Load-and-carry

A relatively recent trend is to install in-pit crushers (Fig. 4.7). These may be fed directly from the quarry face by rubber-tyred shovels in a load-and-carry operation. The crushed rock is transported to the processing plant by conveyers, which generally have lower capital and operating costs than dump trucks. 

Several collapsible 2-quart (1.89-1) canteens have been developed for use in extreme hot conditions where hydration needs are greater (Fig. 14.6). These collapsible canteens are the predecessors of the current on-the-move hydration bladders. However, the collapsible canteens did not have a tube and bit valve to make hands-free drinking possible. Because the large capacity of these canteens made them difficult to cany, many soldiers carried two l-qirart canteens on their fighting load and carried the larger collapsible canteen in or on the rucksack. Five-quart versions (8465-01-254-5759) of these collapsible bladders also existed. 

In the load and carry method the wheel loader scoops up its bucket-load of fragmented rock at the quarry face and directly transports itto the crusher, which is equipped with a special receiving hopper to accept the material discharged from the bucket. With some types of crusher the loader travels up onto a kind of ramp and deposits the load into the crusher opening. The crushed product is conveyed to the cement works by overland belt conveyor. 

On the other hand, besides being used purely for loading fragmented rock into trucks, the wheel loader can also be used for transporting this material over limited distances - up to about 100-150m ( load and carry" operation). 

Never try to load more onto a winch truck than it is designed to load and carry. 

Products. Vibration isolators typically are selected to have a static deflection, under load, that yields a natural frequency no more than one-third the lowest driving frequency that must be isolated (see Eig. 7). The supporting stmcture must have sufficient stiffness so it does not deflect under the load of the supported equipment by more than one-tenth the deflection of the isolator itself (6). In addition to static deflection requirements, vibration isolators are selected for a particular appHcation according to their abiHty to carry an imposed load, and to withstand the environment in which they are used (extreme temperatures, chemical exposure, etc). 

Each basic operation can be divided into one or more unit operations. Size reduction involves cnishing and grinding depending on the size of material handled, and these may be carried out in stages. Separations can be either soHds from soHds, based on size or mineral composition, or soHds from Hquids, ie, dewatering (qv). Size separation or classification is an integral part of any flow sheet, not only to meet product size specifications, but also to ensure a narrow size distribution for subsequent minerals separation circuits and to decrease the load and improve the efficiency of size reduction units which are energy intensive. 

For estimating purposes for direct-heat drying applications, it can be assumed that the average exit-gas temperature leaving the sohds bed wih approach the final solids discharge temperature on an ordi-naiy unit carrying a 5- to 15-cm-deep bed. Calculation of the heat load and selec tion of an inlet-air temperature and superficial velocity (Table 12-32) will then permit approximate sizing, provided an approximation of the minimum required retention time can be made. 

For total-reflux distillations carried out in packed columns, regions of loading and flooding are identified by their effects on mass-transfer efficiency, as shown in Fig. 14-47. Gas and liquid rate increase... 

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