NSK bearings prove reliable
in bucket-wheel excavator
he selection of NSK spherical
rolling bearings in one of the
world’s largest bucket-wheel
excavators has proven to be
an astute decision. Despite
six years of heavy duty operation at RWE
Power’s opencast mine in Hambach,
Germany, the bearings are still going
strong – without any relubrication.
The idea of using NSK bearings
was driven by the need to reduce
maintenance costs on the mine’s
largest machines. Excavator 290,
which is 240m long, 40m wide,
100m high and 14,000 tonnes in
weight, has been in service since
the end of the 1970s.
NSK spherical rolling bearings have been
operating for six years in Excavator 290
without relubrication
With this in mind, the RWE Power product
managers responsible for the conveyor
belt drums set up a pilot project that
involved installing a sealed, dual row
NSK spherical roller bearing with tapered
bore inside the drive drum of belt 2 on
Excavator 290.
T
Every day, ‘Excavator 290‘ at the Hambach
mine moves up to 240,000 tonn es of coal
or, using its 130-tonne bucket-wheel,
excavates large volumes of overburden
which is then transported to a spreader on
conveyor belts in its upper structure.
The four central conveyor belts located
here have to work hard, not only due
to the volume of material transported,
but because they operate 24/7 in an
adverse environment heavy with dust and
moisture.
This is where two NSK spherical rolling
bearings are helping the mine operator
maximise the operational uptime of
Excavator 290.
Sealed, dual row NSK spherical roller
bearing with tapered bores are fitted to
RWE Power’s excavator conveyors
The bearing, which has an external
diameter of 500mm and a shaft diameter
of 300mm, was then replaced at the
scheduled time. Inspection of the removed
bearing revealed that it was in excellent
condition despite having been subject to
continuous, intensive use.
This provided RWE Power with the
confidence to adopt NSK’s spherical rolling
bearing technology, a move that has been
rewarded with excellent service – with zero
maintenance – for the past six years.
Among the reasons for this high level of
performance is the efficiency of the seals,
the high quality grease used by NSK, plus
the Super-TF (STF) raw material used for
the bearing. STF is a carbonitrate steel that
is subjected to a specific heat treatment
that helps retain optimum levels of
austenite content.
STF bearings have twice the service life
in comparison with conventional roller
bearing steels with clean lubricant, and
where there are contaminants in the
grease, bearing life can be increased as
much as ten-fold.
www.nskeurope.com
68
PECM Issue 23