Schulze ring shear tester

The weaknesses associated with the flow through an orifice and angle of repose measurements limit their application for powder flow studies and hopper designs. Consequently, several powder shear testers and methods that permit a more thorough and precisely defined assessment of powder flow characteristics were developed. Shear testers that measure the frictional characteristics of a powder bed under load yield valuable information with regard to powder flow in high-speed tablet equipment. A number of types of shear cell testers are available, but the most common types used in the pharmaceutical industry are the Jenike shear cell and the Schulze ring shear tester.61,62... 

Figure 7.4 Schulze ring shear tester annular trough.

TABLE 7.10 Classification of Powder Flow Properties Using the Schulze Ring Shear Tester... 

Schulze, D. Flowability and time consohdation measurements using a ring shear tester. Powder Handhng Process 1996, 8 (3), 221-226. 

The limitations of the Jenike shear cell are that it is not very useful for measuring bulk solids with large shear deformations, e.g., plastic powders. The level of consolidation stresses required are inappropriate for pharmaceutical materials, and the quantity of material required is often beyond that available in the early stages of development. Alternative shear cells that have been used include annular shear cells (Nyquist and Brodin 1982 Irono and Pilpel 1982) and ring shear testers (Schulze 1996). 

A similar concept with a number of engineering improvements has recently been developed by Schulze (Figure 5). The mechanism is much more sensitive than that employed by earlier ring shear testers, and the cell can be removed for cleaning and also for time consolidation testing. It is commercially available. Excellent correlation has been observed between the Schulze tester and the Jenike shear cell, as well as with more sophisticated research instruments. An automated version is available for situations where high productivity is required. As with the Peschl tester, testing times are about 1/3 of that required for comparable Jenike tests. 

The shear tests were performed using the annular ring shear tester (from Schulze SchiittgutmeBtechnik, D-38302 Wolfenbiittel) sketched on Figure 1. 

D. Schulze, Flowability and Time Consolidation Measurements Using a Ring Shear Tester, Powder handling processing, 8, (3), pp. 221, 1996. 

Standard shear test method for hulk solids using the Schulze ring tester. ASTM International, Designation D6773-02, 2006. 

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