There are two types of bagging scales based on how the product is weighed: gross weigh scales and net weigh scales.
Gross Weigh Bagging Scales
With gross weigh scales, the bag is hung on the scale spout and the bag weight is zeroed out. As the product is added to the bag, the bag is weighed. When the desired weight is achieved, the bag drops off the spout.
Gross weight scales:
- are less expensive
- maybe more accurate with some non-free-flowing products that might become stuck in a net weigh scale’s weigh hopper.
Net Weigh Bagging Scales
With a net weigh scale, the product is first loaded into a weigh hopper. When the desired weight is achieved, the weight hopper’s gate opens and the product is dumped into the bag.
Net weight scales:
- are more expensive due to the additional weigh hopper and control valve components.
- have a faster throughput because, while the operator is closing the last bag, the product for the next bag is being weighed out into the weigh hopper.
- are typically more accurate because there is less product-free fall distance.
Both types of scales are available with a fast bulk and slow dribble product feed to achieve the best accuracy.