Rice Lake Z6 Single-Ended Beam, SS Welded-seal, IP67, OIML C3 - Manual (Page 38)

34 Load Cell and Weigh Module Handbook
Typical Applications
Figure 17-3 illustrates what is perhaps the simplest weigh
vessel. This works well under the following conditions:
Weighing self-leveling materials only.
The vessel is symmetrical about the point of suspension so that
the center of gravity rises along the same vertical line each time.
These restrictions ensure that the content’s center of gravity is
always vertically below the load cell, removing the tendency of
the vessel to bind against the bumpers. Bumpers are provided
to limit the amount of sway produced if the tank were
accidentally hit or subjected to other external forces. Bumpers
can only be used with a self-centering vessel mounting
arrangement, since the vessel cannot remain in contact with
bumpers without causing weight reading errors. The vessel
must also be restrained from rotating to prevent suspension
hardware from unscrewing.
Figure 17-3.
A weigh vessel suspended from a single load cell may be used
to weigh solids if horizontal stay rods are used to eliminate the
side movement caused by shifts in the content’s center of
gravity.
The three load cell suspension system shown in Figure 17-4
uses three S-beam load cells placed 120° apart on a cylindrical
vessel. This avoids the problems of having to adjust the weight
carried by each cell, as the inherent stability of a 3-point
hanging system will ensure equal loading at each point. To
ensure stability, suspension rods should be attached to the
vessel at or above the center of gravity of the filled vessel.
Though this configuration is inherently stable, special attention
is required when significant vibrations, agitation, wind or seismic
activities are possible. In this case, bumpers or horizontal check
rods should also be employed.
Each support point should be equally rigid and deflect by the
same amount when loaded. If not, the load may be transferred
unequally, which may overload one or more of the cells.
Figure 17-4.
The 4-cell suspension system shown in Figure 17-5 is most
common for rectangular hoppers. As mentioned previously,
adjustment will be necessary to equalize the load carried by
each load cell to within 10% of each other.
Figure 17-5.
Note the use of safety check rods in the
suspension mount illustrations. Each
rod passes through a large clearance
hole at the lower end and the nuts are
loose so there is no interference with the weighing accuracy. All
suspended vessel weighing systems must be protected by
safety check rods or chains to prevent damage or injury in the
event of a failure.