Optimizing industrial Ethernet system performance

Over the past decade, manufacturers and processors have increasingly been transitioning plant floor operations to the Ethernet LAN standard (IEEE 802.3), which has reigned supreme in commercial offices for decades. Although the physical layer standard is the same for both, the environments in which their Ethernet systems operate could not be more different.

07/01/2009


Over the past decade, manufacturers and processors have increasingly been transitioning plant floor operations to the Ethernet LAN standard (IEEE 802.3), which has reigned supreme in commercial offices for decades. Although the physical layer standard is the same for both, the environments in which their Ethernet systems operate could not be more different.

In a typical office, the network cabling is installed in a relatively clean, quiet environment with cables hidden behind walls, in ceilings or under floors. Network switches, hardware and connectivity components are sheltered in protected areas.

Industrial facilities present a very different reality. Here, many cables, connectors, switches and active network components are integral to machine automation, instrumentation and control systems, placing them in harsh and potentially hazardous situations. Commercial off-the-shelf (COTS) Ethernet systems are just not up to handling such conditions. Rugged conditions call for ruggedized cables. Only industrial-grade Ethernet system components are built tough enough to withstand the hazards and risks they are exposed to day after day.

The real cost of Ethernet failure

The majority of today’s industrial plants rely heavily on automation, instrumentation and control data communications to relay signals between devices, machinery and the control system to activate events on an exacting and pre-determined schedule %%MDASSML%% with no margin for error. Any glitch or interruption in signal transmission caused by a failure of an Ethernet component can result in loss of critical data, unplanned production downtime, delayed shipments, eroding profit margins and lost revenues. In addition, more severe situations can lead to a reduction in plant safety levels or even full-blown network failure.

For plant managers, maximum productivity with minimal downtime is a key goal; 24/7 network performance and reliability are critical to achieving that goal. If a switch or cabling system in the plant fails, the cost of the part replacement and repair represents only a tiny fraction of the overall costs associated with production downtime %%MDASSML%% no matter what the industry.

For example, the direct cost of downtime for a paper mill has been estimated at $3,000 per hour or more, and can total up to $10,000 per hour for an automotive manufacturing plant. Indirect costs such as lost productivity, impact on downstream processes, cost of shut-down and start-up can send total costs soaring to tens if not hundreds of thousands of dollars, depending on the industry and overall operating costs.

So, when you consider the environmental challenges present in industrial operations, along with the financial and productivity consequences of downtime, it’s easy to see why investing in a rugged, field-proven industrial Ethernet system is not only a sound business investment, but also provides greater peace of mind to plant and top management.

Commercial vs. industrial Ethernet components

Industrial premises %%MDASSML%% whether discrete manufacturing plants, food and beverage or other processing facilities, or power generation and utility plants %%MDASSML%% are typically fraught with environmental conditions and mechanical hazards on the plant floor that can have a negative impact on installed cabling, hardware and connectivity systems. Examples of these hazards %%MDASSML%% and reasons why industrial Ethernet cables, connectors and network hardware outperform their COTS counterparts in harsh environments %%MDASSML%% include temperature extremes, chemical exposure, humidity levels, UV radiation exposure and physical hazards.

Temperature extremes %%MDASSML%% Extreme cold can make COTS cables stiff and brittle, while elevated temperatures can degrade the plastic used in the cables’ construction and cause an increase in attenuation. Industrial-grade cables are available that will operate in a wider temperature range (-40 C to 85 C) than commercial cables (0 C to 60 C).

Commercial-grade hardware (switches, etc.) is designed to operate from 0 C to 40 C, while industrial Ethernet hardware can operate efficiently from 0 C to 60 C, extendable to a range of -40 C to 85 C with the use of a conformal coating.

Chemical exposure %%MDASSML%% Oils, solvents, chemicals and cleaning solutions can soak into COTS cables %%MDASSML%% especially under heat %%MDASSML%% causing the cable jacket to swell and lose mechanical strength.

On the hardware side, corrosive chemicals can damage the electronics in commercial switches, whereas industrial switches are typically sealed to resist these substances.

Humidity levels %%MDASSML%% Industrial-grade switches can withstand up to 99% humidity levels. They can also be sealed to meet IP67 standards.

UV radiation exposure %%MDASSML%% UV radiation can cause COTS cable jackets to decompose at an accelerated rate, compromising mechanical strength and electrical performance.

Physical hazards %%MDASSML%% Routine plant floor activities can pose mechanical risks to cables. For example, machine movement or vibration can result in cables being pulled or stretched with excessive force, which can create electrical and/or impedance imbalances between the pairs, degraded electrical performance and increase susceptibility to ambient EMI/RFI. Plant floor vehicles such as forklifts and moving carts, can accidentally run over cables, causing abrasion, crushing or cut-through.

Even well-made, properly installed COTS Category 5e and Category 6 unshielded twisted pair (UTP) Ethernet cables are not constructed to survive these kinds of hazards. Repeated mechanical abuse can cause COTS cables to succumb over time to classic network failure scenarios %%MDASSML%% from incremental damage and performance degradation, to intermittent operation, to catastrophic failure.

The best way to optimize the performance and long-term reliability of the plant floor Ethernet is with cabling, connectivity and hardware components designed specifically for use in industrial settings. These products are more ruggedly constructed in every way, incorporating design features and materials capable of withstanding all kinds of environmental and physical stressors.

Reliable industrial Ethernet components

Industrial Ethernet physical layer components available in today’s marketplace include:

  • Heavy-duty, all dielectric, indoor/outdoor-rated optical fiber cabling in single-mode and multi-mode constructions

  • Industrial grade Cat 5e (2-pair and 4-pair) and Cat 6 UTP (4-pair) cables with heavy-duty oil- and UV-resistant jackets. Some category cables feature a bonded-pair construction in which the conductor insulation of the pairs is affixed along their longitudinal axis to ensure consistent conductor concentricity to prevent any performance-robbing gaps between the conductor pairs during installation and use

  • Unjacketed and armored cables for more extreme environments; continuous flex cables for use in continuous motion machine systems; low-smoke zero-halogen cables; waterblocked cables; and burial cables

  • Cables designed specifically for use with leading industrial automation networking and communications protocols such as EtherNet/IP (ODVA), Modbus TCP/IP, ProfiNet and Fieldbus HSE

  • Industrial grade connectivity components and active networking devices, including: IP67- or IP20-rated UTP or FTP cord sets, modular jacks and plug kits, connectors, adaptors and ruggedized switches.

    • More than likely, your company currently invests in an array of protective gear such as hard hats, safety glasses, gloves and footwear to protect workers on the plant floor. Doesn’t it make sense to invest wisely to preserve, protect and defend your company’s mission-critical data network infrastructure, as well?

      Even the best industrial Ethernet designs are vulnerable if signals can’t get from one component to another because of damaged cables. Whether Cat 6 or fiber optic, cables that enable reliable operation in harsh physical environments are available.

      Industrial Ethernet networks are vulnerable if cables cannot withstand vibration, abrasion, pinching or other hazards associated with motion found in industrial environments.

      In addition to cables, other industrial Ethernet hardware such as hubs, switches, gateways, routers and wireless devices should be able to withstand harsh environments.


      <table ID = 'id590205-0-table' CELLSPACING = '0' CELLPADDING = '2' WIDTH = '100%' BORDER = '0'><tbody ID = 'id591684-0-tbody'><tr ID = 'id591686-0-tr'><td ID = 'id591689-0-td' CLASS = 'table' STYLE = 'background-color: #EEEEEE'> Author Information </td></tr><tr ID = 'id591698-3-tr'><td ID = 'id591701-3-td' CLASS = 'table'> Brian Shuman, RCDD is senior product development engineer for Belden (www.belden.com). Belden designs and manufactures signal transmission solutions for enterprise, industrial and wireless networking markets, as well as a host of specialty markets. </td></tr></tbody></table>

      Cable toughness: The proof is in the testing

      A few years ago, Belden conducted a series of tests to compare how COTS Category 5e Ethernet cables performed versus industrial-grade Ethernet cables when subjected to various physical and environmental stressors. The rigorous tests proved definitively that commercial cables cannot match the toughness and longevity of industrial-grade cables under these harsh conditions. Tests were performed using state-of-the-art testing equipment and software, and all cables used in the study initially tested as fully compliant with ANSI/TIA/EIA-568-B.2 Cat 5e standards.

      Here is a brief synopsis of four of the tests performed and the results:

      Abrasion %%MDASSML%% Using a fixed drum covered with sandpaper, cables were stretched across a portion of its circumference, and then moved back and forth cyclically for 25 cycle counts. At that point, the conductors of the COTS cable could be seen through breaks in the jacket, which would cause it to lose mechanical and electrical integrity. The pairs of the armored industrial cable were not compromised at all.

      Cold bend %%MDASSML%% Conducted per UL-444, samples of cables were left in a controlled temperature and humidity chamber called a cold box. They remained for one hour prior to testing. They were then tested (at -80 C, -60 C and -40 C) by being partially wound around a 3-inch diameter horizontal mandrel with one end of the cable under tension from an aluminum weight. The cables were then unrolled and visually inspected to check for cracks in the jacket. The COTS cable became brittle and showed visible cracks. The industrial-grade high/low temp cable had no visible damage.

      Crushing %%MDASSML%% In this test, an Instron machine head brings a 2-inch by 2-inch plate down on a segment of cable to crush it %%MDASSML%% with failure defined as the point at which the cable would no longer reliably support Cat 5e performance. Each cable’s electrical characteristics were measured throughout the testing. At 400 pounds of applied force, the COTS cable with PVC jacket failed; it was smashed flat and would not spring back to its original shape. The industrial-grade, black-jacketed armored cable had a failure value at 2,250 pounds.

      Water immersion %%MDASSML%% In this test, the electrical properties of the cables (primarily attenuation) were measured initially. Then the cables were coiled into a dry container, and water was added to submerge them. The cables were tested intermittently over a six-month period. The COTS cable showed increased attenuation as soon as the cable was immersed in water and this continued to degrade over the half-year immersion. After six months of immersion, the industrial-grade cable showed only a slight increase in attenuation %%MDASSML%% and the cable still exceeded the Cat 5e requirements.

      For complete details on the series of nine performance tests administered and their results, visit Belden at www.belden.com and download a copy of the Industrial Ethernet User Guide .

      In the photo on the top, the blue COTS cable with a standard PVC jacket is smashed flat under 400 pounds of applied force, and will not spring back to its original shape. By contrast, the failure point for the armored industrial Ethernet cable pictured on the bottom was 2,250 pounds.



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