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SKF Explorer and SKF Energy Efficient bearings provide sustainable solutions
12. Jun. 2010
Drawing on more than 100 years of engineering knowledge and unmatched
expertise in the field of tribology, SKF is continuously working to
create products that are so much more efficient that over their
operating lives, they save more energy than it took to manufacture
them. At the same time, SKF engineers want to give manufacturers a
proven way to reduce energy use, decrease maintenance costs, improve
machine reliability and contribute to global sustainability.
Success has come in the form of two bearing performance classes, each
designed to provide money- and resource-saving advantages in specific
applications. SKF Explorer bearings provide benefits for heavy load
applications, while SKF Energy Efficient (E2) bearings decrease power
consumption in light-to-normal load applications.
SKF EXPLORER BEARINGS: FOR HEAVIER LOADS SKF Explorer bearings (fig. 1) have been developed to run cooler,
smoother and longer than standard rolling bearings in heavy load
applications. These bearings reduce environmental impact by enabling
downsizing and by reducing both lubricant and energy consumption. Just
as important, this performance class of bearings can reduce the need
for maintenance and contribute to increased productivity.
Key to the performance of SKF Explorer bearings is the optimized
internal geometry. Using proprietary software, SKF engineers analyzed
the interrelationship of the rolling elements, raceways and cage. They
devised methods to reduce friction, heat generation and wear in the
bearing, while enabling SKF Explorer bearings to withstand heavier
radial and/or axial loads.
The rolling elements of SKF Explorer bearings are manufactured to
extremely close tolerances to reduce vibration levels and equalize load
distribution. Cages are enhanced to improve guiding of the rolling
elements and optimize the effect of the lubricant while lowering heat,
friction, noise and vibration levels. The surface topography of the SKF
Explorer bearing rolling elements and raceways is optimized to enhance
the formation of a hydrodynamic lubricant film, maximizing the effects
of the lubricant, while reducing heat generation and wear. Exceptional
strength and durability have been achieved through the use of extremely
clean, highly homogeneous steel, while a unique heat treatment process
results in better dimensional stability in applications where operating
temperatures are high. Today, SKF manufactures a large number of SKF
Explorer bearings covering different bearing types.
Environmental savings and increased uptime A practical example of the savings that can be achieved comes from
Stora Enso, a paperboard producer in Sweden. With sealed SKF Explorer
bearings, Stora Enso has increased uptime, eliminated its lubrication
system and reduced water reclamation costs.
Previously, the company was experiencing continuous bearing failures in
a suction box vacuum system used to extract water from pulp. After just
four to seven months of operation, the bearings were failing, as water
leaked into the bearing arrangement, washing grease out, which also led
to fretting corrosion and finally to premature bearing failure. Grease
in the water had to be extracted and disposed of, adding to water
treatment costs.
Stora Enso installed SKF Explorer sealed spherical roller bearings in
two suction boxes. These sealed bearings, which keep lubricant in and
water out of the bearing cavity, prevent the ingress of water and
contaminants into the bearing.
The SKF Explorer sealed spherical roller bearings in both suction boxes
ran trouble-free for more than 13 months. In addition to extended
bearing service life, the company was able to eliminate the lubrication
system and reduce grease consumption by approximately 3 kg/y per
bearing. Eliminating the need to extract and dispose of grease from
process water realized additional cost savings and environmental
benefits.
SKF ENERGY EFFICIENT BEARINGS: FOR LIGHT TO NORMAL LOADS AND RELATIVELY
HIGH SPEEDS SKF Energy Efficient (E2) bearings belong to a performance class of
bearings that have been specially designed to reduce the frictional
moment in the bearing by at least 30 % when compared to SKF standard
bearings (figs. 3, 5, 7 and 9).
Like the SKF Explorer bearing, the SKF Energy Efficient bearing is the
result of rethinking and redesigning virtually every facet of bearing
design. New theories in tribology, metallurgy, lubrication, sealing and
manufacturing were combined to create new bearing geometries,
specialized cages and refined manufacturing techniques.
A significant breakthrough with the SKF E2 bearing is the development
of new grease formulas to lubricate the bearings and extend the grease
life or lubrication intervals.
The SKF E2 deep groove ball bearing (fig. 2) is particularly well
suited for electric motors (fig. 3), pumps, gearboxes, conveyors, fans
and other applications characterized by light-to-normal loads and
relatively high speeds.
Results have shown that, when applied to a shielded deep groove ball
bearing, the new low-friction grease developed for the SKF E2 bearing
will last at least two times longer than conventional greases used in
similar standard bearings (fig. 4).
Medium size NJ design cylindrical roller bearings, which are typically
used on the intermediate shafts of gearboxes, are also available in the
E2 performance class.
These bearings typically run under combined loads, with axial loads of
up to 30 % of the radial loads. NJ design cylindrical roller bearings
in the gearbox of a wind turbine have been tested. The power losses in
SKF Energy Efficient cylindrical roller bearings were up to 80 % lower
compared to standard SKF cylindrical roller bearings. (fig. 5). The
outstanding frictional moment reduction under combined loads was
achieved by optimizing the roller end face profile and the roller-
flange contact area.
SKF Energy Efficient tapered roller bearings offer a number of
advantages. These bearings, like other SKF E2 bearings, are
characterized by a power loss reduction of at least 30 %. These
improvements were achieved by optimizing the number of rollers,
replacing the steel cage with a new-design polymer cage and by
optimizing the topography of the rollers, raceways and flange (fig. 6).
The result: a lighter-weight, cooler running bearing that consumes less
lubricant and less power (fig. 7).
SKF Energy Efficient spherical roller bearings (fig. 8), like all other
SKF E2 performance class bearings, reduce the frictional moment in the
bearing by at least 30 % (fig. 9). Developed for light-to-medium loads,
these bearings, lubricated with SKF LESA 2 grease, run cooler than SKF
Explorer bearings to reduce lubricant consumption and extend
relubrication intervals.
Return on investment The SKF E2 bearing has proven its worth many times over in applications
worldwide. At the Sangam Group, a textile company in India, SKF E2 deep
groove ball bearings were installed in an electric motor powering a
textile machine. The motor runs at 1,470 r/min, operating 22 hours per
day, 363 days per year. By switching to the SKF E2 deep groove ball
bearings, Sangam Group estimates a yearly energy saving of more than
2,600 kWh per motor, and additional savings provided by the bearings’
longer service life. The company calculated a return on investment of
just 37 days. As a result, Sangam Group installed SKF E2 deep groove
ball bearings in the other motors and pumps in the factory.
At one of the GlaxoSmithKline Consumer Healthcare factories, with the
installation of SKF E2 deep groove ball bearings in electrical motors
for pumps, the return on investment included money savings as well as
contributions to a better environment. The plant reports annual energy
savings per motor of more than 4,500 kWh per year, equalling an annual
savings of 390 euros. A two-tonne reduction in CO2 was realized, and
the company estimates that it gained 20 euros for every euro invested.
Sustainability and savings In conclusion, SKF Energy Efficient (E2) bearings have the potential to
make a significant contribution to global sustainability. In fact, if
SKF Energy Efficient deep groove ball bearings were used on every
industrial motor in the EU and US (and assuming a minimum of 30 % lower
frictional moment), potential energy savings would equal 2.46 billion
kWh/year. And this estimate does not take into account the millions of
motors and other applicable machines in use elsewhere throughout the
world
by Daniel C Statler SKF Group Communications Bearings & units, Downingtown, Pennsylvania, USA
obt bearing shandong obetter bearing co., ltd www.obtbearing.com
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