The selection and engineering of the proper belting is best left up to an expert, who might be found working for a belting manufacturer or distributor or as an independent consultant. A properly specified and manufactured belt will give optimum performance and life at the lowest cost. Improper selection or substitution can have a catastrophic consequence.
There are a number of operating parameters and material conditions that should be detailed when specifying a conveyor belt. Material conditions to be detailed include:
Limit variations in thickness to a sliding scale lf +/- 20 percent for thin covers such as 2.4 millimeters (0.094 inch), and +/- 5 percent for cover gauges greater than 19 millimeters (0.75 inches).
Limit camber or bow to one-quarter of one percent (0.0025). This allows a camber or bow dimension of +/- 25 millimeters in 10 meters (0.75 inches in 25 feet). Camber is a convex edge of the belt; bow is a concave edge of the belt. RMA defines bow (and camber) as the ratio of the distance midway between tow points along the belt edge that are 15 to 30 meters (50 to 100 feet) apart, between the actual belt edge and a tape or string stretched straight between the two points. To express this in percent, calculate the ratio in hundredths and multiply by 100. For example, if 30 meters of belting was out of true by 450 millimeters (by 0.45 meters), this would equal a camber of 1.5 percent. In Imperial measurements, a distance of 18 inches (1.5 feet) over 100-foot length of belting would be a 1.5 percent camber.
Specify the belt surface to be smooth, flat and uniform +/- 5 hardness points. Hardness is measured in the United States in Shore A Durometer. Readings range from 30 to 95 points – the higher the durometer number, the harder the compound. The International Rubber Hardness Degrees (IRHD) scale has a range of 0 to 100, corresponding to elastic modulus of 0 (0) and infinite (100) respectively.
Require the manufacturer’s mark to be eliminated or molded into the bottom, where it will not interfere with belt cleaning and sealing systems, rather than the top cover.
Operating parameters to be detailed when specifying a conveyor belt include: