The Wisdom of Wireless

More engineers install wireless networks.

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The wisdom of working with wireless networks has long been contested among manufacturers. Skeptics worry about the reliability of the equipment and the communications medium—the air—in industrial settings.

In the case of Dundee Precious Metals, some skeptics went a step further. They declared flatly that a wireless network simply wouldn’t work underground and would be unable to link the company’s mines in Bulgaria and Armenia to its headquarters in Toronto. Not only would the signals be unable to penetrate the earth, but also metals in the surrounding ores would interfere with point-to-point transmission.

Despite the initial doubts, its underground wireless infrastructure has been a success, according to Mark Gelsomini, global corporate manager of information technology (IT). He and his staff joined the growing number of engineers who are successfully deploying the latest wireless technology to their operations. During the past decade, this group has discovered how to use wireless to enhance the productivity of their companies’ equipment and mobile workers.

Driving the deployment at Dundee was a desire to improve the company’s ability to track equipment and personnel. Management simply must know where everyone in the mine is before workers can begin blasting, and must have the ability to count heads in emergencies. Like other businesses, the company also wanted to increase efficiency of assets and workers by fostering communications throughout its operations and collecting and analyzing historical data.

To reap these benefits, Dundee’s management invested in a Wi-Fi (for Wireless Fidelity) network from Cisco Mobility Solutions, of San Jose, Calif. Because Wi-Fi and other wireless signals cannot penetrate the ground, the engineering team began the project by installing a network of 250 access points in portions of its Bulgarian mine. Each of these access points is connected to a fiber-optic network in order to connect the transmitters, personal digital assistants (PDAs), phones and laptops to the rest of the company.

When people are within range of an access point, the network can track them within a meter or so. Equipment outfitted with Wi-Fi transmitters can broadcast not only its location, but also information about its status, such as how full it is, how much fuel it has and whether it needs maintenance. Software running in the background collects this information and helps planners to optimize utilization.

The network also allows workers to use push-to-talk Wi-Fi phones underground. “They can make long-distance calls and site calls—because we are all part of one global infrastructure,” says Gelsomini. “Anybody in Toronto can call the extension of someone at the underground mine to see how things are going. Previously, that was not possible.” He reports that telecommunications costs have fallen significantly since implementation in both mines in July.

Making wireless work

Getting these results was not easy. It entailed a tedious process that included a lot of trial and error. Planning began at each mine with a meeting with the general manager, mining engineer and mine captains to decide where they needed coverage. Covering the entire mine was cost-prohibitive because it would have required thousands of access points, so they had to install the network only in the sections that would benefit the most from it.

The next step in the process was to decide where to mount the access points. The goal was to keep the number of these points to a minimum, given the layout of the mine and the composition of the surrounding rock. The tunnels, for example, were often not straight and needed more access points to get around the curves. The density of the rock and the type of metals in it affect whether the minerals will reflect or absorb the signals and therefore influenced access-point locations.

Another variable in the design was the type of antennas used. “We had to go through the tedious process of testing of each individual antenna in the market and pick the best ones for our environments,” says Gelsomini. Once the area of coverage, the type of equipment and the locations of the access points were decided, the required downtime was then scheduled so the technicians could mount the access points to the roof.

Maintainability was another important consideration in choosing and specifying the technology. Mines are dusty, wet and rugged environments that are hard on electronics. Because Gelsomini was expecting frequent failures, he wanted any electrician, or even a miner, to be able to replace a broken access point. Because Cisco’s Wi-Fi technology is not proprietary, “you configure it once,” he notes. “Every access point grabs the configuration from the access controller.” There is no need to dispatch an IT technician to connect it to a laptop and configure it manually.

Maintenance is not a trivial issue in the debate over the wisdom of wireless networks. Despite successes at Dundee and elsewhere, skeptics point out that using wireless networks in industrial environments is still new, especially in control applications, and urge doing your homework beforehand. “We have got to learn how this medium works, how to deploy it, baseline its performance, identify the limits it has and learn to diagnose it when it stops communicating,” cautions Jake Brodsky, PE, a reader of this magazine and a control systems engineer at the Washington Suburban Sanitary Commission, in Laurel, Md.

He points to the difficulties during the introduction of Profibus more than 20 years ago. “Everyone talked about how easy it would be to integrate, how much money we could save in wiring, and how incredibly scalable it was,” he recalls. “The problem was that nobody said anything about what to do when it breaks.” Plants that went down at odd hours of the night for no apparent reason learned these lessons the hard way. “It took us years. The discontent from those early Profibus days still linger even to this day.”

Know your limitations

Although Brodsky has nothing against unlicensed wireless communications, he simply worries about the lack of tools for diagnosing problems. “There is no off-the-shelf equivalent to the two-way radio shop service monitor,” he offers. Some vendors have been designing redundancy into their wireless systems, believing that it will solve the reliability problems prohibiting its use in many control applications. “Redundancy may not save you if the outage is caused by excess traffic,” responds Brodsky. He also has reservations about the quality of a real-time wireless network.

Although most vendors acknowledge that these have been valid concerns, they point out that significant advancements in the technology and improvements to the standards have resolved most of them. An example is the Institute of Electrical and Electronics Engineers’ IEEE 802.11n, a significant improvement over the earlier 802.11a, 802.11b and 802.11g. “These prior standards delivered up to 54 megabits per second (Mbps) of bandwidth, whereas 802.11n delivers up to 300 Mbps,” points out Chris Kozup, director, Cisco Mobility Solutions. Because of this increase in performance, he expects to see a dramatic increase in the use of wireless devices.

The industry also believes that it has corrected the well-known weaknesses in the cryptography of the wired equivalent privacy (WEP) mechanism in the IEEE 802.11 standard that made users skittish about security in the past. Vendors have made significant strides in correcting those security problems with such certifications as Wi-Fi protected access (WPA) and WPA-2 developed by the Wi-Fi Alliance. “When deployed correctly, it is more secure than most wired networks today,” says Kozup.

Vendors also report significant improvements to the reliability of wireless networks. Cisco, for example, has introduced a technology called CleanAir that works in the hardware of the access points to detect and mitigate interference. “This technology is especially important for mission-critical wireless networks—like those used in manufacturing environments—where there is a great need to maintain a high degree of network uptime and a large number of variables,” notes Kozup.

In the end, though, wireless networks operate on a shared medium—the air. So one must take the environment into consideration from the beginning. This means performing a site survey to identify all sources of interference—whether they be motors, machinery or other networks. “When you know what you have, then you can tailor your wireless solution to work within the specific boundaries,” says Marty Jansons, a network consultant at automation industry supplier Siemens Industry Inc., in Norcross, Ga.

The tailoring process usually involves segmenting the plant and isolating the network from the interference. In a case in which an enterprise network already exists, the plan should include a means for isolating the plant network from it. “If your IT department has already put wireless access points throughout the building, they are probably using one of the 802.11 standards,” says Jansons. “If the IT department is using 802.11g, maybe the plant environment could use 802.11a to avoid the possibility of someone with a laptop accidentally connecting to plant equipment.”

Tighter control

Because tailoring the wireless network to the environment requires a fair amount of expertise, most successful installations involve a vendor that can supply the required know-how. Such was the case at Columbus Brick Co., in Columbus, Miss., when management wanted to upgrade Plant 2, its automated facility. Although the plant was already using robots, other automated machinery and supervisory control and data acquisition (SCADA), it had not yet automated the measurement and recording of the weight of the clay entering the plant by truck. Management wanted to automate this part of the process in order to improve control.

Doing so would require building a load cell. Because of the layout of the existing plant and office buildings, especially the location of the clay hopper to the crusher, the only logical place to install a scale was some distance from the buildings.  “At that point, we decided wireless was the most beneficial way to install a truck scale,” says Nigel Hough, engineering director. “It prompted the decision to connect the entire plant wirelessly.”

He asked Siemens for help with the project because the plant was already using the automation vendor’s controllers and networking technology. “Parts of the manufacturing process had been linked with a Profibus-based network, from PLC to PLC,” explains Hough. “It was a hardwired fieldbus system.  For more flexibility, we added the ProfiNet Ethernet network to overcome it limitations.” All of the information goes to the control room and office for viewing and control via a human-machine interface (HMI).

The next stage of the upgrade involved installing wireless radios to span the distance between processes. Areas of the plant that had not been included in the Profibus network because of the cost associated with distance and wires now could be made accessible to the network through wireless communication. All phases of manufacturing are now communicating with one another—from the point of weighing the trucks entering the facility through crushing, extrusion, drying, firing and packaging.

Now that the wireless infrastructure is in place, Hough is exploiting it to convert other wired operations to wireless. The conversion in the drying room promised to enhance control over cars stacked with bricks as they move through the process. Wireless communication should also lower maintenance on the kiln, which suffers from high wire wear due to the heat.

Also on the to-do list is adding intelligence for preventive maintenance. It would control the number of starts per hour and monitor bearings and temperature. “We no longer have to use wires for every aspect of an upgrade or expansion in intelligence, which has given us the flexibility to add technology and cross boundaries that were restrictive before.” For him, there is no question about the wisdom of working with wireless networks.

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