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Scrapers.
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Scrapers
Excavating, loading, hauling, & dumping over
medium distances.Can be used with pusher tractor for increasedproduction.Some models have self loading capabilities
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Types of Scrapers
Push-
Loaded:SinglePowered Axle
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Types of Scrapers
Push-Pull:
Tandem-Powered Axle
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Scraper Option
Auger Loading Mechanism
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Types of Scrapers
Elevating
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One Way Haul Distance vs.
Time, min, Fig. 4-15
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Scraper
ProductionChart
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Average Speed Factors
Length of Haul Section,Ft
150 0.42 0.72 1.60200 0.51 0.76 1.51300 0.57 0.80 1.39400 0.63 0.82 1.33500 0.65 0.84 1.29700 0.70 0.86 1.24
1,000 0.74 0.89 1.192,000 0.86 0.93 1.123,000 0.90 0.95 1.084,000 0.93 0.96 1.055,000 0.95 0.97 1.04
Starting from 0 or Coming to a Stop
Increasing MaximumSpeed from Previous
Decreasing MaximumSpeed from Previous
When machinery are required to accelerate and stop in the same section, apply thesquared value from column one.
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Scraper Fixed Time, min
Favorable Average
Unfavorable
SinglePusher
TandemPusher
Auger Push-Pull*
Favorable 0.5 0.4 0.7 0.7 Average 0.6 0.5 0.9 1.0
Unfavorable 1.0 0.9 1.3 1.4
Favorable Average
Unfavorable
Spot Time
Single Pusher Tandem Pusher
0.2 0.10.3 0.20.5 0.5
Load TimeElevating Scraper
0.81.01.5
Maneuver & Dump Time
Single Engine Twin Engine
1.0 0.9
0.3 0.30.7 0.6
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Scraper Production Example
Problem
Estimate the production of a single two-axle scraper Travel time curves are shown on Figures 4-4 & 4-5.Max Heaped Volume = 31 LCYMax Payload = 75,000 lb
Material: Sandy Clay, 3200 lb/BCY, 2650 lb/LCY,Rolling Resistance = 100 lb/ton,Operating Conditions = Average
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Scraper Production ExampleHaul Route:
Section 1. Level Loading Area
Section 2. Down a 4% grade, 2000 ftSection 3. Level Dumping AreaSection 4. Up a 4% grade, 2000 ftSection 5. Level Turnaround, 600 ft
Load Area4% grade
Dump Area
Turnaround
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Scraper Production Example
Loads per Cycle Does Weight or Volume Limit?
Heaped Cap. Wt. = 31.0 LCY x 2,650 lb/LCY= 82,150 lbs82,150 lbs exceeds the 75,000 lbs Rated Max
Payload of the Scraper.
The maximum scraper volume is l imi ted by w eight to= 75,000 lbs (Rated Wt)/ 3,200 lb/BCY= 23.4 BCY/Load
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Scraper Production Example
5%=
%tonlb20tonlb100
0%=Turnaround
9%=
%tonlb20tonlb100
4.0%=Return
1%=%
tonlb20tonlb100
4.0%-=Haul
:GradeEffective
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Scraper Production Example
Travel Time:Section 2 ~ Down a 4% Grade, 2,000 ft. (1% Eff.)
TT2=1.02 min (Figure 4-4)Section 4 ~ Up a 4% Grade, 2,000 ft. (9% Eff.)
TT4=1.60 min (Figure 4-5)
Section 5 ~ Level Turnaround, 600 ft. (5% Eff.)TT5=0.45 min (Figure 4-5)
TT=1.02 + 1.60 = 0.45 = 3.07 min
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Scraper Production Example
Travel Time:Section 2 ~ Down a 4% Grade, 2,000 ft. (1% Eff.)
TT2=1.02 min (Figure 4-4)Section 4 ~ Up a 4% Grade, 2,000 ft. (9% Eff.)
TT4=1.60 min (Figure 4-5)
Section 5 ~ Level Turnaround, 600 ft. (5% Eff.)TT5=0.45 min (Figure 4-5)
TT=1.02 + 1.60 = 0.45 = 3.07 min
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Scraper Production Example
Travel Time:Section 2 ~ Down a 4% Grade, 2,000 ft.
TT2=1.02 min (Figure 4-4)Section 4 ~ Up a 4% Grade, 2,000 ft.
TT4=1.60 min (Figure 4-5)
Section 5 ~ Level Turnaround, 600 ft.TT5=0.45 min (Figure 4-5)
TT=1.02 + 1.60 = 0.45 = 3.07 min
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Scraper Production ExampleFixed Cycle (Table 4-7) Average Conditions SingleEngine
Spot = 0.3 min. Load = 0.6 min. Maneuver & Dump = 0.7 min.Total Fixed Time = 0.3 + 0.6 + 0.7 = 1.6 minTotal Cycle Time = 3.07 + 1.6 = 4.67 min.Estimate Production
= 23.4BCY/Load x [(50min/h)/(4.67min/Load)]= 251 BCY/h
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Scraper Fixed Time, min
Favorable Average
Unfavorable
SinglePusher
TandemPusher
Auger Push-Pull*
Favorable 0.5 0.4 0.7 0.7 Average 0.6 0.5 0.9 1.0
Unfavorable 1.0 0.9 1.3 1.4
Favorable Average
Unfavorable
Spot Time
Single Pusher Tandem Pusher
0.2 0.10.3 0.20.5 0.5
Load TimeElevating Scraper
0.81.01.5
Maneuver & Dump Time
Single Engine Twin Engine
1.0 0.9
0.3 0.30.7 0.6
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Scraper Production ExampleFixed Cycle (Table 4-7) Load Spot = 0.3 min. Load = 0.6 min. Maneuver & Dump = 0.7 min.Total Fixed Time = 0.3 + 0.6 + 0.7 = 1.6 minTotal Cycle Time = 3.07 + 1.6 = 4.67 min.Estimate Production
= 23.4BCY/Load x [(50min/h)/(4.67min/Load)]= 251 BCY/h
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Push-Loading
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Typical Pusher Cycle Time, min
Loading Method Single Pusher Tandem Pusher Back-Track 1.5 1.4Chain or Shuttle 1.0 0.9
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TimeCyclePusher TimeCycleScraper
=ServedScrapersof No.
Number of Scrapers Served,
Pushers Required & Production
Pusher Oneper ServedNumber Scrapersof Number
=dReq'Pushers
Scraper
ProductionxScrapersof No.xNumber dReq'
PushersNo. =Production
(# of scrapers that can be handled by one pusher w/o scraper delay)
(# of pushers required to service a fleet of scrapers: round up to next integer)
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Scraper Push-Loading Example
Problem The estimated cycle time for a wheeled scraper is 6.5 min.Calculate the number of pushers required to serve a fleet of
nine scrapers using pushers.Determine the result for both backtrack and chain loading
methods.
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Scraper Push-Loading Example
6.5=1.06.5
=Chain
4.3=1.56.5
timecycle pusher timecyclescraper
=Track -Back
11)-4(EqPusher per Scrapersof No.
2or 1.4=
6.5
9 =Chain
3or 2.1=4.39
ServedScrapersof Number
Scrapersof Number =Track -Back
:12)-4(EqRequiredPushers No.of
Cycle Timesfrom Table 4-8
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Optimal Load Time
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Optimum Load Time
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Cycle Time minus Load Time = 3.0 min.
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