Chutes – A Brief History
The fixed ideas of the past
In the 30 years of chute development everyone has developed fixed ideas. Essentially high volume conveyors originated from the grain industry and then moved into sized washed coal.
In terms of the way they worked, they were facile – uniform in size and the materials flowed predictably. Universities started looking at this information and started using models to design bins and hoppers and then developed their models for transfer chutes similarly. When the principles were applied to more complex materials we found that performance outcomes were seriously compromised.
It’s all way more technical than was thought.
Discrete Element Method software (DEM) was first applied to transfer chutes in the early 1990’s. The mathematical complexity of granular flow is extreme and DEM assumed many things. Today we seriously question and in fact substantially challenge many of these assumptions as being invalid. With DEM the design software of preference for transfers, this is a significant issue.
How right are the right angles?
For example, to design material handling transfer systems, historically we have developed and used two well tabulated angles: the surcharge angle (the angle the material sits up at on a conveyor belt) and the angle of repose (the angle it will sit up on in a static environment)
But the flow complexity of granular materials is much more complex and these angles can be totally irrelevant depending on the particular design. It’s design thinking based on unclear assumptions.
Today’s Gulf Stall Flow Technology
At Gulf we looked at site problems and using reverse engineering, developed an improved understanding of granular flow mechanisms that led to the development of our Stall Flow Technology. It takes on board many variables and looks at everything holistically, bringing about new and improved design thinking to all aspects including chute design.