Experimental Investigation of Silo Stresses under Consideration of the Influence of Hopper/Feeder Interface

• Main Authors: Dietmar Schulze, Jörg Schwedes
• Format: Article
• Language: English
• Published: Hosokawa Powder Technology Foundation 2014-06-01
• Series: KONA Powder and Particle Journal
• Online Access: https://www.jstage.jst.go.jp/article/kona/8/0/8_1990021/_pdf/-char/en
• ISSN: 0288-4534; 2187-5537

With the data gathered from an experimental silo, operating with two different kinds of bulk solid (cohesive limestone powder and free-flowing plastic pellets), it is shown to what great extent the geometry of the transition from hopper to feeder influences flow profile and thus the stress pattern within the hopper. The optimal geometry for achieving mass flow and even withdrawal of a bulk solid over the entire outlet area depends on the bulk solid's flow properties and, in the case of the cohesive limestone powder, must be closely adhered to, as the flow pattern of this particular bulk solid is very sensitive to any deviations. Furthermore, it is shown how the load acting on the feeder can be ascertained. While the power required of the feeder for bulk solid removal in the discharging condition can be satisfactorily calculated from Jenike's theory, some well-known analytical methods available for the filled condition of the silo provide results which are too imprecise. The assumption of hydrostatic conditions in the hopper leads to stress values which are several times greater than those actually measured in the experimental silo. With the help of the empirically based equations, DIN1055, Part 6, one can find acceptable solutions for the order of magnitude and for the tendency of the stresses acting on the hopper walls. How one might determine the load on the feeder from these solutions needs further looking into. Through basic physical considerations, the dependency of the force required for removal of a bulk solid from under the outlet on the vertical load acting on the feeder, was found to be of a simple nature, from which an upper limit can be calculated. This was confirmed by measurements made on the experimental silo.