Oliver Platinum Series, Operation Manual, Page: 12 / 61

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II. Functional Operation of the Voyager GVX Gravity Separator
The Voyager GVX series of Gravity Separators is a new line of gravity separator from Oliver that
takes the rugged base of previous separators and adds to it quieter fans and better balance as well
as a never before seen automation package that make the Voyager the Cadillac of Gravity
Separators. There is no finer machine in the world.
The Voyager operates on a concept discovered by Archimedes, a Greek philosopher and
mathematician, who discovered that “All bodies, floating in or submerged in a liquid, are buoyed up
by a force exactly equal to the weight of the liquid they displace.” The specific Gravity of a particle is
the ratio of its density to some standard substance, which is water that has a specific gravity of one.
Everything with a specific gravity greater than one floats in water, and everything with less than a
specific gravity of one sinks.
In the case of the Voyager, the liquid is the air blown by the fans, and the bodies are the particles
being separated. What Archimedes was getting at is that we can use air to lift the particles on the
deck, and that the amount of air needed is related to the specific gravity of the particles that need to
be lifted. Because air is lighter than water, there will be a greater relative difference between the
particles of differing weights. That is what makes the Gravity Separator such a sensitive and precise
machine.
I. The Process of Stratification
Before a product can be separated by weight the product must be fluidized and then stratified
vertically. On Gravity Separators lighter particles are moved upward through the fluidized bed.
Heavier particles sink downward. This produces stratified layers with lighter particles in the upper
layers and the heavier particles in the lower layers. Air is used as the fluidizing medium for the
process of stratification. Stratification occurs by forcing air upward through the particle mixture so
that the particles rise or fall by their weight relative to the air flow.
Consider a voyager machine where product has been added to the deck, but the fans are off. The
product will sit in a mixed group of lighter and heavier particles. Once air is applied, the lighter
particles will start to float, and the heavier ones will stay on the deck. If too much air is applied, then
all of the particles will start to float, and the particles will begin to remix. This process is shown in
Figure 1.
Figure 1: The stratification process (a) mixed product on deck with air off or low (b) stratified
product due to air flow from fans (c) too much air flow and remixing of product.