By Steve Blankinship,
Wireless technology has long performed such routine and mundane chores as opening garage doors, unlocking cars, changing TV channels, and letting us communicate with a variety of awesome gadgets. So it may seem shocking that wireless technology has not taken on a greater role in industrial applications — including greater use in power plants.
“While the rest of the world seems to be going wireless, the control business doesn’t seem to be going there very fast, probably because of concerns over security and other issues,” says Mark Converti, Power Generation Market Manager for Honeywell Process Solutions.
That could be changing. Honeywell has introduced a new line of transmitters designed for a wide variety of in-plant monitoring applications. The XYR 5000 wireless transmitters measure and communicate process variables online without wiring or external power, providing the flexibility to gather information about process and assets in areas where traditional hard-wired transmitters are too costly, difficult or time-consuming to implement.
The line includes devices for accurately monitoring gauge pressure, absolute pressure, temperature, and ultrasonic noise (for detecting steam and gas leaks) and includes an analog input interface for adding wireless capabilities to wired devices. Gauge pressure, absolute pressure, temperature and analog input devices offer accuracy of ±0.1% of full-scale reading at reference conditions and the instruments can transmit information up to 2,000 feet, depending on plant topography. The transmitters use advanced radio technology employing the Frequency Hopping Spread Spectrum, a technique that supports reliable communication between the transmitters and the control room.
The instruments transmit measurements to a base radio networked to a control system or data acquisition device like a recorder or PC. Each base radio accepts the signals of up to 50 transmitters. The base radio is available with a choice of Modbus or 4-20mA analog signal output for flexible communications. Wireless Management Toolkit PC software is available for process or asset monitoring and for remote configuration of the wireless transmitters.
Honeywell XYR 5000 wireless transmitters and the array of sensors that work with them could help usher in an era of increased wireless power plant applications. Photos courtesy of Honeywell.
The sensors work in tandem with Honeywell’s Mobile Workstation PKS, a family of small tablet PCs that can be carried around in all kinds of environments and withstand being dropped without breaking. The 6-inch x 4-inch touch-screen devices can be operated with fingers or a stylus and are fully functional network-connected wireless PCs with their own hard drives.
“For now, we are recommending this technology not be used for critical control,” says Converti. “But it can be extremely valuable in numerous special circumstances both for monitoring and for non-critical control in places where it’s difficult to run wires or where you’d rather not send people if you don’t have to. We see all sorts of non-traditional sensing that will help eliminate the cost of wiring but not be ultra-critical to the process, such as emissions monitoring, coal and ash handling and water treatment.” The Honeywell line represents the first such commercial wireless transmitter products to market.
Honeywell plans to offer power plant customers what it believes are a number of interesting ways to use wireless technology. Customers are also providing some interesting and exciting uses for devices such as the Mobile Workstation PKS. “They tell us they would like to use this during plant shutdowns where they can walk around the plant and recalibrate instruments, take readings, stroke valves, check out newly installed equipment without having to maintain constant 2-way radio contact with the control room,” says Converti.
With the addition of software that includes a predictive maintenance tool, inspectors can easily add work orders with minimum or no paperwork. The system can also be used to conduct maintenance tasks that involve monitoring the process and, if the unit is running, lock out any control actions. “That’s easy to do because everything in the system is password protected.”
Technology has advanced to the point that such wireless applications no longer raise security concerns as they once did. Converti cites a recent article in Control Engineering (July 1, 2003) specifically addressing the security of such technology. The article concluded that the security is very good.
The Frequency Hopping Spread Spectrum (FHSS) technique is used by XYR 5000 transmitters to increase reliability and minimize the unauthorized interception (listening) and jamming (interference) of the RF communications between the field units and the base radio. The RF communication is spread over 50 predetermined, but random frequencies within the band, hopping to a different frequency approximately every 20 to 350 milliseconds. In order to intercept information, a hacker would have to not only know the hopping sequence, but also be able to synchronize to the specific frequency hopping to a very high degree of accuracy.
Futhermore, XYR 5000 devices operate at 31 milliwatts. At such a low power output, someone would have to penetrate the physical plant perimeter in order to actually read the information being sent by the wireless transmitters.
The latest version of Wi-Fi used by Mobile Workstation PKS has up to 128 bits encryption on password access for keyword access. In addition, the wireless routers can limit the number of connections by IP address and MAC address — the built-in Ethernet address that comes with each Ethernet user and is unique to every user. Therefore, use of the device — and who connects to the wireless — can be limited via the Ethernet card. The combination of those two elements means that the technology is as secure as anything on the Internet.
Coal plants in particular provide many locations where the technology could be employed, says Converti. “A power plant is full of potential remote sensing applications — the coal yard, ash handling areas, cooling ponds, feed water inlets or water treatment areas — anything that is a distance away from the main unit or difficult to get to.” Other applications would include emission sensors located high inside stacks and monitoring needs in places difficult to reach with wiring. Uses extend to locations posing health or safety threats to workers — areas exposed to coal dust or high noise, for example. The wireless transmitters are also rated to work in a Class 2, Div 1 environment — meaning they are safe around combustible dusts
“One of our wireless devices is an acoustic sensor,” Converti says. “We are thinking of locating those in places like coal feeders so we can monitor for blockages. The sensor would be listening for absence of noise meaning that something is stuck. If you don’t hear any flow then your chute is probably blocked or jammed..”
He also sees cost-effective applications for temporary needs: “Construction engineering partners often need extra sensors during checkout, and this is a way for them to take to site anything else that they might need — put it in place for the time they are doing their installation and startup, and then afterwards take it out. We think this is a great way to put some quick extra signals into the control system that would normally require significant expense for wiring.”
Converti says he can’t think of a place in a power plant where the technology could not be used. “Since such a large part of what goes on in a power plant is data collection, there are plenty of possibilities. The sky is the limit. We are working with customers now and dreaming up ideas.”