Caterpillar Performance Handbook, January 2017, SEBD0351-47

Estimating Production Off-the-Job ● Example Problem (English) ● Example Problem (Metric)

Mining and Earthmoving

8. Check pusher-scraper combinations: Pusher cycle time consists of load, boost, return and maneuver time. Where actual job data is not available, the following may be used. Boost time = 0.10 minute Return time = 40% of load time Maneuver time = 0.15 minute Pusher cycle time = 140% of load time + 0.25 minute Pusher cycle time = 140% of 0.7 min + 0.25 minute = 0.98 + 0.25 = 1.23 minute Scraper cycle time divided by pusher cycle time indi- cates the number of scrapers which can be handled by each pusher. 6.95 min = 5.65 1.23 min Each push tractor is capable of handling five plus scrapers. Therefore the two pushers can adequately

10. Estimate Compaction: Compaction requirement

= S.F. × hourly fleet production = 0.85 × 1947 BCY/hr = 1655 CCY/hr

Compaction capability (given the following): Compacting width, 7.4 ft (W) Average compacting speed, 6 mph (S) Compacted lift thickness, 7 in (L) No. of passes required, 3 (P) 825G production =

W × S × L × 16.3

CCY/hr =

(conversion constant)

P

7.4 × 6 × 7 × 16.3 3

CCY/hr =

CCY/hr = 1688 CCY/hr Given the compaction requirement of 1655 CCY/hr, the 825G is an adequate compactor match-up for the rest of the fleet. However, any change to job layout that would increase fleet production would upset this balance. Example problem (Metric) A contractor is planning to put the following spread on a dam job. What is the estimated production? Equipment: 11 — 631G Wheel Tractor-Scrapers 2 — D9T Tractors with C-dozers 2 — 12H Motor Graders 1 — 825G Tamping Foot Compactor Material: Description — Sandy clay; damp, natural bed Bank Density — 1770 kg/BCM Load Factor — 0.80 ● ● ●

serve the eleven scrapers. 9. Estimate Production: Cycles/hour = 60 min ÷ Total cycle time = 60 min/hr ÷ 6.95 min/cycle = 8.6 cycles/hr Estimated load = Heaped capacity × L.F. = 31 LCY × 0.80 = 24.8 BCY Hourly unit production = Est. load × cycles/hr = 24.8 BCY × 8.6 cycles/hr = 213 BCY/hr Adjusted production = Efficiency factor × hourly production

= 0.83 (50 min hour) × 213 BCY = 177 BCY/hr = Unit production × No. of units = 177 BCY/hr × 11 = 1947 BCY/hr

Hourly fleet

production

Shrinkage Factor — 0.85 Traction Factor — 0.50 Altitude — 2300 meters

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