The concept below is primarily based around the application of a weigh system associated to PLC control. Whilst the weigh function is at the heart of any Loss in Weight system it does not directly impact on the material flow. The accurate design of the storage vessel and the choice of a suitable material transfer is critical.
The 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 loss-in-weight hopper is rapidly filled via an automatic filling valve. When the hopper reaches a full weight (which has been pre-set within the PLC) the metering feeder starts (or is already running from the last cycle) and feeds product into the process. This process will result in the hopper weight gradually falling. 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 time already pre-set by the operator.
Any difference in the slope of the pre-set weight against time and the actual, 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.
If the weight against time is below the pre-set level 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 filled, the metering feeder will be brought back onto automatic control at the correct speed memorised by the PLC during the previous cycle. This cycle repeats, 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.
This system consists of the following equipment:
a) Vibratory Conveyor mounted on a Load Cell Platform
b) Metering Screw Feeder mounted on a Load Cell Platform
c) Scarfed Vibratory Feeder
d) Tumble Drum
e) Touch Screen PLC control panel with menu functions
The vibratory conveyor loss in weight feeder is designed specifically for the accurate weighing and metering of products. The machine consists of a vibratory conveyor mounted on a low profile load cell platform.
Metering Screw Feeder
Designed to continuously meter flavour at a constant volume to high accuracies. The basic feeder consists of a unique tapered conditioning chamber, complete with a slow rotation agitator. Flavour is directed into a variable speed metering screw, which runs completely and evenly filled and is linked to an electronic feed back drive ensuring accurate speed holding under all load conditions. Resulting in material being metered out at a constant volume of between ±1% to ±2%.
The metering Screw Feeder is mounted on a standard weigh unit and is of a robust design and contains three, cantilever type load cells, which are summated to automatically compensate for any off centre loading that may occur during hopper filling and emptying. Complete with transit locks, overload and side-impact stops the unit’s self-centralising mechanism also eradicates inaccuracies due to temperature change. The solid state design of the system provides for a maintenance free operation and is enclosed in a stainless steel dust cover with removable sides.
Scarfed Vibratory Conveyor
Designed to create a curtain of flavour within the tumble drum for the product to pass through
Designed to gently tumble product through the curtain of flavour and for the product to have flavour on all sides.