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Optimizing Loading and Hauling Cycle Time for Heavy Equipment Operations

This document explores the loading and hauling cycle time, detailing both fixed and variable times involved in heavy equipment operations. It breaks down the components such as spot time, load time, travel time, and resistance variables. The analysis covers rolling and grade resistance, traction factors, and effective grade calculations, underlining implications for equipment management and efficiency. Additionally, it looks at different types of dozers, loaders, and skid steers, along with methods to increase productivity and reduce operational challenges in construction and mining environments.

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Optimizing Loading and Hauling Cycle Time for Heavy Equipment Operations

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  1. Loading and Hauling

  2. Cycle Time = Fixed Time + Variable Time • Fixed Time = spot time, load time, maneuver time, Dump time • Variable Time = travel time • Resistance • Total Resistance = Rolling Resistance + Grade Resistance • Rolling Resistance due to tire flexure and surface penetration • Grade Resistance due to grade of incline

  3. Rolling Resistance • 40#/ton on hard surface rubber tired • 30#/ton if radials • T4-1 • Rolling Resistance increases 30#/ton/1” penetration • Rolling Resistance Factor = 40# + (30# * inches penetration) • Rolling Resistance = Rolling Resistance Factor * tons

  4. Grade Resistance • % of vehicle weight acting parallel to incline surface • Negative going downhill Positive going uphill • 20#/ton • Grade Resistance Factor = (20# * % grade) • Grade Resistance = Grade Resistance Factor * tons • Effective Grade (%) = % Grade + Rolling Resistance/20

  5. Altitude • 3% power loss per 1000 ft • Using turbocharger allows power to stay constant up to 10,000 ft

  6. Traction • Power available to move vehicle • Rimpull – used for wheeled vehicles • Pull available at rim of driving wheel • Drawbar pull – used for tracked vehicles • Power available at hitch • Maximum usable pull = coefficient of traction * wt on driven wheels (for tracked vehicles and all wheel drive vehicles this is total wt) • T 4-2

  7. Performance Curve • Maximum speed for a given load F 4-1, 4-2 • Retarder curves • Maximum speed going downhill in gear

  8. Travel Time • Cannot use max speed • Need to account for start up and stop • Average speed factors T 4-3 • Max spd * Ave spd factor = speed for haul

  9. Dozers • Tractor w/ front mounted earthmoving blade • Crawler • Low ground pressure (6 – 9psi) • Excellent traction • Rubber tired • Hi spd • Can compact soils • Can operate on paved surfaces

  10. Dozers • Attachments • Rakes, scarifiers, rippers • tow compactors, scrapers, wagons • Blades • F4-7, F4-8 • Performance based on power vs blade size • Hp/ ft of cutting edge -> blades ability to penetrate hard soils • Hp/loose cy -> blades ability to push soil

  11. Production • 5 bullets pg 96 show how to determine blade volume • Blade load (LCY) = 0.0139HWL • Fixed cycle time – maneuver, change gears, start loading, dump • Variable time – time to doze and return • Can decrease by using reverse to return • T4-4, 4-5

  12. Job Management • Downhill dozing • Increases blade load • Cycle time reduction • Slot Dozing • Increases blade capacity up to 50% • Blade to Blade • 2 dozers together • Combined capacity > 2x 1 dozer

  13. Care for tracks and undercarriage • Must keep tracks clean • Must keep undercarriage clean and in good repair • Don’t run at hi spd over rough terrain • Minimize turns • Try to balance left and right turns and up & down slope operation

  14. Loaders • Tractor with a front end bucket • Wheeled or tracked • Excavate soft – medium hard material • Load hoppers and haul units • Stockpile material, backfill ditches • Moving material

  15. Loaders • Wheel Loaders • High mobility • Not all terrain but low ground pressure • Modern are articulated F 4-9 • Tracked Loaders • Can operate in most soils and on steeper slopes • Slower over longer haul distances=> less productivity F 4-10 • Backhoe loader F 4-11 • Attachments – augers, snow blades, forklifts, dozer blade, crane booms

  16. Skid Steers • Small wheeled loader w/ rigid axles • Steers by braking wheels on one side • <10,000# weight • Lift capacities of 600 – 6300 # • Can also be tracked • List of attachments pg 100 • Also mini excavators

  17. Material Handlers • Rough terrain forklifts • Common Lull • Max lift 9000# • Max height > 60 ft • Move materials around site • Eliminates hand carrying or use of other equipment for carrying

  18. Loader Production • Average Bucket load x cycles per hour • Cycle time = loading, dumping, making 4 reversals in direction, traveling minimum distance T 4-6, F 4-14 • Bucket Capacity is heaped T3-1 and use fill factor T3-2 • Ex 4-7

  19. Job Management • Cutting tires major problem • L-5 tires – rock extra deep tread should be used when dealing with shot rock • Keep water out – lubricates rock /rubber cutting • Need to know tipping load – may limit amount of material in bucket • Loader size & productivity based on site limitations

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