Specifications

METTLER TOLEDO Weigh Module Systems Handbook
(12/99)10-2
Mounting Pad: This pad is bolted to a tank or other structure so that it receives the
weight of the tank.
Sizing Weigh Modules
To design a tank scale that will weigh its contents 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 weigh modules to a tank designed to hold 2,000 pounds
of a liquid. The tank itself weighs 1,000 pounds 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.
2,000 lb Weight of liquid
+1,000 lb Weight of empty tank
3,000 lb Total weight
x 1.25 Safety factor
3,750 lb Adjusted weight
÷ 4 Number of weigh modules
937.5 lb Weight per weigh module
Since each weigh module will need to handle up to 937.5 pounds, the best choice for
the job would be weigh modules with a capacity of 1,000 pounds each.
If you are designing a Value Line 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).
Applications should have minimal side load or shear.