volumetric and gravimetric feeders
Volumetric feeder provides low cost and easy option in batch or continuous applications, especially when the bulk density of the fed material is consistent or when precise feed accuracy is not so important for the quality of end product. Frequently volumetric feeder is used in gain-in-weight batch application since higher accuracy can be achieved. When process requirement is more demanding, volumtric feeder with gravimetric scale and loss-in-weight control can be used.
Gravimetric systems feeder by weight and use process feedback to make continual operating adjustments for fluctuations in material density and ambient conditions. The result is a very precise feed rate, generally 0.5% to 1% or better. An added benefit is knowing exactly how much material, by weight, is used, an important factor for quality management and inventory control.
In general, the determining factor for the type of feeder you select will be the accuracy level required for your application. If all you need is a constant, reliable flow of material, the less expensive volumetric feeder may be adequate. For precise metering, the advanced control systems found in gravimetric feeders may be the way to go.