Sizing Your Scale - Proper Belt Loading

Belt Loading

When choosing which capacity belt scale to purchase, belt loading is the important factor.  You don't want to purchase a model with a very high capacity and only use a very small % of the load cell's output. This can diminish accuracy somewhat. Belt-Way integrators have a very high internal resolution; therefore,  over-sizing a belt scale  model is not as detrimental as other manufactures can experience. Under-sizing the belt scale for the application's belt loading is to be avoided at all costs.  Unlike static scales that have a set capacity and  typically blank out  or indicate "OL" for over-load conditions, belt scales will not register rates / totals that are in excess of the load cell's maximum signal output. You don't want to be running production and not register a portion of it.  If this factor hasn't been taken into consideration, overloading the scale capacity can occur on main pit run/feed belts that occasionally experience"surge" loading from loaders feeding the belt with pit material. Desired  belt loading  is having a ratio greater than 4:1 between the weight of the material vs. the weight of the actual empty belt itself.  The live-load belt loading should utilize more than 50% of the available load cell output when running at the typical rate, with 65% to 75% being more desirable. Belt loading is affected by material feed rate and belt speed.. The spacing of the idlers does not change the belt loading but it does change the total amount weight applied to the load cells.  Decreasing the spacing between the idler rollers will decrease the total belt load on the scale; however, it makes the material sample the belt scale sees smaller and can decrease accuracy. There may be instances where more than one scale idler is recommended in a scale to increase sample size and sample time. We can provide 1, 2, 3 and 4 idler scales.

Basically, it is a good idea to consult a belt scale expert before purchasing a new scale. Idaho Weighing Systems can properly determine which  size scale will best fit your application with the maximum accuracy. With 6 Belt-Way models to choose from, we can find the best fit.

Give us a call @ 208-970-7748. We will be happy to help in any way we can, We have been providing and installing belt scales for many years and have the expertise to do it right.

Important Variables

In determining the "belt loading" we need to know a few variables to calculate the belt load:

  • Rate: Minimum & Maximum
  • Spacing: Distance between idlers
  • Belt Speed
  • Belt width and *thickness

*Belt thickness is usually  not  a necessary measurement to obtain, but can be important is some applications with wide belts and low belt loading  (i.e wood chips) 

After the belt loading is determined, we can size the scale.

Model          Belt Loading in lbs/ft

Model 45             15 -   90

Model 100          40 - 250

Model 200          80 - 500 

Model 350       165 - 875

Model 500       250 - 1250

Model 1000    500 - 2500  

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IWS Belt_Scale_Quote_Request_Form (pdf)