Baking&Snack - February 2017 - 119

those changes." The system setup allows multiple authorized users, each with a unique ID and password.
TNA North America opted to provide users of its HyperDetect 5 metal detector with annual third-party certification. "Certification is a different process than verification,"
said Mark Lozano, sales manager. "The inspector tests the
sensitivity and balance of the metal detector, and that information is passed along to the user."
FSMA regulations are not the only food safety rules that
concern bakers and snack makers. There are also the requirements of their own HACCP plans and Global Food
Safety Initiative requirements, including SQF, IFS and BRC
inspection and certification programs.
Vision systems examine product qualities of color, shape
and size - factors which, strictly speaking, don't have a direct role in food safety, but the problems they identify do
correlate to less-than-desirable processing and packaging
conditions, according to Joe Crompton, director, controls
engineering, BluePrint Automation.

snack packaging lines between the net-weighing scale and
the bagger. "We changed the geometry of how product
passes from the scale through the metal detector and into
the bag," he said. "The coils' ability to detect metals is weakest in the center of the detection zone. With the new design,
the product does not flow through the center. Therefore,
you get higher detection levels and better accuracy."

Adding learning and visuals
Because tramp metal presents such a danger, many operators verify the accuracy of metal detectors many times
during the production day. This requires an interruption
in service, and even though individual stoppages are short,
they consume considerable time and labor when totaled.
Automatic testing was incorporated into the Halo
software that runs Fortress Technology's Interceptor.
"Company procedures may call for hourly testing, and that
can be awkward when the detector is installed in a difficultto-reach position, say overhead or high up on a vertical
form/fill/seal packager," Ms. Sharpe said. "The unit still has

Advances in technology
Although inline detection equipment has been present in
bakeries for many years, the past decade has seen rapid
advances in controls and technology. Common threads include overcoming product effect and phase angle problems
by monitoring multiple frequencies at once. These systems
are also able to "learn" products on their own and eliminate
noise and product effect, and some completely do away
with manual tuning.
Fortress Technology engineered its Interceptor metal
detector to put simultaneous multi-frequency operation
to work for improving the system's sensitivity. "It was designed specifically for the baking industry because it overcomes the issue of product effect," Ms. Sharpe said. "The
first use was for fast food hamburger buns, a product that
has to meet very strict specs. It does this by processing multiple frequencies over a broad spectrum."
Product effect will cause false rejections because conductive elements, such as moisture, salt or iron, alter the
electromagnetic field of a metal detector, simulating the
presence of metal when none exists, according to Heat and
Control. The simultaneous and continuous use of multiple
electromagnetic fields by the company's CEIA THS/MS21
technology differentiates between metal and product effect.
"This produces consistently accurate metal detection while
preventing product waste and delays for re-inspecting suspect product," the company stated. "It also permits reliable
inspection of products having different characteristics on
the same production line."
TNA took advantage of new technology for its HyperDetect 5 system to solve weaknesses caused by the physical
shape of the metal detector's inspection gateway, according to Mr. Lozano. These systems are typically installed on

The science of detection
Metal detectors apply Faraday's Law of Induction describing
the disruption of a magnetic field by metal moving through
it. X-ray inspection systems depend on the different rates at
which various physical materials absorb such radiation.
Metal detectors use two or more electrical coils with balanced electromagnetic fields. When a food containing something metallic passes through, it unbalances those fields. This
phase shift is detected as a signal and recorded, and the food
product diverted to a reject bin. Modern metal detectors can
pick up signals from metallic pieces as small as 0.1 mm (ferrous) and 1 mm (non-ferrous). They find the presence of ferrous (carbon steel) and nonferrous metals (aluminum, copper
and various grades of stainless steel).
Moisture, salt and certain types of iron enrichment sometimes produce error signals, known as product effects.
Because the phase shift produced differs from that of metals, proper calibration of the detector will allow it to ignore
product effects.
Finding non-metallic contaminants - typically glass and
bone fragments, ceramics, rocks, plastics, rubber and so forth
- requires a different approach. X-ray inspection distinguishes between materials of different densities. The low-power
radiation is funneled through a collimator to produce a thin
curtain of X-rays through which the product passes. A linear
detector array of diodes collects the rays, generating pixels
with a grayscale value proportional to density. The system
generates a visual image of the product, enabling discovery
of foreign materials. X-ray systems can inspect foods packaged in foil and metalized films.

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