Specifications

METTLER TOLEDO Weigh Module Systems Handbook
(12/99)8-2
Top Plate: This plate is bolted or welded to a tank or other structure so that it receives the
weight of the tank. Adjustable bumper bolts limit the movement of the top plate by
bumping against the load cell.
Sizing Weigh Modules
To design a scale that will weigh material accurately, you must use weigh modules with
the proper load cell capacity. There are four main factors in sizing Centerlign weigh
modules for a scale: (1) the empty weight of the weighbridge on which the material will
be placed, (2) the maximum weight of the material to be weighed, (3) the number of
support points or weigh modules, and (4) the type of loading. The two types of loading
to be considered are full end loading and distributed loading.
To understand the difference between full end loading and distributed loading, imagine a
conveyor scale with a weigh module in each of the four corners of its weighbridge. Full
end loading can occur when a small object moves across the weighbridge. Initially, the
object’s full weight will be concentrated on the two weigh modules at the front end of the
weighbridge. Only when the object approaches the center of the weighbridge will its
weight be distributed evenly across all four weigh modules. Distributed loading occurs
when an object with a large surface area moves across the weighbridge. By the time its
full weight is on the scale, part of the load has been transferred to the weigh modules at
the back end of the weighbridge. With full end loading, you will need to size the weigh
modules so that two of them are capable of supporting a full load.
A standard safety factor of 1.25 is normally figured into the calculation to compensate
for uneven load distribution and any underestimation of weights. Certain installations
might have special environmental considerations requiring additional safety factors.
Environmental considerations are discussed in Chapter 4.
Calculating Weigh Module Size
Suppose that you want to size weigh modules for a conveyor section designed to weigh
a 3,000-pound billet of aluminum. The conveyor section itself weighs 2,000 pounds
and stands on four legs. Since the billet will roll onto the conveyor from one side, the
system should be sized for full end loading over two weigh modules. Calculate the total
weight of the scale and its contents, figure in any safety factors, and then divide by two
weigh modules.
3,000 lb Weight of billet
+ 1,000 lb Weight of empty conveyor section (one half)
4,000 lb Total weight
x 1.25 Safety factor
5,000 lb Adjusted weight
÷ 2 Number of weigh modules
2,500 lb Weight per weigh module
Use four 2,500-lb Centerlign weigh modules for this application. If full end loading is not
a consideration, divide the adjusted weight by the total number of weigh modules (4) to
determine the capacity of weigh modules that will be needed.