The test results of Ring Shear Testers are not only applied on flowability measurements, e. g.. for product development or quality control, but also on hopper design for flow. In this case, hopper slope angles and outlet dimensions are calculated in dependence on the measured flow properties, e.g., with the goal to achieve mass flow in the hopper, and to avoid cohesive arches. In case of funnel flow silos, the rathole diameter can be predicted. For both types of flow the influence of the time consolidation is taken into account. Time consolidation refers to the increase in the strength of a bulk solid when it is stored in a silo for a long time at rest.
The new hopper design software reads the data generated by the Ring Shear Testers to interactively tune the required graphs of unconfined yield strength, bulk density, internal
friction, and so on, and then to create a silo design from the selected data. Interactivity is important in order to allow a transparent approach, but also to be able to intervene in critical products, in order to avoid errors by a "stubborn" application of the design methods.
With the new software, time-consuming iteration cycles at stress-dependent friction angles are a thing of the past: All stress-dependencies specified by measured data are taken into account. Thus, e.g. the hopper slope angle can be specified as a function of the outlet size or local hopper cross section, respectively.
The results are output as a comprehensive pdf document, from which all steps of the interpretation can be understood in retrospect. This is indispensable for a complete documentation of a silo design.
In addition to the design of mass flow silos for conical, wedge-shaped, and asymmetric wedge-shaped hoppers, taking into account the time consolidation, the design of funnel flow silos is also included. In addition to newly calculated design parameters (e. g., flow factors, ff) based on Jenike's differential equations in Bulletins 108/123, other known approaches can alternatively be applied.
The software will be shown as a working development version at POWTECH 2019. It should be available later in 2019.