Scraper

During its forward movement, the blade cuts the ground and the loosened earth collected in the body of scraper. When the scraper is fully loaded, it is raised above ground d taken to the site of dumping. The earth from the scarper is than taken out by opening the bottom of it and the earth is laid in layer of required thickness.

1. SUBJECT :- ADVANCED CONSTRUCTION AND EQUIPMENTS SCRAPER

2. Scraper This equipment consists of a large bucket called the scraper and it is attached to a tractor. Varies from 3 to 9 The scraper has a cutting edge or blade at the bottom and it is the possible to dig earth to depth of about 250mm. During its forward movement, the blade cuts the ground and the loosened earth collected in the body of scraper. When the scraper is fully loaded, it is raised above ground d taken to the site of dumping. The earth from the scarper is than taken out by opening the bottom of it and the earth is laid in layer of required thickness. The scraper thus combines three operation. Namely, those of digging conveying and dumping  

3. Scraper operation The basic operation parts of scraper Bowl: the bowl is the loading and, carrying component of a scarper. It has a cutting edge that extends horizontally across its front bottom edge . The bowl is lowered for loading and raised during travel. Apron: the apron is the front wall of the bowl. It is independent of the bowl. It is raised during the loading and dumping operations to enable the material to flow into or out of the bowl. The apron is lowered during hauling to prevent material spillage. Ejector: the ejector is rear vertical wall of the bowl. The ejector is in the rear position during loading and hauling. During spreading the ejector is activated and move forward, providing positive discharge of the material is the bowl.

4. Classification of scrappers There are several types of scrappers, primarily classified according to the number of powered axle or by the method of loading. These are will tractor machine that to hydraulically operated wheeled trailer bowl. In the past, crawler – tractor towed two axle scrappers bowls were manufactured. Pusher loaded a . Single b . Tandem Self loading a . Push pull b . Elevating c . Auger

5. Push loaded scraper the push loaded wheel type tractor scraper has the potential for high travels speeds on favorable haul roads. Many model can achieve speed a great as 54 kmph when fully loaded. This extents the economic haul distance of the units however, this units are at a disadvantages when it comes to individually providing the high tractive effort required for economical loading for the single powered excel only a portion ,on the order of 50 to 55 percentage of the total loaded weight, bears on the drive axle.

6. Single – powered axle pusher-loaded tractor scarper are suited for jobs where haul-road rolling resistance is law end grades are minimum. They become uneconomical when Haul grades are grater then 5 percentage Returns grades are greater then 12 percentage Tandem – powered axle wheel-tractor scrapers have separate engines for the wheel-tractor unit and for the scraper unit. This twin-engine arrangement produces extra power for overcoming high rolling resistance and steep grades.

7. 2 . Self loading scrapers it is although heavier and more costly to purchase than corbel conventional scarper, can be economical in certain application, particularly in isolated work and for stripping material. Push pull-scrapers This are basically and -powered axle scrapers having a cushioned-push block and bail mounted on he front and a hook on the rear about the usually block. these features enable two scrapers to assist one another during loading by pushing pulling one another. The trailing scrapper pushes the lead scrapper as it loads. Then the lead scrapper puss the trailing scrapper to assist in it loading. This feature enables two scrappers to work without assistance from a push tractor. They can also function individually with a pusher. Elevating scrappers This is a completely self contained loading and hauling scrapper. A chain elevator mountain vertical on the front of the bowl, serves as the loading mechanism. The disadvantages of this machine is that the weight of the elevator loading assembly is dead weight during the whole cycle. Such a scrappers are economical in short haul situations where the ratio of haul time to load time remains low.

8. Elevating scrapers are used for utility work dressing up behind hide production spread, shifting material during fine grading operations. They are very good in very small quantity situations. Augers scrapper This is another completely self contained loading and hauling scrapper. Augers scrapper can self load in difficult condition, such as laminated rock, granular materials, or frozen material. In a soft limestone mining operation, 44-cy-capacity tender-power augers scrappers making 3-5 in deep cuts achieved an average load time of about one and half minute. Advantage of scrapper: Most suitable for the ground which is free from mud and rock. Digging and loading operations are performed simultaneously. Load is discharge in finally controlled layer. Efficiency is high for smaller depth of cut. Quite suitable in case of big area is to be excavated.

9. Disadvantages of scraper: Require considerable area for its operation. Hence it is not recommended for use where excavation is on a small localized area. Depth of cut is small. It cannot be used directly if the soil is hard. Rippers may be used for hard soil for subsequent use of a scrapper. Can only cut the ground at its bottom. Therefore, for side cutting, other equipment have been use. Output of a scrapper : Loading Travelling to fill Dumping Turning Returning to the pit Getting back in position to load

10. Factors affecting output of scrapper Type of material to be handled Size o tractor Use of helper Tractor during loading Condition of haul road Haul distance Slope of haul road Altitude

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