Flowability measurement

Other classification systems are used less frequently. Carr " also devised a system to classify materials as to their floodability. He defines the floodability of a material as its tendency to flow like a liquid because of the natural fluidization of a mass of particles by air. In order to so classify a material, the flowability is determined utilizing the method just described. This value is equivalent to a measurement Carr calls the angle of fall, angle of difference, and dispersibility. Though referred to in any of the papers mentioned here, this system is much less utilized then the flowability measurements. Geldart reported on a characterization system of powders according to their ability to aerate and later Molerus modified this system. In a more recent symposium this method of powder classification was examined. ... 

Hausmann R. Bausch A. Bongartz C. 2 nn T. Pharmaceutical applications of a new ring shear tester for flowability measurement of granules and powders. In Proceedings of the 2nd World Meeting APGI/APV. Paris, May 1998 137-8. 

Bell, T.A. 2001. Solids flowability measurement and interpretation in industry. In Handbook of Conveying and Handling of Particulate Solids. Handbook of Powder Technology (A. Levy and H. Kalman, eds), pp. 3-14. Elsevier Science, Amsterdam, The Netherlands. 

GENERAL FORMS OF FLOWABILITY MEASUREMENT 3.1. Free flowing materials - timed funnels... 

Plow chaiacterlstic.s. Angle of repose and flowability are measurable charac teristics for which standard tests are available (e.g., ASTM Test B213-48, Flow Rate of Metal Powders, etc.). A steeper angle of repose would indicate less flowability. The term Hubricity has sometimes been used for solid particles to correspond roughly to viscosity of a fluid. 

Shear cell measurements offer several pieces of information that permit a better understanding of the material flow characteristics. Two parameters, the shear index, n, and the tensile strength, S, determined by fitting simplified shear cell data to Eq. (6), are reported in Table 2. Because of the experimental method, only a poor estimate of the tensile strength is obtained in many cases. The shear index estimate, however, is quite reliable based on the standard error of the estimate shown in parenthesis in Table 2. The shear index is a simple measure of the flowability of a material and is used here for comparison purposes because it is reasonably reliable [50] and easy to determine. The effective angle of internal... 

Flowability is important to the successful scale-up of a tableting process. The rate at which the precompacted blend flows into the hoppers of the tablet press and subsequently into the die cavity could be crucial to dose uniformity. Three measurements are most commonly used to measure flow ... 

Figure H2.2.5 A diagram illustrating the operation of a back extrusion fixture being used to measure the textural properties of a flowable food material.

Fig. 4.2 The angle of repose. It should be noted that the angle of repose is generally not a measure of flowability of solids, and as Jenike (22) points out, it is strictly useful only to determine the contour of a pile. Its popularity stems from the ease with which it can be measured.

Factors Affecting Material Flow. Although material flow is a function of its cohesive properties, factors known to affect material flowability include moisture content, temperature, particle size, and time of storage at rest. Therefore, the flow properties of material should be measured to determine the effects of the environmental conditions discussed below. 

Interparticle Forces, Measurement of Cohesiveness and Flowability of Solid Particles at Ambient Conditions... 

It would be desirable to have simple tests capable of characterising the fluidisation behaviour or flowability of particulate materials on the basis of their bulk properties. To this end, Carr19 developed a system to characterise bulk solids with respect to flowability. Table 6 summarises the properties which are determined. In Carr s method a numerical value is assigned to the results of each of these tests, and is summed to produce a relative flowability index for that particular bulk material. Given the extensive use of these empirical techniques in academia and industry, a brief review on the subject is reported here. Nevertheless, it should be emphasised that these techniques allow measurements of the flow-ability or cohesion of materials solely in their stationary or compressed status and at ambient conditions. A direct relationship between these... 

---