WirelessHART: Radio Technology in Process Engineering
A request becomes reality
In which situations can the cable be eliminated?
There are also new possibilities in the sphere of environmental monitoring. One example is corrosion measurement using CorrTran® MV from Pepperl+Fuchs. Corrosion measurement is applied to critical areas of a vessel or pipeline. These positions are often extremely difficult to access or far away from the control system. A wireless CorrTran® MV can be optimally installed without an extensive wiring. Here, the security of the transmission is not a critical application, and since corrosion is an extremely slow process, it is not time-critical.
Another new possibility is the monitoring of operating elements that are actuated in the field, such as ball valves. Previously the status of such valves had been visually monitored by patrol checks carried out by employees. However, through wireless transmission of the ball valve position, its status is available at all times in the control room. Cyclic patrol checks and confirmation of the correct position of valves before plant start-up are no longer necessary. This not only saves a few Euros in labor costs, plant start-up is faster and production rates are higher. Of course the same applies to all the other manually checked status parameters, such as pressure and temperature.
Radio transmission can also be used for quality assurance and the optimization of important process parameters. These parameters, typically less critical to the process control, are often only temporarily monitored, in the event of the isolation of faults, for example, and in temporary plant installations with low volume requirements and frequent product changeovers.
In these applications, wireless technology improves the information on plant status, material flow and process sequence. It provides a basis for sequence and process optimization, asset management and decisions relating to preventive maintenance. Wireless technology improves the economy of process plants.
The existing infrastructure can be equipped with WirelessHART
WirelessHART enables new applications to be better utilized
Wireless: It's already here
- Is convenient and simple to use
- Is available, as standard, from a number of manufacturers
- Satisfies the needs of process technology in terms of reliability of transmission and range
Such a system is now available from the HART Communication Foundation in the form of WirelessHART.
WirelessHART – now available
Now the next step in the evolution of HART has arrived. The WirelessHART Standard, released in September 2007, is based directly on the HART protocol, but is free of the physical transfer path. HART uses a 2.4 GHz band – license-free and used throughout the world – as a transfer medium for several radio technologies, including WLAN, Bluetooth, and ZigBee. In order to avoid collisions in the 2.4 GHz frequency band, WirelessHART carries out a special search for unused channels within this frequency band and keeps the mutual interference of radio technologies in check.
Evolution of a technology
The WirelessHART Network offers greater transmission security through alternative and redundant transmission paths
- Monitoring of instrument and environmental values
- Asset management and optimization
- Preventive maintenance
- Performance monitoring
- Energy management
The requirements of these applications in terms of availability, transmission paths and speeds are well-matched by the performance capability achievable by radio technology. And the WirelessHART concept also offers a seamless integration in the existing infrastructure, with simultaneous openness with respect to new structures.
Mere theory, or achievable concepts?
A WirelessHART Gateway that manages the wireless network and connects it to a control or SCADA system via a field bus. The signals of the field devices are received and passed on via the appropriate bus protocol in the field bus.
A WirelessHART Adapter that forms the other end of the communication path. Existing field devices can be equipped with this adapter. Three different versions are planned:
- Loop-fed adapters are simply looped into an existing loop where they extract the energy for operation. The existing wiring is used for the conventional 4-20 mA signal transfer; HART is sent wireless via the adapter. Above all, this is an alternative, in order to render the HART capability in the field devices of the installed base usable with low risk.
- Battery-powered adapters supply the field device by means of a battery. At parameterizable intervals the field device is "awakened", the measured value is interrogated, and the field device switches off. Autonomous measuring stations are possible. Depending on the selected time intervals, a battery life of several years can be achieved.
- An externally powered version obtains the necessary energy for the field device and the adapter. In many cases an externally powered connection is available in the field, for example to supply pumps and valves. If no field device is connected, then this version can also serve as a router, in order to make the wireless network denser or to bridge a greater distance.