How Bulk Material Density Can Affect Vibratory Feeders

March 20, 2019

Let’s take a closer look at the variables that affect vibratory feeders. Remember, this is where the mining process starts, right after the aggressively effected excavation work has completed. The maw of the feeder admits a heavy stream of broken down minerals, the dual-excitation stage chews through the bulk material, and a variable frequency drive unit regulates the flow of what’s really an exceptionally coarse river of broken rock.

Overhauling Flow-Inflexible Designs

If the deluge of rocky matter chokes the maw of a vibratory feeder, its feeder tray floods with inconsistently graded material. The overfull equipment bowels will clog the equipment and throttle the aggregate’s flow. What if the material flow drops off? Surely the equipment will cope better with a lighter river of fragmented feeder ore? Actually, counter to expectations, the feeder pan will find itself “starved” of material. For an effective discharge rate, a consistent bulk material density is desirable. This way, the material depth in the feeder pan is held in check, so the equipment’s discharge rate stays safely within its designs specs, no matter the bulk size or volume.

Counteracting Bulk Surging

All of those vibratory components work synchronously. They smoothly regulate high-volume flows, although they’ll hitch slightly if the density of the stream surges. Likewise, a counteracting hitch takes place if the surge suddenly diminishes. Should those slight fluctuations assume hard-to-regulate proportions, probably because the bulk material density is overloading the feeder innards, the equipment housing will whip and thrash. It’s trying to compensate for the excess energies entering the feeder bowl, but that fixed speed design is having little luck. Not to worry, contemporary equipment designs are built to vary their speeds when hit by such bulk surges. The motors vary speed, then a regenerative braking system absorbs and dampens the energy. All that’s required is a little machine tuning.

Accounting for Material Characteristics

Aggregate density is a whole-numbers product. The density grows, then it drops. It’s heavy or it’s light, fast or slow. To really design a mechanism that can offset such density fluctuations, the equipment tuner needs a few more important pieces of flow data in-hand. Particle size is one such factor, then there’s the density of those particles and the energy it has gathered because of bowl or chute inclination.

Using these energy and material parameters, vibratory feeders are tuned. The speed and oscillation stroke length receives attention, naturally. Next, there’s the torque delivered by the twin excitation units and the VFD motor, plus the behaviour of the regenerative braking system. Last of all, the feeder pan height and areal dimensions receive equal attention, for it’s this section that fills with the mechanism-regulated load so that it can discharge a uniformly graded output stream.

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