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Conveyor Belt Grades
The RMA (Rubber Manufacturers Association) established specifications for Conveyor Belting grades several decades ago. Though many early members of the association are no longer manufacturing conveyor belting, the RMA updated the standards to accommodate the new raw materials utilized in belt manufacturing.
The RMA only grades rubber belting for the most commonly used industrial belts (generally SBR, natural or a combination). The carcass fabrics are essentially the same when covered by specialty rubbers such as Neoprene, Nitrile or Chlorobutal. We list the original standards for the three grades of general purpose belts below.
| RMA Original Specifications |
| RMA Grade #1 |
Cover tensiles of 3500 to 4000 lbs. Adhesion between components of 20 to 24 lbs. |
| RMA Grade #2 |
Cover tensiles of 2500 to 3000 lbs. Adhesion between components of 16 to 19 lbs. |
| RMA Grade #3 |
Cover tensiles of 800 to 1000 lbs. Adhesion between components of 12 to 15 lbs. |
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Because cotton was the basic carcass material when the RMA established these standards, adhesions were more difficult to achieve. Today, with synthetic fabrics and RFL treatments, average adhesions are in the 60 to 70 lb. range on most general purpose belts.
Though clouded by the introduction of more modern rubbers such as EBR (Polybutadiene), there is little justification for relaxing the cover tensiles first prescribed -- unless manufacturers want the freedom to use lesser rubbers. We list the new specifications below.
| RMA 1994 Specifications |
| RMA Grade #1 |
Cover tensiles of 2500 lbs. 400% elongation. |
| RMA Grade #2 |
Cover tensiles of 2000 lbs. 400% elongation.. |
| RMA Grade #3 |
No specifications. |
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Rubber & Plastics, Inc. continues to recognize the original conveyor belting specifications and provides complete details of all rubber belting components. We show the comparitive grades of belts common to the industry on the Conveyor Belt Cross Reference Chart, listing the current trade names of various belts in each category.
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