Food & Beverage Asia February/March 2022

PROCESSING AND PACKAGING 53
MAKING IT SIMPLE
Metal detection or x-ray? The flow chart
(Figure 1) is a good starting point for
identifying the right answer. However, there
is an area of indecision where the application
is not packaged in foil and metals other than
aluminium are potential contaminants. As the
chart illustrates, in these scenarios a more
complex evaluation of options is needed.
Figure 1: This flow chart indicates the right detection system for different products
Critical control points (CCPs) should be
Metal contaminants in non-metal
established to mitigate the risks, and product packaging: This can be complicated. Metal
inspection equipment needs to be installed detection systems are more cost-effective
at these points. If the HACCP/HARPC audit but if the product is very large, a bigger
determines that metal is the only likely detector aperture will be needed, which
contaminant, then a metal detection system can reduce the sensitivity of the detector.
is probably going to be the best solution. If Multi- and high frequency technology
metal and/or other contaminants, such as can help, but a bigger metal detection
glass, stone or dense plastics, are likely to system will be required. X-ray strength
be encountered, then x-ray systems will be can be increased for larger products, but
the best solution. However, there are many the cost of installation increases as size
applications where the choice is less clear, increases. If there is a need to protect
and others where the right answer might be against non-metallic contamination,
to deploy both. Consider these examples: the choice will swing towards x-ray.
Aluminium contaminants in nonmetal
packaging: As a lightweight,
packaging; Performing additional quality
Non-metal contaminants in any
low-density metal, aluminium is hard for control issues: X-ray inspection is the only
x-ray to detect as a contaminant; metal solution, and the additional QC checks can
detection is generally the better solution. justify the additional cost of the technology.
Metal contaminants in aluminium foil Fast/variable line speeds; situations
packaging: Metal detection will be unable where there is limited space: Metal
to spot the contaminants amidst the foil detection (at 400m/min) is able to inspect
packaging unless it is a metallised film; at faster speeds than x-ray (120m/
x-ray is generally the better solution.
min), thus possessing an advantage
if other aspects of the application suit
Metal contaminants in gravity-fed metal detection better. Metal detectors
products: X-ray does not work well with are also less space-consuming than
falling, accelerating objects that do not x-ray detectors, so depending upon
have a uniform direction of travel; metal the application, might be more suitable
detection is the only viable solution.
in factories with limited space.
There may also be situations in which more
than one type of product inspection system is
desirable at different CCPs on the production
line. For example, it may be wise to install
a metal detector early in the processing
line to remove large metal contaminants
that could, if left present, cause damage to
machinery downstream, or fragment into
smaller and less easily detectable pieces.
Further down the production line, an x-ray
machine could then check for non-metal
contaminants, as well as carrying out further
quality control checks. A second, and more
sensitive, metal detection systems at the
end-of-the-line could be used to make a final
inspection for smaller metal contaminants.
In summary, the first step in choosing a metal
detector or an x-ray system for product
inspection is to consider its application – the
type of product, the type of likely contaminant,
and the location of CCPs. Metal detection
offers many advantages for raw product
inspection whereas x-ray inspection provides
multiple product and packaging integrity
checks, in addition to contaminant detection.
While more factors
will influence the
decision,
including
space
limitations,
total cost of
ownership and
productivity
targets, the
application
is where the
assessment
begins.
FBA
FOOD & BEVERAGE ASIA FEBRUARY / MARCH 2022