What process control applications are suitable for wireless?
When can a process application eliminate the cable and use open source radio technology?
Gerrit Lohmann and Robert Schosker, product managers for Pepperl+Fuchs, Twinsburg, OH, say that use of wireless technologies will grow as options expand beyond proprietary wireless solutions, allowing easier integration and eliminating cable in certain situations, for process sensors, instrumentation, and process monitoring.
They explain that wireless implementations should be considered for the following applications:
Level measurements in logistics companies previously undertaken manually, such as for storage of intermediate products, in which the wired solution is either not possible or uneconomical due to obstacles between the control room and the storage location.
Environment monitoring, such as corrosion measurement using online corrosion monitoring instruments at important measuring positions, while eliminating the wiring requirement.
Monitoring of operating elements actuated manually in the field, such as ball valves, to reduce or eliminate control sequences and to provide a better overview of the plant state.
Quality assurance through the cyclic measurement and direct transfer to a database (bypassing the control system) of quality-relevant parameters not relevant to the process control system.
Process optimization and fault tracing due to temporarily installed wireless measuring devices, which measure secondary process parameters.
Process control in plants, which are only installed and operated for short periods for the production of intermediate products. This saves the expense of wiring that would be required for each plant revision.
|A WirelessHART Network offers transmission security through alternative and redundant transmission paths. Source: Pepperl+Fuchs.|
In these applications, wireless technology improves 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, thereby improving the economy of process plants.
Industrial wireless compatibility among field devices of various manufacturers was not available until the HART Communication Foundation’s WirelessHART standard was released in September 2007. It 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. For the physical layer, WirelessHART uses radio modules in accordance with IEEE 802.15.4. Radio systems already are established on the basis of this standard, such as ZigBee and WLAN. Hardware already is available.
Look closely at wireless if your operation fits any of the following scenarios:
Obstacles between the control room and storage location
Need to reduce or end control sequences
Provide a better overview of the plant state
Flexible reporting for short production runs