Metal detection

And what are the other sources of failures?

Gouden fluit telefoon touw
Photo: Mathilda Samuelsson – “Gouden fluit telefoon touw” – by Flickr

In a daily situation, there are other sources of failures that must not be underestimated. These failures may be the cause of contaminated products arriving at your consumers.

  • Several following contaminated products on your production line – The first is being rejected. But the resetting of your metal detector takes too much time, so that the next (contaminated) product passes without being rejected. It’s important to test this situation regularly
  • The line is overfull, causing that false positive products are rejected or even no product at all – The detector gets distorted rejecting the false product or none. The product coming behind pushes the product that had to be rejected
  • The bin for the rejected product is full – There is no more room. The product which had to be rejected follows its way to the consumer
  • Elements which are interfering with the detector (for example: things put on the detector, vibrations or electric fields) – A lack of space makes that the detector is often used as a table disturbing the reliability of the device. During the installation and the validation, check that there are no other factors that reduce the reliability
  • Metallic bodies in the form of a needle or a thread generating the orientation effect  passing the detector without being detected
  • Rejected products which are put back on the line – Whatever the cause, but it is important that rejected products are not put back on the line (Examples of causes: being hurried, the end of the day, storage or contaminated products lost to view)
  • Not block the products in the case of a malfunction of the detector from the moment it was still working properly – A badly functioning detector causes extra work. The blocking of products permits to plan the detection once everything is functioning correctly
  • Not analyse the rejected products immediately – To analyse the products once per 2 months is insufficient. Such a frequency prevents you from finding the cause let alone lowering the trend
  • False positives – A high percentage of false positives reduces the attention. At some point, detection is no longer considered an important part of the process

To prevent false products from being rejected, the detector must be well tuned and operate under optimal conditions. This can be achieved by setting up regular maintenance by a competent company.

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