Industrial communications networks: Selecting components that make the grade
Nov. 29, 2016 - Almost 60 years ago, the Unimate robot kicked off an automation revolution that transformed the productivity and cost-effectiveness of manufacturing. Today, automation is expanding once again with a new model. With Industry 4.0, machines talk to machines and operations run as much on information and communications as they do on equipment and people.
Critical in these “factories of the future” are communications and control solutions that deliver 24/7 network performance to support maximum productivity and minimal downtime. The first step to building reliable, high-performing communications connectivity requires understanding the conditions in those environments and selecting components that are able to withstand the rigours of industrial operations.
Automation teams and their information technology (IT) partners recognize that, when it comes to communications networks, the factory floor is a very different world than typical office environments. The back office is generally clean and quiet; cables can be hidden in ceilings or under floors; and switches and other connecting components can be stored in sheltered areas. Contrast this with industrial settings where machines, automation and manufacturing equipment generate noise and vibration, and where exposure to chemicals, UV radiation, moisture and extreme temperatures are likely to be the norm. These environments require a more robust communications network, built on industrial-grade Ethernet and physical assets that can withstand harsh conditions.
Building the industrial Ethernet network
The difference between enterprise Ethernet and industrial Ethernet systems can best be understood by examining the impact that common, manufacturing conditions have on commercial off-the-shelf (COTS) Ethernet components.
Under test conditions that simulate real-world exposure, the durability and reliability of ruggedized connectivity components quickly becomes clear. To determine how different cables hold up, three types have been put to the test:
1. A COTS Cat 5e cable with a standard polyvinyl chloride (PVC) jacket;
2. An industrial-grade Cat 5e cable with a PVC jacket; and
3. An industrial-grade Cat 5e cable with a fluorinated ethylene propylene (FEP) jacket.
When simulating various environmental stressors in industrial environments, testing results have found:
• Extreme temperatures: Extreme cold can make COTS cables stiff and brittle, while elevated temperatures can degrade the plastic used in the construction of cables and cause an increase in attenuation. Industrial-grade cables are proven to operate reliably in a wider temperature range (-40 C to 85 C) than COTS cables (0 C to 60 C).
• Chemical exposure: Oils, solvents, chemicals and cleaning solutions can soak into COTS cables causing the cable jacket to swell and lose mechanical strength. When cables were immersed in containers of oil and then held in a heated chamber — the COTS cable showed signs of deterioration. The industrial cable’s jacket did not, because the materials and jacket thickness are rated for exposure to oil and other substances.
• UV radiation: Exposure to sunlight can cause COTS cable jackets to decompose at an accelerated rate, compromising mechanical strength and electrical performance. When cables were exposed to fluorescent UV sources that mimicked solar radiation levels for 30 days, the COTS cable jacket showed reduced tensile strength, reduced elongation and discolouration. The industrial-grade cables resisted the effects of sunlight and other UV sources and showed no jacket damage.
• Physical hazards: Industrial settings present many mechanical risks, especially for machine automation cables and connectors. Excessive machine movement or vibration can result in cables being pulled or stretched with excessive force, which can degrade performance. Plant floor vehicles can accidentally run over cables, causing abrasion, crushing or cut-through. Industrial-grade, jacketed cables have been proven to withstand up to more than a tonne of applied force without permanent damage and are less susceptible to being cut-through or losing its integrity. Armoured industrial-grade cables can withstand over a tonne of applied force without any disruption to the signal integrity.
The right components ensure industrial-strength performance
The cost of downtime in production environments must take many factors into account. This could include lost productivity, delayed downstream processes, the cost of system shut-down and start-up, and the potentially devastating loss of service to customers.
It’s estimated that the repair and labour costs associated with the failure of a cabling system component or Ethernet switch could be 15 to 20 times the cost of the component itself. It’s easy to see, then, how total downtime costs can quickly soar to hundreds of thousands, even millions of dollars.
Choosing the right connectivity and control components can provide a strong defence. For the physical media layer, there are many solutions available that fully conform to the IEEE 802.3 Local Area Network (LAN) standard for industrial environments, including:
• Jacketed and armoured cables for extreme environments.
• Continuous flex cables for use with continuous motion machines and automation systems.
• Low smoke zero halogen (LSZH), water blocked and/or burial cables.
• Indoor-/outdoor-rated optical fiber cabling in single-mode and multimode constructions. Many feature water-blocking agents for added protection in moisture-laden environments.
• Industrial-grade Cat 5e (two-pair and four-pair), Cat 6 (four-pair) and Cat 6a (four-pair) cables with heavy-duty, oil- and UV-resistant jackets.
• Cables designed for use with industrial automation net- working and communications protocols, such as EtherNet/IP (ODVA), Modbus Transmission Control Protocol (TCP)/Internet Protocol (IP), Profinet and Fieldbus High- Speed Ethernet (HSE).
• Industrial-grade connectivity components, like IP20-rated or IP67-rated sealed patch cords, connectors, modular jacks and plug kits, adaptors and more.
Given the potential for breakthrough advances in productivity, quality and efficiency and the high costs associated with production downtime, it makes sense to invest in infrastructure with networking components designed and rated specifically for use in harsh and demanding environments. The resulting integrated system will deliver the interoperability and consistently reliable performance needed everyday for years to come.
Brian Shuman is a senior product development engineering project manager at the Belden Engineer Center in Richmond, Ind. He has responsibilities in the design, development, testing and technical customer support for copper cables. He is the vice-chair of the ODVA EtherNet/IP Physical Layer Special Interest Group. Additionally, he represents Belden in the TIA TR-42.9 Industrial Telecommunications Infrastructure subcommittee. He is a Registered Communication Distribution Designer through BICSI and a member of IEEE. Shuman earned a B.S.E.E. from Purdue University.
This article was originally published in the November/December 2016 issue of Manufacturing AUTOMATION.
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