No doubt, Industrial Ethernet is taking plant-floor network infrastructure by storm. Manufacturers can use this single-platform solution to provide interoperability when connecting plant operations to corporate and administrative offices, as well as the Internet.
Convergence of plant and office levels on an open, standards-based Ethernet communications platform offers a number of advantages:
- Ubiquitous access to real-time data to improve plant operations.
- Real-time collaboration, inventory visibility, and production planning.
- Shop-floor system integration with enterprise resource planning (ERP) for scheduling, planning, quality tracking, and delivery information.
- Reduced total cost of ownership (TCO) due to faster installation, less costly maintenance and upgrades.
Specifying network-infrastructure components for plant-floor environments differs significantly from installing Ethernet in clean, sheltered office environments. At industrial sites, network components may be exposed to temperature extremes, UV radiation (sunlight), moisture, oil, chemicals and other contaminants. All can degrade the components’ physical integrity and electrical performance, potentially leading to intermittent outages or even total system shutdown.
Even normal plant activities can pose risk to delicate electronics. For example, there may be constant machine movement and vibration, robotic machinery generating power spikes that increase EMI/RFI, and/or vibration caused by forklifts and other mechanized vehicles traversing the work floor. Even the best commercial off-the-shelf (COTS) Ethernet systems aren’t made to withstand such harsh and hazardous conditions.
Plant-floor communications infrastructure components must be tough enough to overcome challenges presented in industrial settings. The following selection guidelines can help ensure that robustness, ultimately producing long-term performance and reliability.
Consider The Real Cost Of Downtime
Industrial plants rely on automation, instrumentation, and control data communications to relay signals between machinery, devices, and control systems that activate events on an exacting and pre-determined schedule—with little or no margin for error.
Network administrators require optimal security and manageability to attain a network uptime of 99.999% or better. Yet analysts report that a large percentage of unplanned downtime in industrial operations stems from network infrastructure problems. According to one such report, 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).
Physical deterioration or electrical failure in critical data-transmission components can lead to unreliable network performance and safety issues, and may lead to loss of critical data, system downtime, or even catastrophic failure. If a switch, connector or cabling system fails, the cost of parts replacement and repair represents only a tiny fraction of the overall costs associated with production downtime.
Indirect costs of Ethernet system failure may include lost productivity, delayed processes, cost of system shutdown and startup, possible lapses in security and safety, and the loss of service to customers relying on the plant’s output. Consequently, total downtime costs can soar to hundreds of thousands, even millions of dollars.
Look For Industrial-Grade Components
When specifying Ethernet physical media, data links, and network hardware for plant-floor installation, it’s important to select hardened, industrial-grade components, Such components must feature rugged construction and durability to provide optimal performance over long service life. High-quality industrial-grade Ethernet products should provide a lifespan similar to that of other automation system components—typically 10 to 30 years, much longer than most COTS products.
Other factors to consider include: conformity with the Ethernet LAN.IEEE 802.3 standard; mean-time-between-failure (MTBF) analysis; mounting options (e.g., DIN-rail-mounted, rack- or panel-mounted, or devices that bolt securely onto machines); and a small form factor to occupy less space and allow greater density within the limited control-panel space.
For the physical media layer (cabling and connectivity), a host of industrial-grade products conform to the Ethernet LAN.IEEE 802.3 standard, while resisting the effects of sunlight, volatile temperatures, moisture, and chemicals. Industrial cables will operate effectively in a wider temperature range (-40°C to +85°C) than commercial cables (0°C to +60°C) (Fig. 1). Selection will depend on each plant’s network configuration and application requirements.
Industrial Ethernet cables/connectivity include:
- Heavy-duty, all-dielectric, 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 and Cat 6 cables with heavy-duty oil- and UV-resistant jackets. Some “Category” cables feature a bonded-pair inner construction. The conductor insulation of the pairs is affixed along the 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 designed for use with continuous motion machines and automation systems.
- Low-smoke zero-halogen (LSZH) cables, and waterblocked and burial cables.
- Cables designed for leading industrial-automation networking and communications protocols, such as EtherNet/IP (ODVA), Modbus TCP/IP, ProfiNet, and Fieldbus HSE.
- 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.
Similarly, there’s a wide a range of options available at the information, control, and device layers (switches and hardware). They support both copper and optical fiber media, and switches can reach data speeds as high as 10 Gbits/s (Fig. 2). At a minimum, all of these components—switches, connectors, and other hardware—should offer robust construction and resistance to high temperatures, vibration, and EMI.
Typical COTS hardware is designed to operate from 0°C to +40°C, while industrial-grade Ethernet hardware operates efficiently from 0°C to +60°C (extendable to -40°C to +85°C). In addition, excessive moisture and corrosive chemicals may inflict serious damage to the electronics in commercial switches, whereas ruggedized industrial switches can be securely sealed to prevent ingress of these substances (conformal coating is also available for humid/moist applications).
Industrial Ethernet hardware components include:
- Hardened managed and unmanaged switches, which come in various copper/fiber port configurations, port densities, industry approvals, and mounting options.
- Firewalls to secure and isolate a network while still permitting the passage of authorized data communications. Firewalls with VPN capabilities also allow secure, encrypted communication from a remote location through the Internet.
- Wireless access points, clients, and bridges in either DIN rail mount or IP67 enclosure-less housings now also support the faster, more secure and noise-immune 802.11n standard.
- Related accessories, such as hardened power supplies, SFP fiber transceivers, and even software that provides network status, alerts, and control from the automation network’s software or PLC.
Build In Bandwidth And Redundancy
With today’s automation and control networks cramming in more Ethernet-cabled devices, an industry best practice is to allow for sufficient bandwidth to handle current needs, with additional headroom to accommodate future expansion. This becomes far less costly and labor-intensive than having to upgrade incrementally over time.
When maximizing network uptime and performance, redundancy often gets overlooked. It’s also considered an industry best practice, especially in mission-critical applications.
Two kinds of redundancy are keys to maintaining uninterrupted signal transmission and maximum uptime:
Power-source redundancy: It specifies switches that have dual power input capabilities, which means that if one power source fails, the other immediately takes over.
Data-path redundancy: The daisy-chain network topologies used by many industrial plants to connect automated machinery and devices have one inherent flaw: If any link between two switches fails, the entire system could potentially go down, since the devices on one network segment can no longer communicate with devices in other segments. The solution is to build a redundant data path into the network topology.
Design For Integration
Another trend gaining traction is to specify network infrastructure components from a supplier that can provide end-to-end, field-proven Ethernet solutions tailored specifically to end-user applications and environments (Fig. 3).
As many companies have discovered, taking a “total system” approach can be more cost-effective over the long run in terms of ease of maintenance, troubleshooting, and upgrades. Moreover, an integrated system typically results more reliable, optimized transmission performance.