X-ray inspection and metal detection: a frontline defence against physical contaminants

Mettler-Toledo product inspection, marketing communications manager Neil Giles

Contaminant detection is a critical aspect of compliance with global safety regulations in both the food and pharmaceutical sectors. There are a number of options open to manufacturers, but many will find that either an x-ray or a metal detection system will suit their requirements.

Which technology will suit best will depend on the risks identified by a Hazard Analysis and Critical Control Point (HACCP) audit, which is carried out to establish potential risks to product quality and integrity. Critical Control Points (CCPs) should be established immediately after the areas where product quality could be compromised – for example, where physical contamination is likely to occur. X-ray inspection and metal detection systems are classed as control measures, which can prevent or minimise physical contamination risks significantly.

X-ray can detect many types of physical contaminants

X-ray systems are best deployed where a number of different physical contaminants such as metal, glass, mineral stone, calcified bone and high density plastic and rubber compounds have the potential to be introduced to the products being manufactured. Effectively, the system is a scanning device that captures a greyscale image of a product as it passes along the line and compares it to a pre-determined acceptance standard. Any products not matching the standard will then be rejected automatically.

X-ray is ideal for a large number of applications and presentations, from pumped products such as slurries, fluids and semi-solids, to bulk and loose products. Packaged products of all shapes and sizes can be inspected with ease by x-ray inspection systems at high line speeds, and products packaged in metalized films and foils present no challenges. In addition, tall, rigid containers such as glass jars, bottles and metal cans also lend themselves to inspection by this technology.

Identifying all metal contaminants

Metal detection is the natural choice for those manufacturers whose HACCP process identifies areas of production where metal is a potential contaminant. Advanced, modern detectors can identify all metals, including ferrous metals such as chrome and steel, and non-ferrous such as aluminium and brass. Non-magnetic and magnetic stainless steels are also easily detectable. Metal detectors are used at various points in the production process and can be situated at the incoming raw material stage, at the end of a production line, or at other key stages in between if identified as risk areas. A variety of different product types are suitable for inspection by metal detectors – from loose, unpackaged items to pumped products such as liquids, pastes and slurries.

The system consists of three electrical coils wound around a rectangular or circular supporting frame to create three loops through which the product is passed. The middle coil is charged with an electrical current and acts as a transmitter. This induces current in the two outer coils. As a result, an electro-magnetic field is created which, when disturbed by a metallic object, will generate a tiny electronic signal. This signal is amplified and analysed and can be used to trigger a reject mechanism or stop the line if configured to do so. A metal detector that has been well designed and configured for its intended application will be capable of finding the smallest of metal contaminants.

Tailoring your contaminant detection system

Ultimately, which technology manufacturers choose will depend on what is being produced on the line. It may be x-ray or metal detection alone, or a combination of both. Before making capital purchases, it is vital to consult a product inspection expert with the experience to offer valuable advice and guidance on individual requirements. By doing so, manufacturers can understand the total cost of ownership of the systems in question and how best to extract maximum value from their investment.