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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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