Rice Lake Weigh Modules/Mount Assemblies - Manual (Page 4)

SYSTEM DESIGN
1-2
Bulk Material Weighing Systems
Custody Transfer
Weighing bulk material on a truck scale is a typical example of
custody transfer weighing where material is being traded for
dollars. The filled truck is weighed and the known tare weight of
the truck is subtracted to determine the net weight of product. This
may be done for invoicing or inventory-control purposes. Typi-
cally, achieving a predetermined weight is not important in this
situation. What is important is knowing how much material
entered or left the facility.
Material Proportioning
Figure 1-2 shows various ingredients being weighed on separate
scales, then mixed. Each scale must be accurate, or there could
be a detrimental effect on the proportions of each ingredient in
the finished product.
Bulk materials are weighed for various reasons. Although this discussion focuses on the weighing of bulk solids, many of the principles
are equally applicable to the weighing of bulk liquids. For the sake of convenience, we have classified bulk material weighing into three
general types:
Figure 1-3
Figure 1-3 shows several materials being mixed to a given recipe
and batched one at a time into a single weigh hopper. As all
ingredients are weighed in the same weigh hopper, the weighing
system must be linear to achieve correct proportioning. It does not
need to be calibrated accurately if the final net weight of product
is not critical.
Loss in Weight
Figure 1-4 shows a situation where the weigh hopper is first topped
up and when the filling process stops, the material is fed out at a
controlled rate. The total amount of material supplied to the
process may be important, but the rate at which product is fed into
the batching process from the weigh hopper is usually more
important.
Bulk Material Weighing Systems
Figure 1-1
Figure 1-2
Figure 1-4