industrial wireless book special edition - Networking ...
industrial wireless book special edition - Networking ...
industrial wireless book special edition - Networking ...
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Case study<br />
Leaky feeder cables provide<br />
non-contact WLAN operation<br />
The Austrian plant manufacturer Berndorf Band produces endless transport and process belts made from<br />
stainless steel. The company has equipped its biggest production hall to date with the latest automation<br />
technology. The production plant makes 3.5mm thick steel bands with a length of up to 270m. Providing<br />
WLAN connectivity for mobile production cells along the length of the hall required a signal field with<br />
<strong>special</strong> properties. Peter Hallas explains.<br />
Long job: The steel belts are almost 300m long and have<br />
to be worked on with movable stations along their length<br />
THE PROCESS and transport belts produced at<br />
Berndorf Band are mainly used in the chemical<br />
industry, food & beverage production and by<br />
producers of timber and laminates. Each band<br />
is produced exactly to customer requirements<br />
from the raw materials which include stainless<br />
steel, carbon steel or titanium. Production<br />
takes place on two lines which simplifies<br />
handling of the band rolls and the individual<br />
processing stations. This makes production<br />
both faster and more flexible.<br />
Communication by radio<br />
In building a new production hall of enormous<br />
dimensions, the company encountered a<br />
challenge in getting power to the individual<br />
PHOTO: SIEMENS A&D<br />
workstation cells. These need to move about<br />
on rails with the actual position of individual<br />
stations determined by the length of the belt<br />
and the processing steps such as welding,<br />
grinding and polishing to be carried out. The<br />
power supply to these stations is provided from<br />
above by loop conductors so that the hall floor<br />
can be kept free of cables and wires, an<br />
essential advantage over the old solution with<br />
cable drag chains.<br />
Communication in the plants takes place via<br />
Profinet and Profibus. This also includes the<br />
entire safety-oriented communication sent<br />
using Profisafe. This data, which includes the<br />
Profisafe layer, has to be sent reliably to the<br />
work stations. To achieve this over the<br />
dimensions of the production required the<br />
installation of a leaky feeder cable, which is<br />
installed under the hall roof together with the<br />
loop conductors for the power supply. This<br />
<strong>special</strong> transmission line cable has deliberate<br />
discontinuities along its entire length. Each<br />
discontinuity acts as an antenna for the<br />
Scalance W access points. The leaky feeder<br />
cable provides a well-defined radio field along<br />
its length and can provide standard two-way<br />
WLAN communication at either 2.4 or 5GHz<br />
with reliability. Using co-located power cables<br />
and feeder, the actual radio path runs to just<br />
a few centimetres into the WLAN interface<br />
components mounted on the movable work<br />
station.<br />
The non-contact data transmission takes<br />
place without wear and is thus maintenancefree,<br />
a major advantage over a wiper contact<br />
application.<br />
The Industrial Ethernet system connects all<br />
the Simatic S7 standard and failsafe CPUs used<br />
in the system within the distributed<br />
automation architecture, as well as the<br />
distributed ET 200 I/O units, each with others,<br />
and with the master WinCC visualization system<br />
and the control panels. Profibus is used locally<br />
within the workstations. There are no differences<br />
between this radio variant and a fixed<br />
wired Profinet communication in the programming<br />
with Step 7 and the connection of the<br />
<strong>wireless</strong> components. An AS-i cable and a link<br />
to the Profibus via a DP/AS-i link reduce the<br />
wiring effort in the band coiling machine. The<br />
system has been running stably since commissioning.<br />
Peter Hallas is with Siemens A&D, Austria<br />
First published in the <strong>industrial</strong> ethernet <strong>book</strong> September<br />
2009<br />
PHOTO: SIEMENS A&D<br />
Loop conductors with co-located leaky feeder provide<br />
data and power to the production line from above<br />
52<br />
<strong>industrial</strong> ethernet <strong>book</strong><br />
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