Gravimetric feeding
In gravimetric feeding, a material is measured out based on its weight or mass.
What are the key characteristics of gravimetric feeding?
In contrast to volumetric feeding, the actual amount of material dispensed is determined by weighing. Deviations can thus be detected and the feed rate adjusted accordingly.
Gravimetric feeding systems are used when bulk materials like powders, granules, pellets, or other solid materials need to be fed into a production process with a high degree of accuracy and reproducibility.
How does gravimetric feeding work?
A frequently used method is loss-in-weight feeding (LIW). Here, feeder and hopper are both mounted on a weighing system. As material is discharged, the total weight decreases. The actual material flow is determined based on this loss of weight over a specific period of time.
The control system continuously compares the measured actual value with the specified target value. If a deviation occurs, the feed rate can be adjusted, for example by changing the speed of a screw.
In contrast, gain-in-weight feeding (GIW) measures a container's weight gain. This method is used particularly in batch feeding.
What are the advantages of gravimetric feeding?
Since gravimetric feeding measures the actually discharged material, it can account for variations in bulk density more effectively than purely volumetric feeding. This ensures high feeding accuracy and reproducible processes.
Gravimetric feeding is thus particularly suitable for applications where the exact composition of a product is crucial or different material properties must be taken into account. The weighing system and feeder used depend on the bulk material, feed rate, desired accuracy, and process control.