Friction-plate

Pump e is of the friction-plate rype and can be used for either vacuum or pressure. 

The success of spheronization depends on whether the extrudate can be suitably deformed into pellets. The ideal extrudate should break up into short, uniform rod-shaped pieces and have sufficient plasticity to be rolled into spheres by the action of the friction plate. In order that the granules... 

Figure 15 Geometry of friction-plate in spheronizer. (A) cross-hatch (B) radial.

The extrudate must be sufficiently plastic to enable the cylindrical rods to be rolled into spheres by the action of the friction plate in the spheronizer. 

Fig. 8 Schematic representation of a spheronizer friction plate with a cross-hatch pattern.

A new variation of spheronizers that was introduced into the market are the so-called air-assisted spheronizers. Basically, they are similar to the standard spheronizers except that they are designed to permit a conditioned air stream to pass from beneath the rotating disk through the gap or slit between the cylindrical wall and the rotating friction plate into the product bed. The addition of such a feature presumably improves pellet turnover and brings about a spiral rope-like motion that facilitates spheronization. 

Figure 348. Common grid patterns of the friction plate of a Marumerizer. (Explanation, see text)...

The still plastic pellet segments are being worked by further contact with the friction plate as well as by collisions between particles and with the wall. Mechanical energy is transformed into kinetic energy and the mass of particles rotates in a torus-shaped ring in the apparatus. Continued processing will cause a gradual deformation into spherical shape. 

The severity of the life of automatic transmission fluid is less severe than that of engine oil. Without the microscopic coke particles, soot, fuel interaction, and other contamination associated with motor oil, ATF must contend only with particles from friction plates and bearings from inside the transmission. Transmissions typically contain a nylon screen or filter of around 150 p to filter out these particles however, changing the fluid is the only way to eliminate them. The metallic particles present can contribute to the oxidation of the fluid and hasten its demise. 

In spheronizers, the design (size and shape) of the grooves on the friction plate surface. 

Variable speed drives are standard options since process conditions vary widely between applications (see below, Fig. 8.14). Also, formulation changes or different production rates will require modified rotational speeds of the friction plate for best performance. 

For continuous cascade operation, the friction plate is lowered in the bowl so that a volume of material always remains inside while excess overflows. The residual volume can be either measured experimentally or calculated, assuming that the cross-section of the rope may be approximated by a fourth of a circle (quarter torus). To obtain a particular spheronization effect, an overall residence time must be maintained. The processing time in each machine can be calculated as the ratio of residual volume divided by the volumetric feed rate (= volumetric throughput). Since bowl diameters are predetermined and fixed by the design, the position of the friction plate in the bowl is the only variable which can be modified to match a certain feed rate or system capacity to the desired or necessary residence time. 

The friction plate speed is scaled-up by maintaining the tangential (or circumferential) accelleration constant. The formula for scale-up is ... 

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