FDBusiness.com

By Cathy Podevyn, Marketing Director, Spiroflow

A flexible screw conveyor (FSC) is ideal to preserve the homogeneity of a mixture even where particle size or density vary widely between the components. This is essential when transferring from a mixer to further process or packaging machinery.

A FSC works by having a rotating helical screw inside a ultra-low friction polymer tube running at speeds normally in the 500-960 rpm range. The flight of a traditional rigid screw sweeps the whole area of its conveying tube, but with an FSC it only impacts a modest percentage of the whole tube cross section. An FSC conveyor works by using the internal friction within a powder or bulk solid to transfer the forward motion of the powder in contact with the spiral to the whole tube contents.  With an angled system a dynamic equilibrium is set up with the spiral action moving some particles upwards but gravity causing other particles to fall back down the centre of the tube; this is why the spiral needs to be run at a fast speed.

Whatever way this works for you, the completion between conveying and fall back means that an FSC constantly mixes the product whilst it is conveyed.  If you want to convey a formulation which tends to segregate then an FSC is an excellent choice, because the re-mixing ensures that your mixture exits the conveyor as well, if not better, mixed than at the conveyor inlet.  Many over-the-counter health products are mixtures of very fine active components mixed with a coarse grade of sugar. To ensure every sachet is the same, many packing lines use FSCs as the final conveying technology to ensure that every sachet contains the same formulation. Be aware however, that not just any FSC supplier could achieve this effect.  Careful design of the discharge chute and integration into the next stage of the process is essential to minimise any elutriation due to free fall or rolling/sifting segregation as the material forms a heap in the receiver.

It is also possible to take two pure components and, by the correct configuration of two FSCs, produce a continuous mixer to prepare and convey a blend with a total equipment length only a little longer than the two feed hoppers for the raw materials.

Finally, the dynamic flow balance also means that the output rate of an FSC does not exhibit the pulsing effect of a rigid screw making them ideal as metering systems, either volumetric or gravimetric, with accuracies down to +/- 0.05% being readily achieved.

Spiroflow has been a Global leader in the field of powder handling and dry bulk solids processing for more than 45 years. To learn more visit spiroflow.com, email sales@spiroflow.com or call +44 (0) 1200 422525 in the UK or (1) 704 246 0900 in the US.