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Addressing Bucket Elevator Capacity Loss

February 8, 2018

When purchasing a continuous bucket elevator, equipment capacity is a key consideration for ensuring that throughput objectives will be achieved. In some cases, the equipment rated capacity determined at the time of purchase is achieved following installation of the elevator, but deteriorates thereafter for a variety of reasons. This blog looks at some of the more common reasons for rated capacity losses in continuous bucket elevators and highlights corrective actions that can be undertaken.

Bucket elevator capacity loss reason #1: material spillage

Material that spills from the buckets while transiting the elevator represents a capacity loss. Spillage can occur for a variety of reasons, but it can be especially problematic on equipment designs that feature overlapping, as opposed to interlocking, bucket assemblies. To prevent material spillage, choose equipment designs that feature fully interlocking buckets, such as the TipTrak™ line of continuous bucket elevators from UniTrak.

Bucket elevator capacity loss reason #2: planned bucket fill not achieved

In designing bucket elevators, equipment vendors calculate machine capacity based on a bucket fill percentage. For example, UniTrak normally calculates bucket elevator capacity based on a bucket fill of 67 percent. In practice, rated capacity can be eroded if the bucket fill percentage that the capacity was calculated on is not achieved in actual operation.

The planned bucket fill may not be achieved for several reasons, including:

  • The elevator is being run too fast. Running too fast can result in buckets by-passing the infeed area too quickly and under-filling as a result. To correct this condition, the elevator speed should be adjusted until the desired bucket fill level is achieved at the infeed.
  • Material infeed rate. Material may be fed into the elevator at too low a rate, resulting in bucket under-filling. In this case, the material flow rate into the elevator should be adjusted and regulated to a rate that fills the buckets to the desired level.
  • Under-sizing of the infeed area, where the equipment infeed is too small to handle the required volume of material, may also contribute to bucket under-fill and consequent capacity loss.
  • Product distribution is uneven across the width of the bucket, leaving much of its volume underutilized. Consider alternative methods of feeding which would result in a more even distribution of material within the buckets.  For example if feeding the elevator perpendicular to the direction of bucket travel, use a bias cut feeding tray or chute, or if using a rotary valve feeder, orient the rotational axis of the feeder to be perpendicular to the direction of bucket travel.

Bucket elevator capacity loss reason #3: discharge outlet under-sizing

A bucket elevator with an under-sized discharge area can result in material build-up and spillage at the discharge area. This results in downstream equipment being underfed with the required material volume. In this case, the corrective action is to refit the elevator with an appropriately sized discharge area.  This can also cause a backup of material into the bucket elevator.

Bucket elevator capacity loss reason #4: drive belt slippage

Slippage of the elevator drive belt on the drive pulley can result in material failing to move through the elevator. Slippage can occur with incorrect belt tensioning. This problem is eliminated with positive drive elevators, such as TipTrak™ conveyors from UniTrak.

Bucket elevator capacity loss reason #5: material failing to discharge

Difficult-to-handle materials, such as those which are sticky or which tend to cake or pack, may fail to fully discharge from the buckets. Flow aids should be used when handling difficult-to-handle materials to ensure complete emptying of the buckets.

Addressing the above issues should resolve many cases of rated capacity losses in continuous bucket elevators. Where equipment has been under-sized due to the manufacturer’s failure to fully understand the application and throughput requirements, the manufacturer will need to be contacted to determine what corrective actions can be undertaken.

UniTrak manufactures the TipTrak™ line of continuous bucket elevators. These elevators are available in a range of configurations and capacities. TipTrak™ elevators feature fully interlocking bucket assemblies and a rubber beltchain which never needs tensioning or lubrication. A wide range of options are available to support specific applications. To find out more about TipTrak™ continuous bucket elevators, please contact our sales team directly.

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