surface mining primary loading tool - witraktor · for electric-powered loading tools and using...

Surface Mining PriMary Loading TooLSelection 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

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

• Electrical infrastructure

• Longevity of the operation

• Annual production target

• Face material

• Material fragmentation

• 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

equiPMenT conSideraTionS

• Life of the surface mining operation

• Electric power availability

• Primary loading

• Multiple loading faces

• Secondary functions such as stockpiling, loading rail cars, feeding the primary crusher, cleanup, and maintaining a surge pile

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 .

Selection Process

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5

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

Product Descriptions

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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 .

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 .

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

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 .


• 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


• High benches• Excessive tramming• Multiple benches• Unstable benches• Low angle of repose material• No cleanup support

hydraulic backhoes


• 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


• Excessive tramming• Low benches• No cleanup support• Multiple faces

hydraulic front Shovels

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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 .


• 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


• Poor underfoot conditions – wet, soft, jagged

• Tight load areas

• Poorly shot material

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Site Conditions

infraSTrucTure

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 sub-stations, which limits their mobility .

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 .

eSTiMaTed Life-of-Mine

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 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 .

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 .

Dark Yellow – IdealMedium Yellow – RecommendedLight Yellow – CapableGrey – Not recommended

*Bench height needs to be optimized for hydraulic backhoe .


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factor condition Wheel Loader

hydraulic front Shovel

hydraulic backhoe

electric rope Shovel

Load Area Single open bench

Double-sided loading

Multiple benches

Confined area

Poor truck positioning

Material Condition Good fragmentation

Tight material

Oversize material

Selective digging

Bench Height High *

Low *

Angle of Repose 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

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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

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 .

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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 .

TracksIn 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 .

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 .

Soft/Spongy Jagged/Rolling Pitched Wet

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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 .

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 .

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)

• Additional support units

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

988-993 345-551 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) .

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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)

Mining Methods/Techniques

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digging rangeS



hydraulic backhoe

15

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

hydraulic front Shovel

16


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SingLe-Side Loading

• Truck is on left-hand side, so that truck driver and shovel operator have direct eye contact

• Shovel can follow a straight working face without major repositioning effort

• 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

doubLe-Side Loading

• Minimized truck spotting time for higher short-term productivity

• Higher risk of collisions

• Well-trained operators required

• 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

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

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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

• Shortest attachment lifting distance possible

• Various options for truck positioning with loading through the body gate or over the side wall

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

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PaSS MaTch

Caterpillar offers a world-class range of wheel loaders, hydraulic shovels, and electric rope shovels, as well as a full line of off-highway 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 guideTruck roPe ShoveL

7495 7495 hf 7495 hd 7395 7295

797f MT6300 ac

4 PASSES

4 PASSES

– – –

795f MT5500 ac

3 PASSES

3 PASSES

– – –

MT5300 ac 3 PASSES

3 PASSES

4 PASSES

– –

793f, 793d MT4400d ac – – 3

PASSES4

PASSES–

789d MT3700 ac – – 3

PASSES4

PASSES–

785d, 785c MT3300 ac – – – – 3

PASSES

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hydrauLic ShoveL PaSS MaTch guideTruck hydrauLic ShoveL

6090 fS 6060 6060 fS

6050 6050 fS

6040 6040 fS

6030 6030 fS

6018 6018 fS

6015 6015 fS

797f MT6300 ac

4 PASSES

6 PASSES

7-8 PASSES

– – – –

795f ac MT5500 ac

3-4 PASSES

5-6 PASSES

6-7 PASSES

– – – –

MT5300d ac 3 PASSES

5 PASSES

6 PASSES

– – – –

793f, 793d MT4400d ac

3 PASSES

4 PASSES

5 PASSES

6 PASSES

– – –

789d MT3700 ac – 3-4

PASSES4

PASSES5

PASSES6

PASSES– –

785d, 785c MT3300 ac – – 3

PASSES4

PASSES4-5

PASSES7-8

PASSES–

777g 777d – – – – 3-4

PASSES5

PASSES8

PASSES

WheeL Loader PaSS MaTch guideTruck WheeL Loader

994h extended high Lift

994h high Lift

994h 993h high Lift

993h 992h high Lift

992h 990h high Lift

793f, 793d MT4400d ac

7 PASSES

– – – – – – –

789d MT3700 ac – 6

PASSES5

PASSES– – – – –

785d, 785c MT3300 ac – – 4

PASSES6

PASSES– 7

PASSES– –

777g 777d – – – – 3-4

PASSES4-5

PASSES4

PASSES5-6

PASSES

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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 .

Applications

free flowing consolidated

Tight Shot face Well fragmented

Selective digging


MobiLiTy and MuLTiPLe uSeS

electric rope Shovels

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 .

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 .

hydraulic Shovels

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 electric-powered hydraulic shovels), because they are not tethered to a trail cable .

Wheel Loader

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:

• 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)


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)

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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 .

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

Buckets and Dippers

electric rope Shovel dipper

Electric rope shovels do not have buckets, they have dippers .

hydraulic front Shovel bucket

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Wheel Loader buckethydraulic backhoe bucket

AEXQ0956

©2013 Caterpillar

All rights reserved .

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 .

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.

surface mining primary loading tool - witraktor · for electric-powered loading tools and using...

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