PRESS RELEASE
The efficient monitoring of transport belts
Christoph Müller, Business Unit Manager Industrial Instrumentation, SICK AG
The preventive monitoring of conveyor belts and the uninterrupted measurement of volume flows on
transport belts are very important tasks in numerous industries: as a result of the raw materials boom,
particularly in Asian economies, deposits are being opened up in more remote areas worldwide –
requiring the commissioning of ever-longer conveyor systems for the efficient loading of ores, coal and
other primary materials. In order to permit the optimization of logistical chains, the loading and unloading
of ships (in both seaports and inland ports), as well as of train wagons and trucks, must be achieved
quickly, without interruption, and with complete filling volumes.
Just as for the extraction of raw materials, or for the supply or discharge of power station fuels and their
combustion residues, it is also necessary for modern factories processing wood pellets, granulates or
food to continuously monitor the supply of raw materials in order to be able to efficiently control
production processes, as well as maintain the hygiene and shelf-life requirements, of for example
vegetables. Continuous filling processes into bags and sacks at the end of such processing steps also
necessitate the control of volume flows. All these process steps are highly relevant for the output of the
particular industry and must therefore be conducted with availability that is as high as possible. At the
same time, however, they are also highly susceptible to mechanical damage – and thus to unforeseen
interruptions of operation – due to the bulk materials involved. The extreme operating conditions and
mechanical loads during the transport and loading or unloading of bulk materials also make operation of
the measurement technology and sensors more difficult for determining both transported volumes and
masses, as well as for the preventive monitoring of conveyor belts. The use of sensor technologies and
measurement equipment that require contact, such as mechanical belt weighers or electromechanical
filling level switches, which are in constant contact with conveyor belts or the bulk materials themselves,
cannot get around this problem and they are constantly subject to mechanical friction – which will
ultimately be responsible for costly downtimes and repairs. In the past, alternative non-contact
technologies offered limited opportunities for use, however, both because of their high prices and, above
all, due to the harsh operating conditions and the attendant dust formation or precipitation.
New developments in the area of laser time-of-flight of light measurement now offer efficient non-contact,
and therefore friction-free, solutions for measuring the volume flows or mass flows of conveyor belts by
means of a more robust continuous detection of height profiles. The same technology can also detect any
uneven distribution of bulk materials in parallel – and thus any belt imbalances or tilting and the resultant
imminent friction. This has become possible thanks to the improved signal evaluation of laser scanners.
A laser scanner is mounted above the conveyor belt where it uses laser pulses to continuously detect the
height profile of the bulk materials passing beneath it by calculating the time of flight. Whereby the laser
beam itself is eye-safe and corresponds to Laser Class 1. The two-dimensional height profile thus
obtained is combined with supplementary information – for example the third dimension of belt speed
obtained by using an encoder, or density information – allowing the sensor to autonomously determine
the transported volume or mass per time unit. At the same time, the height distribution can be used to
reliably detect the above-mentioned tilting or any one-sided loading so that a warning signal can be
transmitted.
What is so special about this design structure is the robust detection of the height profile even in the case
of interfering factors such as bulk material mists, dust or rain. This has been made possible by means of
new signal evaluation technologies that can reliably filter out the correct height profile signal from
amongst the numerous echoes. Thus the German sensor producer SICK offers, for example, laser
scanners with so-called multi-echo technology, whereby the software algorithm can reliably determine the
correct signal from among the various reflected laser pulses and dependably suppress the measurement
of interfering echoes caused by mist or rain. Maximum resolution of the height profile – and thus a high
measurement accuracy – and the measurement of rapidly moving transport belts with speeds of up to 30
meters per second can be achieved as a result of the devices’ rapid scan frequencies of up to 75 Hz and
speedy response times. For the further processing of signals, the SICK Bulkscan system offers six
switching outputs that can be individually occupied, for example as warning or pulse outputs, as well as
continuous outputs such as, for example, transmission of measurement values via TCP/IP (Ethernet).
Whereby the processing and preparation of measurement values takes place directly in the sensor which,
therefore, also has two inputs. No supplementary measurement value computer is required. This results
in simple installation and commissioning.
The advantages of such as a system compared to mechanical solutions are self-evident – greater
availability of transport and filling plants, no need for maintenance, and the longer service life of the
sensor system due to the lack of mechanical friction.
SICK is one of the world's leading manufacturers of sensors and sensor solutions for industrial
applications. Founded in 1946 by Dr.-Ing. e. h. Erwin Sick, the company is headquartered in the German
town of Waldkirch, in the Breisgau region near the city of Freiburg. It is a technology and market leader,
maintaining a global presence with more than 50 subsidiaries and equity investments as well as
numerous representative offices. In the 2014 fiscal year, SICK had around 7,000 employees worldwide
and generated Group revenues of €1,099.8 million.
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