SKF Energy Efficient deep groove ball bearings for higher driveline efficiency

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1 SKF Energy Efficient deep groove ball bearings for higher driveline efficiency Marc Janssens SKF France Abstract The world s environmental and economical challenges have encouraged the development of major successful technical innovations to improve energy efficiency of motor drives (e.g. VFD, copper rotor). Additional motor efficiency improvements likely will require extensive engineering developments and investments. SKF, with over 100 years experience in friction reduction, is offering an easy way to improve driveline efficiency and save energy. As the first bearing company to be certified ISO and listed in the Dow Jones Sustainability Index since its establishment, SKF keeps on working for a sustainable future by continuously offering new sustainable solutions to the market With the announcement in 2007 of a new generation of Energy Efficient bearings SKF is setting the market trend offering additional driveline efficiency improvements and related energy savings. With at least 30% lower friction compared to standard SKF bearings, the realized energy savings have a return on investment beyond 500%. One of additional benefits is a significantly extended bearing service life in most cases more than doubled. SKF Energy Efficient deep groove ball bearings combine an optimized internal geometry, low friction grease, and a new polymer cage. They dimensionally comply with ISO 15:1998 allowing an easy replacement in existing applications. They are initially available as shielded units in a range of selected sizes for shaft diameters from 7 mm to 60 mm, sizes commonly used in electric motors up to 37 kw (50 HP). Product performance and benefits At least 30% savings on energy consumption Doubled bearing service life Smooth-running, less heat generation Dimensionally interchangeable with equivalent standard bearings Available from stock in selected sizes Typical applications Typical use of Energy Efficient deep groove ball bearings is in applications where the grease life criterion is predominant over the fatigue life: Electric motors up to 37 kw (50 HP) Other light to medium-loaded applications with shaft diameters from 7 mm to 60 mm (e.g. conveyors, pumps, fans) In all other cases it is recommended to use SKF Explorer deep groove ball bearings

2 Figure 1. Light conveyor Figure 2. Pump Product simulation SKF designed these bearings using customized computations and CAD applications. To check and optimize the designs, simulation and modeling tools (Bearing Beacon, Orpheus, BEAST) were applied. In terms of friction torque simulation, a significant number of SKF Bfree simulations have been performed in order to verify the obtained energy savings. Following bearings have been simulated: 63 series: 6306 to series: 6205 to 6218 Figure 3. Example of SKF Bfree simulation with standard 6205 and E2 design 6205 Product design Using these advanced modeling and simulation techniques to reduce bearing friction as much as possible SKF designed the following main features for SKF Energy Efficient deep groove ball bearings, Figure 4: A patented polymer cage design with a special geometry to optimize lubrication conditions. This design results in a lighter cage that is less vulnerable to deformation during operation, Figure 5. A new synthetic lithium grease with a very low friction coefficient. The grease quantity has been calculated to optimize its distribution. This is one of the key elements enabling less friction and lower operating temperature. An optimized internal geometry that reduces friction between the rolling elements and the rings. As a result also the running temperature is lower, thus allowing higher operating speeds.

3 Figure 4. New features Figure 5. Comparison of cage deformation Product validation After the design was frozen SKF performed extensive testing primarily focusing on friction torque and service life. The tests were done on SKF friction torque test rigs as shown in Figure 6. They confirmed that the energy savings can reach 50% under light loading conditions, Figure 7. Figure 6. Friction torque test rig Figure 7. Energy savings under light loads Tests also demonstrate that the E2 design induces a lower bearing self-heating, which will also result in a longer grease life and thus in a longer service life in the application. On bearing size 6306 test objectives were defined to validate the energy savings on a wider range of load and temperature conditions: Radial loads C/P=10 and C/P=15 Temperatures 70 C-85 C-100 C Figure 8. Friction torque measurements on 6306, at different speeds & temperatures, C/P=15

4 As indicated in the graphs in Figure 8 above, the obtained results confirm the energy savings previously calculated by the program Bfree. On a wide range of test conditions, the measured friction savings are at least 50% and in some cases 70%, Figure 9. Figure 9. Friction saving under constant radial load, C/P=10 Additional tests under pure axial loads and combined loads have been conducted verifying the important friction reduction, Figure 10. 0,00% Friction saving as function of axial load and speed -10,00% -20,00% % of torque saving -30,00% -40,00% -50,00% -60,00% -70,00% -80,00% 2000 rpm 5000 rpm 2000 rpm 5000 rpm 2000 rpm 5000 rpm 2000 rpm 5000 rpm 600 N 1000 N 2000 N 4000 N Figure 10. Friction saving under different axial loads at 85 C Laboratory measurements of power loss performed on an electric motor (Figure 11) confirmed the results obtained when testing single bearings. A motor equipped with Energy Efficient deep groove ball bearings shows a bearing friction reduction of up to 50% compared to a motor equipped with SKF standard bearings. Furthermore life testing has been carried out on Energy Efficient deep groove ball bearings displaying the significant longer service life in medium and light loaded applications. It has been demonstrated that the service life can be more than doubled compared to standard SKF greased bearings, Figure 12.

5 Figure 11. Test on electric motor Standard Energy Efficient 1 0 Service life Figure 12. Test with 6203 under 150 C, r/min Less power consumption Tests with SKF Energy Efficient deep groove ball bearings show energy savings of more than 30% compared to standard SKF bearings. This is also shown in field applications (see example in customer cases below). Designation: E Z/C3 (shielded bearing) Operating temperature: 80 C Radial load: 0,75 kn

6 Less friction Tests with a motor under free running down mode show that the motor equipped with SKF Energy Efficient deep groove ball bearings runs significantly longer under its inertia after switch off. That proves that the Energy Efficient deep groove ball bearing generates less friction compared to standard bearings. Designation: E Z/C3 (shielded bearing) Operating temperature (after switch off): 60 C Speed at switch off: r/min Cooler running Tests at different speeds show that SKF Energy Efficient deep groove ball bearings are running at lower operating temperatures compared to standard SKF bearings. Designation: E Z/C3 (shielded bearing) Radial load: C/P=10 (8,2 kn) Energy savings In addition to the test results presented above, SKF has estimated typical energy savings over time as follows: 7,5 kw motor running at r/min continuously: savings of 94 kwh/year, comparable to the energy consumption of an energy efficient light bulb of 11 W for 1 year continuously. 37 kw motor running at r/min continuously: savings of 270 kwh/year, comparable to the energy consumption of an energy efficient light bulb of 11 W for 3 years continuously.

7 Customer cases A leader in the geared motor market confirmed SKF s predicted energy savings (Figure13) Motor type: 2,2 kw Speed: r/min First, equipped with standard SKF deep groove ball bearings. Then, equipped with SKF Energy Efficient deep groove ball bearings SKF stated following test results: 30 to 50% friction reduction Customer test confirmed: 46% friction reduction Standard Bearings Z/C Z/C3 SKF energy efficient E Z/C3 E Z/C3 Friction reduction -46% St andard E2 Figure 13. Friction reduction measurement in customer application GlaxoSmithKline Consumer Healthcare Ltd. tested SKF Energy Efficient deep groove ball bearings in a cold water pump motor Motor type: 22 kw Speed: r/min Designation: E Z/3 Energy savings: kwh per year and motor Mr. Pardeep S. Bharma, Manager of Engineering (Figure 14) states: I want to confirm that by using the SKF E2 design bearings in our 22 kw motor we are able to save 0,56 kw per hour. This is fully in line with that which was estimated by SKF Figure 14. Engineering manager GlaxoSmithKline plant

8 For additional information about SKF Energy Efficient solutions, or to request a test sample, contact your local SKF representative or visit Industries/New SKF Offers at The distinctive mark for SKF Energy Efficient products With the contribution of the LIFE financial instrument of the European Community