further material is discharged. This will leave some material inside the press, which can be
handy for forming a plug at the cake discharge when the press is restarted.
Material will leave a press only if there is additional inbound material forcing it out. This
makes it difficult to completely clear material from inside a press without removing the
screen. One technique used successfully is to feed crushed ice into the press. Water must be
fed along with the ice to prevent jamming. When the ice melts, the press will be relatively
clean inside.
There are applications in which the press must be cleaned frequently, such as once a shift, in
order to meet sanitary regulations. In these cases, the screen can be removed from the press
in order to remove residual material. A spare screen assembly may be kept, submerged in
cleaning solution, in order to minimize the downtime required.
Once the screen is removed, the screw and screen are scrubbed with caustic solution.
In one case with a KP-16 press, the liquid discharge drain is blocked shut so that caustic
solution can be allowed to fill the collection pan. This cleaning is performed without
removing the screen from the press.
Cleaning the inside of the screen can be achieved, at least to some extent, by injecting water
through the resistor teeth. Holes must be drilled in the resistor teeth to make this possible.
In laboratory applications, the press may be disassembled for cleaning. The various
components can be dipped in an appropriate solution or placed in an autoclave.
It is unusual that the outside of the screen ever needs to be cleaned. Spray systems for this
can be built into the press at the Vincent factory. Alternatively, a pressure washer or
swabbing with acid solution can be used.
Maintenance
Checking Screw-to-Screen Clearance
Generally, the clearance between the screw and the screen is 1/32", plus or minus 1/32". The
screw should not rub the screen hard, as it can cause wear and premature failure of the
screen. Tighter clearance is used with materials that blind the screen, such as onion skins.
Greater clearance, 1/16", is used with eggshells, pectin, xanthan gum, and corn husk. With a
clearance greater than 3/16", the dewatering performance of the press can start to deteriorate;
this depends a lot on the type of material being dewatered.
The easiest way to check for screw wear is to open the cone, clean out the material and
measure the distance between the screw flight and the inside of the screen. For precise
measurements:
Wedgewire screens - a feeler gauge can be slipped through and along a slot until it
hits the edge of the screw. Measure from the outside of the screen in to the edge of
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