My friends at Fluke Networks recently published an excellent article detailing the mistakes many of us make when wiring our EtherNet/IP, PROFINET IO, and Modbus TCP networks. It’s seldom that I yield this space to others, but I thought this very worthy of attention by the control engineers and others that follow RTA. I learned a lot about testing, labeling, and the fallacy of using link lights to debug your network.
They have a very worthy blog with quite a few very worthwhile articles. You can find the original at Ten Dumb Industrial Ethernet Mistakes Smart People Make, or you can enjoy it right here:
June 18, 2020 / General
Whether you’re a process or plant engineer, a technician, or an electrician, you’ve got to be an expert in a wide array of areas today—including Industrial Ethernet (IE). Sooner or later, you’re going to run into a problem caused by others who aren’t as well-versed in the vagaries of this networking technology. Here are ten of the worst problems that you may face when dealing with Industrial Ethernet. Hopefully, you can find and correct them (or, better yet, avoid them) before they lead to plant downtime.
- Using office-grade connectors, cables, and network gear. It’s true that much of the customer- and office-grade equipment out there will work with Industrial Ethernet. But the question is, For how long? Non-industrial gear isn’t ready for the vibration, moisture, electrical interference, chemicals, and more that you’ll find in a plant. Smart people realize this, but sometimes they use the suboptimal gear for a quick fix to get operations back up and running. Since quick fixes are often forgotten, it’s best to avoid using non-industrial gear for your Industrial Ethernet.
- Careless cable routing. Some cabling is designed to handle the worst of all the MICE (mechanical, ingress, climatic, and electromagnetic) environments, so you can be a little looser in how you route that cable. In most instances, however, cabling has some limitations, and you need to be aware of those limitations when routing it. Is it too close to electromagnetic interference sources? Are there areas where it will get too hot or exposed to harsh chemicals or just plain water? The worst part about making this mistake is that the cable will function properly—until things change just enough to cause a failure.
- Not labeling your cabling installations. Just as plants have requirements and standards for the labeling of piping and conduit, so does cabling (see TIA 606-B). The issue here isn’t safety, but time and frustration. Knowing which cable goes where can save vast amounts of time when troubleshooting or upgrading.
- Not testing cabling before installing a new line. Verifying your cabling can save hours of time when you’re installing and starting a new system. While a quick check of the cable takes only seconds, problems like an improperly terminated connector or a cable that’s too long can take hours to troubleshoot, leading to finger-pointing and project delays.
- Not testing extended cabling parameters. Basic cable testing as described in number 4 above can help ensure that the cabling is installed properly, but it can’t tell you how it will perform. Advanced testers measure many more parameters, such as crosstalk (which affects the throughput of the cable), resistance and return loss (which can indicate connectors that are susceptible to vibration or moisture), and transverse conversion loss (which indicates susceptibility to electromagnetic interference). Ensuring that cabling meets performance standards for these parameters provides assurance that the cabling will work not only at startup but well into the future.
- Using “digital extension cords.” One quick fix that’s often attempted for a cable that isn’t performing properly is to connect it to an unmanaged switch somewhere in the middle of the link and run a cable from there to the end device. While this sometimes works, it adds a point of failure, which is especially problematic if the device is an office- or consumer-grade product. Worse, when connected like this, the device can’t be controlled and is in fact “invisible” to network management or any tech trying to troubleshoot a problem.
- Trusting the “Link Light” LED. Connecting a cable to a device and seeing the Link LED illuminate is satisfying, but it’s not a guarantee that the communications link is working properly, or even at all. The link light will typically come on whether the communications are solid or barely working—which means the very little margin for error. Most experienced networking techs can tell you stories of the time the light came on when the link didn’t work at all or wasn’t even connected. That’s why they don’t trust those lights, and neither should you.
- Performing “swap-’til-you-drop” troubleshooting. When your Industrial Ethernet network stops working, it looks good and feels good to start fixing things. Unplug and plug things. Try a different switch port. Route a new cable. Replace a controller. Unfortunately, this scattershot approach has multiple problems. First, you could waste a lot of time fixing things that aren’t broken. Second, it can be costly to replace things that aren’t broken. Third, and worst of all, since you don’t know what the problem was when your communications start working again, you can’t be sure you’ve really solved the issue or if it will be back again to ruin your day tomorrow.
- Being unprepared for the leading cause of Industrial Ethernet failures. Research shows that the most common cause of Industrial Ethernet failures is cabling and connectors. The good news is that with a small investment you can be ready to quickly pinpoint and repair them. Having a cable tester—even a basic one—on-site not only enables you to determine if the cabling is at fault (if not, you can focus on the real problem) but also tells you where the problem is—most commonly a connector. Having termination tools and replacement connectors (maybe even spare cabling) onsite will save hours or days compared to purchasing them or hiring an expert.
- Neglecting fiber inspection and cleaning. If your Industrial Ethernet installation includes fiber, you know that the most common cause of fiber failure is contaminated connector end faces—an especially severe problem in dirty or dusty factory environments. Since fiber connections handle more data and are more likely to be critical, failure can be catastrophic. Avoid problems by inspecting and, if necessary, cleaning and re-inspecting any fiber connections whenever they are connected or re-connected.
Thanks again to the great folks at Fluke Networks!