Gravimetric feeding: accuracy and repeatability
Gravimetric Feeders fall into 3 categories:
- Batch Feeders – by controlling weight a weighed batch (Kg) is dosed, cab be loss-in-weight or gain-in-weight.
- Rate Feeders – by controlling speed a variable speed rate (Kg/hr) is dosed.
- Recipe Feeders – by controlling both speed and time a variety of recipes can be delivered already mixed.
By the addition of load cells the main benefit is that the required dosing is confirmed by the weighing, whereas with volumetric dosing a degree of trust is required on historic performance
The RPM can be adjusted by means of:
- Continuous hydrostatic variable-speed motors with manual or electrical control: minimum flow rate equal to 1/5 of maximum flow rate.
- Continuous hydrostatic variable-speed motors with manual or electrical control: flow rate having maximum value of approximately zero.
- Gearmotors with motors piloted by vector inverters and additional power ventilation, when necessary, with minimum flow rate equal to at least 1/10 of maximum flow rate.
Batches obtainable according to the spirals/screws and reduction ratios applied of the screw extractor or screw batcher.
When operating by weight, gain in weight or loss in weight, load cells are used.
In this case of the gravimetric feeder precision depends on the type of cells used and the incidence of the tare on the single desired weighing. Depending on the configuration, the batch programmers manage several ingredients and formulas.