|Thayer Model No.||No. of Weigh Idlers||Belt Width (W)(inches)||Idler Spacing (Inches)||Minimum Load (lbs/ft)||Maximum Loading (lbs/idler)||Mass Counter-Balanced Weigh Bridge||Belt Speed(ft/min)||Accuracy (%)||Load Cell Support|
|Full Scale||3:1 Load|
|STANDARD CONFIGURATION BELT SCALES|
|1||14-48||36-60||7.2||300||YES||10-1000||1||2||SG / LVDT|
|2||14-48||36-60||5.4||300||YES||10-1000||±¼||±½||SG / LVDT|
|2||24-60||30-60||12||800||YES||10-1000||±¼||±½||SG / LVDT|
|3||24-60||30-60||8.8||600||YES||10-1000||±¼||±½||SG / LVDT|
|3||30-72||30-60||8.8||1600||YES||10-1000||±¼||±½||SG / LVDT|
|4||24-60||36-60||6||525||YES||10-1000||±⅛||±¼||SG / LVDT|
|6RFS-8||6||30-72||36-60||4.3||1200||YES||10-1000||±1/10||±⅛||SG / LVDT|
|8RFS-8||8||30-72||36-60||4.3||1200||YES||10-1000||±1/10||±⅛||SG / LVDT|
|LIGHT LOADING BELT SCALES|
|2||24-60||48-60||0.1 x W||W 2 / 75 lbs/ft||YES||10-1000||±¼||±½||SG|
|NTEP APPROVED COMMERCIAL BELT SCALES|
6NAR-6 (8″ stringer)
8NAR-8 (8″ stringer)
How important is accuracy and how much is it worth?
You can answer that question if you know how much your material is worth. You probably wouldn’t be considering the purchase of the Belt Scale if you were not concerned about how much things cost. The information you receive from a Belt Scale tells you a lot about what is happening in your plant and, of course, one of the key bits of information is how much material has passed over the scale.
This weight information may be used for a lot of purposes ‐ Invoicing, Production, Inventory, Waste Measurement, Material Balance, Bonus Payments, Measuring Plant Efficiency, etc. At the end of the year’s operation the tonnage and most importantly, the dollars can add up to a considerable amount.
|JUST 1/4% ERROR CAN MAKE A BIG DIFFERENCE|
|COST OF MATERIAL LOST BY THE SCALE INACCURACIES OF ONLY 1/$% FOR AN 8 HOUR SHIFT, 5 DAYS A WEEK FOR 1 YEAR|
|COST/TON||@ 200TPH||@ 500TPH||@ 1,000TPH||@ 2,000TPH||@ 5,000TPH||@ 10,000TPH|
FREQUENCY OF CALIBRATION
There is a correlation between frequency of calibration, number of idlers on the scale weighbridge and the accuracy required. While it may be possible to achieve a reasonably high degree of accuracy for a short time with a single idler scale in a good installation it is obvious that the single idler scale is more susceptible to belt effects and changes in alignment and therefore the calibration should be checked more frequently. Likewise, a multiple idler weighbridge will not have to be checked frequently if 1% accuracy is all that is required.
A common mistake made in the selection of belt scales is choosing a single idler scale or short weighbridge because the accuracy required is only 1%. It may be possible to achieve 1% but it might require calibrating once a day.
HOW OFTEN SHOULD CALIBRATION BE CHECKED?
The frequency of calibration is best determined from actual operating experience. Initially the tests should be performed more frequently (once a week) to establish a confidence level based on accuracy required and the number of times an adjustment had to be made. The tests should be based on the As‐Found‐Error (AFE).