5
In some cases the press will tend to jam, overload, and trip out on high amps. In
this situation it may be necessary to program the controls so that the cone
automatically goes open on high amps, re-closing at a lower set point. This
arrangement requires a solenoid operated 4-way air valve, replacing the manual
valve which is provided with the press.
In other cases of jamming a simpler arrangement is to install a Cone Timer. A
timer is used to periodically open the cone. The closed period is determined by the
amount of time required for press cake to accumulate in the press. The duration of
the "cone open" period is long enough to dump most of the press cake that has
formed. This type of operation may be used if the press periodically experiences
jamming or overload due to fluctuations in the amount of material being fed into the
press. Alternatively, it may be used with slippery or slimy press cake that cannot
be dewatered to sufficient firmness to force the cone open. Cone Timer panels are
available from Vincent at no charge.
Some applications require the use of a specially programmed variable frequency
drive. In this case the VFD is not used to change the speed of the press, but,
rather to set it for auto-reversing operation. By having the screw run backwards for
three or four turns every few minutes, some difficult-to-dewater materials can be
pressed much more effectively. This operation can help a great deal with material
which tends to blind (cover over) the openings in the screen. Vincent has loaner
VFD's if you want to give it a try. The technique works well on bar screens; care
must be taken with perf screens so that the screw does not snag the screen during
the reverse cycle.
Once through start-up, the cone is almost always permanently left in the closed
position at whatever air pressure has been found to be effective. A plug of cake
will be left around the cone whenever the press is turned off; this will clear on its
own accord on restarting the press.
However, some materials may set up and become hard, or freeze, within the press
when the press in turned off. This is especially true in the case of pressing wet
coffee grounds or outdoor installations. For these applications it is advisable to
open the cone for a period of one minute before turning off the press. This allows
the press to partially empty itself, fluffing the material left in the press. Vincent can
provide information for automating this procedure.
VACUUM EFFECT
In some applications, increased screw press capacity can be obtained if the area
outside of the screen is under a vacuum. This can be achieved by mounting the
To Next Page
Loading...
Need help?
General