Industrial Ethernet reaches the outer limits
Unlike the protection of climate-controlled telecom closets, a new set of rules for cable runs and termination applies to Industrial Ethernet.
A new market for LAN applications has come out of the closet and is finding its way to the factory floor. Previously, information technology (IT) on the factory floor was limited to isolated software programs for material and process control planning for on-time production scheduling, or just simple manual intervention and reporting. But today, IT for outside the office is evolving to include a fully advanced networking system, as firms look to tap real-time information from their production operations to gain a competitive advantage.
Networks on the factory floor are not new, but various control vendors have perpetuated different proprietary and open networks, making information swapping throughout the plant a less than simple exercise. Only in the last few years have companies looked to leverage the existing Ethernet-based networking already in place in the front office to perform similar data communications on the factory floor. This trend has created a new market called Industrial Ethernet, and driven by the potential for device interoperability, simplified network maintenance, and reduced cost, the number of implementations is steadily growing.
By using principles, products and standards for structured cabling that already exist in the commercial environment, it should be an easy transition to apply these to the industrial environment to reduce interconnection complexity. But there are major differences that create a new set of challenges, such as extreme or harsh conditions that don't exist in typical commercial installations.
"In the factory, not only do you have a much more difficult environment to deal with, but the premise wiring is only a piece of the total story," says Bob Neagle, manager/Industrial Ethernet Group, Woodhead Connectivity (www.connector.com). "In these applications, there is network cabling between work cells, within a work cell, and even on a specific piece of machinery. Trying to rigidly apply the TIA 568 structured cabling standards isn't always feasible."
Industrial Ethernet is the logical network to manifest on the factory floor and other harsh environments, since most likely it is already in place in the office and so can easily communicate between computers.
Existing cable and connectivity manufacturers are designing ruggedized products to withstand these environment challenges. In addition, the TIA TR-42.9 subcommitte is puttng together guidelines for a cabling system for industrial installations that will support a multi-product, multi-vendor environment.
Defining the outer limits
Many manufacturers who have expertise in producing cable and connectors in harsh environments are already providing products for this market while the standards continue to evolve. "Three years ago, Brian Payson of Woodhead and I designed an Industrial Ethernet connector, RJ-Lnxx, which was the first RJ-45 [8-pin modular] connector to come out of the gate with a patent provisional for this specific market," says Mark Fillion, product design manager with Woodhead Connectivity. "But, as the broad range of environments is defined, so comes the redesigning of products, and the end users and standards committees will work together to decide the winning solution."
Industrial Ethernet is the logical network to manifest on the factory floor and other harsh environments, since most likely it is already in place in the office and so can easily communicate between computers. Unlike the protection of climate-controlled telecom closets, however, a new set of rules for cable runs and termination applies to Industrial Ethernet. "The challenge is coming up with a structured cabling system arrangement that serves a vast array of situations," says Peter Sharp, senior telecommunications consultant for the engineering consulting firm, Giffels Associates Limited (www.giffels.com), Toronto, Ontario, and chairman of the TIA TR-42.9 standards subcommittee. "On one extreme, you have a dirty steel mill, rich with solvents, water and oil, which is a very hostile environment for cabling. And on the other hand is the clinical laboratory and with very small distances, where cleanliness is a main criteria and where RF or other sources of electrical interference may be present."
The main differences are not the structured cabling principles but a new generation of heavy-duty products and sensible pathways so that the cable can withstand the harsh environments and other obstacles not found in the office. Industrial Ethernet, however, has gone beyond the factory floor to expand its applications to a range of harsh environments, such as oil fields, outdoor telecom equipment, military devices, and point-of-sale displays.
Other factors to consider when installing cabling products for varied industries include temperature extremes (such as in petroleum factories and outbuilding kiosks), water (such as in food processing plants) and humidity, direct moisture and vibration (for outdoor relay messaging and outdoor communications). "Industrial Ethernet now defines such a broad subject, which encompasses hundreds or thousands of volts in electrical power, thousands of amps in current, and measuring RF (radio frequencies) in megawatts," notes Sharp.
Industrial Ethernet products will need to be flexible to provide real-time high-speed communication, as well as machine control from PC applications to programmable logic controls (PLCs) and input/output (I/O) modules from many major vendors. Unlike the telecommunication closets used in an office environment, industrial applications will not require many moves, adds and changes, or modularity of patch panels.
Enclosures and connectors will need to meet NEMA safety regulations as well as stringent environmental and mechanical specifications. They will consist of enclosed distributed control cabinets, and I/O in the work cell areas—both sealed and unsealed.
One of the most challenging product developments will be fluctuation in temperatures outside of the current specifications. Current connectivity is manufactured to tolerate temperatures between –10°C and +60°C, typical of most office and light industrial environments. It is common, however, for temperatures to exceed this range in harsh environments for an extended period of time, causing transmission failures and reliability issues. New designs must offer the full industrial temperature range from –25 to +85°C.
"Several grades of copper Ethernet cable exist," states Neagle, "Due to the data encoding, most of the energy of a 100-BaseT Ethernet data stream lies below 70 MHz . Because Category 5 four-pair cable delivers better signal-to-noise ratios, since it filters high-frequency noise, it proved better than Category 6 and more cost-effective than fiber, at this point, in the industrial environment," notes Neagle.
A major concern is common mode rejection, because that gives the biggest gain in noise reductions. Common mode noise is the voltage present on all conductors with respect to grounding. Due to the number of sources in industrial environments, communications systems are highly susceptible to common mode noise problems. "Extremes of temperature, humidity, sunlight and the environments associated with industrial applications may cause problems with a cable's electrical and mechanical performance," explains Jeff Mahall, director of marketing for Helix/HiTemp Cables (Draka Comteq; www.drakacomteq.com). "Any one or a combination of these conditions can cause cables to become stiff and brittle, and be susceptible to cracking. Should the jacket become compromised, the long-term electrical integrity of the cable can deteriorate."
Mahall adds that since the installed environment will vary, the key to the cable's reliability will be jacketing and shielding. The solution, he says, will most likely be an all-weather Category 5e (now referred to as Cat5i)—a 4-pair UTP or STP-designed to meet military specifications, such as MIL-C-24640A water penetration requirement. The jacketing should be a tough UV- and abrasion-resistant black PE jacket, and can be armored if required.
Connection to the outside world
Connectors play a crucial role in Ethernet's overall performance. By proxy, the current data standard at the time was to use Category 5 and the 8-pin modular connector with a protective boot. But not all such off-the-shelf connectors are suitable for industrial environments because performance tests for vibration, shock, sealing, and temperature ranges vary considerably. These factors determined the materials selection and product design.
"Some modifications and tooling had to take place," states Brian Payson, vice president of engineering, Woodhead Connectivity, who got the ball rolling with regards to the first connector for the Industrial Ethernet market. "But key to the overmolding design was to be able keep out moisture and chemicals. We decided upon a threaded coupling and housing, similar to a military spec screw type."
"When I designed the first ruggedized connector," says Fillion, "the foremost criteria were that it had to achieve Category 5e performance specifications and provide a sealing method to keep out contaminants. We created a submersible test head where the cable and connector could be immersed for 30 minutes." To keep the connector's factory-designed latching feature functional, the mated system was designed with two O-rings. "The RJ-Lnxx connector met the IEC testing factor (IP67), which covers ingress from both liquids and foreign objects, and also clamps down to minimize vibration in compliance with the IEC 60068-2-6 standard," explains Fillion.
In the past three years, since the introduction of the first Industrial Ethernet connector, RJ-Lnxx has undergone changes due to industry feedback and real world usage. A variety of receptacle styles are offered to meet different application needs, including a 110 punchdown, direct printed circuit board (PCB) mount, or as a bulkhead pass-through.
Installers can assemble the plug end so that patch cords can be made in the field, or the plug ends can be ordered to length. Several cable types are offered, including a specialty Kevlar-wrapped version with an unmatched temperature range of –70°C to 105°C. "These diverse designs address the needs of the factory as well as other harsh environments, such as oil fields and marinas," adds Neagle.
Carol Everett Oliver is principal of Everett Communications (firstname.lastname@example.org) and a freelance writer for the cabling industry.
The Industrial Ethernet market is still lacking the efficient industry standards that exist in the commercial structured cabling environment. In the premises market, the TIA-568 standard provides precise guidelines for designing a structured cabling system. It was first formulated in 1990 and was a joint effort between the TIA and IEEE (who, several years earlier had finalized the Ethernet standard).
A sealed device, such as 8-pin modular connector will likely be recognized by the TIA as the basic connector for Industrial Ethernet.
The TIA assembled the TR-42.9 standards group to go beyond the scope of existing commercial building standards. "While some of the basic concepts apply, the differences in a factory environment make it hard to apply TIA-568 in its entirety," notes Peter Sharp, senior telecommunications consultant for Giffels Associates Ltd in Toronto. "Propagation problems are significant where large transmission distances are combined with high levels of electrical noise far in excess of what might be found in typical commercial buildings." Sharp adds that the use of a structured wiring system does not necessarily allow for the shortest cabling route between two points. "So, there will be some resistance in the industry where short run, point-to-point wiring is the norm," he says. "But be sure that the structured wiring approach will be the one topology that will receive the greatest preference in the standard."
Just as the TIA-568 has evolved over the last decade, so will the standards for Industrial Ethernet. This subcommittee will eventually publish industrial standards to match the EIA/TIA-568/569/606 commercial cabling, connectors and network architectures, as well as pathways and spaces, and corresponding connector and equipment documentation schemes.
Defining the environment will be the most difficult first step. "The hostility of a typical space is an eye opener," says Sharp. In the industrial environment, you have to protect the cable, but by so doing, the electrical behavior of the cable itself is affected. So, there is an interaction between the support and the cable. The interaction of cabling and pathways must be researched and must be included in this document as well."
Sharp adds that the initial goal will be to issue a document that is useful to a wide readership of people wanting to design and install a telecommunications system in an industrial plant. The three main objectives for the first edition of TIA TR-42.9 is:
- Ensuring an understanding of the electrical environment and being able to quantify it;
- Defining what parameters need to be measured and controlled to make the cabling less susceptible to electrical interference (such as welding and RF noise in the megawatts range), and to consider the pathways ;
- To investigate and recognize a sensible connector, and refine the basic components and interface.
If these standards committees are emulating the commercial structured cabling practices already in place, then the 8-pin modular device will be recognized as the basic connector. Component options still need to be refined, but the TR-42.9 standards committee will come out with recommendations, as well as alternates. While it appears that everyone agrees that the standard needs to specify a sealed connector, there are currently several different mating approaches, including coupling nut, bayonet, "ear tab," and push-pull.
"The industry tries to promote interoperability, so the connectors made by different manufacturers have to work together," says Sharp. "But for that to occur, the electrical plug-and-socket interface has to be understood." Sharp continues, "The 42.9 subcommittee is not only comprised of members from the manufacturing side of structured cabling products, but also end users and system designers. The diversity of the people involved will make the standard unbiased and not weighted to one type of manufacturer. This will open up the markets."