Question

The contractor was awarded a contract to construct a parking lot for a small shopping center. The contractor plans to use single pusher scraper for site grading with a chain loading method.
It has been decided there will be total 11 scrapers, and for each scraper the estimated cycle time is 7 mins.

a) how many pushers are required to serve a fleet of 11 scrapers.b) the expected production of the scraper fleet if only 1 pusher is available. (production of a single scraper assuming adequate pusher support is 317 BCY/hr.

Answer 1

Additional information

Loading Method Single Pusher Tandem Pusher

Back-Track 1.5 1.4

Chain or Shuttle 1.0 0.9

Answer:

(a) 3 back-trucks and 2 chains

(b) 2491 BCY/hr

Explanation:

(a)

The number of scrapers per pusher

$Back-track=\frac {7}{1.5}=4.667$

$Chain=\frac {7}{1}=7$

Number of pushers needed

$Back-truck=\frac {11}{4.667}=2.357\approx 3$

$Chain=\frac {11}{7}=1.57\approx 2$

(b)

Production=(Number of pushers* Number of scrappers* Production per scrapper)/ Required number of pushers

$Production=\frac {1}{1.4}\times 11 \times 317 BCY/hr= 2490.7\approx 2491 BCY/hr$