Some say tablets and smartphones are fomenting a quiet revolution in industry. Mobile human machine interfaces (HMIs) and wireless applications allowing access to remote sites seem suddenly affordable. But what about the digital infrastructure that enables them? Can mobile connectivity really free workers from clipboards and control rooms today?
Mobile connectivity has on-call engineers and technicians reveling in a new kind of freedom at the water and wastewater divisions in Haverhill, Mass. No longer shackled to their monitors in the control room, operators can go home at the end of the day thanks to an Apple iPad outfitted with 4G long-term evolution (LTE) mobile phone technology. Using the high-speed link to the plant’s control network, the operators have access to real-time information and can respond to alarms from home—or anywhere else—after hours.
The mobile connectivity established there and for other remote-site applications suggests that industry just might be on the verge of an information revolution like the one already underway among consumers. With the proliferation of high-speed connectivity, some industrial users have established a similar kind of access to real-time information that consumers have been enjoying with their smartphones while on the go. Others are just now considering what mobile applications can justify investment in the digital infrastructure needed—whether that infrastructure is made up of 4G cellular service, wireless mesh network access points, line-of-site radios or something else.
For the municipal water plant in Haverhill, building the infrastructure took more than a decade of steady, incremental investment. The project began with the automation of standard operating procedures on the company’s Proficy iFIX HMI and supervisory control and data acquisition (SCADA) system from GE Intelligent Platforms (GE IP). Then, Haverhill added Proficy Workflow software for measuring and managing plant operations.
Because the automation software improved the consistency of responses to events, water plant manager John D’Aoust decided to extend its reach. He bought three laptops for his on-call operators and installed the GE software on them. Using cellular dongles on these portable devices, the operators were able to tap into the water plant’s network from home. A series of alarms alerted the on-call operator to any problems, and the software permitted taking corrective action, as if the operator were in the control room.
Because the small fleet of laptops required periodic updates and maintenance, D’Aoust decided to reduce his costs by consolidating them. “The upside of moving from three laptops to an iPad is that there’s only one machine to maintain, and the price per iPad is considerably less than having to purchase multiple laptops,” he explains. “There’s a time savings, and it lowers the complexity of our system.”
As is the case in most mobile applications, security was the principal technical hurdle to overcome at Haverhill. The solution to securing the iPad connection was to reformulate the plant’s virtual private network (VPN). In the end, the plant also changed providers to make it work.
Companies can also go so far as to lock down their tablets and other mobile devices with protocols that restrict their use to the plant’s Wi-Fi, according to Matt Wells, GE’s general manager for automation software. “It depends on the application,” he says, “but for control-oriented mobile applications, the devices tend to be very specific.”
Speed Promotes Analytics
Besides giving Haverhill’s on-call operators the ability to monitor and control the plant remotely, another important benefit of the LTE connection is the ability to run analytics. During storms when water flows are high, for example, the operators can use the data and a model of the plant to decide on a course of action for treating wastewater. GE IP’s Proficy Troubleshooter extracts the necessary information from the historical data and uses it to calculate five key performance indicators (KPIs) that predict how the plant will perform. Before having this technology at their disposal, the operators had to refer back to historical data in a Microsoft Excel spreadsheet and piece it together manually.
Wells at GE IP sees analytics as one of the practical benefits that fast 4G communications bring to remote applications. “As data transmission rates increase on cellular networks, you can put much more intelligence at the end point and link it to the central server,” he says. “This allows you to run more analytics to increase the reliability of local and remote assets.” The software can look continuously for trends in the behavior of equipment and predict failures weeks in advance so users can schedule maintenance.
Besides developing analytics, automation vendors are also exploiting high-speed connectivity to give machine builders tools to service their products remotely. “It’s expensive to fly a service technician to a machine,” notes Andres Suazo, product marketing specialist for serial and process fieldbus at Phoenix Contact USA. To help builders to control these costs, the staff at Phoenix Contact has developed a cloud-based service that links to cameras, programmable logic controllers (PLCs) and other devices. “You can put them on a machine and connect remotely to the devices,” says Suazo.
LTE communications also assists in the development of new code. Not only are transmission speeds fast enough to send the code to a controller from afar, but they also permit the technician to view the program functioning in real time.
4G Alternatives: Wireless Mesh Networtks
Although the continuing expansion of 4G LTE coverage across the continental U.S. is transforming it into a feasible means for communicating with remote assets, other important advances exist. An important one is high-speed wireless mesh networks, according to Bert Williams, marketing director for Tropos wireless networks at ABB.
Wireless mesh networks “provide reliable, high-speed network connectivity for remote and mobile applications,” Williams explains. “The two-way communications provided by these networks enables a wide variety of applications that can lower costs, increase efficiency, and enhance safety and security at remote sites.”
One set of applications that benefit from the response times provided by mesh networks are those using voice over Internet protocol (VoIP) to establish communications with workers at remote locations. “VoIP can’t support human conversation unless latency is subsecond,” says Williams.
Mesh networks can also offer a more reliable data link than a cellular data service—as one power utility discovered after automating its meter reading system. Because the percentage of successful readings fell far short of its goals, the utility replaced the cellular data service that it had been using with a high-speed wireless mesh network from ABB Tropos. As a result, the percentage of successful readings soared above its original goal.
“Simply put, the wireless mesh network provided more reliable connectivity than the cellular data service,” reports Williams. “And, because of the network’s high speed, the utility was also able to implement a distribution automation system over the same communications network it used for reading meters.”
Williams urges users to base wireless remote communications on industry standards, such as OPC-UA (Click here to see “OPC-UA Offers Security for Remote-Site Applications”). Not only do industry standards allow a network to support devices and applications from a variety of vendors, but they also secure the network and remote application in a time-tested and proven manner.
Be sure to consider the remote sites as part of the network when applying those standards, says Williams. “Automation networks are often well-secured at the core, but the edge is ignored, creating opportunities for intrusion,” he notes.
As much as technological innovation has made subsecond connectivity possible, automation vendors warn that it can be overkill or even inappropriate in many industrial processes. “In general, mobile connectivity is about monitoring performance and changing process parameters,” says Robert Trask, PE and senior systems architect at Beckhoff Automation.
Trask identifies the appropriateness of wireless communications with what constitutes real time for the application. “If a process is filling a tank, for instance, real time is measured in seconds,” he says. “In such cases, sensors, valve actuators and motor signals can be placed on a mobile or wireless network and be adequately controlled.”
The story, however, is quite different in motion control, especially on highly synchronized machines. “Here, real time is measured in milliseconds and increasingly in microseconds,” notes Trask. In these cases, copper or fiber-optic cables are the best backbone for high-speed communications.
Distance, Latency, Downtime
Despite the speeds possible with wireless nowadays, wireless communications are subject to latencies. “Additional time is required to have the message encoded and decoded at several points along the way,” explains Trask. “Many people point to phone conversations as evidence that the latencies are small, and that is certainly true for the human ear. For an industrial process, though, those latencies become a problem.”
Control over long distances, moreover, is often unpredictable and can pose safety, as well as efficiency, problems. “What if the network goes down?” asks Doug Farrell, product manager for industrial data acquisition at National Instruments. Because a control system can go haywire when starved of data, he recommends closing these control loops locally and, where possible, establishing the connections over standard Ethernet networks.
Farrell’s justification for this advice is that a wireless network can go offline for many reasons. “For example, 900 MHz radios are largely unregulated, meaning they are open to flooding by anyone,” he offers. “Satellite communications are susceptible to rain fade and can significantly drop bandwidth when rain clouds move into the area.”
Because LTE communications tend to be more reliable in these situations and have higher bandwidth than these other technologies, Farrell sees this means of connectivity as the most promising in remote locations. He does provide one important, countervailing drawback, however: You are depending on a third party to provide the infrastructure. “It is important to consider what happens when a cell tower goes down for maintenance,” he says.
Another factor to consider is limited availability. Although 4G LTE cellular communications have been expanding, it is still mostly available in highly populated areas, which is not where most remote applications are. The level of service varies, moreover, because service providers periodically revise their infrastructures to take advantage of new technology that permits faster data-transfer rates.
“While AT&T will be shutting down its 2G network by 2017, many Third World countries are just now finishing their 2G networks and starting to build 3G in metropolitan areas,” notes Suazo. “In Australia, cell provider Telstra is phasing out some 3G frequencies for 4G LTE, and South Korea is already working on developing a 5G network.”
Radios: Wireless on a Budget
Because water utilities usually work with a city council or other public body to approve capital outlays, the cost of establishing mobile communications tends to be a much greater concern for them than communications speed. Consequently, engineers involved in these projects must look for innovative ways to use technology on a relatively small budget.
An example is the way in which the municipal water utility in Tolleson, Ariz., used radio to give its field technicians remote access to its SCADA system. Its technicians had been gathering operating data manually a couple times a day with clipboards by driving to wells, pumps, tanks and other assets. When management decided that it was time to automate this process and create real-time visibility into the operations, it sought expertise from Quantum Integrated Solutions, a system integrator based in Tempe, Ariz. Because the assets were miles apart, Quantum linked the assets with Trusted Wireless products from Phoenix Contact, which are designed around the 900 MHz radios.
Though the 9,600-baud system is slow compared to the latest 4G LTE connections, the rate is plenty fast for an application sensing flow rates, pressure, levels and the on-off status of pump motors. “Without digging any trenches or getting permits, we were able to link remote sites that were previously islands of information,” says Patrick Kelly, a Quantum engineer.
Phoenix Contact’s radio technology saved the utility money because installing a PLC at each site was unnecessary. Quantum installed a radio, I/O expansion cards and an antenna to broadcast data from the site to a master Rockwell Automation Allen-Bradley PLC. Because the radio I/O device translates the data into a PLC format, it looks like a remote PLC to the master unit. “It links the I/O and PLC as if they were wired together,” explains Kelly.
Because the radios are a line-of-sight technology, implementation began with a survey to determine the type of antennas to use, where to mount them, and at what height. To bounce the signal around some obstacles along one path, Quantum installed a repeater on a tank. The Trusted Wireless technology permits the repeater to double as an I/O device that also collects level and pressure readings at that location. “They didn’t have to buy extra hardware,” notes Kelly.
To give technicians access to operations data while they are in the field, the utility’s IT department installed aircards on the laptops they carry with them. Using a VPN over a cellular connection to the Internet, the technicians can get into the SCADA application to check the status of the equipment and investigate alarms. “Rather than having to drive back to the control room, the techs look at the data right there in their trucks, wherever they are,” says Kelly. “So they know if they have a failure, low pressure or high flow almost instantaneously.”
Kelly reports that the programming was a little tricky, but not a problem for the experienced programmers at Quantum. “By thinking outside the box and using the appropriate products, you can get low-cost connectivity and enormous functionality in applications that historically needed more hardware,” he concludes.
