The Benefits of Automatic
Metal Detector Testing
By Mike Bradley, Global Head of Sales (Metal
Detection) Mettler-Toledo Product Inspection
Traditional methods of testing gravity fed
metal detectors and those installed on
Vertical Form Fill and Seal (VFFS) packing
lines typically involve frequent and timeconsuming
stoppages, potential risks
to operator safety and often generate
inconsistent results. In many cases, the
test methods used do not confirm that
the operational specification of the metal
detector is being achieved. Automatic
metal detector testing systems
overcome these issues and can aid food
manufacturing quality, efficiency and
productivity.
The “Drop-Through”, “Fishing Line”
and “Test Rod” methods are all routine
performance monitoring test processes
for vertical metal detection inspection
systems. Manual testing often requires
teams of operators to put their safety
at risk by climbing ladders and reaching
over machinery so that they can drop
or insert test samples into a throat or
gravity-fall metal detector. These test
processes are unable to accurately verify
the operational specification of
the metal detector. This is because they
do not confirm centerline testing – the
least sensitive part of the metal detector
– as the placement of test samples
passing through is generally random. In
addition, manual testing processes can
carry cross-contamination risks and can
potentially compromise food product
quality, as the test samples come into
direct contact with the product.
Mettler-Toledo has delivered a solution
to all these problems, while also
helping to improve Overall Equipment
Effectiveness (OEE) and productivity:
its Automatic Test System (ATS) on
Safeline metal detection systems, won
the CFIA Innovation Award for Quality,
Hygiene, Security and Environment in
France in 2019 and has been recognised
as accepted best practise by a major UK
high street retailer.
ATS is suitable for use in vertical food
inspection applications such as snacks,
crisps, confectionery, infant formula,
bulk flour and nutraceutical powders,
plus granulates such as sugar and food
additives. Test samples are transported,
by pneumatic control, up discreet nonmetallic
tubes inside the metal detector’s
aperture to a defined position within the
sensing coils. The test samples are then
released, simulating the presence of a
contaminant in free-fall under gravity. A
software algorithm correlates centerline
sensitivity with edge of aperture
sensitivity, eliminating the random
nature of vertical metal detector testing.
Reduced Test (RT) Mode is an additional
feature available on some throat and
gravity-fall metal detection systems.
When RT Mode is active, the metal
detector monitors its online sensitivity
performance and provides an alarm
should the sensitivity drop below the
specified level allowing companies to
reduce the frequency of testing by up to
80%, without increasing their risk. This
directly, and in some cases dramatically,
improves productivity as production is
now stopped less frequently for testing
allowing productivity gains to be realised.
Major Italian savoury snack producer
PATA S.p.A has 30 throat-style metal
detectors on its production line, of
which five have ATS installed. RT Mode
is included as standard on the Mettler-
Toledo Profile metal detectors that it
uses. ATS and RT Mode have provided
several benefits for PATA and for other
food manufacturers that use them:
#1 ENSURE COMPLIANCE
34 FDPP - www.fdpp.co.uk
ATS is the only method of testing
that confirms centerline (worst-case)
sensitivity performance. As such, it
delivers test results of ongoing working
performance that can be trusted.