The Transparency of Wireless
Picture an operator in the control room of a chemical plant. As his or her eyes scan the HMI screens, they pause briefly on the indication for a tank level measurement. Can the operator tell how that measurement got from the sensor to the control system? The answer is probably no, and the operator doesn’t care anyway. As long as the information is correct and timely, how it got there is not a concern. It’s transparent to the people running the plant.
That bit of level information could be sent via analog wiring, digital wiring, fieldbus, or wireless. The choice of transmission technique should represent a balance of cost and reliability within the plant context. Wireless networking has entered into that equation in new ways over the last few years and changed the balance dramatically. All of which raises the question: Does integrating wireless into a larger existing plant control environment represent a new challenge to control architecture?
When HART and fieldbus networking platforms emerged, they had much promise, but were not immediately attractive to operators since implementation required upgrades to both hardware and software. Wireless system providers took note of this lesson, and have done much to avoid reliving those difficulties.
“It has to be so simple that my mother can use it,” says Bob Karschnia, VP of wireless business for Emerson Process Management (EPM). “The technology has to be invisible, so we’ve spent a higher amount of time making sure it’s easy to use than we typically would. We wanted to make it so you can put it into your legacy systems because, without that, you run into the situation where you have to upgrade your whole DCS to use wireless.
“Otherwise you’re no different than you were with Foundation Fieldbus, which meant that you had to make a radical change to your plant architecture and devices to make it work. We’ve tried to build this so that it migrates easily into existing systems.”
Easy, yes, but users still have to deal with the mechanics of making it happen. While some wireless devices can form their own mesh networks, the communication doesn’t reach the control room without a little help. Users have to find ways to integrate those data points into the control architecture.
Wireless devices communicate with gateways that serve as the interface to wired networks. “We’re integrating the signals into the control system using Modbus, OPC, or HART,” says Jeff Becker, global wireless business director for Honeywell Process Solutions (HPS). “Once it’s in the control system, it looks like any other signal. There’s not necessarily any difference to the operator or control system whether it’s a wired or wireless device. The control system can’t tell that it’s a wireless device.”
Dealing with security
One of the major elements of an integration strategy involves your view of wireless security. If you consider it safe, you’re more likely to bring it directly into your control system. If you’re more suspicious, you can place a firewall in the path and create protective barriers between the devices or network, and your control level operations.
“The biggest hurdles are security concerns,” says Andrew Nolan, wireless consultant for HPS. “I’m not going to say security, because I don’t think we’ve had any issue with overcoming it. But almost every customer we’ve talked to has had concerns about bringing in wireless, so the biggest thing we address is how to make it work within their security architecture and make their IT department satisfied that it is a secure system.”
Security issues, both real and perceived, vary with the nature of your wireless application. The two examples discussed in the sidebars of this article reflect two major application areas in industrial contexts: wireless instrumentation and wireless Ethernet. They are vastly different in approach, and we should consider integration and security aspects separately.
Much of the current discussion has to do with wireless instrumentation, involving devices with integral transmitters. The two leading standards for this are WirelessHART and ISA SP-100. These protocols are similar in that they deal with individual instruments that communicate with a gateway and possibly each other. The devices themselves are in a sleep mode much of the time to conserve battery power and only wake up on a prescribed time cycle or when they have something to report.
The networks for these are very sophisticated and have a high level of security built in, using encryption and careful control of how devices gain admission to the network. Consequently, it is not very practical for a hacker to break in to a network via the instrumentation. However, someone who wanted to meddle with the control system could attempt to create a rogue node in the system, or try to insert a bogus measurement value as a real one.
“Adding a rogue point doesn’t help you, because nothing in the control system is looking for the data,” says Karschnia. “But can you spoof it, and pretend you’re the real temperature point when you’re not? To do that, I have to stop the real device from reporting, and inject my own reading in there. This is called a ‘man in the middle.’ It’s a well-known attack technique, and we’ve built the defense against it into our system. With security, attacks are never impossible, but we can make them highly unlikely.”
Once instrumentation data gets to the gateway, it still has to reach the control system. Security conscious users may push the data via a wired Modbus connection or Ethernet. However using a wireless Ethernet backhaul is a very convenient way to extend wireless convenience, but at the same time it extends the possible attack surface for the system.
Some industrial wireless architecture uses 802.11 wireless Ethernet (Wi-Fi) as an extension of larger wired networks, or as a means to connect with gateways collecting data from wireless instruments. (So far, there are few individual industrial wireless instruments that communicate via Wi-Fi.)
|Standard wired 4-20 mA analog instruments send data continuously, so charting a changing process variable is essentially a smooth curve.and how often the control system updateds the HMI.|
Karschnia notes that customers generally accept the security of the device level communication, but that’s not their only concern. He says, “What users worry about is the 802.11 Wi-Fi connections from the gateways through the wireless plant level networks, and that’s where the security concern is. It’s TCP/IP based, and they’re very worried about that. There are lots of best practices for wireless backhaul available. Make sure you use those to prevent security problems.”
Caution is appropriate, but that does not reduce its usefulness, even when protected properly. “It’s pretty much become a de facto standard that you protect the front-end point where your wireless network comes in with a firewall,” Nolan adds. “Bring it through the level-three network and then down into the control system. That’s worked well for monitoring or SCADA applications, but the next big jump is that customers want to bring it natively integrated into the DCS and down to the control layer. But if they do that, having a separate firewall segment is probably not going to be the best network architecture.”
Given that much of wireless development has been relatively recent, products and protocols have had cyber security elements built in from the outset. The practical question is: Do most IT departments understand this, or are your wireless policies designed around older and less secure equipment. “Virtually any vendor who is making a wireless product for the industrial marketplace today understands that security is simply a given,” says Nolan. “It has to be there in the product and it has to be effective or their product will not be accepted. The growth of wireless deployments will drive those security policies, not so much to relax, but to take into account the current state of the technology and how secure it can be. That will allow more applications to go deep into the control system.”
When it works well
One customer I interviewed for this article told a less successful story. His company tried wireless Ethernet in a rugged environment, but decided to save money buying consumer-grade hardware. It failed in the field, and by the time they were able to replace it with industrial grade equipment, the operators had returned to their cumbersome cables and were not interested in trying wireless again.
When deployed in appropriate applications with the right equipment, industrial wireless has shown that it can be integrated without difficulty and without presenting inordinate security risks. As Honeywell’s Becker puts it, “Most customers treat a wireless device like it’s just another transmitter. It’s no big deal, because they select applications that are appropriate for wireless. It would be a different story if we were suggesting, ‘install this on your cat cracker.’ However, putting it on a tank farm, or installing for extra measurements is acceptable within the limitations of wireless.
“We wanted to make it as easy as possible to implement wireless field instrumentation and wireless systems. If it was that much different and harder to do, there would be a bigger barrier to implementation and acceptance. But the differences have been designed out of the product from very early on.”
So, is wireless technology ready for your mom to use? “We spent an inordinate amount of time making sure we could integrate into any system,” says Karschnia. “It allows us to do it in an easy fashion so customers can use it with any system they have, quickly and easily. It’s the transparency of technology, and that’s when things start to take off.”
Nolan looks for a time when all these technologies melt together.
“Our system is going to blur the line between wired and wireless I/O. It’s going to look like I/O to the control system, and that’s getting closer to fulfilling the wirelesspromise—making the underlying infrastructure, whether wired or wireless, no longer the focus. It’s simply bringing I/O in, and bringing it in a much more flexible and cost effective manner.”
|Peter Welander is process industries editor. Reach him at PWelander@cfemedia.com . Also read: .|
Chevron gathers well pressure data: ‘It’s no different’
Chevron maintains an active oil field production unit in the San Joaquin Valley near San Ardo, CA. Here it pumps steam into older wells to increase down-hole pressure and to help warm the thick oil so it can flow more easily. These wells are spread over a large area, between two and three square miles, and it is important to monitor each well.
Mohammad Heidari is an automation engineer for Chevron, and he works in the San Joaquin Valley production sites. Over the years he has tried various wireless platforms to simplify data collection but always found those methods cumbersome and expensive.
“I was involved in an application where we installed pressure transmitters into the process,” says Heidari. “Typically in such applications, we have to bring the transmitter to a processor via a wire, set the scaling at the processor, and then connect it to the local area network to push the data to the server where we monitor, collect, and store it. There’s a lot involved, and there are occasions where we only want to monitor one process variable. For example, we have a well where we want to monitor pressure. It could be a mile away from any power source or any processor. Getting an appropriate uninterruptible power supply could cost a minimum of $3,000 to $4,000. And then we would have to put some kind of radio connected to the transmitter and send the data to some kind of receiver somewhere. There was programming involved, a lot of hardware, and it was pretty labor intensive. We could spend as much as $10,000 in the process.”
When Emerson brought out its Smart Wireless product, Chevron tried it on one well as a test. Heidari was impressed with the idea of having the pressure sensor, battery power supply, and wireless transmitter integrated in one package rather than as discrete items. With the gateway in place, he found gathering and using the data to be very simple.
“We decided to do a pilot installation,” he recalls, “so we went ahead and put the transmitter in place and then the gateway. In less than two hours, I was in the office looking at data. I couldn’t believe it. That same day I think we bought 30 devices. You have a gateway, and you assign an IP address to the gateway and connect it to your network. You configure the IP address in the network, and that’s pretty much it. You set how often you want to update the data, and then you can go to your office, launch your Internet browser, type in the IP address, and you can see your process. This was not available until recently. The cost, labor, and time are reduced tremendously. Probably one-fourth or one-fifth of what it used to cost.
“Our operation cannot tell if a device is wired or wireless. Only we know. The SCADA or control engineer knows the backbone, but the operators have no idea what it is. It’s no different. The gateway is connected by Ethernet to the network. You only need one IP address to talk to all those end devices.”
DiGeronimo Aggregates upgrades for wireless infrastructure
Strictly speaking, this isn’t a wireless application quite yet, but it is a work in progress toward that end. The DiGeronimo Aggregates plant in Independence, OH, has been in operation for 150 years producing expanded shale aggregate. The quarry is on site, and the material is processed in a 235 ft. rotary kiln built in the 1960s.
Recently the plant underwent major upgrades as it changed from oil as the main kiln fuel to more economical coal. Eric Dombrowski, vice president for DiGeronimo explains: “We went from a system that was almost pre-archaic to where we are now. This facility was first opened in the 1860s, and a lot of the systems were pretty simple. We were originally feeding oil as our fuel, and in order to be competitive, we had to go to coal. To get the permit, we had to put in the lime injection FGD (flue gas desulfurization) system. We looked at the other equipment and our baghouse was pretty much shot, so all those systems—coal feed, lime slurry FGD, and baghouse—were all brand new. That’s when we brought in Hull and Associates and said, ‘We don’t want to have all these isolated systems all doing their own thing. Let’s get this whole facility under one central control with expandability for future projects.’”
System integrator Hull & Associates designed a system that would tie all the separate control platforms together on a main Ethernet network using Wonderware software to support one comprehensive HMI. One of the project objectives was to provide walk-around control using wireless tablets.
Andy Holtom, electrical engineering division leader for Hull & Associates, worked on the DiGeronimo project. He recalls, “We put the wired Ethernet infrastructure in, and in a couple key electrical rooms there are docking stations where operators can plug in the tablets and use them. Then the idea is that we’ll put in wireless so they can take the tablet out. The last step is putting those wireless points in. We’ll put transmitters in various locations to broadcast around the facility. We know where they’re going to go, they just need to be purchased and plugged in.”
Dombrowski noted that this last phase was held due to the softening economy, but will be implemented as soon as possible. He understands the value of walk-around control in that plant environment. “We’re a 24/7 operation, and there are times when we only have two or three people during third shift,” he says. “So if an operator’s doing inspections down the kiln or walking off the kiln floor, when the wireless is in, he can still watch the operation while he’s away from the controls.
“We have two or three future plant expansions that were planned into it that will broaden the footprint of the plant. As those get incorporated into the PLC, there’s a lot more reason to be in different locations and being able to control different devices.”