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Loss-in-weight feeders have evolved from mechanically ponderous devices to the sophisticated microprocessor controlled instruments of today. Weighing and control advancements over the years have made loss-in-weight (gravimetric) feeding the preferred method wherever the combination of high gravimetric accuracy, ingredient containment, and material handling capability are needed.

However, loss-in-weight feeding does possess some shortcomings, especially at higher feed rates. First, during the feeder's required hopper refill phase, weight-based control must be temporarily suspended and replaced with volumetric control. It is in this refill phase that significant feed rate errors can occur due to volumetric control inaccuracies. And second, higher feed rates have historically meant physically large and expensive systems. In some cases required space could only be obtained at the cost of significant structural changes to the plant itself. These refill challenges are especially great when feeding tough to handle powders.

SRT combines a refill control concept called the Refill Array with precision digital weighing to deliver improved feeding accuracy during hopper refill, substantially reduced headroom requirements, the elimination of material handling problems associated with large feeder hoppers, smooth and quick transitions into and out of hopper refill, and lower total installation costs.