Thermo Scientific APEX 100 User Manual page 293

of the aperture. When a complete conveyor system has been supplied by Thermo Fisher
Scientific, these considerations have already been factored in to the design of the
system.
Factors That Can Influence the Operation of the Detector
It has been proven that causes external to the APEX, are the main reasons for faulty
operation or random false triggering. When installing the APEX on an existing or custom-
built conveyor system, this information below should be carefully studied. Only when
correctly installed will the equipment perform optimally. The APEX may have been
installed correctly initially, but conditions change and these may cause intermittent
problems with the metal detector. If the APEX develops fault symptoms such as
intermittent triggering, the factors below should be carefully studied before any
electronic servicing is contemplated.
Conveyor Belt
Any conveyor belt passing through the APEX must be totally metal free. Sometimes
metal particles or grease that has become loaded with metallic dust, becomes embedded
in the conveyor belt during use. Spilled product may also become embedded in the
belting. This generally occurs with woven belts and the contamination will trigger the
APEX each time it passes through the aperture. Plastic, plastic-covered, or rubber belts
should be used whenever possible. The joint in the belt must be made of a non-metallic
fastener or vulcanized.
Carbon-loaded anti-static belts can cause random alarm signals, especially when the
APEX is operating at a high sensitivity.
Aperture Clearances
The conveyor belt, product guides, and the product must be completely free of all metal
and must not touch the aperture in any way, whether on the top, bottom, or sides of the
aperture. The belt must not be allowed to wander from side to side and rub on the inside
of the aperture, because this could damage the aperture lining or cause false tripping.
Before fitting product guide-rails, check that they are completely metal free by passing
them through the APEX (if possible) before installation. Suitable guide-rail materials
include polyethylene, polypropylene, PBVC, wood, and wood laminates.
Metal in the Packaging Material
Packaging material must be totally free from metal clips, fasteners, labels, metallic ink,
and foil. Certain types of low-grade cardboard, especially recycled cardboard, may
contain pieces of metal or metallic foil that may be detected when operating at high
sensitivity.
Mounting
The support structure used for mounting the APEX to the conveyor, should be
constructed in a way that minimizes the amount of vibration transmitted to the APEX.
This structure must be flat and parallel. This minimizes possible twisting torques to the
case of the detector, which will distort the electromagnetic field and cause false
triggering.
Thermo Scientific APEX User's Guide Page 293