Loma IQ2 User Manual page 133

116
Installing the metal
detector
Care must be taken when fitting a belt that all metallic swarf and filings have been cleared
away and that all rollers are coated, preferably with PVC, to prevent rust formation. Rust on
the rollers or swarf will be picked up onto the underside of the belt and will cause false
triggering.
Care must be taken to ensure that the belt tracks easily and does not track off touching the
aperture sides. Apart from cutting a groove into the aperture wall, vibrations will be
transmitted causing false triggering. It should be noted that most slatted belting use metallic
pins to join the slats. These must be replaced by non-metallic pins.
Skid plate
It is imperative that the belt does not touch the bottom or sides of the aperture. The belt
must be supported through the aperture by a non-metallic skid plate such as Tufnol, Darvic,
Phenolic (dry applications) or Delrin (wet applications). This must extend beyond the metal
free area and be firmly fixed to the conveyor frame to be level with the infeed and outfeed
decking. It must be strong enough not to bow under the product weight as it passes through
the aperture. There must be at least 10mm clearance between the bottom and sides of the
skid plate and the bottom and sides of the aperture.
Care must be taken to prevent anything touching the aperture top or bottom or sides
including product passing through, skid plate, guide rails, etc. Care must be taken in
conveyor system design to prevent product build-up at the sides and under the skid plate
which eventually will cause false triggering.
Electrical interference
The detector head has been designed with a high immunity to mains borne interference. If
trouble is experienced, the offending devices should be located and suppressed at source
where it is much easier to control. The detector may have to be run at reduced sensitivity if
this is not possible. We must also highlight the possible problem of other metal detectors
that may be in the vicinity. These could cause interference if operating on the same
frequency. We advise a distance of not less than 27x the smallest aperture dimension (ie
height or width) between the detectors.
All inductive devices, such as reject solenoid valve coils, motor starter contactors and similar
devices, should be suppressed by fitting suitable suppressors across the inductive load as
close as possible to the coil. Other devices such as thyristor control gear should be
suppressed in the best possible manner. Airborne interference is more difficult to deal with
as it is being picked up by the search coil acting as an aerial. Common sources are radio
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