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Different data dictate different devices

July 30, 2019
The Industrial Internet of Things is not the same as your home or office network

The Industrial Internet of Things (IIoT) will bring into life devices that we may not be able to imagine. Some will be wired, and some wireless, but most will be Ethernet-based.

Ethernet/IP has become a mainstay in our world and is open-source as such since it is maintained by a third party—ODVA.

IIoT vs. IoT is different. IoT deals with home and building automation using thermostats, lights and programmable plugs, typically all connected in a closed network like a house.

IIoT isn’t as homogeneous. Oilfield data and devices are remote, as are so many data points in any industrial applications. Industrial Ethernet is different, and here’s why we need to know as much about it as we can.

I have mentioned before the industrial network has to be available 100% of the time. It is not email or Web browsing. Real-time information is being transferred in great quantities.

In the province of Ontario, Canada, where I live, the Ministry of the Environment has a five-minute update on water chlorine values and alarming. If the local and/or remote network goes down for any reason and the site loses data, the municipality is reprimanded and can be heavily fined. In some cases, especially if something happens locally to harm the public, the operators can be jailed.

Serious stuff—nothing like email.

So, what makes an industrial network different from an email network as such?

The dynamic host configuration protocol (DHCP), or automatic IP address allocation, is largely used in office networks and, of course, run in an office environment where the temperature is relatively constant and there aren’t toxic liquids and/or gases in the neighborhood, as long as you don’t count the local office coffee machine.

Most industrial devices use static IP addresses, which suggests manual configuration. There have been many instances where a duplicate device is introduced to the network on a temporary basis, but the device does not have the ability to let anyone know.

One of the biggest issues with manual configuration is the link speed. Auto-negotiation is a common selection on the network configuration, but this can cause issues.

In my experience, especially with wireless connections, the loss of communication occurs frequently, and then the fun starts. Once the link is broken, the devices begin an automatic reset of communications to redefine the link. I have experienced link reset times exceeding five minutes on wireless devices, which meant lost production time since the device went into error waiting for the link to come back up. Twenty minutes was not uncommon.

This was reduced or eliminated by changing the wireless bridges that we were using to a fixed link speed and duplicity. Ten megabytes with half duplex worked well since the amount of data was relatively small.

In the case of the water system I was in charge of, real issues showed up when the wireless broadband systems were updated and configured with auto-negotiation, while the connected devices were fixed speed. Upset cart to be sure.

More obscure issues include the age of the devices and the mix of TCP/IP stacks and normal Ethernet and Ethernet/IP devices. Older devices sometimes need a firmware upgrade to function normally, so don’t be afraid to follow that path.

One of the biggest issues in industrial Ethernet is the environment—toxic environments, noise, temperature variations, power issues and moisture. The network hardware needs to be able to survive in these environments, which means special cables may be required as well as industrial-grade switches and routers and power filters. An RJ45 Ethernet connector may not be rugged enough, and/or you may need an IP60 solution.

Cable protected from physical issues, such as having a “teck” exterior, and noise-resistant sheathing, may be required.

One of the hardest situations to diagnose in an industrial network—wired or wireless—is device intermittency. In one application, there was a switch at the farthest point in the building that housed some computers and PLCs. There was also some communications that went back to the maintenance room, which was close to the fiber exit point to the building to go to a remote server room.

When I did a traceroute diagnostic, it was discovered that there were seven devices—switches—on the path without any repeaters, even though the recommended number was three. Also there were a few runs that exceeded the 100-m distance restriction using standard Cat. 5E cable for 100-MB communications.

Fiber was run directly to that end of the building to repair the configuration. The more switches involved, the more complicated matters become, so network design is paramount.

Cable loops, foreign devices and HMI broadcast data are just a few other things an office network doesn’t have to deal with. Be aware of your network environment, and your industrial network will serve you well. You will be dependent on it forever.

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About the author: Jeremy Pollard
About the Author

Jeremy Pollard | CET

Jeremy Pollard, CET, has been writing about technology and software issues for many years. Pollard has been involved in control system programming and training for more than 25 years.

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