MERRICK MC3 35.00.EX, Operation And Maintenance Manual, Page: 30 / 69

Hopper Parameters
The Hopper Parameters are related to the physical properties of the weigh hopper.
Fill
Weight
Heel
Weight
Empty Weight
Hopper Related Weights
Fill Weight
The Fill Weight is the target weight for the fill sequence. It must be greater than the Heel
Weight. When the
Autofill Device
logical input is turned On (see Logical Inputs, page
35), the controller will turn off the
In Fill
logical output when the hopper reaches this
weight. The output should be used to control the hopper fill gate.
Heel Weight
This value represents the weight at which the hopper should be refilled. Normally there
will still be material left in the hopper. The
Heel Weight
sometimes has to be set
surprisingly high. There are several reasons for this:
•
The push from the material falling into the hopper when filling can cause mass flow
through the feeding device.
•
If there is an agitator in the hopper, there has to be enough material to make the
agitator effective.
•
There has to be enough head pressure into the feeding device to have a
reproducible relation between the Speed Demand Signal and the actual material
flow.
One easy way to determine a good
Heel Weight
is to set it low, run the feeder in Manual
Speed and observe
Rate:
in the Batch Statistics screen. It should initially stay almost
constant. Typically, at some weight it will start changing. The
Heel Weight
should be set
above this weight.
The default behavior is to start re-fill whenever the weight goes below the
Heel Weight
.
This will happen inside an ongoing batch. It is possible to change this behavior by
modifying some registers. The default value for all of them is zero.
R[269] A non-zero value will cause the hopper to re-fill after a batch has finished if the
batch setpoint is greater than the hopper weight minus the heel weight. The
effect is that the hopper will re-fill after the batch has finished if the next batch will
cause the hopper weight to reach the heel weight.
R[278] A non-zero value will prevent re-filling inside a batch sequence. Typically, the
heel weight must be significantly higher than the max batch weight for this to
work.
R[279] A non-zero value will cause a re-fill at the Start Batch command, if the batch
setpoint is greater than the hopper weight minus the heel weight. The effect is
that the hopper will re-fill before the batch starts if it will cause the hopper weight
to reach the heel weight.
Empty Weight
The Empty Weight value is used to determine when the hopper is empty. It should be set
to a value representing the amount of material that may be left in the hopper and that the
35.00.EX O&M Manual 26