Sensor designed to sustain frequent cleaning
By Jane Byrne,
13-Feb-2009 Source of Article: http://www.foodproductiondaily.com/Quality-Safety/Sensor-designed-to-sustain-frequent-cleaning A new
inductive proximity sensor designed for metal object and machine part
detection is high temperature, washdown and
detergent resistant and is targeted specifically at applications in the food
and beverage industry, claims Omron.
Tom Kahn, product
marketing manager for proximity sensors, Omron
USA, said that the company’s new E2EH sensor
can be used with bottling and filling machines, dairy industry clean-in-place
applications, bakery ovens and other food and drink handling applications
that require a wide temperature range. He said the sensor has
an in-built amplifier and can deliver maximum sensing capability in the
110-120°C range, as compared to the industry standard inductive proximity
sensor range of 60-70°C. Detection method Kahn explained that
the E2EH, like most inductive proximity sensors, uses the eddy current kill
oscillator method to detect metal objects: "The sensor core induces a
magnetic field above the sensing face that a passing metal object causes to
collapse. This change of state is detected as a signal that an object is
present." Speaking to
FoodProductionDaily.com, Kahn said that the design of the new sensor was
customer led, with requests from food and beverage industry clients for
improvements to the company’s previous version, which was high temperature
resistant but had a separate amplifier and was not designed for the rigours
of detergent washdown. “That sensor was
designed primarily for embedding in mould halves for plastics fabrication and
use detecting objects entering/leaving conveyor ovens,” explained Kahn. Research He said that Omron
studied what caused failures in fully-potted sensors exposed to cycles of
extreme heat and cold in both air and water to find a more efficient way to
build a reliable proximity sensor: “Potted sensors fail
most often due to thermal shock caused by the expansion and contraction that
occurs as a sensor cycles between high and low temperatures. It can allow
condensation to be sucked inside when temperature drops quickly. “As a by-product of
this research, Omron formulated a potting resin and special production
technique that smoothly filled the internal cavity without voids, which had
been a source of cracking, causing a seal failure point and eventually
permitting ingress of washdown liquid,” continued Kahn. Material selection He said that the
E2EH’s 316L stainless steel shell, plastic face, potting compound and wiring
termination were all selected for their ability to protect the sensing core
and electronics against the corrosive effects of washdown
with high concentration detergents at elevated temperature and pressure over
a long exposure time. “The formulation of
316L stainless steel offers an extended range of corrosion resistance to the
aggressive detergents and disinfectants used in food and beverage processing
such that the E2EH exceeds IP69K rating requirements and carries an ECOLAB
certification.” Kahn added that the
sensing range of its new tool is slightly longer than the industry standard
10mm range for a 30mm diameter sensor: “The important difference is that
the E2EH does not need to shorten the sensing range due to use at high
temperatures or exposure to thermal swings, in comparison to conventional
sensors.” Functionality He maintains that the
E2EH has other uses besides metal object and machine part detection in that
it has been used successfully in packaging applications to detect the foil
layer in a tamper-evident seal lid under a plastic cap, such as those in use
on cylinders of grated Italian-style. And he said that the
sensor is available in three different sizes to accommodate the various food and drink industry applications and the space
available in any given sensing site. In terms of cost, Kahn
said that the E2EH will be priced higher than a conventional inductive
proximity sensor in the “The cost difference
is easily justified by the sensor’s ability to offer reduced labour and parts
costs arising from less frequent replacement. Other sensors fail and need to
be replaced often due to their inability to sustain long exposure to
temperature extremes and corrosive chemicals,” he claims. The E2EH sensor is
available through Omron Europe as well, said the company. |
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