7
If dissolved (soluble) solids are present, the suspended (insoluble) solids (fiber) in
the press liquor are generally measured by filtering and washing a sample and
drying the filter paper in an oven. Dissolved solids will be washed from the sample
during the washing process.
START-UP
Before putting power to the screw press, it is advisable to bump the motor or even
rotate the screw by hand. This will prevent damage to the press in case tramp
material has been left in the press. Also, the screw may have shifted so as to hit
the screen. (Minor rubbing is normal; it will go away once there is material in the
press.) To turn the screw by hand, remove the fan guard on the motor and turn the
fan blades.
The screw of the press turns in a counterclockwise direction, when viewed from the
drive end of the press.
If problems are encountered, they are apt to be blinding, jamming, channeling or
purging. There is a section for each of these ahead in this manual.
FEEDING
Material can be fed into the press many ways. Commonly, screw conveyors,
pumps, transition chutes, pre-thickener screens or cyclone separators are used.
Consider making provision for return of overflow material, in the event that more is
fed to the press than it can take. Spill containment should be considered.
Sometimes either a static (sidehill or parabolic) or rotary drum screen (RDS) must
be mounted over the inlet hopper to prethicken the flow ahead of the press; the
tailings (solids) from the screen can be funneled into the press. This arrangement
is desirable when the feed to the press is dilute.
Also, material can be dropped from a shredder or cyclone separator into the press.
A shredder is used to increase capacity and dewatering in the case of low bulk
density materials like lettuce leaves, alfalfa, onion peel, and cornhusk, or to prevent
blockage.
Most commonly, the best screw press performance is achieved if the material in
the inlet hopper stays just at the top edge of the screw. Usually presses work best
with only atmospheric pressure in the inlet hopper. In order to minimize static
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