10 Tips to Remember About Industrial Ethernet
1. Compare network security options.
Do not take chances with network security. A Wi-Fi-enabled computer can connect to multiple networks at the same time. But, your employees can give a hacker a pathway into your network simply by powering up a laptop. imagine the mess an eco-terrorist could make if he did not like the look of your smokestack. Even well-intentioned employees can bring a network down simply by blundering around in areas where they should not be.
- Many wireless systems employ industry-standard WEP (Wired Equivalent Privacy). A hacker can get around WEP in a few hours. Look into more powerful standards like Extensible Authentication Protocol (EAP) and Tunneled Extensible Authentication Protocol.
- Don’t just talk about changing your passwords a regular basis. Do it. Make passwords strong and difficult to guess.
- Never assume that your industrial Ethernet products have built-in security features. At the very least, you should use inspection-type firewalls (such as packet filters) to control any access based on IP source address, destination address
- A consumer plug-and-play device (printer) can flood your factory LAN with traffic in a “broadcast storm” as it tries to self-configure or
advertiseits presence to every other node on the network.
- Faulty devices can spew zillions of “runts”, abnormally short Ethernet frame, into your network. Using switches, instead of hubs, will take care of those problems.
- Duplicate IP addresses can deactivate devices that otherwise appear to be functional – perplexing to diagnosis.
2. Document your installation process.
When devices need to be replaced, it needs to happen quickly. Below are essentials you will need to know quickly, so document devices in advance – and know where the information is kept.
- Replacement part numbers
- IP addresses
- Gateway addresses
- Menu settings of devices like serial servers, data collectors, routers and configurable switches
- Functions like DHCP enabled/disabled, static vs. dynamic IP addresses
3. Think through IP addresses.
There is no standardized way to set IP addresses in automation, but, don’t just wing it. Have a plan in place.
- Whether you use DHCP or set IP addresses manually, IP assignments should be semi-permanent.
- Understand the client software IP address requirements as they relate to the hardware devices in a client/server application. Note that, in a PLC-style control system, the PLC is a client and all of the I/O devices are servers, which is the exact opposite of the arrangement in an office LAN.
- Office devices are often designed by name; industrial devices are typically just assigned IP addresses.
- Documentation should clearly indicate the mechanism by which the IP address of a replacement device should be set.
- Communicate and work with your IT department in choosing IP addresses so that conflicts do not arise in the future.
4. Invest and implement network reliability upfront.
“An ounce of prevention is worth a pound of cure.” You get what you pay for in this world. If you have Velcroed a cheap office store Ethernet hub into your panel and plugged the DC adapter into an outlet strip, you are going to pay for it when your network goes down. Ruggedize your communications with
- Use DIN rail mounting (not Velcro).
- Use low-voltage AC/DC connections instead of AC adapters.
- Look for industrial-grade temperature specifications and industrial-grade physical construction.
- Deploy fault interrupt relays.
- Look for advanced functions like port management and features that facilitate troubleshooting, like port mirroring.
- Broadcast storm filtering to prevent network overload.
- Back yourself up in advance with sound advice from real people and readily available, reliable technical support if and when trouble does come.
5. Separate the office and factory with appropriate level equipment, routers, bridge, firewalls.
Don’t overlook easy opportunities to save money when designing your communications network. You may very well discover that significant savings lie right under your nose. All kinds of possibilities exist.
Know when and where to use office-grade LAN equipment versus when and where to step up to industrial-grade specifications for the factory floor – and how to safely separate the two networks.
Consider legacy coaxial cable and telephone wiring. For example, you could convert a USB signal to an Ethernet package and use a pair of Ethernet extenders to send data up to 2,600 m (8,500 ft) via coaxial cable or up to 1,900 m (6,200 ft) over a pair of unused straight copper wires. That old copper cabling may be worth some money down at the recycling center, but it is probably worth a lot more if it stays right where it is.
Ethernet-enable legacy serial ports and devices.
Do not abandon your legacy serial equipment investments. In fact, the serial communications protocol remains so useful that the number of deployed serial devices is expected to continue growing. Connect legacy serial devices to Ethernet with serial servers and let them keep doing their jobs.
- Communicate with equipment and devices from any networked computer
- Increase productivity by knowing what remote devices are doing before getting trouble reports
- Reduce trips to the factory floor and service calls
7. Follow wiring codes and best practices when installing cable.
- Install shielded twisted pair (STP) wire anywhere that physical protection or local codes require the use of conduit for added protection.
- Attach the STP shield to ground at only one end of the cable. Connecting at both cable ends may create ground loops.
- If you need to terminate the shield at both ends, wire a metal oxide varistor (MOV) shunt in parallel with a 1M Ohm resistor and 0.01- to 0.1-mF capacitor to limit most ground current.
- Your conduit should maintain at least a 10 cm distance from 120 VAC; 15 cm from 220 VAC; 20 cm from 440 VAC. If you do not use conduit, double those distances.
- Check cables with a cable tester, not just an Ohmmeter. A tester identifies continuity problems such as shorts, open wires,
mis-wiring, reversed or crossed pairs, and shield integrity.
- Metal cable trays should be conductive from end to end.
- Avoid proximity to power lines and sources of electrical transients. High-voltage lines should intersect the cable at a 90º angle.
8. Office-grade vs. industrial-grade connectors.
RJ-45 “telephone connectors” do not stand up to industrial applications. Their contacts have a small surface area and vibration can wear away the thin layer of gold that covers the underlying nickel, making the connection susceptible to corrosion and oxidation. A tug on the cable can also damage a connection. They are not a good choice for your robotic welder when downtime may cost a hefty $15000 per minute.
Fortunately, there are alternatives. IP65 or IP67 cables keep out liquids, maximize contact surface area and improve the sturdiness of the design. All of them facilitate feeding Ethernet cables through panels. Worth the spend.
9. Consider industrial protocols and compatibilities.
There are numerous open standards for representing industrial data on Ethernet, like Modbus/TCP, Ethernet/IP, Foundation Fieldbus, and PROFINet. The Fieldbus wars are not over yet. Some vendors use proprietary standards. A particular protocol may have its own variations within itself. Yet, it is possible to define structures and make them interoperable. Again, do not commit to anything until you have done your homework.
10. Deploy wireless with care.
Initially, wireless was not intended for the factory floor. Since it is there now, here are some helpful tips:
- Make sure there is ample signal strength for those who need to access the network. Position Wi-Fi antennas so they cover all the required space. Walk around with a signal meter to ensure that they do.
- At the same time, do your best to restrict transmission to desired areas only. You can use directional antennas to restrict radiation.
- It’s one thing to do data acquisition with wireless, but quite another to run I/O from your PLC. Keep the control stuff on physical cables wherever possible.
- Use some form of data encryption for your network and that employees understand and comply with security policies.