Roll torque

The roll torque on each roll can be determined in a similar way by... 

Reductions in the roll force and diameter accompanying the increase in precompaction pressure lower the size, weight, and cost of roller presses. In contrast, roll drive requirements remain almost unchanged " if the production rate is kept constant. This is due to increases in the roll torque factor T in the roll drive power equation (106). 

FOC drives are capable of providing precise speed control and are used for applications calling for high performance and precision (e.g. machine tools, high-speed elevators, mine winders, rolling mills, etc.). These drives are capable of regulating a number of variables at the same instant such as speed, position, acceleration and torque. 

If the reaction on the rolls appears halfway along the length marked /, as shown on the lower roll, the torque is... 

The torque required to drive the rolls increases with yield strength so hot-rolling (when CTy is low - see Chapter 17) takes less power than cold-rolling. It obviously increases with the reduction in section (t - t2). And it increases with roll diameter 2r this is one of the reasons why small-diameter rolls, often backed by two or more rolls of larger diameter (simply to stop them bending), are used. 

It is required to find the torque without slippage that can be transmitted by a hub that is assembled by an interference fit to a powered shaft. The hub outside diameter D = 070 mm, and the shaft diameter d = 050 mm, as shown in Figure 4.55. The length of the hub is 100 mm. Both hub and shaft are machined from hot rolled steel SAE 1035 with a yield strength Sy A(342,26) MPa (see Table 4.6). Given that the hub is stopped suddenly in service due to a malfunction, and considering only the torsional stresses, what is the probability that the shaft will yield ... 

The product of force F and the rolling radius (R) of the tires on the drive wheels is the wheel torque (T). Power depends on both torque and rotational speed (N). By definition, power is given by P = 2tiNFR = 27tNT. Wlien driving at constant speed, the driver adjusts the accelerator pedal so the drive-wheel power exactly matches the power required (P,) to overcome the resistance of the vehicle (discussed later in this article). To accelerate the vehicle, the driver further depresses the accelerator pedal so that the power available at the drit c wheels (PJ exceeds P,.. 

The wheel torque is equal to the product of the rolling radius of the drive wheels and the propulsive... 

A cylindrical steel pressure vessel (AlSl SAE 10.85, cold rolled) with a wall thickness of 0.1 in. and an inside diameter of 1 ft is subject to an internal pressure of 1,000 psia and a torque of 10,000 ft-lb (see Figure 2-30). What is the effective stress at point A in the wall What is the factor of safety in this design ... 

Variable, high-torque machine hains operating at moderate speeds Run-out table rolls Vertical pump shafting... 

For the same experimental conditions as described in the flow experiments, (i.e., 10 pm glass particles, pure water flowing solution) centrifuge tests yield a higher force to release particles. The torque required for particle release is the same in both experiments hence, particle release in the flow cell is initiated by a rolling rather than sliding motion (Figure 9). 

The shell of a rotary dryer is usually constructed by welding rolled plate, thick enough for the transmission of the torque required to cause rotation, and to support its own weight and the weight of material in the dryer. The shell is usually supported on large tyres which run on wide rollers, as shown in Figure 16.10, and although mild steel is the usual material of construction, alloy steels are used, and if necessary the shell may be coated with a plastics material to avoid contamination of the product. 

Among the formulation variables that control extrudability of a product, several studies (25,26,33-35) point to the fluid or moisture content of the wet feed material being more critical than others. The force or torque of extrusion and power consumption are often inversely proportional to moisture content of the extrudate as seen from Figures 11 and 12 (26,36-38), while the particle size of pellets increases linearly with water content when extruded with gravity feed basket and roll extruders (33). Using instrumented gravity feed and radial screw extruders, a three- to fourfold decrease in the force has been noted, with a 10% increase in water content of feed material (37). 

Here, M is the torque of the rolling object, hr is the coefficient of rolling friction, FL is the normal force (load), Ff is the friction force and R is the radius of the rolling object (see Fig. 11.4). In this case the friction coefficient is not dimensionless but has the unit of length. Other definitions use... 

The incipient gas velocity for a particle rolling along the wall can be determined by the torques exerted on the particle. Assuming that the drag force, gravitational force, and lift force are exerted through the central point of the sphere, the balance of the torques about the uppermost point of the particle-wall contact plane (see Fig. 11.8) can be given by... 

Ultimately, the feed system is not only responsible for conveying powder to the rolls, but also aiding in an initial deaeration of the blend. Weggel7 found that the torque on the feed system screw(s) is directly related to the precompaction pressure. He concluded that by maintaining a constant back pressure, the resulting compact quality can be better controlled. 

The apparatus used for the first tests included a 3/4-inch diameter, 20 1 L/D laboratory extruder. The second series of evaluations was run on a Brabender torque rheometer equipped with mixing head. The third tests utilized large scale processing equipment including a two-roll,... 

Fig. 5.10. Johanson s theoretical roll press design torque factor (T) versus (d + S)jD [13].

We now turn to the theory of rolling particles off surfaces. We use the treatment of Bhattacharya and Mittal to compute the radius of the smallest particle that can be moved due to the torque exerted on the particle by the wall shear. As the particles sit on the surface, there will be a very small deformation Xq caused by the adhesive force between the particle and the surface. This deformation is given by the following equation ... 

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