Reduced yield can take several forms. First, the quantity of product that the elevator delivers to downstream equipment may be lessened through losses from spillage, failure of some product to discharge from the buckets, etc. Secondly, the quality of product delivered by the elevator may be compromised as it moves through the equipment. Both types of losses, quantity and/or quality, represent yield losses.
For the first case, addressing the causes of spillage or failure of material to discharge will improve the quantity of product delivered by the elevator. Material spillage can be a function of equipment design as well as operating procedure. For example, bucket elevators designed with interlocking buckets, as opposed to those which merely overlap, will always be more effective at preventing spillage. In addition, overfilling the buckets, either by presenting material to the elevator at too fast rate or running the elevator at too slow a speed, can result in material spillage. The solution in either case is to affect the necessary adjustments to material feed rates and/or the run speed to achieve the optimal bucket fill.
Failure of material to fully discharge from the elevator buckets can be addressed using discharge aids, such as “bucket knockers,” which are designed to dislodge material from the elevator buckets at the point of discharge. In addition, conveying materials that are inherently sticky and that have a propensity to adhere to the bucket surfaces may require the use of buckets with Teflon-coated or dimpled surfaces.
Quality degradation often manifests itself through particle attrition or breakage. The solution in this case is to use an elevator designed for high-care conveying and which is capable of gentle handling. This will prevent particle attrition or breakage and ensure that what goes into the elevator is what comes out.
