SKF designed a spherical roller bearing for the
168m tall Las Vegas High Roller ferris wheel.
manufacturing parameters, to deliver the
best combination of characteristics. Small
adjustments to raceway geometry can
have a big impact on the bearing’s ability
to cope with irregular loads, for example,
while the use of precisely controlled casehardening
of raceways provides rolling
surfaces of sufcient hardness, while
retaining a tough core to prevent bursting
in failure conditions,” adds Dysiewicz.
COMPUTER SIMULATION
Testing of cutting disc bearings presents
another challenge for manufacturers.
“There is no test rig available that can
adequately reproduce the rigours of realworld
operation and operating conditions
can vary signicantly from project to
project. As a result, bearing design
engineers must rely on a combination
of experience and computer simulation
when evaluating a new design,” he points
out. The condition of bearings removed
from worn cutting discs can also
provide useful information about their
operating conditions. “Expert analysis
of wear and damage to bearing
surfaces can reveal opportunities to
modify operation and maintenance
procedures to maximise bearing
life. In cases where projects have
faced unexpectedly challenging
ground conditions, SKF engineering
teams have even been able to
use insights gained from damaged
bearings to produce customised
solutions designed to offer improved
performance.”
Since disc replacement
operations are conducted
underground, they must be as
straightforward as possible, requiring
minimal use of time, manpower
and specialist tools. The reliable
operation of the taper roller bearings
inside the discs, however, relies on
an appropriate level of pre-load, which
must be set by the maintenance team
when the bearings are mounted. “In
practice, operators have limited ability to
assess bearing preload in the eld and
must rely on the torque measured on
the arrangement during assembly,” he
further comments. “To assist operators
in this critical assembly step, the TRBs
used in cutting discs are manufactured
to tight dimensional tolerances, thereby
ensuring the closest possible correlation
between mounting torque and preload.
Other factors come in to play as well,
however, including the condition and
SKF slewing bearings are built to withstand
huge loads as cutter heads bore into solid rock.
lubrication of mounting hardware, so
careful inspection of components and
adherence to standard mounting protocols
are essential. Bearing suppliers can
also provide support to operators in the
development of appropriate disc bearing
replacement procedures and the training
of maintenance personnel.”
SLEWING BEARINGS
While all cutting disc bearings employ a
broadly similar design, TBM manufacturers
are setting higher and differing demands
on the design of the main slewing bearing.
“This is the most critical bearing of the
TBM and the link between the pinion
drives and the cutter head, while also
taking over the huge loads induced
during tunnelling operations. Slewing
bearing assemblies can range in size
from less than two metres in diameter
for micro-tunnelling applications, up to
more than eight metres for the largest
tunnelling machines. Manufacturers may
use different bearing arrangements,
depending on the size of the machine,
From Formula One to ferris wheels
SKF manufactures virtually every type of ball and roller bearing. They are available in various crosssections,
and satisfy a huge variety of operating conditions and application performance requirements.
The company’s bearings can be found in a wide range of applications: from Formula One cars and
railway vehicles to wind turbines, quarrying equipment, and food and beverage applications. The size
range of its bearings is also impressive, with the smallest bearing having an inner bore of 3mm and
the largest being a spherical roller bearing designed for the 168-metre tall Las Vegas High Roller ferris
wheel – see image at the top of this page and also the cover shot.
SKF has just nished redesigning the bearings on the world’s oldest and largest double-deck
tram eet for Hong Kong Tramways, to improve comfort and facilitate maintenance. The company is
also working with Epiroc on its Mobile Miner machines, developing a combined radial and axial roller
bearing with an outside diameter of 2.18 metres that can withstand the tough conditions in which this
equipment has to work. SKF standard bearings are also being used by Benevelli S.r.l. in Italy, which
creates electric motors for a range of applications, including six lines of transaxles exclusively for
electric vehicles.
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