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A solution to end-of-line detection bottlenecks?

16 January 2017

Do you run a production line that handles a variety of product variables? If so have you considered a multispectrum metal detection solution? 

Contamination by foreign objects in the food production process can come from many sources so the correct selection and implementation of metal detection equipment is one of the key elements in identifying and removing ferrous, non-ferrous and stainless steel contaminants from the finished product and ensuring the regulatory compliance of a process and protection of a brand.

Retailers are sensitive to anything that might harm their reputation, so impose stringent ‘Codes of Practice’ on their suppliers to maximise consumer safety and product quality.

Many food production lines will most likely handle several different versions of a product, except for those with a very high and consistent demand, which may then be dedicated to a single item. These varying demands present contaminant detection equipment with significant challenges.

Every food product has some form of ‘product signal’ that represents how the product itself appears to a metal detector. These signals vary tremendously, so that a wet product will have a big signal, whereas dry powders exhibit a bulk effect signal, particularly when inspected in large quantities such as 25 kg sacks. 

If a product is already packed when it passes the detector, then the packaging will also add to the product’s signal profile, with inert plastic presenting minimal or no signal and metallised film having a large footprint. A traditional metal detector can be tuned to accurately identify a single product signal and then reject any products that pass through it, that have a different profile and hence are likely to contain a contaminant.

However, if the product changes – either to a different item altogether or due to changes such as a change in moisture levels, or temperature variation – then the detector may start to reject an increasingly large amount of perfectly good product due to ‘false positives’. Every time the product being checked changes, the equipment needs to undergo a product re-learn which results production downtime.

A multispectrum solution
Multispectrum detectors overcome this issue because they are able to operate over multiple frequencies at the same time, and are therefore capable of cancelling out a much wider range of product signals. This means much less downtime between changes in the product on the line. In addition their higher sensitivity increases their accuracy for the same product signal, allowing them to detect much smaller contaminants.

For example, if a regular detector can identify a 4mm diameter stainless steel contaminant, a multispectum device will quite often be able to detect a 2mm diameter piece in the same product. This represents an 800% increase in sensitivity as the volume of a 2mm diameter item is one-eighth that of a 4mm diameter one.

The higher sensitivity, and wider range enables a production line to be set-up for many different products without the need for constant stops for reprogramming of the detection parameters. The multispectrum device can cope with the much greater number of product signals that a group of different food products will present to the detector.

In general, metal detection is performed at the very end of the production line. For this reason packaging is likely to be scanned alongside the food being produced, adding further complications to the detection requirements making multispectrum devices more appealing. Aluminium, which is regularly used in food applications can be particularly difficult for X ray and other devices to see.

Ready meals are one example of a pre-packaged product that has a wide profile range and so needs a flexible detector. CEIA technology, available in the UK from MDS, is able to meet this need and is said to exceed the specified detection requirements of both Tesco and Marks & Spencer.

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