
Section 3
Electrical
Functions
Bar Screen Sequence
1. After the Mensch Screen has been properly installed/adjusted, motor rotation
checked and all control panel devices (timer(s), overload(s), current sensing relay,
etc.) have been set, automatic operation may proceed. Go to the local control station
and make sure the Emergency Stop button is pulled out, the Hand-Off-Auto selector
switch is in the "Auto" position, and all personnel are clear of the equipment.
2. Then go to the main control panel and open the door. Then turn on the circuit
breaker for the drive motor. Close the door and place the main disconnect in the
“On” position. Then turn the control power selector switch to the "On" position. The
white control power indicator light should be on at this time.
3. The Mensch Screen will be started by the software based frequency/duration timers
in the PLC or by the ultrasonic differential level detector (ULD). When the frequency
timer times out the duration timer will be initiated. The duration timer will then
energize the screen run relay (CR12) via software logic in the PLC. The CR12
contact in line 6 will close and the motor starter coil, run indicator and run relay
(CR2) will be energized. If the set point in the duration timer is set for a short time
period, the Mensch Screen will make one cycle and park at the end travel limit
switch (LS-1). The ultrasonic differential level detector (ULD), in line 19, may also
start the Mensch Screen. When the ULD detects the preset/adjustable differential
level set point the ULD-1 contact in line 40 will close giving an input to the PLC. The
software logic will then energize the screen run relay (CR12). The CR12 contact in
line 6 will close and the motor starter coil, run indicator and run relay (CR2) will be
energized. The Mensch Screen will continue to run as long as a differential level
condition is present. If a high upstream level condition is detected above the ULD-2
set point, the ULD-2 contact in line 41 will close and CR12 will be energized starting
the Mensch Screen. The Mensch Screen will continue to run until the high upstream
level drops. This high level condition will also cause the conveyor and washing press
to run continuously until the condition is no longer present. The end travel limit
switch in line 39 forms a holding circuit within the PLC to allow the Screen to
consistently park at this switch when a run signal is no longer present.
4. The Mensch Screen is protected from overtorque by the current sensing relay
(CSR1) in line 13. Should the Mensch Screen encounter an obstacle the drive motor
current will increase. Once this increase equals the preset of CSR1, the CSR1
contact in line 12 will close turning on CR4 and the Screen Overtorque pilot light.
The normally closed CR4 contact in line 4 will open stopping the drive. The normally
open CR4 contact in line 44 will close giving an input to the PLC. Turn the Hand-Off-
Auto selector switch to the "Off" position. Then press the Screen Reset push button
to reset. The jam must be cleared and the controls again set for automatic operation.