Tunnel Metal Detectors for Conveyors

What is a tunnel metal detector?

A tunnel metal detector inspects raw or processed foods or non-food products for metal contamination. Food processing companies use tunnel metal detectors to comply with food safety standards and retailer codes of practice. When integrated with a conveyor system, all types of metal contaminants can be detected and rejected, preventing metal contaminated products from reaching the end consumer.

Where can I use a tunnel metal detector?

A tunnel metal detector is a versatile industrial metal detection solution that can be used in a wide variety of product inspection applications. Tunnel metal detectors can be integrated with conveyor systems, to inspect raw, processed, or packaged food or non-food products for all types of metal contaminants. A HACCP analysis will establish the most relevant critical control points, indicating the best installation location for the metal detector.

How can we integrate a tunnel metal detector within a food production line?

The easiest way to do this is to buy an integrated metal detection system consisting of a tunnel metal detector and a conveyor system, from a single supplier. METTLER TOLEDO Safeline manufactures a wide range of tunnel metal detectors and conveyor systems designed for food and non-food processing applications. Our metal detection systems for conveyorized applications can be tailored to suit specific inspection requirements, including a choice of aperture sizes, reject mechanisms, failsafe system components, conveyor belt materials, connectivity options and more.

How does a tunnel metal detector work?

The majority of tunnel metal detectors are balanced coil systems. Three coils are wound onto a non-metallic frame and each coil is exactly parallel with the other two. We explain exactly how tunnel metal detectors operate in our Metal Detection Guide. You can read more about this from page 8 of the guide.

Related Content: Metal Detection Guide

How sensitive is a tunnel metal detector?

The sensitivity of a tunnel metal detector can vary depending on the application, the metal detector manufacturer and the metal detector itself. Sensitivity performance is determined by the diameter of a sphere made from a specific type of metal. The sphere must be reliably detectable when placed in the center of the aperture of a tunnel metal detector. A tunnel metal detector loses sensitivity the larger the aperture size.

Dry products such as confectionery and cereals, are relatively easy to inspect. Detectors operating at high and ultra-high tuned frequencies (typically in the region of 800kHz and above) deliver high levels of overall sensitivity and are especially good at detecting stainless steel type contaminants.

When inspecting wet or conductive products such as fresh meat, poultry, cheese, fish and metallized film packed products, the situation is different. The wet product itself creates a 'product effect signal' in the detector – and this signal needs to be cancelled out before inspection can begin. Innovative multi-simultaneous frequency technology can be used to overcome product effect, detecting significantly smaller metal contaminants.

How do I choose the right tunnel metal detector?

METTLER TOLEDO Safeline offers a wide variety of industrial tunnel metal detectors for use in food and non-food processing applications. These can be used at various stages of the production process, including inspecting raw materials, in-process to protect downstream equipment, or after final packaging to provide peace of mind that there is minimal risk of subsequent contamination.

Profile Advantage technology is ideal for challenging applications that are subject to product effect where food is hot, wet, chilled, frozen, or packed in metallized film, using multi-simultaneous frequency and product signal suppression technology. Whereas Profile technology is optimized for dry product inspection.

We also offer a number of other tunnel metal detection solutions for bulk and compact product inspection, as well as combi systems, which are integrated with a dynamic checkweigher to provide multiple product inspection capabilities within a single unit, offering a compact footprint.