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6230 Rolling Bearings in Electric Motors and Generators Rolling bearings in electric motors and generators ® SKF, CARB, ICOS, INSOCOAT, MARLIN and SYSTEM 24 are registered trademarks of the SKF Group. ™ SKF Explorer is a trademark of the SKF Group. © SKF Group 2008 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 been taken 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 or consequential arising out of the use of the information contained herein. Publication 6230/I EN · February 2008 This publication supersedes publication 5230 E. 1 Rolling bearings in electric machines 1 2 Bearing arrangements 2 3 Product data 3 4 Lubrication and sealing 4 5 Mounting and dismounting 5 6 Bearing damage and corrective actions 6 7 SKF solutions 7 Rolling bearings in electric motors and generators A handbook for the industrial designer and end-user 2 Foreword This SKF applications, lubrication and maintenance handbook for bearings in electric motors and generators has been devel- oped with various industry specialists in mind. For designers of electric machines1), this handbook provides the information needed to optimize a variety of bearing arrangements. For specialists working in various industries using electric machines, there are recommendations on how to maximize bearing service life through appropriate mounting, mainten- ance and lubrication. The recommendations are based on experience gained by SKF during decades of close cooperation with manufacturers and users of electric machines all over the world. This experi- ence along with customer input strongly influences product development within SKF, leading to the introduction of new products and variants. General information about the selection and calculation of ball and roller bearings is provided in the General Catalogue. This publication deals with questions arising from the use of rolling bearings in electric motors and generators. Data from the General Catalogue is only repeated here when it has been thought necessary for the sake of clarity. 1) In this handbook, when the term electric machine is used, it refers to both an industrial electric motor and a generator 3 Contents The SKF brand now stands for more 1 Rolling bearings in electric machines than ever before, and means more to you as a valued customer. 9 Design requirements While SKF maintains its leadership 15 Bearing selection as the hallmark of quality bearings throughout the world, new dimensions 17 Calculation example in technical advances, product support and services have evolved SKF into 21 Deep groove ball bearings a truly solutions-oriented supplier, creating greater value for customers. 23 Cylindrical roller bearings These solutions encompass ways to 25 INSOCOAT bearings bring greater productivity to customers, not only with breakthrough application- 27 Hybrid bearings specific products, but also through leading-edge design simulation tools 29 Angular contact ball bearings and consultancy services, plant asset efficiency maintenance programmes, 31 Spherical roller bearings and the industry’s most advanced supply management techniques. 33 CARB toroidal roller bearings The SKF brand still stands for the very 35 Spherical roller thrust bearings best in rolling bearings, but it now stands for much more. SKF – the knowledge engineering 2 Bearing arrangements company 37 Selecting a bearing arrangement 47 Preloading with springs 3 Tolerances and fits 52 Shaft and housing tolerances 54 Recommended fits 4 4 Lubrication and sealing 7 SKF solutions 59 Lubrication 104 SKF Engineering Consultancy Services 62 Grease selection 105 SKF calculation tools 64 Relubrication intervals 107 Application specific solutions 70 Grease life in sealed deep groove ball bearings 112 Condition monitoring 72 Oil lubrication 74 Seals 5 Mounting and dismounting 77 Mounting 85 Dismounting 6 Bearing damage and corrective actions 91 Electrical erosion 94 Inadequate lubrication 96 Material fatigue 96 Damage from vibration 97 Damage caused by improper installation and set-up 99 Insufficient bearing load 99 Other damage 5 SKF – the knowledge engineering company From the company that invented the self- The SKF Group is globally certified to aligning ball bearing more than 100 years ISO 14001, the international standard for ago, SKF has evolved into a knowledge engin- environmental management, as well as eering company that is able to draw on five OHSAS 18001, the health and safety manage- technology platforms to create unique solu- ment standard. Individual divisions have been tions for its customers. These platforms approved for quality certification in accord- include bearings, bearing units and seals, of ance with either ISO 9000 or QS 9000. course, but extend to other areas including: With some 100 manufacturing sites world- lubricants and lubrication systems, critical for wide and sales companies in 70 countries, © Airbus – photo: exm company, H. Goussé long bearing life in many applications; mecha- SKF is a truly international corporation. In Evolving by-wire technology tronics that combine mechanical and electron- addition, our distributors and dealers in SKF has a unique expertise in fast-growing by-wire ics knowledge into systems for more effective some 15 000 locations around the world, technology, from fly-by-wire, to drive-by-wire, to linear motion and sensorized solutions; and an e-business marketplace and a global distri- work-by-wire. SKF pioneered practical fly-by-wire a full range of services, from design and logis- bution system put SKF close to customers for technology and is a close working partner with all tics support to conditioning monitoring and the supply of both products and services. In aerospace industry leaders. As an example, virtually all aircraft of the Airbus design use SKF by-wire reliability systems. essence, SKF solutions are available wherever systems for cockpit flight control. Though the scope has broadened, SKF and whenever customers need them. Over- continues to maintain the world’s leadership all, the SKF brand and the corporation are in the design, manufacture and marketing of stronger than ever. As the knowledge engin- rolling bearings, as well as complementary eering company, we stand ready to serve products such as radial seals. SKF also holds you with world-class product competencies, an increasingly important position in the mar- intellectual resources, and the vision to help ket for linear motion products, high-precision you succeed. aerospace bearings, machine tool spindles and plant maintenance services. SKF is also a leader in automotive by-wire technol- ogy, and has partnered with automotive engineers to develop two concept cars, which employ SKF mecha- tronics for steering and braking. Further by-wire development has led SKF to produce an all-electric forklift truck, which uses mechatronics rather than hydraulics for all controls. Bearings Lubrication Seals and units systems Mechatronics Services 6 Harnessing wind power The growing industry of wind-generated electric power provides a source of clean, green electricity. SKF is working closely with global industry leaders to develop efficient and trouble-free turbines, providing a wide range of large, highly specialized bearings and condition monitoring systems to extend equipment life of wind farms located in even the most remote and inhospitable environments. Working in extreme environments In frigid winters, especially in northern countries, extreme sub-zero tempera- tures can cause bearings in railway axleboxes to seize due to lubrication starva- tion. SKF created a new family of synthetic lubricants formulated to retain their lubrication viscosity even at these extreme temperatures. SKF knowledge enables manufacturers and end user customers to overcome the performance issues resulting from extreme temperatures, whether hot or cold. For example, SKF products are at work in diverse environments such as baking ovens and instant freezing in food processing plants. Developing a cleaner cleaner The electric motor and its bearings are the heart of many household appliances. SKF works closely with appliance manufacturers to improve their products’ per- formance, cut costs, reduce weight, and reduce energy consumption. A recent example of this cooperation is a new generation of vacuum cleaners with sub- stantially more suction. SKF knowledge in the area of small bearing technology is also applied to manufacturers of power tools and office equipment. Maintaining a 350 km/h R&D lab In addition to SKF’s renowned research and development facilities in Europe and the United States, Formula One car racing provides a unique environment for SKF to push the limits of bearing technology. For over 50 years, SKF products, engineering and knowledge have helped make Scuderia Ferrari a formidable force in F1 racing. (The average racing Ferrari utilizes more than 150 SKF com- ponents.) Lessons learned here are applied to the products we provide to auto- makers and the aftermarket worldwide. Delivering Asset Efficiency Optimization Through SKF Reliability Systems, SKF provides a comprehensive range of asset efficiency products and services, from condition monitoring hardware and soft- ware to maintenance strategies, engineering assistance and machine reliability programmes. To optimize efficiency and boost productivity, some industrial facil- ities opt for an Integrated Maintenance Solution, in which SKF delivers all
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