Coping With Proliferating Electronic Cabling

Heavy reliance on electronic communications and a need for flexibility are hallmarks of today's industrial facilities. As a result, engineers must pay careful attention to how electronic communications cabling is routed throughout their plants.

01/01/1998


Heavy reliance on electronic communications and a need for flexibility are hallmarks of today's industrial facilities. As a result, engineers must pay careful attention to how electronic communications cabling is routed throughout their plants.

Costly communications systems need to be protected and yet be easy to upgrade, reconfigure, or relocate. Even a well-designed electronic network can fall short of expectations if it is locked into an inflexible, difficult-to-change cabling infrastructure.

Wire management systems

Wire management systems were developed to route and protect power wiring, a role they continue to perform. However these systems are also well suited for communications lines, because they offer accessible and secure pathways for wire and cable.

Wire management systems can be grouped into three categories, based on where they are installed: overhead, infloor, and perimeter. Each of these systems, when properly planned, provides the flexibility to accommodate both routine and major changes.

Overhead distribution systems

Overhead systems are versatile in both physical layout and cable accessibility. Single channel and divided configurations come in a variety of sizes and cover and hanging options.

Center spine cable trays consist of a central support member from which extend a series of rungs that support the cable, much like a backbone and ribcage. The central member is suspended from single hangers. Cables can be laid in, minimizing the need for labor-intensive cable pulling. A version with rungs on only one side of the spine is available for wall mounting.

The preferred designs have screw-in rungs that can be removed and replaced. The rungs should have factory-installed end caps to prevent injury to installers and damage to cables. Some brands include a stiffener bar to reinforce the hanger and offset uneven loads.

Solid-bottom cable trays offer greater protection and higher weight capacity than center spine. These systems accommodate large numbers of branch lines, and dividers can be installed to separate power and data lines and to organize cabling. Solid-bottom cable trays can be specified with or without covers. Ventilation louvers can also be specified for cooling. Trays are hung with either center rod hangers, C-hangers, or trapeze hangers; or they can be wall mounted using brackets.

Ladder cable trays look like extension ladders suspended horizontally by trapeze hangers. They offer strength and large capacity and are thus well suited to heavy-duty power distribution. Ladder trays have the drawback that cables must be pulled rather than laid in place.

Wireway is a totally enclosed wire management system that does not include provision for activation (such as by surface-mounted outlets or jacks) of the wiring or cabling contained within. Hinged or screw-on covers provide complete protection and convenient access. Wireway differs from solid-bottom cable tray mainly in the requirement that the cables must be totally enclosed.

Design issues. Cabling from an overhead distribution system must eventually be dropped to floor-level equipment and workstations. There are various ways to accomplish this. Solid-bottom cable tray or wireway can be installed vertically against a wall or a suitable support column. Drop-out fittings guide the cables from overhead cable tray or wireway into these vertical enclosures.

Another option is service poles that distribute power wiring and communications cabling from overhead systems to individual work spaces on the plant floor where the communications systems are accessed by modular jacks on the pole.

Some manufacturers offer solid bottom cable trays and wireways in a variety of colors. Color has practical value in a large and complex facility where different colors can serve as guides to the cabling contained in the system.

Infloor distribution systems

In contrast to overhead systems that can be repositioned with relative ease, infloor distribution systems are more permanent and in most cases must be designed in before concrete is poured.

Infloor trench systems consist of "tubs" and cover plates that are available in a wide variety of sizes. The tubs carry wires and cables in single or multiple channels while the cover plates, installed flush with the floor surface, serve as a part of the floor. The system is unobtrusive, yet readily accessible.

Infloor trench systems allow direct connections to machinery and equipment from beneath, thereby safeguarding the integrity of the cable system.

Poke-thru systems lend themselves to retrofit applications in multistory buildings. Poke-thru fittings are installed in holes that have been core drilled through concrete floors. They carry wiring and electronic cabling from an overhead area to the floor above. The newest poke-thrus are fire rated and can accommodate Category 5 cabling.

Design issues. Planning an infloor trench system can be likened to designing a grid of streets to serve a geographic area. Type and spacing of the streets depends on the nature and density of property use.

Similarly, a facility with small work cells and modest equipment size may require a small-to-medium-capacity trench system in a 10 3 10-ft grid pattern, while a plant employing large, heavy equipment may require a high-capacity system in a 20 3 20-ft pattern. The physical layout of the facility and the anticipated frequency of changes must also be taken into consideration.

Unlike an office, where all the workstations are typically linked to a single computer network and a central telephone system, an industrial facility may have many smaller "networks" in addition to large voice and data networks. For example, CNC machining equipment must be linked to a computer, and large machines often require remote controls. Overhead and perimeter systems could accommodate these connections, but links between machines and their controls are often best managed through an infloor system.

Perimeter distribution systems

A perimeter system routes cabling along building walls in a secure and easily accessible manner. Cable is installed by laying in; no pulling is required.

Perimeter systems include raceway, wireway, or a combination of the two. Available in a variety of materials, both offer single or multiple channels, but raceways may contain electrical outlets and/or communications activation devices while wireways do not.

Design issues. A perimeter wire management system is a good choice for longer runs from one section of a facility to another, or in areas adjacent to walls where workstations can access the cabling systems. Perimeter systems are also frequently used in combination with overhead or infloor systems.

For example, voice and data cabling may run through a trench duct to a workstation area located on the manufacturing floor. Cabling is then routed from the trench to surface raceways that are attached to workstation partitions, providing convenient access to the communications networks.

Other cabling considerations

All these wire management systems are designed to accommodate common types of communications cabling. However, high-performance Category 5 and fiber optic cabling present some special considerations.

Maintaining the precise bending required is essential to ensure noise reduction integrity and overall performance. Well-designed wire management systems include specialized cable dropout and radiused fittings that ensure specified cable bend radii are maintained at all times and in all locations.

Flexibility now -- and in the future

In today's complex and competitive environment, electronic cabling involves more than just cable and connections. Wire management systems provide industrial facilities with both operational (short term) and systems (long term) flexibility.

The result is added value to both new and renovated buildings by lowering operational and systems costs.

-- Edited by Gary Weidner, Senior Editor,

847-390-2689, gweidner@cahners.com

Key concepts

Electronic wires and cables are proliferating throughout facilities.

Cable management systems can add value to both new and existing buildings.

Advance planning for a flexible installation is the key to successful cable management.

Is it a raceway or wireway?

Raceway includes almost any enclosed channel that holds wires, cables, or busbars. It may incorporate activation devices such as switches or jacks.

Wireway is a type of raceway used only to convey wires and cables. It has hinged or removable covers along its length, allowing cables to be laid in.

More info

For questions regarding this article, the authors may be contacted as follows: Janet Stanley, Wiremold Canada (overhead systems), 905-457-6528; Tim Hill, Walker Systems (infloor systems), 304-375-1136; and John Hoffman, The Wiremold Company (perimeter systems), 860-233-3638.





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