Consulting-Specifying Engineer - August 2008 - (Page 63) Equipment Lifecycles Category 5e cabling is terminated on a communication rack. The photo shows the proper termination process to maintain the best cable performance. The cables are neatly dressed and the cable bend radius is not exceeded. Source: CH2M HILL This is a close view of Category 5e unshielded twisted pair cabling that is terminated on the backside of a Category 5e rated patch panel. To limit the amount of cross talk and impedance changes, no more than a 0.5 in. of cable jacket is removed, and only a minimum amount of untwisting of the cable pairs takes place. Source: CH2M HILL industry has been working with 10G Ethernet speeds longer, and it has a mature product line for 10G Ethernet. You also can stretch beyond the 100 meter channel distance limitation set out by the cabling standard. Still, the downside is that the optical network interface cards typically cost more than the twisted-pair variety. Even with an all optical data network, some twisted-pair copper cabling may be required for telephones and power of Ethernet devices. The industrial environment The industrial environment doesn’t see the same turnover in bandwidth-greedy network applications as in commercial and office environments. Too much turnover in applications used in manufacturing or processing can lead to costly disruptions. The industrial environment has a different mentality regarding the type of data being networked. It will still have an office network susceptible to the bandwidth issues faced in a commercial environment, but the industrial networks are more purposeful in traffic. Network traffic is planned: A network designed to communicate between a server and programmable logic controllers (PLCs) in a batch plant won’t arbitrarily decide to download a video from the Internet. With this in mind, an environment that has a moderate to minimum amount of EMI can operate with Cat 5e cable. This is assuming that in this environment the cabling will most likely be routed in electrical metallic tubing conduit or, if necessary, a ventilated cable tray. A solid bottom tray with a cover may add additional EMI protection to the unshielded twisted-pair cable. The alternative to the Cat 5e cable is the fiber optic cable for industrial environments. It is not susceptible to the effects of EMI and it can go much longer distances. Where there are PLCs located throughout a manufacturing or processing area, it is not always feasible to locate a network switch to provide coverage for 100-meter limited twisted-pair cable. As noted before, the commercial building standard does not allow extending beyond 100 meters. For an industrial environment, as long as engineers don’t extend beyond the Ethernet protocol for distance over the fiber optic cable, it is within good engineering judgment to step beyond the commercial building standard. In either environment, it is important to choose a quality cable manufacturer or a certified installer. The commercial environment isn’t as harsh as the industrial environment, but you will likely start pushing the bandwidth limitation of the cable plant in a commercial environment. For very harsh industrial environments, some cabling manufacturers manufacture cable components designed to keep the cable connectors clean and free of contaminates. Kuhlman’s areas of expertise include telecommunication system design, local area network system integration, facility management system network design, structured cabling, and specialization in fiber optics. He has 20 years of experience in communication infrastructure and is a member of Consulting-Specifying Engineer’s editorial advisory board. Consulting-Specifying Engineer • AUGUST 2008 63
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