March 1, 2009

Reduce Costs with Wireless Instrumentation

Robb Sparks

Work Well with Web Apps

The possible applications for a wireless network go beyond process measurement. Most power plants will find use for two wireless networks running simultaneously. The field network discussed above consists of self-organizing process measurement instruments such as temperature, pressure, and pH transmitters utilizing 802.15.4 radios. The plant network however, utilizes familiar 802.11 Wi-Fi or 802.5 WiMAX. These higher-bandwidth protocols do not enjoy the reliability benefits of a mesh topology, but their enhanced data throughput allows for interesting applications.

For example, state transmitters installed on safety showers or eyewash stations can sound an alarm in the control room upon activation. Operators can then dispatch emergency personnel before even receiving a distress call. The wireless network can also support a personnel locator service that reads radio frequency tags embedded in plant workers’ identification badges and reports their positions to the plant control room. This provides control room staff with increased situational awareness and may help them avoid potentially dangerous situations.

A wireless plant network can also support voice communications over mobile devices similar to cell phones. Such a device can even be used to call up documents such as work orders and wiring diagrams. Plant security and work monitoring may be further enhanced via a surveillance system utilizing wireless cameras.

An example is the experience of Lower Colorado River Authority engineers at the Sim Gideon power plant in Texas, as reported in the March 2008 issue of POWER. Faced with the requirement for a new public address system, engineers calculated that it was 40% less expensive to establish a wireless network than to install a conventional wired one. Once the public address system was up and running, plant engineers were able to expand the network to include a personnel locator service without adding new gateways or other infrastructure.

Wireless instruments are changing the scope of what is possible in process analytical measurement. Their low cost and ease of implementation make it practical to measure points that are prohibitively expensive to wire. The improvements in process awareness and redundant measurement allow plant operators to tighten process control, increase performance, and extend the time between maintenance shutdowns. New advanced wireless systems provide comprehensive solutions for implementing a modern self-organizing network.

--Contributed by Robb Sparks (robb.sparks@emerson.com), power industry manager for Emerson Process Management, Rosemount Analytical Liquid.