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Bearing Handbook for Electric Motors

Bearing Handbook forElectric Motors The world s best machinery isSKF EquippedImprove your product s performance with SKF engineeringand application knowledge, design and testing expertise,and a wide range of customers are continually raising their expectations ofproduct performance and reliability demanding equipmentthat consumes less energy, runs quieter, faster and longer,and requires less maintenance. Frequently, this also meanslighter, more compact meet these growing challenges and stay competitive, you need a trusted source of knowledge and applicationexperience to provide you with solutions that for long-term results, you need a working partner that offers one source of responsibility from concept to completion. That source is solutionsFrom a position as the world s leading Bearing manufacturer,SKF has evolved to being a provider of cost-effective andknowledgeable solutions.

Handbook for Electric Motors. ... The contact between the bearing ring and a properly machined and dimensioned bearing seat should not require the use of bonding agents to prevent movement or turning. 4 There is a speed limit to which rolling bearings can be operated. Generally, it is

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Transcription of Bearing Handbook for Electric Motors

1 Bearing Handbook forElectric Motors The world s best machinery isSKF EquippedImprove your product s performance with SKF engineeringand application knowledge, design and testing expertise,and a wide range of customers are continually raising their expectations ofproduct performance and reliability demanding equipmentthat consumes less energy, runs quieter, faster and longer,and requires less maintenance. Frequently, this also meanslighter, more compact meet these growing challenges and stay competitive, you need a trusted source of knowledge and applicationexperience to provide you with solutions that for long-term results, you need a working partner that offers one source of responsibility from concept to completion. That source is solutionsFrom a position as the world s leading Bearing manufacturer,SKF has evolved to being a provider of cost-effective andknowledgeable solutions.

2 You can take advantage of SKFknowledge through our proprietary services and software toshorten the time required to develop and test your knowledge-engineering services, for example, include life calculation analysis, dynamic systems modelling, and 3-dimensional virtual test rigs to simulate and troubleshootsystem vibration. SKF product solutions go beyond bearings,housings and seals, to include complete lubrication systems,industry-leading condition monitoring systems, advanced linear and rotary actuation systems, and unique solutions in mechatronics combining mechanical and electronic elements in a single SKF EquippedWhen your product is SKF Equipped , it tells yourcustomers that your resources include the best instate-of-the-art technology, and that your prod-ucts contain some of the very best componentsavailable on the Installation Tips.

3 2, 3 Speed Ratings ..4, 56200 and 6300 Series .. 6, 7N, NJ, NU 200 EC and 300 EC Series .. 8, 9 Shaft and Housing Diameters6200 Series .. 10 6300 Series .. 11 N, NJ, NU 200 ECSeries .. 12 N, NJ, NU 300 EC Series .. 13 Shaft Shoulder Dimensions6200 Series .. 14 6300 Series .. 15 Minimum Radial LoadN, NJ, NU 200 EC Series .. 16N, NJ, NU 300 ECSeries .. 17 Grease Relube Recommendations6200 Series .. 186300 Series .. 19 N, NJ, NU 200 EC Series .. 20 N, NJ, NU 300 EC Series .. 21 Vibration Frequencies6200 Series ..226300 Series .. 23N, NJ, NU 200 EC Series .. 24 N, NJ, NU 300 ECSeries .. 25 ABMA-SKF Product Comparison ..26, 2721. Handle with care. Never pound directly on a Bearing or ring . If abearing is dropped, it is best not to install it. Store bearings horizontally in a dryplace in their original unopened package and never place bearings on a dirtysurface; periodically turn over sealed and shielded bearings to prevent greasefrom settling to one Inspect the shaft and for size and damage; removenicks and burrs with emery paper, and wipe clean with a soft cloth.

4 Replace orrepair shafts and housings showing obvious signs of wear or damage. A shaftplaced in a vise for mounting should be protected from vise jaws with a sheet ofsoft Avoid heat-mounting operations, never bring aflame in direct contact with the Bearing and never heat beyond 230 F. Also,immediately hold a heat-mounted Bearing in place against the shaft shoulderuntil it cools and locks in place. Otherwise, the Bearing may creep away fromthe proper Use identical replacement bearings should beidentical to the bearings they replace. Contact an SKF Authorized Distributor orSKF for interchange Use the right tool for the heaters, oil injection kits, andhydraulic nuts are among the specialized tools available for mounting anddismounting bearings over 4 in. Their use lowers the possibility ofdamaging bearings and speeds the Pay attention to the Bearing s press a press for any bearingunder4 in.

5 Pressure should be applied only to the Bearing ring with thepress fit, which is usually the ring that rotates after the Bearing is to the ring without the press fit will damage the tips for maximum Bearing operation37. Don t wash new manufacturers take great care topackage and ship bearings that are dirt-free and ready for lubrication. There susually no need to wash them or remove the protective slushing Proper lube is manufacturers evaluate several factorsbefore determining the type of lubricant required for specific bearings. Be sureto follow their recommendations. Temperature and contamination conditionswill influence the frequency of lubrication Rotate idle installed in equipment that is subject tovibration while the shafts are stationary may incur false brinelling damage,which also occurs when equipment is not properly protected during can appear as bright, polished depressions on the inner and/or outer races,as well as on the rolling Look for danger alert for three sure signs of improperbearing operation: excessive noise and increases in vibration and instruments like hand-held vibration pens, digitalthermometers, and electronic stethoscopes help spot bearings in pooroperating the cause of Bearing are built to last, sofrequent failures may point to an installation or lubrication problem.

6 SKFbearing analysis experts can identify the cause of Bearing failure and help youprevent it in the contact between the Bearing ring and a properly machined anddimensioned Bearing seat should not require the use of bonding agents toprevent movement or is a speed limit to which rolling bearings can be operated. Generally, it isthe operating temperature that can be permitted with respect to the lubricantbeing used or to the material of the Bearing components that sets the limit. Thespeed at which this limiting Bearing temperature is reached depends on thefrictional heat generated in the Bearing (including any externally applied heat)and the amount of heat that can be transported away from the type and size, internal design, load, lubrication and cooling conditionsas well as cage design, accuracy and internal clearance all play a part in deter-mining speed capability.

7 In the accompanying tables two speeds are listed:(Thermal) Reference Speed and (Kinematic) Limiting : The new Reference and Limiting Speeds are not to be used as adirect substitution for the previous Oil and Grease speed ratings. Consult SKFto determine the actual reference speed limit for your operating speedsThe reference speed for a given Bearing represents the permissible operatingspeed of said Bearing when subjected to the specific operating conditions ofload, lubrication type and method as outlined in ISO 15312. This standard hasbeen established for oil lubrication but is also valid for grease and uses the fol-lowing reference conditions: A temperature increase of 90 F (50 C) above an ambient temperature of68 F (20 C), (thus a Bearing temperature of 158 F (70 C), measured onthe Bearing stationary outer ring or housing washer.)

8 Radial Bearing : a constant radial load, being 5% of the basic static load rating Co. Thrust Bearing : a constant axial load, being 2% of the basic static load rating Co. Open bearings with Normal oil lubricated bearings: Lubricant: mineral oil without EP-additives having a kinematic viscosity at158 F (70 C) of: v = 12 mm2/s (ISO VG32) for radial bearings, and v = 24 mm2/s (ISO VG68) for thrust roller bearings Oil bath with the oil reaching up to the middle of the rolling element in thelowest grease lubricated bearings: Regular lithium soap grease with mineral base oil having a viscosity of 100 to200 mm2/s at 104 F (40 C) ( ISO VG 150). Filling approximately 30% of the free space in the reference speed will be reached after 10 to 20 hours running time. Underthese specific conditions the reference speed for oil and grease lubrication willbe ratings5 Speeds above the reference speedIt is possible to operate bearings at speeds above the reference speed if thebearing friction can be reduced, for example by lubrication systems with small,accurately measured quantities of lubricant or when heat can be removedfrom the Bearing by circulating oil lubrication with cooling of the oil, by coolingribs on the housing, or by directed cooling air increase in speed above the reference speed without taking any ofthese precautions would only cause Bearing temperature to rise increase of Bearing temperature means that lubricant viscosity is low-ered and film formation is made more difficult, leading to even higher fric-tion and further temperature increases.

9 If, at the same time, the operationalclearance in the Bearing is reduced because of increased inner ring temper-ature, the final consequence would be Bearing speedsThe speed limit is determined by criteria that include: the stability and orstrength of the cage, lubrication of cage guiding surfaces, centrifugal and gyra-tory forces acting on the rolling elements, and other speed-limiting gained from laboratory tests and practical applications indicatesthat there are maximum speeds that should not be exceeded for technical rea-sons or because of the very high costs Speeds shown in the tables are based on the demands of high speedrunning applications and are valid only for the specific design and cage designshown in the tables. It is possible to run bearings faster than the limitingspeeds, but several factors must be reviewed and improved such as the run-ning accuracy, cage material, lubrication, heat dissipation and design of thebearing.

10 It is therefore advisable to contact SKF Applications Engineering foradvice. For enclosed and open bearings using grease lubrication, additionalparameters have to be considered such as lubrication of cage guiding surfacesand the shear strength of the lubricant, which is determined by the base oiland thickener. Open balls bearings with low friction typically have Reference Speeds greaterthan the Limiting Speed. In these cases the permissible speed must be calcu-lated from the operating conditions and the lower value between the permissi-ble and Limiting speed sealed double shieldedopenreferencelimitinglimitinglim itingspeedBearingr/minr/minr/minr/min620 017,00028,00034,00056,000620115,00026,00 032,00050,000620213,00022,00028,00043,00 0620312,00019,00024,00038,000620410,0001 7,00020,00032,00062058,50014,00018,00028 ,00062067,50012,00015,00024,00062076,300 10,00013,00020,00062085,6009,00011,00018 ,00062095,0008,50011,00017,00062104,8008 ,00010,00015,00062114,3007,0009,00014,00 062124,0006,3008,00013,00062133,6006,000 7,50012,00062143,4005,6007,00011,0006215 3,2005,3006,70010,00062163,0004,8006,000 9,50062172,8004,5005,6009,00062182,6004, 3005,3008,50062192,4004,0005,0008,000622 02,4003,8004,8007,50062212,2003,6004,500 7,0006222 3,4004,3006,7006224 3,2004.


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