Pre-screening by means of a fix installed grid, sieve or a vibrating sieve inside the tipping station supports not only a constant quality output but also contributes to a smooth feeding operation when raw materials tends to be lumpy.
Often, when powders are tipped into a tipping station out of paper bags, parts of the paper bags drop into the process. Undetectable by metal detectors, the paper pieces might find its way to the mixer or even worse to the packaging machine. A fix grid avoids this kind of error.
A vibrating screen or sieve is used, when a powder raw material has lumpy characteristics and does not simply flow as desired. The vibration will loosen the material and support the material flow. Mesh size and form of the grid depend on throughput and material properties.