Loss in weight feeder

When high accuracy is required, to control precisely the powder feedrate, Sodimate can supply Loss in weight feeder. Accuracy relies on the screw feeder constant and reliable feedrate. In addition weighing cell control the weight accuracy.

2 types of installations can be designed with weighing equipment:

  • Batch process with an accuracy on the quantity loaded
  • Continuous flowrate control accurate over time and quantity.

The operation is as follows:

Phase 1: Filling.

The mechanical arch breaker and the feeder under the silo quickly fill the hopper up to the highest level.

Phase 2: Computing.

The Loss in weight installation begins and the product is discharged from the hopper. The weighing sensors measure a consistent flow rate that is compared to a setrate saved in the PLC given by an operator or an external signal. If the two rates are inconsistent, the PLC will increase or decrease the feeder’s speed to match until the two rates are exactly the same.

Phase 3: Refill.

Once the lowest possible level is reached, the loss in weight hopper must be refilled. The installation goes into blind phase, i.e. the electronics are no longer able to measure the input or output. The flowrate then switches to volumetric control according to a taring realized at the start-up. This blind phase must be as short as possible to not reduce the accuracy, that is why the feeding flowrate from the silo is about 10 times higher than the desired flow.

Gravimetric feeder to feed into a pneumatic conveyor
Gravimetric feeder to feed into a pneumatic conveyor

Waste incineration plant : Powder Activated Carbon gravimetric feed for Dioxines removal in Flue Gas Cleaning application.
Waste incineration plant : Powder Activated Carbon gravimetric feed for Dioxines removal in Flue Gas Cleaning application.

Advantages of the Loss in weight system

  • Reliable dry consumption
  • Automatic calibration
  • Low/High Level alarms
  • Scaling possible at any time
  • Troubleshooting mode
Example of PID of a weight dosing installation feeding a pneumatic transfer
Example of PID of a weight dosing installation feeding a pneumatic transfer