Filling Scales

Filling Scales are used to increase the level of accuracy obtained in a container.

Containers are often filled by weight. These can include Drums, cylinders,Tanks,pails,Cartons,totes, and almost any other type of box. While it may be more convenient to fill by volume, there are a number of parameters that can affect the accuracy. Depending on the type of material being filled, it may compact differently depending on the temperature or the relative humidity. The particles may cling to each other by static electricity. The filling force may push the material together, or may allow it to incorporate air. The density of the material may differ. Therefore, filling scales may be needed to increase the level of accuracy obtained. The weight can be independently determined by use of the scale, which will generally be underneath the item being filled. Of course it is important to de-couple the filling tube or hose from the container, so that it does not affect the reading. It may also be useful to control the rate of filling. A rapid feed rate may apply a downward force into the container, and onto the scale, also causing errors. It is very useful for filling scales to include setpoints for control purposes.

Generally set by the operator, a setpoint may give a visual and electrical signal that can be used to automatically turn off the feeding device, which may be a pump, augur, conveyor or similar. A second setpoint will often be set somewhat lower than the first, and may be used to slow down the rate of feed. This will provide enhanced accuracy. Scales used for this purpose should be quite rugged, to accommodate the high forces that may be applied when the full container is removed from the scale platform. Stainless steel load cells are the best choice for this purpose. It is also convenient to use a scale with a low platform height to provide easy access for loading and unloading.