Loss-in-Weight Feeder
A loss-in-weight feeder is a gravimetric feeding system that consistently and precisely feeds bulk materials into a production process.
How is the feeding rate measured?
To achieve this, the hopper and feeder are weighed together. As material is discharged, the total weight decreases. The actual feed rate is determined based on this loss of weight over a specific period of time.
This measuring principle is known as loss-in-weight (LIW). Loss-in-weight feeders are particularly well-suited for processes that require a consistent and accurate material feed.
How does a loss-in-weight feeder work?
During feeding, the weighing system continuously measures the feeder's decrease in weight. The control system compares the determined actual feed rate with the specified target value. In case of deviations, the feeder's delivery rate is adjusted accordingly – for example by adjusting the speed of a screw.
When the material supply in the hopper drops to a defined value, it is refilled from an upstream supply bin. During the refilling process, the feed rate cannot be calculated based on weight loss. In this phase, the feeder continues to operate based on previously defined feeding parameters. Once refilling is complete, gravimetric control resumes.
Where are loss-in-weight feeders used?
Loss-in-weight feeders can be used for various bulk materials like powders, granules, pellets, or fibers. The technical design is tailored to the properties of the respective material and the specific process requirements. Possible options include screw feeders or vibrating feeders, for example.
Since loss-in-weight feeding measures the actually discharged material, it can account for variations in bulk density more effectively than purely volumetric feeding. This allows high feeding accuracy and a controlled material flow – key requirements for reproducible production processes and consistent product quality.