Rotating rollers

Nine strips of pure, fully annealed copper were deformed plcistically by being passed between a pair of rotating rollers so that the strips were made thinner and longer. The increases in length produced were 1,10, 20, 30, 40, 50, 60, 70 and 100% respectively. The diamond-pyramid hardness of each piece was measured after rolling. The results were... 

Figure 4.19. Layout of a unit for centrifugal casting (molding) of tubular blanks 1 - rotary mold 2 - mold rotation rollers 3 - heating chamber 4 - blank 5 - rotary gripper of finished pipe extender 6 - exhaust ventilation.

Roller mills apply stress to single solid particles between two rotating rollers. The diameter of the rollers is between 0.5 and 1.5 m, and the minimum gap width allows only fine milling. A second type of roller mills operates at higher roller pressures and treats a bed of solids. These high-compression roller mills can be used for ultrafine milling. 

Figure 2-7. Peristaltic pumps. Peristaltic pumps are used to transfer liquids at low to moderate pressures in a controlled way. A flexible pipe containing the liquid is squeezed by rotating rollers causing the liquid to move in the direction shown.

After impregnation with scouring liquor, the fabric is quickly pre-heated in a steam chamber or by an infra-red radiation. When it has reached a high enough temperature, the fabric is introduced into a transportable reaction chamber heated by steam injection, where it is stored in a rotating roller. The reaction time is of the order of 1-1.5 h at 100 C. 

The most widely used roller presses are double roll presses which achieve compaction by squeezing material between two counter-currently rotating rollers (Figure 222), much in the same manner as the operation of rolling mills. Pockets or indentations, which have been cut into the working surfaces of the... 

Figure 228. Five successive momentary conditions of briquetting between two counter-currently rotating rollers with matching pockets...

Much of this knowledge is still phenomenological in character. A comprehensive theory of densification of particulate matter between counter-currently rotating rollers is not yet available, even though many similarities exist with the much better investigated and defined deformation of metals in rolling mills.2 ... 

Theory of rolling The basic principle of compaction of particulate solids between two counter-currently rotating rollers (Figure 230) is similar to that used in calenders for plastic foils or in rolling mills for metals. The first can be adjusted to extremely narrow gap tolerances across press rollers with face widths of up to 2 meters and production speeds of approximately lOOm/min in the latter enormous pressing forces can handle ingots of more than 35 tons weight. 

Particulate matter Since pressure agglomeration between counter-currently rotating rollers deals with particulate matter, results of this theory are only applicable in a general way. If smooth rollers are used, a very close correlation can be obtained. Today, however, roller surfaces for agglomeration are in most cases equipped with some sort of a profile in order to improve the bite on the material which is a never-ending problem because of the noncontinuity of particulate matter. In the case of surface profiliations zones (2) and (3) cannot freely develop due to interlocking between the material and roller surface. This is most pronounced for briquetting. 

In roller presses and pellet mills, converging space (volume) between two counter-rotating rollers and, respectively, the pressure generating device and the extrusion surface. (See also nip angle.)... 

Densification between two counter-rotating rollers. (See also compacting.)... 

Fig. 8.123 Conditions in the nip between two smooth, counter rotating rollers during the compaction of particulate solids. Definitions of geometry, angles, and roll force.

Fig. 6.9-8 depicts three typical hot briquetting systems for DRI. Hot feed in the form of reduced pellets and/or lumps and/or fines is forced by a vertical screiv feeder into the nip between two counter-rotating rollers with matched pockets [B.48, B.97]. The briquettes are pillow shaped, 90-140 mm long, 50-60 mm wide, about 30 mm thick, and weigh 450-800 g each (Fig. 6.9-9). Although the rollers are set closely together, a distance of 2-3 mm is maintained between their surfaces to make sure that there is...

Fig. 6.9-11 Left five successive momentary conditions of briquetting between two counter currently rotating rollers with matching pockets showing that molds are never completely closed. Right sketch of a defective pillow-shaped briquette from a roller press [B.48, B.97]...

For the compaction of dean processed metal swarf, two methods are available. The non-continuous confined volume punch-and-die process (Fig. 6.9-18 a) and the continuous compaction in the nip of two counter-rotating rollers (Fig. 6.9-18 b). 

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