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Integration of the crushing and
screening plants within the ambit of
mining activities is on the rise. This
is more so with in-pit crushing and
on-site boulder handling and eliminating
blasting to a maximum extent on the
face. Still the involvement at middle
and lower levels on these process
equipment is not as acute in drilling,
blasting, loading and hauling. In many
cases the operations up to the crusher
hopper and beyond are managed
separately. For a successful end to end
operation awareness of the
inter-dependence is very necessary.
How much a new entrant is then aware of
the constraints that could affect the
sequence of production functions?
Perhaps the understanding of issues that
caused the stoppage or delays in earlier
plant without much protection or
instrumentation could focus on the areas
where things have improved or still
required more attention. The cycle times
are not meaningful if the hopper does
not accommodate the input to the
required flow levels. This is even more
pronounced when the operation is
scheduled as continuous and designed to
run continuously without interruption in
which case the maintenance time calls
for greater care and understanding of
the plant.
Everyone is aware that flow of material
is the determining factor and this is
easily said than done on account of any
number of variables in the loading,
hauling, dumping or crushing operations.
This guideline or rather a check point
listing highlights some areas that cause
interruptions and need attention and
precautions. The checklist covers the
crushing plants and conveyors since
these are not under the scope of mining
in many cases.
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Breakage
of safety pins and replacement of pins
and bushes
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Presence
of external bodies coming out in the
system like metal plates etc.,
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Bearing
housing bolts failure
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Damage to
grate bars
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Start up
system delays
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Boulder
jams in the hopper
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Chute jams
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Improper
unloading resulting in spillage outside
the crusher hoppers or passage
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Overloading of feeders
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Flywheel
alignment
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Voltage
fluctuations
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Holes in
chute plates requiring welds
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Mismatching of feeder and hopper feeds
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Hammer
failures including wear-outs
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Pitman
collar requiring attention
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Wet
material
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Heating up
of main bearings
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Chute
plates falling down
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Push
feeder shaft breakage
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Flywheel
bush failure
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Secondary
crusher sleeve bolt failure
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Secondary
crusher tripping
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Alignment
of motors
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Screen
jamming
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Condition
of the belt and change cycle. Repairs
requiring stoppage of belt to prevent
further damage
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Slipping
of belts
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Overloading of belts bypassing feed
control
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Turning of
belts
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Failure of
“bold-backs”
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Failure of
roller sets
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Clearing
drum spillage and accumulation
It would be an advantage to be present
when the maintenance cycle is on and
also while the start up operations are
on. It may be surprising to note even
where self lubricating and totally
enclosed conveyor drives and idlers are
installed, the material flow gets
retarded when care is not taken around
the tail drums, skirt-boards, chutes and
screens. The main hopper is being
prominently visible and since the haul
cycle is directly affected, gets
immediate attention generally but
technology brings in over confidence and
then small accumulations develop forcing
attention and resulting stoppage.
While the objective of this note is not
for discussing maintenance points and
detailed operational tune up, the above
is a list of failures actually observed
at different locations and the analysis
of these points led to improvement and
preventive maintenance as well as
strengthening. A budding mining engineer
will do well to keep a starting point as
each plant has its own design,
functions, and limitations as seldom
plants work to the design levels or
theoretical available timings in a
mining related plant and the most
practical available time is MAT factor.
This factor could be the starting point
for analysis and would yield startling
facts often gone unnoticed and result in
tangible improvements and also generate
interest in the overall working.
It is prudent to go through the
literature provided by the manufacturers
and recommendations.
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