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Detecting metal through packaging

14-Apr-2004

A high frequency metal detector designed to offer food manufacturers and packers heightened sensitivity for non-ferrous and stainless steel metals has been launched. Pure, high resistance non-ferrous and stainless steel metals have consistently posed the major challenge to standard metal detectors as they are difficult to detect through aluminium packaging.

But equipment manufacturer Lock Inspection Systems claims that its MET 30+ hf detector, which employs a single high frequency, can effectively and safely inspect packaged dry foods such as biscuits or crisps and does not need to be reconfigured after inspecting each product. This, the company claims, reduces downtime and increases efficiency and operating speeds.

"We developed the MET 30+ hf detector in response to industry demand for improved sensitivity on non-ferrous and stainless steel metals for dry applications," said Lock technical director Hitesh Hirani. "A single, ultra-high frequency guarantees the highest levels of sensitivity, which means food manufacturers can rest assured their products are inspected to the highest standards."

The system is currently available as a horizontal unit, employed at the end of the line for final screening of dry, polywrapped, finished products. Lock is developing a waferthin model for space-restricted lines as well as a vertical fall option for free-flowing goods such as coffee granules, sugar and cocoa later this year.

The MET 30+ hf detector incorporates Lock's proprietary ADC software, which displays signals from the metal detector in graphical format. Data can be viewed on-screen so any changes in signal can be identified immediately and the detector adjusted to match the product being inspected.

Attention to food safety on the production line has never been greater. Flakes or slivers from machinery as well as swarf or wire from sieves, cutters or drilling during maintenance work can infiltrate the line at any stage during the production process, and new food safety legislation obliges food manufacturers to implement systems to safeguard the supply of food.

Andrew Hallitt, mechatronics division manager for equipment supplier Sartorius, believes that there is also a great deal of downward pressure from supermarkets, retailers and of course consumers on food producers to implement stringent safety measures. All these pressures are forcing the food production industry to go that extra mile.

"People, care," he said, referring to food safety. "If you look at the British media, the papers are full of scare stories concerning food contamination. Anything that gets in the press is a big deal."

Sartorius has also launched a machine to detect ferrous and stainless steel contamination in aluminium foil wrapped products. Like Lock's system, the Observer metal detector is designed to detect contamination in composite packaging such as food sachets, ready-to-eat meals and aluminium lids on yoghurt pots.

The Observer works on magnetism. Because aluminium does not have any magnetic properties, it is practically transparent.

"This is brand new technology," said Hallitt. " The magnet gets hold of any contaminants, and can detect stainless steel within foil-packaged food, which to date has only been possible with an x-ray."

The firm claims that conventional detectors, which operate on the basis of electromagnetic alternating fields, are limited when they encounter packaging, or parts of packaging, made of aluminium. On the other hand, tests using x-rays are expensive and require elaborate safety measures to ensure protection against radiation.