What process control applications are OK for wireless?
When can a process application eliminate the cable and use open source radio technology? See how wireless can be applied today, and glimpse solutions coming in 2009.
When can a process application eliminate the cable and use open source radio technology?
When should you go wireless? Examples
-Obstacles between the control room and storage location;
Pepperl+Fuchs , Twinsburg, OH, say that use of wireless technologies will expand as options expand beyond proprietary wireless solutions, allowing easier integration and eliminating
They explain that wireless implementations should
-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.
A WirelessHART Network offers transmission security through alternative and redundant transmission paths, says Pepperl+Fuchs.
-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.
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. Wireless technology improves 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. 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. However, according to Lohmann and Schoskerto, "simply refer to WirelessHART as WLANis an oversimplification."
Pepperl+Fuchs plans to offer WirelessHART adapters for field devices.
HCF explains how WirelessHART works .
By early 2009, Pepperl+Fuchs expects to have aeldbus.)
By early 2009, Pepperl+Fuchs also expects to offer the following:
-A WirelessHART Adapter that forms the other end of the communication path. Existing field devices can be equipped with this adapter. Three versions are planned.
-Loop-fed adapters that 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 wirelessly via the adapter. Above all, this is an alternative to render the HART capability in the field devices of the installed base usable with low risk, say Lohmann and Schoskerto.
-Battery-powered adapters supply the field device by means of a battery. At selectable intervals, the field device is “awakened,” the measured value is interrogated, and the field device switches off. Autonomous measuring stations are possible. Depending on time intervals,
-An externally powered version that obtains 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 also can serve as a router, to make the wireless network denser or to bridge a greater distance.
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– Edited by Mark T. Hoske , editor in chief
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