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Feeding accuracy is key to quality in any process that controls the flow rate of bulk solid materials comprising the end product. Traditionally, repeatability testing (a statistical measure of the consistency of the feeder's discharge stream) has been conducted using one-minute catch samples to reflect the feeder's ongoing, ‘steady state' performance.

However, for many of today's more critical processes, the required timescale of feeder performance has shrunk drastically. A prime example of this type of application is high-speed plastics compounding where the formulation is proportioned as it enters the extruder, and experiences only a few seconds of mixing before passing through the die. An even more stringent application includes deposition operations where expensive or critical coatings or additives are dropped onto a product passing beneath. In this instance, a product unit may pass under the coating stream in as little as a fraction of a second. This paper addresses the question of the process timescale as applied to gravimetric feeder performance in general with a specific focus on loss-inweight feeding.