Loaders are used extensively in construction operations to handle
and transport material, to load haul units, to excavate, and to
charge aggregate bins at both asphalt and concrete plants. The
loader is a versatile piece of equipment designed to excavate at or
above wheel or track level. The hydraulic-activated lifting system
exerts maximum breakout force with an upward motion of the bucket.
Large rubber tires on wheel models provide good traction and low
ground-bearing pressure. A wheel loader can attain high speeds,
which permits it to travel from one job site to another under its
own power.
DESCRIPTION
Most wheel loaders are diesel-driven, rubber-tired machines
(Figure 4-1). They are available in varied sizes and capacities.
Some small skid steer type loaders maybe gas driven, but they are
seldom used for major earth moving operations, and more often used
for site clean-up. A
power-shift transmission with a torque converter gives the loaders
fast-movement capability in both forward and reverse, with a minimum
of shock. This lets the machines maintain a high production rate.
The hydraulic system gives the operator positive control of mounted
attachments and assists with steering. Most loaders have pintles or
towing hooks for towing small trailers or light loads.
ATTACHMENTS
The most common loader attachments are a shovel-type bucket or a
forklift (Figure 4-2). The loader’s hydraulic system provides
the power necessary for operating these attachments. Hooks (designed
for lifting and moving sling loads) and snowplows are other
available attachments.
BUCKET
Buckets may be general-purpose (one-piece, conventional) or
multipurpose (two-piece, hinged-jaw) (Figure 4-2). The
bucket attaches to the tractor unit by lift arms. Buckets are made
of heavy-duty, all-welded steel and vary in size from 2.5 to 5 cubic
yards. The bucket teeth are bolted or welded onto replaceable
cutting edges. Bolt-on, replaceable teeth are provided for
excavation of medium-type materials. The multipurpose bucket
provides the capability to use the loader as a dozer and to grab
material.
FORKLIFT
A forklift can be attached to the tractor unit in place of a bucket.
Designed for material handling, the fork attachment is made of steel
with two movable
Figure 4-1 - Loaders
Figure 4-2 - Loader
Attachments
When loading the bucket, it should be parallel with the ground so
its cutting edge can skim the travel surface and remove ruts,
obstacles, and loose material on the forward pass. As the cutting
edge contacts the bank or stockpile, move the loader forward at a
slow speed and increase the power.
While penetrating the material, raise the bucket. Crowd the
material into the bucket and roll the bucket back to prevent
spilling. Maintain the bucket in an upward position while backing
away, to prevent spilling.
Proper positioning of the equipment that will receive material from
the loader is necessary for maximum production. This cuts down on
maneuver time.
When loading trucks from a bank or a stockpile with a single loader,
use the V-loading method. Use the following steps for the V-loading
method (Figure 4-3).
Figure 4-3. Loading Trucks With a Loader (V-Loading Method)
CAUTION |
Keep the loader bucket as low as possible. A low bucket position provides better balance and operator visibility. When traveling with a full bucket over rough terrain or terrain that can cause the loader to slide, always operate at low speed. Failure to do so can result in loss of control, causing serious injury or loss of life
and property damage. |
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• Keep the loader in as high a gear as possible without causing the
tires to spin excessively.
• Regulate the depth of cut using the lift control lever.
this case, work from the edges.
Figure
4-5. Backfilling a Trench With a Loader
Table 4-1. Bucket Fill Factors for Wheel Loaders |
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Material |
Wheel Loader Fill Factor* |
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Loose material: |
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Mixed moist aggregates |
0.95 to 1.00 |
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Uniform aggregates: |
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up to 1/8 inch |
0.95 to 1.00 |
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1/8 to 3/8 inch |
0.90 to 0.95 |
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1/2 to 3/4 inch |
0.85 to 0.90 |
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1 inch and over |
0.85 to 0.90 |
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Blasted rock: |
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Well blasted |
0.80 to 0.95 |
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Average |
0.75 to 0.90 |
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Poor |
0.60 to 0.75 |
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Other: |
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Rock-dirt mixtures |
1.00 to 1.20 |
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Moist loam |
1.00 to 1.10 |
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Soil |
0.80 to 1.00 |
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*Decimal of heaped-bucket capacity, for adjustment to LCY
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Table 4-2. Average Cycle Times for Wheel Loaders |
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Loader Size, |
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Heaped-Bucket Capacity |
Wheel-Loader |
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(Cubic Yards) |
Cycle Time (Minutes) |
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1.00 to 3.75 |
0.45 to 0.50 |
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4.00 to 5.50 |
0.50 to 0.55 |
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NOTE: Includes load, maneuver with four reversals of |
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direction (minimum travel), and dump. |
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• Work-site dimensions, the depth of cut, and the amount of movement
required.
• Surface conditions and weather, including the season of the year
and drainage.
• Equipment condition.
Rated heaped-bucket capacity = 2.5 cubic yards
Bucket fill factor for moist loam (Table 1) = 1 to 1.1, use an
average of 1.05
Cycle time for a 2.5-cubic-yard wheel loader (Table 2) = 0.45 to 0.5
minute, use an average of 0.475 minute
• Determine the total time required. The formula used to determine
dozer production (Chapter 2(Dozers), Production Estimates, step
10) is an alternate method to Travel Time.
• Determine the total number of wheel loaders required to complete
the mission in a given time. The formula used to determine dozer
production (Chapter 2(Dozers), Production Estimates, step 11)
is can be used.
• Use caution when removing and replacing the lock rings.
• Do not work between the wheels and the frame while the engine is
running.
• Use caution when operating close to the edge of a trench or when
working under overhangs created by digging into banks or stockpiles.
• Travel with the bucket at or below axle height.
• Do not carry or lift personnel in the bucket.
• Ground the bucket and set the parking brake before leaving the
machine.
o
40+
years’ experience in the mining industry with strong mineral
processing experience in Precious metals, copper, industrial
minerals, coal, and phosphate
o
Operational experience in precious metals, coal, and phosphate plus
in petrochemicals.
o
Extensive experience studies and feasibility in the US and
international (United States, Canada, Mexico, Ecuador, Columbia,
Venezuela, Chile, China, India, Indonesia, and Greece).
Chapter 2: Dozers
Chapter 3: Scrapers
Chapter 4: Loaders
Chapter 5: Excavators
Chapter 6: Dump Trucks