Belt conveyors thickness

Comparative costs for conveyor systems can be based only on studies of specific problems. For example, belt-conveyor idlers are available in a range of quahties that may make the best unit cost three times as much as the cheapest. Bearing quahty, steel thickness, and diameter of rolls all affect cost, as does design for easy maintenance and repair. Therefore, it is necessary to make cost comparisons on the basis of a specific study for each conveyor application. 

A safe estimate of power requirement for double drum dryers is approx 0.67 HP/(rpm)(100sqft of surface). Maintenance can be as high as 10%/yr of the installed cost. Knives last from 1 to 6 months depending on abrasiveness of the slurry. Competitors for drum dryers are solid belt conveyors that can can handle greater thicknesses of pasty materials, and primarily spray dryers that have largely taken over the field. 

Belt conveyors keep speeds < 1 m/s for fines otherwise speeds in the range 2.7-4 m/s burden thickness [cm] = 0.17 (volumetric capacity, dm /s)/ (Belt speed, m/s)(Belt width, m). Belt width 0.5-0.8 m. 

The filled sacks are conveyed, by the shortest possible routes, to the despatch loading bays. The number of transfer points from one one belt conveyor to another should also be as few as possible, for at each transfer the sack receives a jolt, causing its contents to shift over to one side. As a result the sacks become somewhat lopsided in thickness and more difficult to stack. Arrangements to achieve smooth jolt-free transfer from one belt to the next will avoid abrupt changes in level, e.g., by means of curved transition belts. 

This type of "belt" conveyor is equipped with a cold-rolled hardened steel band in lieu of a "rubber" belt and is used for special purposes. The thickness of the band is usually in the range of 1.0 to 1.5 mm. Because of the flat and smooth surface of the band, the material can very suitably be discharged by means of ploughs (or scrapers). Such conveyors are not very suitable for the handling of hot materials unless the band acquires a uniform temperature across its whole width otherwise buckling is liable to occur in consequence of differential thermal expansion, causing serious trouble in the operation of the conveyor. 

Alternatively, the doctor blade can impinge onto a small conveyor belt system which supports the travelling fabric. This mechanism is less commonly used than the rigid roller as it leads to reduced control of the thickness of the spread. For precision work, using very consistent cloth, an accurately machined chromium plated steel roll can replace the rubber covered roller. 

Figure 11.11. Continuous horizontal vacuum filters especially suited to free settling and draining solids, (a) Principle of the conveyor belt filter units may operate up to 0.S m/sec with a cycle time up to 10 min and produce cake thicknesses up to 15 cm. (b) Showing the construction of a grooved rubber belt support for the filter cloth of the belt filter (Purchas, 1981). (c) Rotating horizontal vacuum filter the unit has readily accessible piping and is amenable to thorough washing of free draining solids (Dorr-Oliver Inc.).

Continuous transport of the solids against the solution is employed in several kinds of equipment, including screw, perforated belt, and bucket conveyors. One operation carries a bed of seeds 3-4 ft thick on a perforated belt that moves only a few feet per minute. Fresh solvent is applied 1/5 to 1/3 of the distance from the discharge, percolates downward, is collected in pans, and is redistributed by pumps countercurrently to the travel of the material. 

The mold may be split or one-piece. The finished part is removed either by splitting the mold or, in the case of a one-piece mold, by collapsing the part with a vacuum. This process can be very labor intense. However it is also automated requiring relatively no labor. Automatic systems fill molds with plastisol carried by conveyor belts through an oven as it is being slushed (the mold is put into a control motion pattern). The plastisol can gel repeatedly to a thickness of 0.06 in. (15.2 mm). The excess plastisol is poured out of the mold and automatically returned to the main tank for reprocessing. The molds proceed to another oven where curing is completed. 

Another example of the application of encapsulated sources of radioactive radiation in technical installations is the control of material transport on conveyor belts. The counting rate of the ratemeter is a measure of the thickness or the density, respectively, of the material transported by the belt. By multiplication by the velocity of the conveyor belt, the mass of the transported material is obtained. In the same way, solids transported with gas streams can be determined. 

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