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“We made a strategic choice to start where customers could get the fastest and easiest return,” says Bob Karschnia, vice president of wireless for Emerson Process Management, referring to the company’s release a couple of years ago of wireless, self-organizing solutions at the instrumentation level. “This is because field sensor networks can be easily installed and deliver significant value without the need for investing in a plant-wide wireless infrastructure,” he says.
But a wireless field device isn’t just a different kind of transmitter; it is the product of a real breakthrough in technology and practice that is just now being seen for what it is, according to Peter Zornio, chief strategic officer for Emerson Process Management. “The adoption of wireless technology,” Zornio explains, “will be driven by the ability to extend and manage the flow of information around the plant truly without limits. This will drive work process and operational practice change as this new capability is utilized. That’s the definition of a technology discontinuity.”
Indeed, the implementation of process control strategies has long been constrained by a simple set of instrumentation costs: the transmitter itself, the time and labor required for engineering and implementing the installation, the running of wire back to a central control room and the distributed control system input/output (I/O) hardware itself. Over the years, the cost of transmitters has steadily decreased, as has the cost of I/O. It is the middle part the installation and the wiring of the device to the control system that continues to be the limiting factor.
ADD NEW MEASUREMENTS QUICKLY AND EASILY
Early adopters of wireless have been able to access many such measurements, and not all of them have been traditional analog process variables. For example, one early adopter uses wireless to advise in real time when pressure relief valves open and close. This minimizes the fines from regulatory agencies for accidental environmental discharges.
Another early adopter uses wireless to annunciate activation of emergency stop buttons, pressure and temperature switches and other alarms to the centrally located operator.
Other early adopters are monitoring water temperature and pressure at eye-wash stations and the actuation of safety showers remotely. With the addition of people-locating applications, operators are even able to tell who it was that actuated that safety shower or eye-wash station and route the appropriate assistance to the scene faster and with greater efficiency.
Early adopters also are monitoring additional process variables for process optimization. Temperatures, pressures and flow rates that were far too expensive to monitor at the operator console can now be brought there wirelessly.
WIRELESS SLASHES MEASUREMENT COSTS
There are an estimated 26 million wired HART devices installed and in service around the globe. But fewer than 25% of the installed HART devices have their digital data, including diagnostics, connected to the control system or to an asset management system. For years, it was difficult to connect the digital information stream to controllers and systems that were designed toonly see analog data streams.
But with WirelessHART adapters, like Emerson’s soon-to-be-released Smart Wireless THUM Adapter, all this will change. The THUM adapter is a device that sits on the 4-20 mA DC loop and is typically screwed into the unused conduit port on the transmitter. It draws its power from the loop, extracts the HART digital data from the field device and communicates via WirelessHART protocol to a gateway and, thence, into the host system.
Croda Inc., an international specialty chemicals manufacturer, uses wireless temperature transmitters from Emerson mounted on chemical tank cars to send minute-by-minute readings to a central host, improving process performance and boosting overall safety.
Because the tank cars are moved frequently, hard-wiring of temperature sensors was impractical. Previously, an employee had to climb to the top of each car once a day to check the temperatures and record each reading. This was a time-consuming procedure that, during wet or icy conditions, presented a fall potential. With wireless, operators are alerted to any unexpected temperature rise in the tank cars, while saving about $15,000 per year in reduced maintenance.
“The wireless solution not only saves us time and money, since plant personnel no longer have to monitor those tank cars daily, it has also greatly enhanced the overall safety of the plant and our personnel,” says Denny Fetters, instrument and electrical designer for Croda. “No matter where a tank car is positioned on-site, the quality of the transmissions is unaffected, and the signals integrate seamlessly into our control system.”
At PPG Industries’ Lake Charles, La., facility, wireless temperature transmitters monitor the temperature profile of the plant’s steam headers. The applications had always been desired, but difficult to implement, according to Tim Gerami, PPG senior design engineer. PPG engineers also wanted to use wireless for some of the redundant measurements they really needed for plant optimization and asset management.
WIRELESS ADAPTER TO LIBERATE HART DIAGNOSTICS
“There were others where the wireless part looked good,” Gerami notes, “but it was just point-to-point, rather than mesh. It would work, but it limited the number of devices in a given plant—maybe 50 per radio, 16 channels. That would be difficult in a plant. You need more than a hundred transmitters and several hundred eventually. A mesh network has the potential to be virtually unlimited.”
Gerami makes the game-changing nature of wireless clear. “It’s an enabler for things you wouldn’t ordinarily do,” he says.
Wireless instrumentation, together with Emerson’s DeltaV digital automation systems, now are making it possible to do exactly that—provide a wireless-enabled, united information system on a unified network throughout the plant. This capability makes possible entire plant designs not feasible just a few short years ago.
One major life sciences company designed a multi-story plant in a building with twelve-inch thick reinforced concrete floors and walls. Modular process equipment can be moved around and reconfigured at will, and because instrumentation communicates wirelessly, reconfiguration requires no re-instrumentation. Indeed, one gateway installed on the third floor maintains communication with all the field devices on all four floors and on the roof of the building.
“Looking to the future was one of the reasons to try out the use of wireless sensors,” says Ruud van Dijk, TAQA Energy engineering manager, of his company’s successful test of Emerson Smart Wireless technology at its natural gas production site in Alkmaar, The Netherlands. “Basically, there was no room for more wires at the site in Bergermeer, and connecting new sensors would have entailed breaking open some hundred meters of paving to install extra wires. This is expensive and time-consuming.”
“Of course we already have years of experience with wireless data transfer in office environments,” adds John Pietersz of TAQA’s metering and control department. “But it is a different matter on the processing level. This world is very reluctant when it comes to introducing new technology.”
The TAQA team determined that it needed the flexibility and robust reach of the self-organizing mesh network architecture of Smart Wireless. “In the case of the Smart Wireless system, this radius is 200 meters,” Pietersz says. “It already leaves a lot of elbow room, but what is special about the solution is that the sensors can pass on each other’s signals. This means that you can apply sensors far outside the initial radius of 200 meters without having to install extra base stations. Future expansions will then only require the purchase of a transmitter, which will naturally also yield economic advantages.”
“We have also bought an Emerson AMS asset management system,” Pietersz adds. “Currently we only manage the wireless sensors with it, but we will be putting other instrumentation into the system in the near future.
In short, the wireless era has begun well for us.”
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Self-Organizing Mesh Networks vs. Point-To-Point
Emerson Process Management’s Smart Wireless field networks use self-organizing mesh technology that is tried and tested and the basis for the recently approved WirelessHART standard. Each wireless device in a self-organizing network can act as a router for other nearby devices, passing messages along until they reach their destination.
This capability provides redundant communication paths and better reliability than solutions that require direct, line-of-sight communication between each device and its gateway. Whenever there’s a change in the network or in conditions that affect communications, the devices and gateways in a self-organizing network work together to find and use the most efficient path for each message a path that optimizes data reliability while minimizing power consumption.
Self-organizing network technology also reduces the effort and infrastructure needed to set up a successful wireless network. One of the difficulties of setting up the traditional point-to-point wireless network is the requirement to do a site survey to be certain that every node in the system has a line-of-sight path. This survey work is expensive. Plus, the resultant point-to-point network may require as many as five times the number of infrastructure nodes as a self-organizing network.
Another advantage of self-organizing networks is that they are dynamic. As new obstacles are encountered in a plant, such as scaffolding, new equipment or moving vehicles, the networks can reorganize around them. All of this happens automatically, without any intervention by the user.
Emerson’s Smart Wireless and now all WirelessHART self-organizing networks use IEEE 802.15.4 radios with channel-hopping as the physical layer. They are designed and tested to be tolerant to almost all interference and can co-exist with other wireless networks in your plant. The networks are also highly scalable and capable of one-second scanning with low latency. Emerson’s wireless devices based on this technology have been proven in use to demonstrate greater than 99% data reliability.
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