Surface Mining
Primary Loading Tool
Selection Guide
Wherever there’s loading, we’re there.
Loading applications vary between mine sites, so it’s important to have appropriate loading tools.
Caterpillar is the only mining equipment manufacturer to offer every type of loading tool for surface
mining – electric rope shovels, hydraulic front shovels, hydraulic backhoes, and wheel loaders.
This guide presents an overview of these tools and describes how to use each type most effectively.
Together, you and your customer can use this information to make highly informed decisions for
every mine plan.
Contents
Selection Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Product Descriptions. . . . . . . . . . . . . . . . . . . . . . . . .5-7
Site Conditions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-12
Mining Methods/Techniques. . . . . . . . . . . . . . . . 13-19
Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20-21
Buckets and Dippers. . . . . . . . . . . . . . . . . . . . . . . 22-23
Selection Process
Surface mining-specific needs and working face attributes are primary selection considerations. The overall goal is to maximize profit
with a loading system that meets targeted hourly production at the lowest cost-per-unit of material moved.
Mine Site Considerations
Equipment Considerations
• Electrical infrastructure
•Life of the surface mining operation
• Longevity of the operation
•Electric power availability
• Annual production target
•Primary loading
• Face material
•Multiple loading faces
• Material fragmentation
•Secondary functions such as stockpiling, loading rail cars,
feeding the primary crusher, cleanup, and maintaining a
surge pile
• Penetration characteristics
• Material angle of repose
• Face height and angle
• Bench width
• Maneuvering space
• Multiple loading faces
• Floor conditions
• Job set-up
• Load area support equipment needs
• Blasting restrictions
4
The electric rope shovel, hydraulic front shovel, hydraulic
backhoe, and wheel loader fit into primary loading functions in
surface mining applications. The equipment that is best for the
job depends on the characteristics of the job site.
Product Descriptions
Electric Rope Shovels
Electric rope shovels offer the lowest cost-per-ton loading
solution for long-life mines. Although they have traditionally
required electrical infrastructure, Caterpillar is developing an
off-grid power solution to allow non-electrified mines to consider
this loading tool option.
They are most efficient when the work face is between 12 and 18
meters (39 and 59 feet) high. Line of sight is high above the truck
being loaded, giving the rope shovel operator excellent visibility
of the truck bed.
Due to the large size of the machine, it is possible to use a
double-side loading method for added efficiency. This method
allows the rope shovel to load one truck while another truck gets
into position on the other side, for continuous loading. Trucks are
positioned up to 7 meters (20 feet) away from the rope shovel’s
crawlers throughout the loading cycle, helping to reduce or
eliminate collisions during truck spotting.
An electrically powered machine, the rope shovel’s immense
payload capability, low maintenance requirements, and
high reliability make it the lowest total cost-per-unit loading
tool available.
Favorable Conditions
• Working a single face of the correct height
• Solid, level floor
• Wide benches to facilitate truck maneuverability
• Well-shot material
• Cleanup and ground support
• Good trail cable management
Unfavorable Conditions
• Poor underfoot
• Low faces
• Poorly shot or unshot material
• Multiple face location
• Selective digging
5
Product Descriptions
Hydraulic Front Shovels and Hydraulic Backhoes
Hydraulic shovels combine the benefits
of high digging forces with large capacity
buckets. They can selectively dig deposits
anywhere in the face, giving operators
added flexibility. Hydraulic front shovels
are usually used in tight material (12 m/
40 ft plus) to penetrate tough material.
benches may be narrow. Truck positioning
and proper truck match are critical. The
operator’s eye level is also sufficient
for same level loading if the truck is not
extremely oversized.
Hydraulic shovels are also available as
AC version with electric drive, which
offers lower cost-per-ton for electrified
mine sites, similar to electric rope
shovels.
Hydraulic backhoes work best when
positioned on an upper bench with
haulers at a lower level for high
productivity and best operator view into
the truck bed. They are also capable of
same-level loading if required. Bench
height should correspond to stick
length for adequate reach in loading
and dumping.
Hydraulic Front Shovels
Hydraulic Backhoes
Free-flowing faces with low angles of
repose favor the front shovel due to the
limited reach of the backhoe.
Hydraulic shovels work well in poor
underfoot conditions (soft or jagged
floors) and in tight quarters, where
6
Favorable Conditions
• Selective digging
• Multiple face heights
• Single face loading
• Multiple targets
• Tight load area
• Tough digging
• Can work in poor floor conditions
• Define dig pattern and maintain
Unfavorable Conditions
• Excessive tramming
• Low benches
• No cleanup support
• Multiple faces
Favorable Conditions
• Low to moderate bench heights
• Truck spotted either on top of bench
or on the floor below the backhoe
• Tight load area
• Short swing – 60°
• Well-shot material
Unfavorable Conditions
• High benches
• Excessive tramming
• Multiple benches
• Unstable benches
• Low angle of repose material
• No cleanup support
Surface Mining Primary Loading Tool Selection Guide
Wheel Loaders
Large wheel loaders have grown in size over time to match
increasing off-highway and mining truck payload capacities.
They increase productivity with consistent high bucket fill
factors and are used effectively as primary loading tools where
mobility is paramount. In conditions common to crushed-stone
applications, wheel loaders keep loading floors clean, work
between multiple faces, and transport oversize material away
from loading area. Productivity remains high even when the
machines encounter face conditions such as free-flowing
material or material with low angles of repose.
These reasons, plus traditionally low owning and operating
costs, have made wheel loaders very popular in mines
worldwide.
Although wheel loaders articulate at a full 40 degrees, they still
need ample maneuvering room. Caution should be noted with
wheel loaders in tight box cuts. Due to the lack of room, the
loader may grind tires and decrease their life. This occurs by
not keeping the loader moving fore and aft while making tight
maneuvers and chewing the rubber from the tread.
Favorable Conditions
• Level, dry, smooth, firm floors
• Sufficient crossfall and drainage in wet areas to minimize
tire damage
• Well-fragmented materials that minimize crowding time,
particularly in the toe-area of the cut
• Lower face profile
• Multiple faces and frequent traming
Unfavorable Conditions
• Poor underfoot conditions – wet, soft, jagged
• Tight load areas
• Poorly shot material
7
Site Conditions
INFRASTRUCTURE
ESTIMATED LIFE-OF-MINE
Mine sites equipped with an electrical infrastructure have the
option to choose electric rope shovels and/or electric powered
hydraulic shovels for their loading tool needs. Using electric
machines lowers the operation’s overall cost and reduces
emissions. They do require trail cables connected to substations, which limits their mobility.
The expected longevity of the mine site also plays a role in
loading tool selection. Electric rope shovels are designed to have
an operating life of 120,000 hours, making them a viable option
for mines with estimated lives that meet or exceed a timeframe
of 20 years.
For non-electrified mine sites, diesel-powered hydraulic shovels
and wheel loaders remain the primary loading tool options.
Diesel-powered machines offer a distinct advantage in mobility
and flexibility, despite a higher operating cost. However, with the
introduction of our off-grid power solution, non-electrified mines
now have the option to use electric rope shovels. Greenfield
mines in the planning process must weigh the long-term cost
implications between investing in an electrical infrastructure
for electric-powered loading tools and using diesel-powered
equipment only.
8
For mine sites with shorter estimated lives, hydraulic shovels
and wheel loaders may be more viable options. Hydraulic
shovels and wheel loaders are designed to have an operating
life of approximately 50,000 to 60,000 hours without exchange of
major steel structures, dependent upon application and proper
maintenance.
Surface Mining Primary Loading Tool Selection Guide
Loading Conditions
There is no single loading tool that will do all things on all jobs; each has a definite application range in which it is regularly used and is
suitable economically. This chart shows generally accepted guidelines for matching equipment to loading conditions.
Factor
Condition
Load Area
Single open bench
Wheel
Loader
Hydraulic
Front Shovel
Hydraulic
Backhoe
Electric
Rope Shovel
Double-sided loading
Multiple benches
Confined area
Poor truck positioning
Material Condition
Good fragmentation
Tight material
Oversize material
Selective digging
Bench Height
Angle of Repose
High
*
Low
*
Steep
Shallow
Floor – Shape
Level and firm
Uneven or undulating
Floor – Surface
Dry, good traction
Wet, good traction
Wet, low traction
Wet and jagged
Bucket/Dipper Performance
Achieve rated capacity
Match multiple targets (truck size)
Dig above grade
Dig below grade
Cleanup
Blast cleanup
Scaling face
Load area cleanup
Digging out toe
Travel
Multiple loading sites
Mobility for blasting
Load and carry
Secondary Tasks
Blending
Dark Yellow – Ideal
*Bench height needs to be optimized for hydraulic backhoe.
Medium Yellow – Recommended
Light Yellow – Capable
Grey – Not recommended
9
Site Conditions
Blasting and Fragmentation
Good blasting and fragmentation techniques play an important
role in the productivity and life expectancy of your loading tools,
whether you’re using an electric rope shovel, hydraulic shovel, or
wheel loader. Benefits include:
•Improved bucket fill and reduced bucket load time result in
better loader productivity, longer loading tool life, and reduced
cost per ton of material loaded
•Improved primary loading tool productivity, as less time is
spent digging out and placing oversized pieces of material for
secondary breakage
•Reduction of oversized pieces of material and associated
secondary breakage costs
•Reduced congestion in the loading area caused by a shortage
of oversized pieces of material rocks, leading to improved
truck exchange time
•More consistent truck payloads
•Less tipping impact at hoppers and crushers
•Reduced crushing costs and improved crusher throughput,
lowering crushing cost-per-ton
10
Improved fragmentation through blasting can have downsides
as well:
•Higher cost of drilling
•Increased cost of explosives
•More fines produced
Typically, the improvements in loading tool productivity more than
offsets the higher costs associated with drilling and blasting.
Surface Mining Primary Loading Tool Selection Guide
Floor Conditions
Solid, flat floors are ideal for all loading systems, but changing floor conditions require a careful choice of track shoes for hydraulic
shovels and electric rope shovels, and tires for wheel loaders, that are the best fit for the operation.
Tracks
In most surface mining applications, the narrowest single
grouser shoes are generally the most durable choice. In soft,
spongy conditions, a wider shoe provides better flotation. On
jagged or rolling ground, hydraulic shovels and electric rope
shovels will often “pad” a floor by adding fines to form a stable
loading platform. This can prevent the shovel from rocking
on the undercarriage during the loading cycle, as rocking
significantly reduces undercarriage life and operator efficiency.
Wheel loaders, which do not experience these undercarriage
constraints, also do an excellent job of adding fines and
filling in low areas to construct a better working surface.
Soft/Spongy
Jagged/Rolling
Electric rope shovels and the larger hydraulic shovels rely on
support equipment, like track-type tractors or wheel dozers, to
adequately prepare ground conditions.
Most loading systems can work on pitched slopes, or pitched
seams, but wheel loaders typically are less effective than
hydraulic shovels on steeper grades. Electric rope shovels are
also not well suited to work on highly pitched slopes or seams. If
floor conditions are severe (wet) or change cannot be controlled,
wheel loader production may decrease. Tracked machines are
better suited for such conditions.
Pitched
Wet
11
Site Conditions
ground pressure
Nominal ground pressure and gross machine weight are
indicators of machine flotation in poor underfoot conditions.
Hydraulic shovels exert approximately one-third of the ground
pressure compared to similar-sized wheel loaders.
Ground Pressures
Tire or Track
Electric Rope Shovels*
7295-7495
220-374 kPa (32-54.1 psi)
Hydraulic Shovels
6015/6015 FS-6090 FS
167-251 kPa (24-37.4 psi)
Wheel Loaders
988-993
Changing floor conditions, such as rainwater or the freeze/thaw
cycle, must also be taken into account. Good mobility, traction,
and flotation must be considered during the entire range of
conditions. The operator has the ability to adapt the face and
floor conditions for the loading tool to ensure
continued productivity:
•Face height
•Floor padding (adding rock fines to the floor)
345-551 kPa (50-80 psi)
* The 7495 HF includes a high-floatation undercarriage specifically
designed for soft ground conditions, similar to what is found in the
Canadian oil sands. The ground pressure for the 7495 HF is 216 kPa
(31.4 psi).
12
In general, ground pressures increase as machine size
increases. Very large machines, like electric rope shovels and
larger scale hydraulic shovels, must have a solid sub-base to
operate effectively. Also, wider tracks or tires will reduce
ground pressure.
•Additional support units
Surface Mining Primary Loading Tool Selection Guide
Mining Methods/Techniques
the loading process
In many ways, loading is the central part of any earthmoving process. The entire system’s productivity is governed by the loading
tool’s productivity. There are strong links to the muckpile condition upstream and the truck fleet downstream of the loading tool.
If the loading process is productive and cost-effective, the entire material moving process will be as well.
$
Blasting
Loading
Cost
Rock strength
Crowd/rimpull
Repairs
Laminations
Breakout
Tires and U/C
Drill pattern and angle
Bucket shape
Bucket/GET
Hole size
Penetration
Labor
Explosives
Fill factor
Powder factor
Productivity
Productivity
A good indicator of material ability is the average time it takes
to fill the bucket/dipper. A proper loading tool productivity study
measures the four-part loading cycle:
1. Dump
2. Travel empty or swing empty
3. Dig
4. Travel loaded or swing loaded
The total cycle time is the sum of segments 1 through 4.
•Loading time should take less than 16 seconds, regardless of
the loading tool.
•Loading times longer than 10-16 seconds may be an indication
that the material/muckpile is not properly conditioned for the
loading tool. It could also be an indication of the operator’s
skill level.
Note: Load times are averaged and will vary cycle to cycle as the
loading face changes. Handling oversize pieces of material or
digging the toe of a highwall will increase individual dig times.
Typical cycle times (in seconds):
Electric Rope Shovels
28-44 sec (avg 37)
Hydraulic Front Shovels
21-32 sec (avg 26.5)
Hydraulic Backhoes
21-31 sec (26)
Wheel Loaders
28-42 (avg 35)
13
Mining Methods/Techniques
digging ranges
Electric Rope Shovel
Hydraulic Backhoe
14
Surface Mining Primary Loading Tool Selection Guide
Hydraulic Front Shovel
Wheel loaders, hydraulic front shovels,
and electric rope shovels are positioned
in front of the working face. All three are
able to dig from the bottom to the top
of the face in one fluid motion, but only
the hydraulic front shovel has selective
digging capability. Selective digging
refers a machine’s ability to penetrate
the face at any height. Hydraulic
backhoes are generally positioned at
the top of the face, allowing the machine
to dig below grade via a digging motion
that moves toward the machine, enabling
selective digging capability.
Wheel Loader
15
Mining Methods/Techniques
SINGLE-SIDE LOADING
DOUBLE-SIDE LOADING
•Truck is on left-hand side, so that truck driver and shovel
operator have direct eye contact
•Minimized truck spotting time for higher short-term productivity
•Shovel can follow a straight working face without major
repositioning effort
•Well-trained operators required
•Good floor conditions are easy to maintain
•Support equipment can clean the excavated area behind
the shovel without interfering the loading action
•Always mine the face from right to left, then travel back
and continue
•Tracks 45° towards face, travel motors to rear
Hydraulic Backhoe Top loading –
Truck on upper level
•Applied for drop cuts and difficult-to-access or wet areas at
the pit bottom
•Increased lifting effort and larger swing angle requires longer
cycle time
•Approximately 15% to 20% lower productivity
16
•Higher risk of collisions
•While loading to the right side, both shovel operator and truck
driver are on the blind side
•Shovel cannot follow straight working face and has higher
repositioning effort
•Permanent clean-up support required
•Tracks 90° towards face, travel motors to rear
Surface Mining Primary Loading Tool Selection Guide
Typical Hydraulic Backhoe application –
Truck on lower level
•Lowest risk for collision with proper bench height due to clear
separation of loading and hauling equipment
•Excellent operator view into the truck body
•Potential for short swing angles
Drive-by loading
•Truck spotting time eliminated for highest productivity, because
the next truck does not need to reverse for positioning
•90° swing angle
•Loading through the gate is more difficult due to limited space
for dumping
•Shortest attachment lifting distance possible
•Various options for truck positioning with loading through the
body gate or over the side wall
17
Mining Methods/Techniques
PASS MATCH
Caterpillar offers a world-class range of wheel loaders, hydraulic shovels, and electric rope shovels, as well as a full line of offhighway and mining trucks designed to work together for maximum productivity. The loading tool must be matched to the truck, with
the correct bucket/dipper size, to optimize loading cycles.
Rope Shovel Pass Match Guide
Truck
Rope Shovel
7495
4
797F
MT6300 AC
Passes
795F
MT5500 AC
Passes
MT5300 AC
3
3
7495 HF
7495 HD
7395
7295
4
–
–
–
3
–
–
–
4
–
–
4
–
4
–
Passes
Passes
3
Passes
Passes
793F, 793D
MT4400D AC
–
–
789D
MT3700 AC
–
–
785D, 785C
MT3300 AC
–
–
18
Passes
3
Passes
3
Passes
Passes
Passes
–
–
3
Passes
Surface Mining Primary Loading Tool Selection Guide
Hydraulic Shovel Pass Match Guide
Truck
Hydraulic Shovel
6090 FS
4
797F
MT6300 AC
Passes
795F AC
MT5500 AC
Passes
MT5300D AC
793F, 793D
MT4400D AC
3-4
3
Passes
3
Passes
6060
6060 FS
6
Passes
5-6
5
4
–
777G
777D
–
–
6015
6015 FS
7-8
–
–
–
–
6-7
–
–
–
–
6
–
–
–
–
6
–
–
–
6
–
–
7-8
–
5
Passes
3-4
–
6018
6018 FS
Passes
Passes
785D, 785C
MT3300 AC
6030
6030 FS
Passes
Passes
–
6040
6040 FS
Passes
Passes
789D
MT3700 AC
6050
6050 FS
Passes
4
Passes
5
Passes
Passes
3
Passes
4
Passes
Passes
–
–
4-5
Passes
Passes
3-4
5
Passes
Passes
8
Passes
Wheel Loader Pass Match Guide
Truck
Wheel Loader
Extended High Lift
High Lift
994H
994H
7
–
994H
793F, 793D
MT4400D AC
Passes
6
789D
MT3700 AC
–
785D, 785C
MT3300 AC
–
–
777G
777D
–
–
Passes
993H
993H
–
–
5
Passes
4
992H
992H
–
–
–
–
–
–
–
–
–
6
–
7
–
–
High Lift
Passes
Passes
–
–
3-4
Passes
High Lift
Passes
4-5
Passes
4
Passes
990H
High Lift
5-6
Passes
19
Applications
Working the Face
Excavating and loading operations account for a significant
portion of total material movement costs, so it is prudent to
search for the most cost-effective approach.
There are several types of excavating faces:
•
Well Fragmented – The ideal conditions for all loading tools.
•
Selective Digging – Both hydraulic front shovels and hydraulic
backhoes are able to selectively dig. The narrow bucket and
ability to load anywhere in the face makes it a good selective
loading tool for extracting specific material without disturbing
or handling unwanted material.
•
Consolidated/Poorly Shot – Hydraulic shovels may work in this
situation. Other site needs may drive the selection process. In
some cases hydraulic shovels can even work in free digging
rock applications, such as limestone. Pre-condition is a
certain grade of natural fractures in the deposit, such as layer
boundaries or fissures.
•
Free Flowing – Favors the wheel loader, but a hydraulic
backhoe could be placed on top of the pile for high production
applications with proper support equipment. This type of
material produces high fill factors and fast cycle times,
resulting in high productivity.
All the loading tools can work these types of faces, but each
one has its best fit. For instance, a loading tool with high digging
forces applied at an easy loading face would be a waste of
capability, raising the cost-per-unit. Or a wheel loader digging in
consolidated excavation might result in low productivity and high
component wear (GET), driving up unit cost.
Breakout forces and digging range play a part in each machine’s
digging ability.
•
Electric Rope Shovels provide breakout forces that can
facilitate digging of the toughest materials. However, digging
well-blasted material is preferred, as it reduces wear and tear,
limits downtime for maintenance, extends operating life, and
provides high rates of productivity.
•
Hydraulic Shovels have the ability to dig tougher materials,
partly due to the higher breakout force per length of cutting
edge. The bucket can penetrate at the weakest spot of the
working face, which is typically the border area of individual
layers, and can follow the direction of the layers. These higher
cutting forces provide better loading, particularly for material
that is fragmented and keyed together, or material that does
not flow well into a bucket.
•
Wheel Loaders have adequate breakout force for all but the
toughest materials.
Free Flowing
Consolidated
Selective Digging
Tight Shot Face
20
Well Fragmented
Surface Mining Primary Loading Tool Selection Guide
Mobility and Multiple Uses
Electric Rope Shovels
Hydraulic Shovels
Wheel Loader
Electric rope shovels have limited mobility.
The sheer size of the electric rope shovel
places stress on the crawler links during
tramming, increasing maintenance costs
as a result of excessive movement. In
addition, electric rope shovels require a
trail-cable that is connected to a nearby
sub-station, limiting the rope shovel’s
ability to move great distances quickly
and frequently.
Due to slower travel speeds compared
to wheel loaders, the hydraulic shovel’s
mobility tends to be limited. In most
mining applications the hydraulic
shovel is a primary loading tool, and
is therefore used primarily for the
loading of overburden and ore in the
mine. However, hydraulic backhoes
can also be used for auxiliary jobs
(e.g., drop cuts and preparation of
ramps). Moreover, diesel-powered
hydraulic shovels offer more mobility
than electric rope shovels (and electricpowered hydraulic shovels), because
they are not tethered to a trail cable.
With their ability to quickly move from
face to face, wheel loaders have a
mobility advantage over hydraulic shovels
and electric rope shovels. This provides
a degree of flexibility not available with
track machines. Tires provide wheel
loaders the flexibility to save time:
Similar to hydraulic shovels, electric
rope shovels are considered primary
loading tools in a mining application.
They are primarily used for the loading
of overburden, and in some cases ore,
in the mine.
•Moving out for a blast
•Moving to a new face
•Moving to a stockpile for a blending
operation
•Hopper and crusher loading
•Moving back to the service shop for
maintenance
Mobility is a key attribute that allows
the wheel loader to do multiple tasks
throughout a mine site.
Support Equipment and Bench PREPARATION
With any loading system, “good housekeeping” habits are
necessary in the load area to avoid unnecessary undercarriage
maintenance and tire failures due to running over loose rocks on
the floor. A wheel dozer or wheel loader can be used as cleanup
support by pushing loose material back into the face, most often
in the loading area where the trucks are staging, but in some
cases for the electric rope shovel and hydraulic shovel working
areas. The wheel loader is very mobile and has a wide sweeping
bucket. It is therefore well suited to handle its own cleanup
chores. To a certain extent, the hydraulic shovel is also able to
clean up the loading area; however, in most cases the use of
support equipment is more economical.
maximum travel speeds (forward)
Electric Rope Shovel
1.3 km/hr (.82 mph)
Hydraulic Shovel
6015/6015 FS-6090 FS
Large Wheel Loader
21.7-38.6 km/hr (13.5-24 mph)
21
Buckets and Dippers
Bucket and Dipper Options
Caterpillar offers a wide range of purpose-built, high
performance buckets and dippers, each designed to function
as an integral part of the wheel loader, hydraulic shovel, and
electric rope shovel. The combination of the correct bucket or
dipper with the correct machine will provide the best possible
performance in a particular application.
Electric Rope Shovel Dipper
Electric rope shovels do not have buckets, they have dippers.
22
Choosing the correct bucket or dipper can:
•Reduce cycle and loading times
• Lower operating costs by 10 to 20 percent or more
•Eliminate unnecessary stress and fatigue for the machine,
bucket, and operator
Hydraulic Front Shovel Bucket
Surface Mining Primary Loading Tool Selection Guide
Hydraulic Backhoe Bucket
Wheel Loader Bucket
23
Caterpillar Loading Solutions
The success of your operation has a lot to do with selecting the
proper loading machine. The goal is to achieve the best results
at the lowest cost. First-hand knowledge and experience in
analyzing field data and site conditions can greatly increase
efficiency and improve production.
Deciding on one machine over another is a complicated process.
Cat wheel loaders, hydraulic shovels, and electric rope shovels
offer an established reputation in the industry for quality, with
exceptionally low owning and operating costs.
For more information, visit https://mining.cat.com.
CAT, CATERPILLAR, their respective logos, “Caterpillar
Yellow” and the “Power Edge” trade dress, as well as
corporate and product identity used herein, are trademarks
of Caterpillar and may not be used without permission.
AEXQ0956
©2013 Caterpillar
All rights reserved.