Specifications

METTLER TOLEDO Weigh Module Systems Handbook
(12/99)9-2
Top Plate: This plate is bolted or welded to a tank or other structure so that it receives the
weight of the tank.
Hold-Down Bolts: These bolts connect the top plate to the base plate in order to check
any uplift forces that might cause the tank scale to tip. Clearance must be maintained
between the bolt and the top plate so that the bolt does not receive any of the weight that
is being transferred to the load pin or ball-and-cup assembly.
Sizing Weigh Modules
To design a scale that will weigh accurately, you must use weigh modules with the
proper load cell capacity. There are three main factors in sizing weigh modules for a
tank scale: (1) the weight of the empty tank, (2) the weight of the tank’s contents when
full, and (3) the number of weigh modules. The number of weigh modules will equal the
number of legs or supports that the tank has.
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 add Ultramount weigh modules to a tank designed to hold
100 kilograms of a liquid. The tank itself weighs 50 kilograms and stands on four legs.
Assume that only the standard safety factor is needed for this installation. To determine
what size weigh modules you will need, calculate the total weight of the tank and its
contents, figure in any safety factors, and then divide by the number of weigh modules.
100 kg Weight of liquid
+ 50 kg Weight of empty tank
150 kg Total weight
x 1.25 Safety factor
187.5 kg Adjusted weight
÷ 4 Number of weigh modules
46.875 kg Weight per weigh module
Since each weigh module will need to handle up to 46.875 kilograms, the best choice
for the job would be weigh modules with a capacity of 50 kilograms each.
If you are designing an Ultramount weigh module system for a dynamic loading
application such as a conveyor scale, you will need to consider four factors: (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–full end loading or distributed loading. With full
end loading, you will need to size the weigh modules so that two of them are capable of
supporting a full load.
To calculate weigh module size for a conveyor scale with four support points, add the
maximum weight of the material to be weighed and the weight of the weighbridge. Then
multiply this total weight by a safety factor to determine an adjusted weight. If full end
loading is a factor, divide the adjusted weight by 2 (the smallest number of weigh
modules that will need to support the full load) to determine the capacity of weigh
modules that will be needed. If full end loading is not a consideration, divide the
adjusted weight by 4 (the total number of weigh modules).