• Constant Rate Feeding
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Loss in Weight Feeders - Constant Rate Feeding



Principle and Operation


The Rospen loss-in-weight feed system has been designed to weigh and control the output of variable products continuously to weight accuracies of ±0.25% to ±1%.

The general principle of operation is as follows:

  • The loss-in-weight hopper is rapidly filled via an automatic filling valve. At a hopper-full weight, pre-set within the PLC, the filling
  • The metering feeder starts (or is already running from the last cycle) and feeds product into the process; thus the weight in its product hopper gradually falls.
  • The falling weight is measured every few milli-seconds and this information is averaged and stored by the PLC or as a
    falling weight per unit time (Kg/Sec). This weight per unit time is compared to a weight per unit time already pre-set by the operator via the HIM and stored in memory.
  • Any difference in the characteristic slope of the falling weight per unit time and the slope of the pre-set weight against time, is fed to a process controller and used to speed up or slow down the product feeder in order to make the two slopes identical.
  • At a pre-set hopper low weight, the metering feeder is locked onto it’s last average speed and the filling valve opened again, so rapidly filling the hopper.
  • When the hopper is again filled, the metering feeder will be brought back onto automatic control at the original correct speed that was memorised by the PLC during the previous cycle.
  • Thus the cycle will repeat, with the PLC going through a continuous learning curve which will get more accurate with each cycle.
  • The cycle time will be approx 10:1 running to filling e.g. 10 mins run to 1 min fill, or 5 mins to 30 seconds fill.

 

 

Downloads
Download PDFLoss in Weight Feeders PDF