Silica sand is a form of quartz that has become sand due to erosion by millennia of water and wind. It has a wide range of applications: It’s used in the glass, ceramics, chemical and foundries industries, as well as in agriculture and water filtration. It’s also used by the oil and gas industries as a proppant to keep a hydraulic fracture from closing. A fine form of silica sand is also used as a filler for rubber, paints and plastics.
When mining silica sand, the sand is put through an industrial screener that screens at a specific diameter. This separates out the larger granules from the smaller ones. If necessary, the smaller granules can be further separated to obtain the smallest diameter. Of course, exactly what diameter is required will depend on the end user.
To assure that the sand meets these requirements, it is evaluated for compressive strength and shape, after which it must be washed, dried, and screened to size. The final processing of frac sand requires precise screening. Generally, there are two types of screeners that are used in the production of frac sand: inclined vibrating screener and gyratory sifter machine. Most inclined vibrating screeners use a linear or elliptical motion to convey the material down the screen surface. Gyratory sifters use a more gentle sifting motion, utilizing primarily horizontal motion to convey the material.
As with inclined screeners, gyratory sifters have their advantages and disadvantages. Gyratory sifters have a tendency to be more expensive than your typical inclined screener, and they have lower throughput in the same basic footprint as compared to inclined screeners. However, gyratory sifters are more efficient, producing cleaner, more accurate cuts. Additionally, the gyratory motion of the sifter tends to spread the material out on the screen for more effective use of the screen area.