Of all the earthmoving kit rolling around out there, the scraper must be the strangest of them all. Used in bulk earthworks, you will often see scrapers being used in the development of highways and land subdivisions, where large amounts of dirt need to be moved quickly and cost effectively.
Rarely used in dry hire, these highly specialised machines require experienced operators to work to their best potential. Although available in 'pull-type' arrangements (think a scraper bowl being towed by a tractor), you're more likely to see self-propelled models with one engine located in the front tractor unit or, in the case of a tandem powered scrapers, the addition of a second engine propelling the wheels at the rear of the scraper.
Regularly used in mining and agricultural applications, scrapers come in two configurations using either an 'elevating' or 'open bowl' setup.
Unlike 'open bowl' scrapers that hydraulically lower a cutting edge into the ground, the 'elevating' scraper is self-loading and uses a hydraulic or electrically powered chain-type elevator to lift the material into a raised bowl.
With the ability to average a little over 50km/h loaded, its little wonder that these machines allow earthmovers the ability to quickly load and dump earth on the run, yielding fast cycle times and some of the lowest costs per tonne of earth moved in the industry.
Specifically designed to handle steep grades greater than 5%, the tandem-powered scrapers are highly versatile and can operate independently, in a push-pull configuration with another scraper or, in particularly tough conditions with the support of a bulldozer pushing from behind.
Like so many other segments of the earthmoving market, Caterpillar are the dominant player in this sector. Offering 16 models, they provide a range of scraper sizes with bowls as small as 17.6m3 in the 621K through to 56 m3 in their flagship 657G.
Albeit durable, scrapers have many moving parts that require regular maintenance to ensure reliable operation. While some might argue the higher costs of maintaining a dual powered scraper, these machines assure more work days per year by working through underfoot conditions that generally stop two-wheel-drive scrapers.
In the Hunter Valley, they are the most common mining scrapers, with the 637 and 657 machines found on many sites. Rounding out three tandem driven options that also includes the 627, they are often the scraper of choice for mining contractors.
This article was originally published by the Components Only team in the November - December 2018 issue of "@ The Coal Face" magazine.Published 22 November, 2018