The use of wireless technology in industrial automation systems offers a number of potential benefits, from the obvious cost reduction brought about by the elimination of wiring, to the availability of better plant information, improved productivity and better asset management. However, its practical implementation faces a number of challenges: not least the present lack of a universally agreed standard. This article looks at some of these challenges and presents the approach being taken by Yokogawa.
The wireless landscape
In order to understand the ways in which wireless technology can aid the implementation of industrial automation systems, it is first important to clarify what is meant by the word ‘wireless’ in this context. Essentially, wireless can act at several levels within a plant:
* RFID – at the simplest level, radio-frequency identification can aid asset inspection and tracking, safety, security and location.
* Wireless sensor networks – this is possibly the area where most attention is currently being focused and embraces aspects such as condition monitoring, wireless instruments and measurements.
* Wireless LANs, covering areas such as mobile operator terminals, data-logging, security, maintenance and IT. Wireless WANs, including long-distance broadband backhaul and high-bandwidth video applications.
When implemented within a typical plant, each of these aspects can bring benefits as well as new opportunities. For example, the fact that plant and process information is available anywhere via wireless sensor networks leads to greater quality of information, with the benefits of distributed control and plant asset management spread throughout the plant.
Another important benefit is improved workforce productivity. The fact that there are no wires leads to reduced installation and commissioning effort, while the fact that workers – whether operators or maintenance engineers – can now be truly mobile. Improved plant management results from the improved availability of video surveillance and people tracking for better safety and security, along with a reduced need to access hazardous or remote plant areas.
Of all the elements highlighted above, wireless sensor networks are currently attracting the most attention as most of the benefits directly relate to this area. Apart from the benefits of eliminating signal and power wiring, wireless sensor networks open up measurement applications in sites that are hard to access, or where the wiring cost cannot be justified. They can also prove invaluable for the modernisation of existing facilities, for temporary installations, or for locations where a power source is not available. Wireless sensor networks offer enhanced plant asset management through the freeing up of cable resources for higher-priority measurements in existing installations, the replacement of many traditional pressure gauges and temperature indicators and the ability to make measurements that could not previously be justified. There is also a reduction in ‘blind spots’ through the ability to make measurements on rotating or moving equipment and in remote locations. A further point is that, once established, wireless sensor networks are scalable: additional sensors can be added at low cost and temporary measurements can be incorporated for process diagnostics and optimisation.
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