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Continuous Loss-in-Weight Blenders Chapter 2: Functional Description 17
Lower Mass Flow Weigh Hopper Assembly
The lower mass flow weigh hopper, otherwise known as the weighed common hopper, is
used to determine the actual processing rate of the processing machine so that the blender can
be slaved in to run at the learned rate. The hopper is constructed of spun aluminum and is of
the mass flow type (See the glossary in the Appendix). It is supported by a load cell, and will
carry a weight of material depending on how much is flowing into the hopper from the
metering augers, and how much is flowing out of the hopper, dictated by the processing rate
of the processing machine.
The computer uses the mass flow hopper flow rate (the differential rate), along with the
known total rate from the weight loss feeders to determine the actual processing rate of the
processing machine. The blender output rate is then adjusted to match the learned processing
rate. This method of operation provides very accurate slave in of the blender to the
processing rate, and eliminates the need for a mixing hopper.
The lower common weigh hopper is also equipped with a high level proximity level sensor to
allow manually adjusted volumetric operation of the blender in the event of computer failure.
Figure 4: Weigh Hopper Assembly
Note: The lower or common mass flow weigh hopper uses the change in weight over
time, of material contained in the hopper over time to calculate it’s discharge
rate (differential rate). This learned discharge rate is then summed with the
known total metering rates of the blender feeders to learn the actual processing
rate of the processing machine. The blender output rate is then adjusted to
match the learned processing rate, eliminating the need for a blender mixer.
“Fixed Rate” mode
The lower mass flow weigh hopper may be replaced by a collection hopper with “high” and “low “
level switches on higher capacity blenders. This configuration controls the blending system rate
based on material level
rather than material weight.