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  1. 1. Scraper
  2. 2. Introduction • Tractor pulled scrapers: Designed to load, haul and dump loose material in controlled lifts • High versatility – Used to load and haul a wide variety of materials – Economical over wide range of haul lengths and haul conditions – Self loading – not dependent on other equipment – Not as efficient as exclusively designed machines – Off highway and <1 mile scraper is better than trucks – Ability to deposit loads in layers of uniform thickness
  3. 3. Construction Parts : Bowl, Apron and Ejector Bowl: • Loading and carrying component • Has a cutting edge that extends horizontally across front bottom edge • Lowered for loading, raised during travel Apron: • Front wall of the bowl, independent of bowl • Raised during loading and dumping, lowered during haulage – to avoid spillage Ejector: Rear vertical wall, gets activated and moves forward, helps positive discharge of material
  4. 4. Production Cycle 1. Loading 2. Haul travel 3. Dumping and Spreading 4. Turning 5. Return travel 6. Turning and positioning to pickup the next load
  5. 5. Types Based on method of loading & number of axles 1. Pusher Loaded ( Conventional ) a) Single powered axle b) Tandem powered axles 2. Self Loading a) Push – pull, tandem powered axles b) Elevating type c) Auger type
  6. 6. Pusher loaded atch?v=isSp7a2x-r8 • High speeds on favorable haul roads • 35 mph (50 km/hr) when fully loaded • Lack of high tractive effort reqd for loading • Necessary to supplement with help loading
  7. 7. Self loading - Push – pull type • Tandem powered axle scrappers having a cushioned push block & bail mounted at front • A hook on the rear above the usual back push block • These features enable one another during loading • Trailing scrapper pushes the lead scrapper as it loads • lead scrapper pulls the lead scrapper to assist in loading • Each can individually work with a pusher
  8. 8. Self loading – Elevating type • Self contained loading & hauling Loading mechanism: Chain mounted elevator – mounted vertically on front of bowl Disadvantages: Weight of elevator assembly – dead wt during haul cycle Applications: utility work, dressing up behind high production spreads, shifting material during high grading operations
  9. 9. Auger Type • Can self load in difficult conditions Ex: Laminated rock, granular materials, frozen material • Has independent hydrostatic system located at centre of the bowl • Types – Single and Tandem powered Dis: – Non – load wt is added during haul (wt of mechanism) – More costly to own and operate
  10. 10. Volume of Scraper • Struck or Heaped capacity of the bowl (Cubic yard) Struck capacity: Volume that a scraper would hold if the top of the material was struck off even at the top of the bowl Heaped capacity: struck capacity plus a heaped load at a 2:1 angle on top up to a point in the centre (1/3 more than struck) SAE – 1:1