Scrapers

• Scraper are the machines devices to scrap the ground and load it simultaneously, transport it over required distance, dump and then spread the dump material over the required thickness level, and return to the pit for next cycle.

Types of Scrapers

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

Pusher loaded

• High speeds on favorable haul roads
• 35 mph (50 km/hr) when fully loaded
• Lack of high tractive effort required for loading
• Necessary to supplement with help loading

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

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

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
• Disadvantages:
  • Non – load wt is added during haul (wt of mechanism)
  • More costly to own and operate