Rice Lake Z6 Single-Ended Beam, SS Welded-seal, IP67, OIML C3 - Manual (Page 40)

36 Load Cell and Weigh Module Handbook
19.0 Low-Accuracy Systems: Partial Mounting on Flexures
As noted earlier, low-accuracy weigh systems may be partially
supported on flexures if the following conditions are met:
The vessel contents are self-leveling.
The vessel is symmetrical around a vertical line through the
content’s center of gravity.
These restrictions ensure that as the vessel fills, the center of
gravity of the contents rises along a vertical line whose
location is fixed relative to the support points. This ensures
that each load cell always sees the same proportion of the
load.
The horizontal cylindrical tank illustrated in Figure 19-1 is
mounted on two flexures at one end and two load cells at the
other.
It is very important that the vessel is level and the ends are
identical in shape. This is a lower-cost weighing system which
will work satisfactorily if low accuracy is acceptable.
Flexures may also be used with tension applications.
Figure 19-2 is an example of a circular vessel suspended from
one load cell and two flexures (or simply tension rods in this
case).
Figure 19-1.
Care must be taken to separate the flexures and load cells to
opposite sides or ends of the vessel. In Figure 19-2, for
example, the flexures could not be placed on one diagonal
and the load cells on the other.
If these vessels are to be calibrated electrically, then the
geometry of the vessel must be known accurately. This allows
the percentage of the load carried by the load cell(s) to be
calculated. A practical alternative is to calibrate with a known
weight of liquid. It is not practical to calibrate these vessels
with test weights since they could not be placed with any
precision at the center of the vessel.
These arrangements should be avoided when the potential
exists for weight to be transferred from one support to
another. This can be caused by wind-loading, thermal
expansion/contraction of pipes, etc.
Figure 19-2.