When signals need to be exchanged long distances and the installation site is exposed to the elements, cable and contact-based systems very quickly reach their limits. In the industrial sector, the wireless InduraNET p system from Pilz Automation Safety L.P. has demonstrated its suitability for everyday use. Now it is proving to be a reliable signal and data transmitter under difficult conditions in a wastewater treatment plant.
The scraper bridge rotates its way round the third secondary settling tank, which has been in operation at the wastewater treatment plant in Bergen auf Rügen, Germany since early 2008. Two blades remove floating sludge and scum on the floor of the tank. At the same time, the station moving along the bridge collects messages on conditions and potential faults. These messages are transmitted wirelessly to the control station, about 90 yards away, via InduraNET p (Industrial Radio Network). In 2005 Bergen's local authority put the expansion of its wastewater treatment plant out to public bid. The requirement manual specified various status conditions to be communicated to the control station.
As with all applications using rotary joints or slip ring transmission systems, contact-based communication systems are limited to linear or rotational movements. InduraNET p was developed for a rugged industrial environment. Its distinguishing features are robust and interference-free communication, plus high availability and coexistence capability with other wireless services.
An InduraNET p network consists of a base station and a remote station; allowing for two-way communication. A maximum of 10 InduraNET p networks can cooperate within a single environment. Pre-assembled cables are used to connect the base and remote station to industrial antennas. At the plant the remote station is positioned on the blade; the controls for the drives, pumps and snow sweeper are issued via the I/O modules. The base station is located in the control cabinet. InduraNET p does not adversely affect any other industrial wireless systems. Busy frequencies are marked as unusable for a certain time period. InduraNET p has a strong immunity to signals from other wireless services. The compact antennas enable efficient wireless communication despite constantly changing conditions in relation to the propagation of the radio waves.
InduraNET p is used in conjunction with the decentralized I/O system PSSuniversal, which can process safety-related signals and/or standard control signals. The configuration of the wireless network is stored on a chip card, plant availability is therefore assured, should it be necessary to exchange the station hardware. Even outside classic industrial applications, this technology shows its strengths wherever there's a need to transfer a wide range of signals. The plant operator intends to fit InduraNET p systems to the two older secondary settling tanks. Service and maintenance intervals will be extended, making the plant more available and reducing costs.