contactball bearing and incorporated them into thestandard double-row angular contact ballbearing’s dimensional package.
Each feature of the MRC Pump Bearing directlyaddresses the most common operationalchallenges faced by ANSI-style pumps: highloads and poor lubrication—which lead to highbearing operating temperatures—lubricantdegradation, and ultimately premature failure.
40° Contact AngleSteeper than the contact angle of the standarddouble-row angular contact ball bearing, the Pump Bearing’s 40° contact angle gives the bearing increased thrust capacity.
Machined Brass CageProven in single-row angular contact ball bearingsto be robust for performance in heavy duty andpoor lubrication conditions. Takes longer to failand produces noise on impending failure,therefore giving operators a longer time to reactfor maintenance and effectively reducingunexpected downtime.
CB Axial Internal ClearanceBuilding on the success of the reduced end play in single-row angular contacts, the PumpBearing’s new optimized axial clearance pro-motes load sharing between the two rows ofballs and reduces the possibility of skidding in the inactive ball set.
ABEC-3 (P6) Tolerances A feature found in MRC single-row angularcontact ball bearings, ABEC 3 (P6) tolerancescontribute to better control of the bearing’smounted condition and, ultimately, smootherbearing operation.
The MRC Pump Bearing
U = Split inner ringP = 40O contact angleG = Snap ring (standard)
5300UPG series 40º double-row angular contact ball bearings
22
MRC Bearing Services 1-800-MRC-7000
1) Fillet radius indicates maximum fillet radius on shaft or in housing which bearing corner will clear2) For thrust rating, multiply C by 1.08 and Co by 1.933) Values have been determined through historical application and practice4) Rating for one million revolutions or 500 hours at 331⁄3 RPM
The MRC Pump Bearing is equipped with robust machined brasscages that perform better in heavy duty applications and marginallubrication conditions.
The MRC Pump Bearing’s dimensions are identical to those forstandard DRACBB’s with comparable bore sizes.
5300UPG series 40º double-row angular contact ball bearings
During operation, one row of balls in the MRC Pump Bearing supports the primary axial load, while the other row of balls handles thrust in the opposite direction.
PITCH MIN. REQD. THRUST FOR SPEED RATING 3) RECOMMENDED RECOMMENDED
7200DU and 7300DU series 29° angular contact ball bearings
The MRC 7000DU series is a medium contactangle bearing. Similar in design to the MRC7000PDU series, the lower contact angle allows for higher speeds, lower thrust loadrequirements and greater radial loads.
• ABEC-1• Heavy-stock, stamped steel cages• GA preload• Stocked as universally ground half pairs
Due to the 29° contact angle and smaller balls,this bearing can run with a relatively low thrustload. It also runs well with a combination ofmoderate thrust and radial load.
The 7000DU series should be considered forapplications where thrust is moderate and thepump has a history of running hot. Many olderstyle API pumps were equipped with the 7000DUbearing-type. When replaced with a 40° angularcontact bearing, these older pumps often runmuch hotter.
These bearings are stocked with flush groundfaces (GA preload). When heavier thanrecommended shaft interferences are employed,a bearing with an axial clearance (CB) may benecessary. Special axial clearances can beobtained on a Made-To-Order basis.
26
MRC Bearing Services 1-800-MRC-7000
1) Fillet radius indicates maximum fillet radius on shaft or in housing which bearing corner will clear2) For thrust rating, multiply C by 0.81 and Co by 1.473) Listed values are for machined brass cages and have been determined through historical application and practice4) Rating for one million revolutions or 500 hours at 331⁄3 RPM5) Based on 1800 RPM for 7220DU through 7224DU
Tabulated vaules are for back-to-back (DB) or face-to-face (DF) mounting arrangement
28
MRC Bearing Services 1-800-MRC-7000
1) Fillet radius indicates maximum fillet radius on shaft or in housing which bearing corner will clear2) For thrust rating, multiply C by 0.81 and Co by 1.473) Listed values are for machined brass cages and have been determined through historical application and practice4) Rating for one million revolutions or 500 hours at 331⁄3 RPM5) Based on 1800 RPM for 7318DU through 7332DU
Tabulated vaules are for back-to-back (DB) or face-to-face (DF) mounting arrangement
MRC 7000PDU bearings are especiallyrecommended for pumps, motors and otherdevices that generate heavy axial loads at highspeeds. 7000PDU bearings are not intended torun in pumps that generate only small- or no-thrust loads. See the table on pages 32 and 33for minimum thrust loads. The bearing with anaircraft-style machined bronze cage runs particularly well in applications where thrustloads vary greatly during operation and periodsof ball skidding are unavoidable. Similarly, thisbearing type resists destructive vibration forceswhen cavitation occurs.
Experience has shown that this bearing, with aland-guided, machined bronze cage is veryforgiving when ball skidding occurs. With oillubrication, this cage type runs cooler than most other executions.
• ABEC-1• Land-guided, machined bronze cage• Stocked with GA preload (other preloads
available on a Made-To-Order basis)• Stocked as universally ground half pairs
The MRC 7000PDU series angular contact ballbearing has been traditionally supplied with thefaces ground flush (GA) and used with an h5shaft fit. When heavier interference fits areemployed, a bearing with axial clearance (CB)may be needed. Call 1-800-MRC-7000 forassistance in selecting special axial clearances.
31
7200PDU and 7300PDU series 40° angular contact ball bearings with land-guided, machined bronze cage
32
MRC Bearing Services 1-800-MRC-7000
1) Fillet radius indicates maximum fillet radius on shaft or in housing which bearing corner will clear2) For thrust rating, multiply C by 1.08 and Co by 1.933) Listed values are for machined bronze cage and have been determined through historical application and practice4) Rating for one million revolutions or 500 hours at 331⁄3 RPM5) Based on 1800 RPM for 7219PDU through 7232PDU and 7317PDU through 7328PDU
7200PDU and 7300PDU series 40° angular contact ball bearings with land-guided, machined bronze cage
Tabulated vaules are for back-to-back (DB) or face-to-face (DF) mounting arrangement
35
Single-row 40º angular contact ball bearings are the most popular pump thrust bearings inservice today. MRC 7000PJDE series bearingsare compliant with API 610 requirements.
Proven Track RecordLong service life and reliable performance haveearned MRC angular contact ball bearings anexcellent reputation in the pump industry.The standard product features which havecontributed to this exceptional performanceinclude: ABEC-3 precision tolerances,a 40° contact angle, controlled internal CBaxial clearance, one-piece ball-guided machinedbrass cages and universal grinding. Thesefeatures have allowed MRC single-rowduplexed bearings to accommodate combinedaxial and radial loads, high speeds and poorlubrication conditions.
Technical Improvements*Improved materialsMRC 7000PJDE series single-row angular contactball bearings are manufactured from an extremelyhigh quality bearing steel with a very low oxygencontent and a minimum number of impurities. Therings are manufactured from forged blanks, andboth rings are heat treated to provide dimensionalstability up to 300° F (150° C). These advantagesallow the bearings to maintain built-in clearancesover their entire service life.
Improved internal geometryTwenty-first century computer-aided design andmanufacturing programs have permitted subtleimprovements in the bearings. These small, buteffective, modifications to the bearing’s internalgeometry lead to measurable improvements inboth performance and service life. One benefit ofthis fine tuning is that MRC single-row 40º ballbearings are less sensitive to axial overloading.
Improved precision tolerancesMRC 7000PJDE series single-row angular contactball bearings are manufactured to ABEC-5 (P5)running accuracy and ABEC-3 (P6) dimensional
accuracy. This feature provides smoother andtruer operation with less heat generation, lowervibration, and more precise shaft guidance.
Improved ball qualityThe balls used in MRC 7000PJDE series single-row angular contact ball bearings are one ISOgrade better than the balls previously utilized.The more precise ball diameter improves runningaccuracy even at high speeds, while reducingnoise and bearing operating temperature.
New cageMRC 7000PJDE series single-row angularcontact ball bearings have an improvedmachined brass cage which has been manufac-tured to closer tolerances. The new cage willallow for superior ball guidance as well as betterlubricant film formation.
*MRC continuously works to improve the performanceand durability of our products. With these technicalimprovements, you will notice the longer service life and higher reliability associated with our single-row 40ºangular contact ball bearings. While a significant numberof the bearings incorporate the technical improvementsdescribed above, the implementation of the improve-ments across the entire product range is an ongoingprocess. Please contact MRC before ordering todetermine which sizes have been converted.
7200PJDE and 7300PJDE series 40° angular contact ball bearings with ball-centered cage and CB clearance
36
MRC Bearing Services 1-800-MRC-7000
1) Fillet radius indicates maximum fillet radius on shaft or in housing which bearing corner will clear2) For thrust rating, multiply C by 1.08 and Co by 1.933) Listed values are for machined brass cage and have been determined through historical application and practice4) Rating for one million revolutions or 500 hours at 331⁄3 RPM5) Based on 1800 RPM for 7218PJDE through 7224PJDE
7200PJDE series 40° angular contact ball bearings with ball-centered cage and CB clearance
MRC single-row 40º angular contact ball bearings can also be manufactured as hybrid bearings. Thesebearings combine SAE 52100 steel rings with silicon nitride (ceramic) rolling elements. They are typicallyutilized in applications where there is ineffective lubrication, excessive contamination, or stray electricalcurrents. Even under poor lubrication conditions, metal-to-metal contact between the raceways and balls iseliminated due to the use of the ceramic material. Hybrid bearings can achieve a service life that is three to30 times longer than the standard all-steel bearing under these adverse conditions. For more information,please contact MRC Bearing Services at 1-800-MRC-7000 and ask for our applications engineeringdepartment.
Tabulated vaules are for back-to-back (DB) or face-to-face (DF) mounting arrangement
38
MRC Bearing Services 1-800-MRC-7000
1) Fillet radius indicates maximum fillet radius on shaft or in housing which bearing corner will clear2) For thrust rating, multiply C by 1.08 and Co by 1.933) Listed values are for machined brass cage and have been determined through historical application and practice4) Rating for one million revolutions or 500 hours at 331⁄3 RPM5) Based on 1800 RPM for 7316PJDE through 7328PJDE
7300PJDE series 40° angular contact ball bearings with ball-centered cage and CB clearance
MRC single-row 40º angular contact ball bearings can also be manufactured as hybrid bearings. Thesebearings combine SAE 52100 steel rings with silicon nitride (ceramic) rolling elements. They are typicallyutilized in applications where there is ineffective lubrication, excessive contamination, or stray electricalcurrents. Even under poor lubrication conditions, metal-to-metal contact between the raceways and balls iseliminated due to the use of the ceramic material. Hybrid bearings can achieve a service life that is three to30 times longer than the standard all-steel bearing under these adverse conditions. For more information,please contact MRC Bearing Services at 1-800-MRC-7000 and ask for our applications engineeringdepartment.
Tabulated vaules are for back-to-back (DB) or face-to-face (DF) mounting arrangement
Single-row 40º angular contact ball bearings are the most popular pump thrust bearings inservice today. MRC 7000PJDU series bearingsare compliant with API 610 requirements.
Proven Track RecordLong service life and reliable performance haveearned MRC angular contact ball bearings anexcellent reputation in the pump industry.The standard product features which havecontributed to this exceptional performanceinclude: ABEC-3 precision tolerances,a 40° contact angle, controlled internal GApreload, one-piece ball-guided pressed brasscages and universal grinding. These featureshave allowed MRC single-row duplexed bearingsto accommodate combined axial and radialloads, high speeds and poor lubricationconditions.
Technical Improvements*Improved materialsMRC 7000PJDU series single-row angularcontact ball bearings are manufactured from an extremely high quality bearing steel with avery low oxygen content and a minimum numberof impurities. The rings are manufactured fromforged blanks, and both rings are heat treated to provide dimensional stability up to 300° F(150° C). These advantages allow the bearings to maintain built-in preloads over their entireservice life.
Improved internal geometryTwenty-first century computer-aided design andmanufacturing programs have permitted subtleimprovements in the bearings. These small buteffective modifications to the bearing’s internalgeometry lead to measurable improvements inboth performance and service life. One benefitof this fine tuning is that MRC single-row 40º ballbearings are less sensitive to axial overloading.
Improved precision tolerancesMRC 7000PJDU series single-row angularcontact ball bearings are manufactured toABEC-5 (P5) running accuracy and ABEC-3 (P6)
dimensional accuracy. This feature providessmoother and truer operation with less heatgeneration, lower vibration, and more preciseshaft guidance.
Improved ball qualityThe balls used in MRC 7000PJDU series single-row angular contact ball bearings are one ISOgrade better than the balls previously utilized.The more precise ball diameter improves runningaccuracy even at high speeds, while reducingnoise and bearing operating temperature.
New cageMRC 7000PJDU series single-row angularcontact ball bearings have an improved pressedbrass cage which has been manufactured tocloser tolerances. The new cage will allow forsuperior ball guidance as well as better lubricantfilm formation.
*MRC continuously works to improve the performanceand durability of our products. With these technicalimprovements, you will notice the longer service life and higher reliability associated with our single-row 40ºangular contact ball bearings. While a significant numberof the bearings incorporate the technical improvementsdescribed above, the implementation of the improve-ments across the entire product range is an ongoingprocess. Please contact MRC before ordering todetermine which sizes have been converted.
7200PJDU and 7300PJDU series 40° angular contact ball bearings with ball-centered cage and GA preload
41
1) Fillet radius indicates maximum fillet radius on shaft or in housing which bearing corner will clear2) For thrust rating, multiply C by 1.08 and Co by 1.933) Listed values are for stamped brass cage and have been determined through historical application and practice4) Rating for one million revolutions or 500 hours at 331⁄3 RPM5) Based on 1800 RPM for 7218PJDU through 7224PJDU
42
MRC Bearing Services 1-800-MRC-7000
7200PJDU series 40° angular contact ball bearings with ball-centered cage and GA preload
MRC single-row 40º angular contact ball bearings can also be manufactured as hybrid bearings. Thesebearings combine SAE 52100 steel rings with silicon nitride (ceramic) rolling elements. They are typicallyutilized in applications where there is ineffective lubrication, excessive contamination, or stray electricalcurrents. Even under poor lubrication conditions, metal-to-metal contact between the raceways and balls iseliminated due to the use of the ceramic material. Hybrid bearings can achieve a service life that is three to30 times longer than the standard all-steel bearing under these adverse conditions. For more information,please contact MRC Bearing Services at 1-800-MRC-7000 and ask for our applications engineeringdepartment.
Tabulated vaules are for back-to-back (DB) or face-to-face (DF) mounting arrangement
44
MRC Bearing Services 1-800-MRC-7000
1) Fillet radius indicates maximum fillet radius on shaft or in housing which bearing corner will clear2) For thrust rating, multiply C by 1.08 and Co by 1.933) Listed values are for stamped brass cage and have been determined through historical application and practice4) Rating for one million revolutions or 500 hours at 331⁄3 RPM5) Based on 1800 RPM for 7316PJDU through 7328PJDU
7300PJDU series 40° angular contact ball bearings with ball-centered cage and GA preload
MRC single-row 40º angular contact ball bearings can also be manufactured as hybrid bearings. Thesebearings combine SAE 52100 steel rings with silicon nitride (ceramic) rolling elements. They are typicallyutilized in applications where there is ineffective lubrication, excessive contamination, or stray electricalcurrents. Even under poor lubrication conditions, metal-to-metal contact between the raceways and balls iseliminated due to the use of the ceramic material. Hybrid bearings can achieve a service life that is three to30 times longer than the standard all-steel bearing under these adverse conditions. For more information,please contact MRC Bearing Services at 1-800-MRC-7000 and ask for our applications engineeringdepartment.
Tabulated vaules are for back-to-back (DB) or face-to-face (DF) mounting arrangement
The three PumPac® series are matched sets of40° and 15° angular contact ball bearings withcomputer optimized internal design. The 8000series has one 40° bearing mounted back-to-back with one 15° bearing. The 8000AAB serieshas two tandem mounted 40° bearings matchedback-to-back with one 15° bearing. The 8000BBseries has two 15O bearings mounted back-to-back.
The PumPac 8000 series is used in centrifugalpumps, large vertical electric motors, compres-sors, centrifuges, and other applications subjectto thrust loads while operating at relatively highspeeds. The bearings are mounted so that the40° bearing takes the primary thrust (axial) load.
Traditionally, matched sets of 40° angular contactbearings are used to obtain maximum theoreticalfatigue life; but, in most instances, only a fractionof the calculated life is actually achieved. At theheart of these premature failures are phenomenaknown as ball sliding and ball shuttling in theunloaded or inactive bearing. Angular contact ballbearings used in high speed (3600 RPM) pumpsand other applications require a minimum axialload for proper operation. Without axial load,centrifugal and gyroscopic forces in the unloaded
bearing will cause the balls to rotate at an anglecontrary to their true rolling axis; and, as a result,the balls will momentarily lose contact with theraceway. In addition, a microscopic wear orlapping process occurs, giving the appearance ofa burnished or polished raceway. While the oilfilm thickness separating the ball and raceway isreduced, friction and heat are generated, oilviscosity is lowered, and wear is accelerated.This thermally unstable condition dramaticallyreduces bearing service life.
The main benefit of the PumPac bearing systemis that the 15° bearing is designed with consid-erably less internal clearance than the 40°bearing, making it less susceptible to the centrifugal and gyroscopic forces which result in ball sliding and shuttling. This bearing alsoprovides additional radial stiffness, helping to maintain the integrity of the shaft andmechanical seals. The 40° loaded bearingprovides sufficient axial rigidity under theimposed thrust load.
47
8000 series PumPac®
40O/15O angular contact ball bearings
48
MRC Bearing Services 1-800-MRC-7000
1) Fillet radius indicates maximum fillet radius on shaft or in housing which bearing corner will clear2) For thrust rating of bearing (A), multiply C by 1.75 and Co by 3.85. For thrust rating of bearing (B), multiply C by 0.83 and Co by 2.003) Values have been determined through historical application and practice4) Rating for one million revolutions or 500 hours at 331⁄3 RPM claculated according to actual bearing raceway geometry5) Based on 1800 RPM for 8224, 8238, and 8322 through 8336
1)
8000 series PumPac® 40º/15º angular contact ball bearings
40° (A) Bearing
MRC BORE OUTSIDE WIDTHFILLET RADIUS BASIC RADIAL LOAD RATING 2) BALLS PER ROW PITCH MIN. REQD.
5)THRUST FOR
5)
BEARING d DIAMETER B ra r b DYNAMIC 4) STATIC NUMBER DIAMETER DIAMETER THRUST AT 25000 HRSNUMBER mm D mm mm mm C Co mm mm 3600 RPM L10 @ 3600 RPM
1) Fillet radius indicates maximum fillet radius on shaft or in housing which bearing corner will clear2) For thrust rating of bearings (AA), multiply C by 1.75 and Co by 3.85. For thrust rating of bearing (B), multiply C by 0.83 and Co by 2.003) Values have been determined through historical application and practice4) Rating for one million revolutions or 500 hours at 331⁄3 RPM claculated according to actual bearing raceway geometry5) Based on 1800 RPM for 8224AAB, 8238AAB, and 8322AAB through 8336AAB
8000AAB series PumPac® Triplex 40°/40°/15° angular contact ball bearings
MRC BORE OUTSIDE WIDTHFILLET RADIUS BASIC RADIAL LOAD RATING 2) BALLS PER ROW PITCH MIN. REQD.
5)THRUST FOR
5)
BEARING d DIAMETER B ra r b DYNAMIC 4) STATIC NUMBER DIAMETER DIAMETER THRUST AT 25000 HRSNUMBER mm D mm mm mm C Co mm mm 3600 RPM L10 @ 3600 RPM
8000BB series PumPac® Diamond 15°/15° angular contact ball bearings
The PumPac Diamond series consists of two “B” bearings from the regular PumPac series.These 15° angular contact ball bearings areplaced back-to-back, so that the etching on thebearing outside diameters form a diamond. Thisbearing system is designed to carry primarilyradial loads with light thrust loads in eitherdirection. It incorporates all of the other PumPacfeatures including the land-riding, machinedbrass cage and special heat treatment foroptimum dimensional stability.
The PumPac Diamond is used in centrifugalpumps and motors where the thrust loads arelight and radial loads predominate. Doublesuction impeller pumps, including the popularaxially split case or “between bearings” design,and pumps with closed impellers usually benefitfrom this bearing solution. The 15° contact anglecauses the bearings to run cooler in these typesof pumps. Vibration is also substantially reduced.Even though the calculated life of the PumPacDiamond may be less than that for a 40° bearingsolution, longer service life in a low thrust loadapplication can be expected. PumPac Diamondbearing sets are supplied in pairs, strappedtogether, ready for assembly. PumPac Diamondcan not be installed backwards, because bothbearings are identical. In high temperatureapplications, it may be necessary to provideextra clearance in the set to avoid radial preload.Call 1-800-MRC-7000 for assistance indetermining the correct clearance.
56
MRC Bearing Services 1-800-MRC-7000
1) Fillet radius indicates maximum fillet radius on shaft or in housing which bearing corner will clear2) For thrust rating, multiply C by 0.51 and Co by 1.003) Values have been determined through historical application and practice4) Rating for one million revolutions or 500 hours at 331⁄3 RPM claculated according to actual bearing raceway geometry.5) Based on 1800 RPM for 8238BB, and 8326BB through 8336BB
8000BB series PumPac® Diamond 15°/15° angular contact ball bearings
The extraordinary feature of the MRC 9000Uand 9000UP series angular contact ballbearings is the split inner ring that allows theassembly of an optimum ball complementwhile accommodating thrust in eitherdirection. The thrust capacity in eitherdirection is equal to the equivalent size7000DU or 7000PDU bearing.
• ABEC-1 tolerances
• Split inner rings
• 9000U: 29° contact angle
• 9000UP: 40° contact angle
• Land-guided machined bronze cage
The split inner ring bearing can be matched intandem with a single 7000 or 7000P series typebearing with the same contact angle. This config-uration yields two bearing shared thrust capacityin one direction and one bearing thrust capacityin the opposite direction.
The spilt inner ring bearing is usually paired with a 7000 or 7000P series bearing for use in pumpsor motors, as a 97000U2 or 97000UP2 set. Theletter “P” identifies the bearing or set as having a40° contact angle.
• 97000U2: 29° set consisting of one 9000UDT and one 7000DT
• 97000UP2: 40° set consisting of one 9000UPDT and one 7000PDT
This bearing set is commonly used in verticalmotors or pumps to handle the primary thrustload. Because two bearings acting in tandemshare the thrust load, this solution offers anextremely high thrust carrying capacity. Reversing thrust load can be accommodated on the back side of the split inner ring bearing.
Another common application of this bearingsystem is stirrer motors for ethylene reactors. Inthis application, the bearing depends upon thereactor’s plasma for lubrication. MRC offers avariety of materials and cage designs to provideoptimum service life with marginal lubrication.
For proper mounting orientation, please refer tothe stuffer provided in the bearing box.
97000U2 (and 9000U) series 29° angular contact split inner ring ball bearing sets
97000UP2 (and 9000UP) series 40° angular contact split inner ring ball bearing sets
97000 U2 97000 UP2
60
MRC Bearing Services 1-800-MRC-7000
1) Fillet radius indicates maximum fillet radius on shaft or in housing which bearing corner will clear2) For thrust rating of 97000U2 series, multiply C by 1.32 and Co by 2.94
For thrust rating of 97000UP2 series, multiply C by 1.76 and Co by 3.863) Listed values are for machined bronze cage and have been determined through historical application and practice4) Rating for one million revolutions or 500 hours at 331⁄3 RPM5) Based on 1800 RPM for 97222UP2 through 97230UP2 and 97318UP2 through 97320UP2
97000U2 (and 9000U) series 29° angular contact split inner ring ball bearing sets
97000UP2 (and 9000UP) series 40° angular contact split inner ring ball bearing sets
® MRC is a registered trademark of SKF USA Inc. Marathon and ZMarC are registered trademarks of SKF USA Inc. The contents of this publication are the copyright of the publisher and may not be reproduced (even extracts) unless permission is granted. Every care has beentaken to ensure the accuracy of the information contained in this publication but no liability can be accepted for any loss or damage whether direct, indirect orconsequential arising out of use of the information contained herein.
Increase mean time between failure of heavy-duty slurry pumps with unique shaft solutions from SKF.
When a heavy-duty slurry pump is subject-ed to severe cavitation and abrasives, the resulting wear and damage to the impeller cause an imbalanced condition. Though it is virtually impossible to eliminate the imbal-ance, it is possible to substantially reduce the damage that it causes.
To reduce the damaging effects of impeller imbalance, the SKF total shaft solution, combines unique bearing and seal arrangements with SKF adapter sleeves and special mounting tools. With this combina-tion of SKF products, your pump bearings will run cooler, smoother and longer – providing extended service life for your customers and added value for you.
The SKF self-aligning bearing solutionSKF’s unique self-aligning bearing system uses a spherical roller bearing in combination with a spherical roller thrust bearing on the dry end of the pump shaft, and a CARB® toroidal roller bearing on the wet end of the shaft. This unique bearing system can sub-stantially reduce vibrations caused by impeller imbalance. The CARB bearing also accommo-dates thermal elongation of the shaft within the bearing, to avoid the problem of induced axial loads on the bearings; enabling the system to tolerate heavier axial loads for improved flow rates and efficiency.
Technical data sheet
EA Technical data sheet CS2 v03 | 2006-05-25 M – Master
1 SKF bearings for the locating positions When an SKF Explorer spherical roller bearing and an SKF Explorer spherical roller thrust bearing are combined properly, they can:
Accommodate up to .5° of shaft misalignmentResist wear and damage caused by con-taminants to extend service life Maximize the effects of the lubricant to reduce heat generated by the bearings, and increase service lifeAccommodate considerably heavier thrust loads than other types of similarly sized thrust bearings Simplify mounting or dismounting when used in conjunction with adapter sleeves
•
•
•
•
•
2 CARB bearings for the non-locating positionTo accommodate thermal expansion of the shaft, pump designers traditionally use a cylindrical roller bearing on the wet end of the shaft. However, these bearings do not accommodate the vibrations or shaft deflections that typically occur at the first signs of impeller imbalance. As a result, SKF recommends using a CARB bearing on the wet end of a shaft.
Key benefits include:Accommodate thermal expansion of the shaft within the bearing, to virtually elimi-nate the problems caused by induced axial loads
Tolerate shaft misalignment to reduce edge loadingTight fit on the inner and outer rings prevent fretting corrosion and limit shaft vibrations
•
•
3 Adapter sleeves/ hydraulic nuts Mounting and dismounting a bearing on a tapered shaft is a precise and time-con-suming task. Done incorrectly, internal clearance will be either too small or too large, and the bearing will fail prematurely. To install bearings in heavy-duty slurry pumps accurately and easily every time, the SKF drive-up method is recommended. This method uses a hydraulic nut, a hydraulic pump, adapter sleeves, lock nuts and locking devices that were specially designed to maximize bearing service life.
EA Technical data sheet CS2 v03 | 2006-05-25 2 M – Master