Switching to More Efficient Networks

A growing number of users are also moving to faster versions of Ethernet. Both managed switches and faster connections help facilities better control operations.

Whether tablets will advance beyond data collection to take over control of equipment remains uncertain. “If someone spills solvent on one, it’s done. And if you add enough protection, you might as well start with an HMI that has a factory-grade IP rating,” comments one machine builder. Image: Phoenix Contact
Whether tablets will advance beyond data collection to take over control of equipment remains uncertain. “If someone spills solvent on one, it’s done. And if you add enough protection, you might as well start with an HMI that has a factory-grade IP rating,” comments one machine builder. Image: Phoenix Contact

When Keith Kolkebeck sets up networks, he faces most of the worst elements of industrial environments. High moisture and vibration levels are common in water treatment plants, systems must produce more volume in less time, and there’s little tolerance for unexpected shutdowns.

Kolkebeck sets up control systems for water treatment facilities, where technical issues are often exacerbated by government regulators. Those challenges vary widely since he’s responsible for creating reliable networks for several East Coast water utility companies.

“The biggest challenge is to do a proper design from the beginning. If you don’t do that, it’s going to be a nightmare,” says Kolkebeck, who works at United Water in Harrington Park, N.J.

Recently, he upgraded a network in a 200 million gallon water treatment plant, replacing a serial network with an Ethernet architecture. Key components are a large Cisco fiber optic switch in a conditioned area and a number of managed Ethernet switches located throughout the facility. Many of these Phoenix Contact switches are in harsh environments, making fault tolerance an important issue.

“We went to managed switches because they gave us a failover link. If one piece of fiber went down, we could switch to another. These switches are housed in a challenging environment,” Kolkebeck says.

This shift to managed switches is only one of the ongoing transformations in industrial networking. A growing number of users are moving to faster versions of Ethernet, often employing fiber optic cable to boost speeds and distance. At the same time, technologies like Power over Ethernet are also gaining acceptance.

Seeking management
The growing use of managed switches comes as Ethernet expands its role in factories, linking most equipment in the facility at a time when many industrial products run at higher speeds and send more data over networks. Smarter switches can make it much simpler to keep facilities running efficiently.

“As more devices connect via Ethernet, traffic rises. As that happens, the need for managing traffic becomes more important,” says Mark Devonshire, product manager for Stratix switches at Rockwell Automation (www.rockwellautomation.com) in Milwaukee. “Using managed switches gives network managers more flexibility.”

Many factors have made managed switches a mainstay of many architectural schemes. Beyond fault tolerance, they provide improved diagnostics and reduce management issues. The latter factor is important in utilities, where managers satisfied with specialized equipment that’s been working fine are often reluctant to replace it.

“We have some challenges with a few 10- to 15-year-old PLCs that can’t handle the speeds of Ethernet,” Kolkebeck says. “That’s part of why we use managed switches. They can control the proper speed. Everything in this facility is on Ethernet.”

Over the past few years, vendors have made big improvements in these switches. Costs have come down while benefits have been improved. Many of the configuration steps are now automated, eliminating one of the stumbling blocks for managed products.

“Ninety percent of our switches are managed. We need to know what’s going on,” Kolkebeck says. “In the past, setting up managed switches added significant costs. Now, managed switches are pretty easy to configure. Within 10 minutes, they can be up and running.”

Many industrial networks have far more unmanaged switches than the 10 percent at United Water sites. Unmanaged switches are less expensive, so many users like to employ them in spots where they don’t need the additional computing power.

“There are still a lot of unmanaged switches in industrial networks,” says Ken Austin, Ethernet marketing specialist for Phoenix Contact (www.phoenixcontact.com)  of Middletown, Pa. “Many people look at managed switches mainly when they need the benefits of redundancy. That’s when they can justify the expense of a managed switch.”

Adding redundancy isn’t always as simple as doubling up on hardware. In some networks, this form of fault tolerance can cause conflicts. One example comes in systems that use multicasting. When messages are broadcast to many nodes, some systems may think that these data packets came via the backup cable. If packets are classified as redundant, the device that received them may ignore the instruction.

“There are some inherent issues when you combine multicasting and redundancy,” Austin says. “There can be times when PLCs and other multicasting products will not respond to some queries on the network. We’ve developed functions that improve interoperability on multicontroller networks.”

A universal scheme
Managed switches help companies move towards one of the goals behind the shift to Ethernet: linking front office computers with plant floor systems. Intelligent switches help engineers segment sections of the network so local traffic doesn’t bog down the entire network. They can also help ensure that critical automation tasks aren’t held up by e-mail traffic spikes.

“More people are talking about converging plant and IT networks into a single network,” says Mike Hannah, product business manager for networks at Rockwell Automation. “People really value that, but there are some challenges to implementing it. You really have to have a good, solid design. That’s part of why we’re seeing the need for more managed switches. They let people prioritize some of the traffic.”

While corporate executives strive to link the entire enterprise using a single network, the specialists tasked with achieving that goal face myriad concerns. One of the foremost is to isolate some sections on the plant floor so they can communicate in real time.

>> PoE Expands: Click here to read how Power over Ethernet is beginning to see more interest. 

In applications like motion control and video inspection, bandwidth demands are high. At the same time, there is significant fallout if time-sensitive messages are delayed. Determining how to divide communications into sub networks is a growing challenge for many companies.

“A lot of networks today are very flat, everything connects to everything,” Devonshire says. “That’s not necessarily the right path. You need to ensure proper segmentation, especially when you have a mix of real time devices and video co-existing on the same network. Network segmentation will be an area of focus in the future.”

Segmenting networks also makes it simpler for equipment operators and network managers to see how systems are performing. Many companies now focus on processes, monitoring equipment performance and network traffic to see when changes may suggest problems. For example, when network traffic changes noticeably, it can mean a device is having problems or an intruder has gotten into the network.

“With many managed switches, there are logs you can pull so you can look at trends and search for criteria outside the norms. That’s a big help,” Kolkebeck says.

Benefits like improved diagnostics are prompting network architects to extend the reach of Ethernet. The types of equipment that connect via Ethernet continues to expand, helping companies move to a single architecture.

This shift reduces the number of field buses in a facility, which can bring a reduction in maintenance expenses. These field buses won’t go away any time soon, but their use is declining as industrial users increase their use of Ethernet.

“The overall trend is for more and more devices to go to Ethernet, especially at the machine level,” Hannah says. “Areas that may have been using field buses are starting to see the value of going to an all-Ethernet solution. A lot of groups that have used Ethernet for HMIs and other applications are using it for more things.” 

More ports, more speed
As the number of managed switches increases, the number of ports on these boxes is also rising. Hannah notes that the average number of ports per switch is increasing, moving from six to eight a few years ago to 12-24 today.

However, this trend may flatten out. Equipment makers are beginning to embed switches into their products, letting these devices link to other equipment. These embedded switches often adhere to ODVA standards, so compatibility issues should be rare, says Hannah. Employing these products can help users reduce the number of switches in their infrastructure.

“Many people say they need more ports on a switch, but with newer technology, embedded switches move the switch into a device,” Hannah says. “You can have a point I/O block with an embedded switch. When you use products like that, often the need for more switches isn’t as great as people first think.”

>> Future of Industrial Computing: In this video, Gary Mintchell, Co-Founder and Editor in Chief, ponders industrial computing and thin clients. Visit http://bit.ly/awvids080

While there are some issues that may slow growth in the number of switches and ports, there aren’t many questions about the trend for networking speeds. Faster versions of Ethernet that have become the mainstream in commercial applications continue to slowly move into industrial environments.

The adoption of gigabit (Gbit) Ethernet is being driven by the increasing use of high bandwidth equipment. Cameras used in automated inspection and physical security monitoring are both linked to the network, bringing the hefty bandwidth requirements of video.

“We’re seeing a lot more Gbit Ethernet than we did a couple years ago,” Austin says. “It’s driven by video surveillance and the growing use of high speed cameras for inspection.”

Shifting to faster networks requires more than simply installing new switches. Many of the cables now used for Ethernet aren’t designed for higher frequency communications. Often, companies that need to upgrade are setting the stage for further advances by replacing copper wiring with fiber optics.

“The big challenge to going to Gbit Ethernet is to make sure your layer 1 product, cabling, is suitable for Gbit technology,” Austin says. “Customers often need to make changes in this physical layer. We’re seeing many companies using fiber optic cables."

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