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16-80 Edition 47
Hydraulic
Mining Shovels
Cycle Times
CYCLE TIMES
The cycle time of a hydraulic mining shovel is an
important productivity factor, and a key driver for high
or low performance. There are two main areas that
influence cycle times. One factor is the pure technical
capability of the hydraulic mining shovel. The engine
output and associated hydraulic power defines the maxi-
mum available oil flow, which consequently determines
the speed of the hydraulic cylinders and swing drives,
and ultimately the achievable working speed of the
machine. The other factor is site specific parameters,
such as operator skill, bench height (in particular for
hydraulic front shovels), and swing angle, will impact
cycle times considerably. Material fragmentation and
penetration resistance make a big difference, as well.
Large hydraulic mining shovels are used as the prime
mover in most applications. Therefore, the set-up of the
loading area is pre-considered to be favorable for pro-
ductive loading conditions when defining cycle times.
Those are for example:
For backhoe
machines
For face shovel
machines
Truck position
lower level
same level
Average swing angle 60°–90°
90°
Bench height
similar to
stick length
75% of max.
reach height
A complete working cycle of a hydraulic mining shovel
can be separated into four segments:
●
Bucket fill
●
Swing loaded
●
Dump
●
Swing empty
However, the bucket fill process constitutes the main
fraction of the loading cycle, with a portion between
40% and 50% of the total time. This is heavily influenced
by the material parameters, therefore, the different cycle
times, shown for each model in the attached diagram,
only consider the increasing effort to fill the bucket:
●
Ideal loading conditions
—Loose material, such as dry
sand, soil and gravel, or re-handled or tipped material
with no effort to achieve a good fill. Bucket can pene-
trate anywhere in the face or pile without resistance.
●
Average loading conditions
— Soft overburden with
low grade of compaction, and well-shot material with
good and consistent fragmentation. Operator doesn’t
have to concentrate on loosening or finding the right
spot for penetration.
●
Fair digging conditions
— Shot rock with partially
interlocked sections, or compacted overburden, requir-
ing some effort to loosen the material.
●
Difficult digging conditions
— Inhomogeneous shot
rock with some oversized boulders and interlocking,
or unblasted material. Also free digging applications
in sediment type of rock with fractures and layers
which allow to penetrate the material. Considerable
effort required to break out material.
●
Severe digging conditions
— Poorly shot rock with a
large amount of oversized boulders and/or heavily
interlocked material in the majority of the face. Also
free digging operations with high digging resistance.
In those conditions neither cycle times nor bucket fills
are predictable.