AEC 1426-i Twin-Shear Granulator - Manual (Page 20)

1426-i Granulator Chapter 5: Maintenance 19 of 37
5-3 Testing the Interlock Switches
Test the proper operation of interlock switches daily, or at least weekly, depending on
machine usage. Two- or three-shift operations require daily testing of the interlock switches.
Because granulate material or dust can collect or build up inside the belt guard, periodic
cleaning and removal of material may be required to maintain proper operation of interlock
switches and the belt drive. An inspection port is provided on the belt guard to observe the
belt movement and rotation. Depending on plant operating conditions, a flashlight may be
required to observe the movement.
Always be sure that the tapped holes for the interlock actuator bolts are free of dirt, plastic
dust, or particles before replacing the actuator bolt.
Do not use air wrenches to remove or install interlock switch actuator bolts. The time
required to un-thread the actuator bolts with conventional manual wrenches should allow the
rotor to come to a complete stop.
WARNING! Always be sure the rotor has come to a complete stop before opening any
cover, guard, or hopper.
If testing determines that an interlock switch is not working, be sure to shut down the
granulator, pull it out of service, and lock out the main power before removing the front
cover, opening the hopper, or attempting to gain access to the interlock switches. The
interlock switches and mechanisms can be accessed by removing the belt guard on the right
side of the granulator. In some cases, it may be necessary to remove or slide back the
flywheel to completely remove the interlock switch assemblies.
Use the following procedure to test the interlock switches:
1. Press the Stop/Start Button to shut down the granulator.
2. Disconnect and lock out main power supply to the granulator.
3. Using the wiring diagram supplied with your granulator or by tracing the wires from
the interlock switches, locate the interlock switch wire numbers on the terminal strip
in the control panel. They will usually be marked #1 & #3, #3 & #4, and #4 & #5,
etc. depending on how many switches are used on your machine.
4. Connect the leads of an ohmmeter across each interlock switch or across all interlock
switches (wires #1 & #5). Set the ohmmeter on the lowest resistance scale. When the
interlock actuator bolts are in place and properly activating the switch, the ohmmeter
will read zero resistance.
5. Loosen the actuator bolt of each interlock switch (usually about 3 or 4 turns) one at a
time, until the ohmmeter reads infinite resistance. If the meter reads infinity before
the bolt can be completely removed, the interlock is working. If the actuator bolt can
be completely removed and the resistance does not read infinity, the interlock is NOT
working, and the complete mechanism, including the switch, must be removed and
disassembled to determine the cause of the malfunction.
If an ohmmeter is not available, the interlock switches can be checked by loosening the
actuator bolt while the machine is running, until the power to the motor disconnects and shuts
down the machine. The indicator light on the Stop/Start Button will go out or you may be
able to hear a change in sound when the power disconnects. If the actuator bolt can be
completely removed and the power does not disconnect, the interlock switch is not working
and the complete mechanism needs to be removed and disassembled to determine the cause
of malfunction.