Metal detection

What is used for metal detection

180507Equilibrium 888 Felipe Gabaldon
Photo: “Equilibrium 8_8_8” – Felipe Gabaldón by Flickr

The metal detector will be placed in your production line. All products pass through the detector and are inspected. Contaminated products will be rejected.

When you install a metal detector, you are modifying your food safety system. A modification of your quality and food safety system needs to carried out for its integration. A creation of a dedicated procedure about the topic is necessary. This document will contain at least the following elements:

  • The responsibilities and the competences
  • The type, the location and the sensitivity of the metal detector
  • The method of the rejection mechanism
  • The procedure which is followed at the start of a production lot
  • The procedure which is followed at the end of a production lot
  • The frequency at which the performance of the metal detector is tested
  • The procedure which is followed to test the performance of the metal detector
  • The location and the manner of placing the test samples. They should be placed at the most difficult place to be detected and then rejected, see the chapter below
  • The procedure that is followed, when products are rejected, see the chapter below

On the packaged product

The metal detector is located as far as possible in the process. The detection is done, if possible, on the packaged product, so that it can’t be contaminated anymore. On a product in a metallic packaging, technical modifications are necessary before the detection can be done.

The rejected products are kept in a closed room. Only authorised employees have access to these products.

It’s important to analyse the rejected products as quickly as possible to determine the cause of the contamination. This control is done on a detector isolated from the line. This detector has at least the same accuracy.

After this inspection, the rejected products are treated as non-conforming.

A trend analysis should be made. As soon as possible, preventive actions will be taken to reduce metal contamination.

Different types of metal

The metals are classifiable into 3 types, depending on their behaviour in the metal detector. Ferrous, non-ferrous and stainless steel, mentioned in descending order of detectability. The minimum detection limit is therefore in ascending order.

There are different types of stainless steel (eg 304 and 316). Depending on the types used in your company, you will need to adapt the test material. For this, you take the worst detectable type, to make sure the others will be rejected.

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