Photoelectric sensors beneficial in heavy-duty applications

During peak production periods, well over
one million glass bottles per day are made
on the container glass production line that uses machines manufactured by Heye
International. Detecting and counting the bottles in the high-speed flow is not
the only challenge faced by the SICK WL12G-3 photoelectric sensors that are in
use in the plant; they also have to withstand the extreme operating conditions.
As a result of the bottle temperature of over 600¡C and the radiant heat, the
sensors and reflectors alongside the conveyor become very hot.

The ClearSens WL12G-3 photoelectric sensor for
transparent products and the high-temperature
SW50 reflector come from SICK’s range of heavy-duty sensors. Both of these form part of the heat-resistant
and highly available ‘best-in-glass’
system solution at Heye International. They meet high standards and fulfil
users’ requirements for reliable operation under the toughest conditions.
However, when different types of critical operating conditions are combined,
the challenge becomes serious. In Heye International’s container glass
production machines, the sensors have to withstand high ambient temperatures,
significant mechanical stresses, soot particles, glass dust, and tiny particles
of oil and water vapour in the air and the effects of chemicals such as
hydrochloric acid.

Heye International: “We are Glass People”

With its slogan “We are
Glass People”, Heye International GmbH from Obernkirchen in Germany underlines
its leading global position in the field of services and systems for the
container glass industry. The company, which has been part of the international
Ardagh Group since 2003, manufactures machines and equipment for the efficient
production of container glass under its HiPERFORM brand. Its HiSHIELD testing and inspection systems can be
used with a wide variety of hollow glass containers, while its specialist
HiTRUST services include project management and planning, designing and
constructing new production facilities and improving the efficiency of existing
processes. As a supplier of high-performance machinery and production optimisation and project management services,
the company’s objective is to make glass the most successful packaging material
in the world.

Highest stresses at
the ‘hot end’

HiPERFORM machines are used at what is called, the ‘hot end’ of container glass
production. During peak periods, the machines can make more than one million
bottles a day over three shifts at the fluid glass melt, which has a
temperature of more than 1,000¡C. When the bottles are transported in a continuous flow to the next stage of
production, they are still at temperatures of up to 650¡C. This heats up the air in the production area to
over 120¡C. The operating conditions of the sensors that count the bottles and
monitor the flow are made even more difficult by contaminants and moisture in
the air and the heavy vibration of the machines.

‘Best-in-glass’ –
the ClearSens WL12G-3 photoelectric sensor for transparent materials

With these challenges in mind, employees of the product
development and production maintenance departments at Heye International
evaluated several different sensor alternatives. Non-optical systems proved to
be unsuitable because of their inadequate operating distance, inappropriate
size, poor detection results and slow response times. There were also problems
with optical sensors. Through-beam photoelectric sensors were rejected because they involve twice the
amount of assembly and installation work for the senders and receivers.
Photoelectric proximity sensors failed primarily as a result of their operating
distance and the critical hot surface of the glass bottles.

The ‘best-in-glass’
solution proved to be the ClearSens WL12G-3 photoelectric sensor for
transparent materials from SICK, combined with the SW50 high-temperature
reflector. The sensor’s metal housing, which has an enclosure rating up to IP
67, makes it highly mechanically rugged and resistant to a range of aggressive
chemicals. It has a maximum safe operating ambient temperature of +60¡C.
However, in long-term use at Heye International, installed behind a heat
shield, it can withstand more than +80¡C. With a sensing range in this
application of two metres, this auto-collimation
sensor guarantees to provide an impressively reliable detection function and,
at the same time, has high operating reserves, for example, if a coating builds up on the sensor lens. This is made
from scratch-proof PMMA (acrylic glass), which is resistant to chemicals and ageing. The switching frequency of the
photoelectric retro-reflective sensor is 1,500 hertz, which ensures that
the individual bottles in the transport flow are detected and counted reliably.
This is where the reflector comes in. It is installed on the other side of the flow of
bottles from the sensor, where the temperatures are also high. Standard plastic
reflectors would melt and become deformed after only a short time because of
the intense heat. This does not present a
problem for the SW50 high-temperature reflectors from SICK. They have a pane of
borosilicate glass mounted in an anodised
aluminium frame, which allows them to withstand temperatures up to 300¡C over
long periods. As a result of their past
experiences, the team at Heye International also put a great deal of importance
on the ease of use of the sensor. The bottle and container glass machines are
in operation around the clock. For this reason, it is essential that the
sensors can be operated during the third shift when there is no maintenance
engineer available.

The portfolio of
heavy-duty sensors – the ‘survivors’

The system solution
consisting of the WL12G-3 photoelectric retro-reflective sensor and the SW50
high-temperature reflector, in use at Heye International is only one of a whole
range of options for reliably automating processes using sensors under the
toughest conditions. When moisture is a problem, the photoelectric sensors from
the W4 Inox product family are the ideal solution, for example, in wet or damp
areas in the food processing industry or filling and packaging machines. The
W12-3 product family produces impressive results in applications where sensors
come into contact with greases, oils, coolants and lubricants. For example, when processing and packaging
animal and vegetable fats, using machine tools or manufacturing sheet metal in
a steel mill where the air has high oil content.

In areas where sensors
need to be highly mechanically rugged, the first choice is the W24-2 product
family from SICK. These sensors have zinc die-cast
housings that make them a tough, long-lasting and reliable detection solution,
even in challenging environments where heavy items such as steel coils and
railway rails are being handled. In cases
where optoelectronic sensors are not the best answer, SICK’s portfolio of
heavy-duty products also offers other highly effective alternatives, such as
the IMB product family of inductive
sensors. They are shock and vibration-resistant, have a corrosion-resistant
stainless steel housing and can withstand constant water spray or immersion in
water, permanent contact with aggressive cutting oils and cooling lubricants,
and temperatures ranging from -40¡C to 100¡C.

Heavy-duty sensors from
SICK function reliably under the toughest conditions and not only in the bottle
and container glass production plants manufactured by Heye International. They
ensure the highest possible levels of availability for machinery and processes.

Written by Roland
Hackenjos, Product Manager for Industrial Sensors, SICK AG, Waldkirch

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