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Quest for a Robust EtherNet/IP Network

Learn how to design and build a rugged and reliable physical media foundation to enable seamless plantwide information sharing.

Aw 1511 Article21
EtherNet/IPTM has become an increasingly popular choice for mission-critical industrial automation and control applications across manufacturing and process applications because it offers a single, IT-friendly,  multidiscipline network platform for information, control, safety, time synchronization and motion applications.

The industrial EtherNet/IP communications platform is built on the same standard networking platform — Ethernet LAN Standard IEEE 802.3 — as that of the enterprise, enabling common network infrastructure assets, such as development and test tools, to be used across both manufacturing  production information systems and the corporate enterprise.  This reduces the number of assets to manage, enabling better asset utilization, which supports lean initiatives.

Key Benefits of EtherNet/IP Convergence
In addition to system integration, enhanced visibility and interoperability, EtherNet/IP convergence offers a host of other benefits for plantwide information sharing, such as:

• Access to real-time data to improve overall plant operations.
• Real-time inventory visibility and more collaborative reviews of production data.
• Faster, less costly plant upgrades, expansions and changeouts when required.
• Improved shop-floor system integration and coordination with site operations such as historians, asset management and manufacturing execution systems (MES).

Implementing EtherNet/IP convergence in industrial settings can be challenging. One of the main challenges is to ensure long-term performance and reliability of the physical media layer (OSI Layer 1), which is the foundation supporting critical plant-floor signal transmissions and data communications. This article explains why it is important to specify environmentally hardened physical media — cables and connectivity — tough enough to withstand the rigors of the typical plant environment.

Infrastructure Risks in Harsh Environments
Unlike the office Ethernet, industrial communications and control networks need to operate consistently and reliably under harsh and often extreme environmental conditions. Challenges might include:

• Electromagnetic interference (EMI).
• Power/voltage fluctuations.
• High temperatures.
• Extreme outdoor temperatures.
• Moisture or humidity.
• Dust, dirt, oil, solvents and potentially corrosive chemicals.
• Mechanical hazards.
Given these risks, it is easy to see why the EtherNet/IP network for the manufacturing or processing plant has to be designed and constructed differently. Any physical deterioration or electrical failure in data transmission components can lead to unreliable network performance and/or safety issues, and might cause loss of critical data, costly downtime or even catastrophic failure.

Consider the Real Costs of Network Failure
Analysts report that an overwhelming percentage of unplanned downtime in industrial operations is caused by a network infrastructure failure. According to one industrial study, fully 72% of network faults can be attributed to failure at the OSI (Open Systems Interconnection) Layer 1 — Physical Media, Layer 2 — Data Link, and/or Layer 3 — Network.

Industrial operations 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 predetermined schedule, with little or no margin for error. Maximum uptime and productivity is the key goal, and consistently reliable network performance is essential to achieving that goal.

If a network component should fail, the cost of replacing the part represents only a fraction of the overall costs associated with a production shutdown, whereas the indirect costs can be substantial.

For example, downtime in an automotive assembly plant capable of producing one vehicle per minute would stand to lose profits of about $2,000 to $3,000 per minute for small car production, and up to $8,000 per minute for SUV and pick-up truck production. If a failure occurs within OSI Layer 1, the impact is felt immediately across Layer 2 and Layer 3. That’s why it's so critical to invest in a high-quality, robust EtherNet/IP physical media infrastructure for the plant.

Select Industrial-Grade Physical Media
Commercial off-the-shelf (COTS) Ethernet cables and hardware, such as those used in typical office environments, simply are not designed to withstand the extreme environmental conditions typically present in industrial settings. Ruggedized industrial-grade components are built and engineered specifically to perform consistently over long service life.

One criterion to apply in specifying industrial EtherNet/IP components is Mean Time Between Failure (MTBF). The component manufacturer should be able to provide a MTBF analysis as evidence that their industrial-grade Ethernet products are made to provide a lifespan similar to that of other automation system components — typically 10 to 30 years. By comparison, typical commercial-grade products are built to achieve about a 5-year average lifespan.

Another key factor is to select cabling and connectivity components that offer full conformity with the Ethernet LAN IEEE 802.3 standard and all other applicable industry standards and specifications. Today’s marketplace offers a plethora of environmentally hardened cabling solutions designed specifically for use in harsh environments.

The Proof is in the Testing
In a series of rigorous tests conducted by Belden comparing the performance of COTS cables versus industrial-grade cables, results clearly show that commercial cables do not stand up as well as industrial cables. Tests were performed on state-of-the-art testing equipment, and all the cables used in the study initially tested as fully compliant to ANSI/TIA/EIA 568-B.2 Cat 5e standards.

Following is a summary of four of the tests performed and their results.

1. Abrasion. 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.

2. Cold Bend. 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 -80oC, -60oC, and -40oC) by being partially wound around a 3-in.-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.

3. Crushing. In this test, an Instron machine head brings a 2-in-by-2-in. plate down on a segment of cable to crush it — 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 lbs. of applied force, the COTS cable with PVC jacket failed; it was smashed flat, and it wouldn't spring back to its original shape. The industrial-grade, black-jacketed armored cable had a failure value of 2,250 lbs — more a ton.

4. Water Immersion. 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 — and the cable still exceeded the Cat 5e requirements.

EtherNet/IP Compliant Cabling
Ruggedized cabling options are vast and varied. Industrial-grade cables are constructed of heavy-duty materials that resist the effects of sunlight, volatile temperatures, moisture, oil and chemicals. They will perform effectively in a wider temperature range (-40oC to +85oC) than commercial cables (typically 0oC to +60oC). Selection will depend on each plant’s network configuration and application requirements.

Industrial EtherNet/IP-compliant cabling and connectivity products include:

• Heavy-duty, all dielectric, indoor/outdoor-rated optical fiber cables in single-mode and multimode constructions. Some feature water-blocking agents for added moisture protection.
• Cat 5e and Cat 6 cables with heavy-duty oil- and UV-resistant jackets. Some feature a Bonded-Pair inner construction in which the conductor insulation of the pairs is affixed along their longitudinal axis to ensure consistent conductor concentricity and prevent performance-robbing gaps between the conductor pairs during installation and use.
• Upjacketed and armored cables for extreme environments.
• Continuous flex cables for use with continuous motion machines and automation systems.
• Low smoke zero halogen (LSZH) cables, water-blocked and burial cables.
• Industrial-grade connectivity components, such as: IP67- or IP20-rated UTP or STP patch cords, connectors, modular jacks and plug kits, adaptors, faceplates and surface mount boxes.
• Industrial-grade Cat 5e RJ45 and Micro (M12) cordsets and patch cords, including high flex versions.

Allow Additional Headroom
Building in extra bandwidth at the start is a recommended best practice in designing the industrial Ethernet infrastructure. Allowing additional bandwidth not only boosts network speed and efficiency, but also ensures that the automation and control network built for today’s needs has sufficient headroom to accommodate future network expansion.

This approach is far less costly and disruptive than having to upgrade incrementally if additional devices and/or control systems are required.

Reaping the Rewards of EtherNet/IP Convergence
Adoption of an integrated, converged EtherNet/IP approach to network design and installation continues to grow. Installing a standard Ethernet infrastructure on both the enterprise and industrial sides represents a practical, cost-saving strategy for industrial organizations seeking to maximize sustainability and return on IT assets, while reducing their total cost of ownership.

In selecting and installing field-proven, end-to-end EtherNet/IP solutions that provide for seamless integration, many companies have already realized the benefits of better, more reliable performance, lower maintenance costs and faster, easier upgrades — benefits that mean greater peace of mind for everyone involved.
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