This is the Plant I recently worked on.  It has 2 screen decks,  3 crushers; 1 jaw, 1 cone and 1 impacter.  The impacter spins at 9,000 RPM's "flinging" rocks at it's walls to break them up and knock off the clay.  The cone is a standard 4' gyratory type crusher.  

The loader puts the raw material into the feeder, which then sorts out the material into 2 types; 6" and larger and smaller than 6".  Anything larger than 6" falls into the JAW crusher which uses a swinging type action to crush the oversized rock into manageable pieces for the cone.  The material travels to the first SCREEN and is sorted into 3 parts.  1 inch and larger, smaller than 1 inch and sand.  The sand is taken away and goes to the "waste sand" pile.  The material that is larger than 1 inch is moved to the CONE, which uses a gyratory action to further break down the rock.  the material that is smaller than 1 inch, but larger than sand moves to the IMPACTER feed belt without going through the CONE.  The purpose of this is to speed the process up by not putting material that is already small enough through the CONE and JAW.  This cuts down on wear and tear on the parts also.  The material is now almost all rock.  It falls into the IMPACTER and gets broken up more.  Then the material moves to the second SCREEN.  It is sorted into 4 parts; oversized (larger than 3/4'), 3/4', 3/8' and sand or ROCK DUST as it is called also.  The oversized material is "returned" to the IMPACTER, where it will be broken up again and resorted by the second SCREEN.  The 3/4' rock gets dumped to a STACKER and drops onto a pile.  The 3/8' rock and ROCK DUST first go through the LOG WASHER or SAND SCREW respectively.  This "cleans' the material, ensuring no FINE dust is present to make the cleanliness value or CV stay in specs.

The QA/QC inspector pulls samples once an hour and runs them through tests to make sure the finished material is within is proper size.  If not, then small changes must be made to the plant to get the material in spec.  This usually requires a screen change, as the screens will get holes in them letting larger rock fall through and contaminating the piles.

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