Mettler Toledo LJ16 Spécifications télécharger pdf (Page 105)

METTLER TOLEDO Weigh Module Systems Handbook

(12/99)11-2

on an indicator. Both the top and bottom of the load cell have an opening designed to

accept a threaded rod.

Spherical Rod End Bearing: For tank or hopper scale applications, a threaded rod end

bearing is screwed into the opening on each end of the load cell. These two bearings

are positioned so that one is turned at 90 degrees from the other.

Clevis/Pin Assembly: A U-shaped clevis is connected to each rod end bearing with a

clevis pin. This assembly forms a ball joint that rotates to compensate for when a weigh

module suspension system is not perfectly vertical. A hitch pin is used to lock each

clevis pin into place.

Jam Nuts: These four nuts are tightened to hold the threaded components in place,

preventing the weight of the hopper from unscrewing them.

Sizing Weigh Modules

To design a hopper 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 hopper scale: (1) the weight of the empty hopper, (2) the weight of the

hopper’s contents when full, and (3) the number of weigh modules. The number of

weigh modules will equal the number of supports that the hopper 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

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 hopper designed to hold 20,000

pounds of grain. The hopper itself weighs 5,000 pounds and is supported by four

threaded rods. 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

hopper and its contents, figure in any safety factors, and then divide by the number of

weigh modules.

20,000 lb Weight of grain

+ 5,000 lb Weight of empty hopper

25,000 lb Total weight

x 1.25 Safety factor

31,250 lb Adjusted weight

÷ 4 Number of weigh modules

7,812.5 lb Weight per weigh module

Since each weigh module will need to handle up to 7,812.5 pounds, the best choice for

the job would be tension weigh modules with a capacity of 10,000 pounds each.

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Mettler Toledo LJ16 Spécifications Page 105