Rice Lake Weigh Modules/Mount Assemblies - Manual (Page 49)

WEIGH MODULES
2-20
S-Beams
Rice Lake Weighing Systems
Weigh Modules
ITCM Mounts
The ITCM assembly is a particularly convenient method of sus-
pending a weigh vessel. The combination of clevises and rod end
ball joints ensures that forces detrimental to accurate system
performance are isolated from the load cell. In addition, the
unique electrical isolation provided to the load cell by this assem-
bly helps prevent damage from stray currents.
Allowable Movement
Figure 2-38 illustrates the use of the ITCM weigh module. This
mounting arrangement prevents most of the potential problems
caused by extraneous forces acting on S-beam load cells.
(a) (b) (c)
Figure 2-38
Construction and Features
1) The ITCM consists of a high-precision rod end ball joint which
is screwed into each end of the S-beam. The rod end ball joint
has a “ball” which is free to rotate in a TFE bearing; see Figure
2-38 (c). A clevis is attached to the rod end ball joint using a
shoulder screw.
2) This arrangement provides excellent alignment between the
center lines of the rods and the center line through the cell’s
load holes.
3) This arrangement allows movement in the directions indi-
cated by the arrows and also allows rotation, thus ensuring
that extraneous forces are not transmitted to the load cell.
4) The ITCM also incorporates an insulating system which will
not allow the flow of stray currents through the load cell. The
parallel ground strap provides further protection with an
alternate path to ground.
5) ITCM’s are available in mild steel in capacities from 100 lb to
20,000 lb using the RL20000 load cell.
NOTE: A single ITCM is often used to convert a mechanical truck
or hopper scale to electronics. This allows you to take advantage
of process control or data collection options available with elec-
tronic weighing. The conversion can be accomplished by inserting
an ITCM assembly in the steelyard rod without affecting the
operation of the mechanical beam or dial which may be retained as
a backup.
Typical Applications
Figure 2-39 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.
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. This
is discussed further in the Vessel Restraints section.
Figure 2-39