Eriez Xtreme, Reference Manual

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Figure 6
Non-metallic/Plastic Bearing Block
All three insulating methods are reliable. However, it only takes a small metal shaving or burr to
cut through and short-circuit the insulators. A check of the integrity of the insulation with an
ohmmeter will ensure everything is correctly installed. Insulating either end of the shaft will
prevent current loops but will also prevent testing with an ohmmeter. For this reason, isolating
both ends during testing is recommended.
Build-up of a static electric charge on the conveyor belt can also cause false tripping. A static
charge can build up on pulleys or idlers that are insulated on both ends. To prevent this build-
up and subsequent false tripping, the insulation must be modified to ensure a ground. After the
integrity of the insulators is checked with an ohmmeter, one end of each shaft should be
electrically reconnected to the conveyor frame. If the sleeve insulating method has been used,
the setscrew of one of the bearings should be extended to make contact with the shaft. This
may require drilling a small hole through the sleeve and inserting a sharp pointed setscrew. If
the bearing block insulating technique has been used, simply remove one of the shoulder
washers on one end of the shaft. If using the plastic bearing block method, the opposite
bearing block is metallic and grounded already. The integrity of the insulators can easily be
rechecked when using any of the three methods.
NOTE:
If a drive pulley is powered by a metal chain, it is not necessary to remove the insulators on
either end of the shaft as described above. The metal drive chain will bleed off any static
charge that may accumulate on the pulley. If a non-metallic belt drive is used, insulate the
conveyor pulley on the side opposite the drive motor.
MECH
18